DPTZ‐DBTO2, showing thermally activated delayed fluorescence (TADF), with near‐orthogonal electron donor (D) and acceptor (A) units is reported. It is shown that DPTZ‐DBTO2 has minimal singlet–triplet energy splitting due to its near‐rigid molecular geometry. However, the electronic coupling between the local triplet (3LE) and the charge transfer states, singlet and triplet, , and the effect of dynamic rocking of the D–A units about the orthogonal geometry are crucial for efficient TADF to be achieved. In solvents with low polarity, the guest emissive singlet 1CT state couples directly to the near‐degenerate 3LE, efficiently harvesting the triplet states by a spin orbit coupling charge transfer mechanism (SOCT). However, in solvents with higher polarity the emissive CT state in DPTZ‐DBTO2 shifts below (the static) 3LE, leading to decreased TADF efficiencies. The relatively large energy difference between the 1CT and 3LE states and the extremely low efficiency of the 1CT to 3CT hyperfine coupling is responsible for the reduction in TADF efficiency. Both the electronic coupling between 1CT and 3LE, and the (dynamic) orientation of the D–A units are thus critical elements that dictate reverse intersystem crossing processes and thus high efficiency in TADF.Here, a comprehensive photophysical investigation of a the emitter molecule  In contrast, if the D–A geometry is allowed to relax toward planarity, the singlet–triplet energy gap rapidly opens up preventing RISC, and TADF becomes inefficient. Therefore, an optimum D–A geometry exists that maximizes TADF. Moreover, as we previously observed1CT singlet and the local triplet 3LE strongly influences the TADF efficiency. Shifting the 1CT state away from the local triplet state 3LE leads to a significant quenching of the TADF emission.In light of our recently reported results with D–A and D–A–D analogues of DPTZ‐DBTO2, focusing on the observation of aggregation induced emission and delayed fluorescence. However, this article did not show photophysical evidence of TADF in DPTZ‐DBTO2, or device data, which we report here in detail to reveal new insights into the TADF mechanism.During the preparation of this manuscript Tang and co‐workers22.1DPTZ‐DBTO2 yields very small overlap between the Highest Occupied Molecular Orbital (HOMO) and Lowest Unnocupied Molecular Orbital (LUMO) , and gives rise to a singlet excited state with strong charge transfer character. This is further supported by the X‐ray molecular structure, which shows a configuration that minimizes the overlap of the phenothiazine N‐10 lone pairs with the dibenzothiophene‐S,S‐dioxide unit, Figure DPTZ‐DBTO2 molecule has crystallographic C2 symmetry, the phenothiazine units are folded by 34° along N…S vectors and on average are inclined by 82° to the planar dibenzothiophene‐S,S‐dioxide π‐system. The subunits in DPTZ‐DBTO2 are thus sterically “locked” in nearly perpendicular D–A orientation, confirmed by single‐crystal X‐ray data, Figure The conformation of the D and A subunits in DPTZ‐DBTO2 were measured by cyclic voltammetry (CV), −5.2 ± 0.1 eV and −3.0 ± 0.1 eV, respectively, in excellent agreement with the corresponding individual D (HOMO: −5.2 ± 0.1 eV) and A (LUMO: −2.9 ± 0.1 eV) unit energies, , showing that the HOMO–LUMO gap in DPTZ‐DBTO2 is determined by the HOMO and LUMO levels of the donor and acceptor, respectively.The HOMO and LUMO energy levels of DPTZ‐DBTO2, as a function of D–A dihedral angle were determined from TD‐DFT calculations, Figure EST energy varying between 0.8 eV for a planar geometry, and less than 0.01 eV for a D–A dihedral angle larger than 80°  and dibenzothiophenedioxide (A) contributions, indicating negligible conjugation across the donor–acceptor units, which are almost entirely electronically decoupled. Following optical excitation, mainly of the phenothiazine unit at 337 nm (3.68 eV), the DPTZ‐DBTO2 emission in nonpolar methylcyclohexane (MCH) appears broad, peaking at around 540 nm (2.30 eV), in excellent agreement with the energy difference between the HOMO and LUMO levels of phenothiazine and dibenzothiophene‐S,S‐dioxide, respectively (2.2 ± 0.1 eV) determined by CV data. The emission is strongly redshifted relative to the D and A emissions, even in nonpolar solvent, and no 1LE (1D or 1A) emission is observed in solution at room temperature (RT). However, residual 1LE (1D and 1A) emissions are detected around 450 nm in zeonex.The absorption spectrum of DPTZ‐DBTO2 is thereafter identified as the 1CT state, emitting at 2.61 ± 0.02 eV in MCH at RT, as determined from the emission onset, see FigureDPTZ‐DBTO2 emission redshifts, peaking at 580 nm (2.13 eV) in toluene, and at 605 nm (2.05 eV) in chlorobenzene, but the intensity decreases significantly . Complete emission quenching is observed in strong polar media, such as ethanol, as is normally observed in exciplex and twisted intramolecular charge transfer states,The emissive singlet state in DPTZ‐DBTO2 phosphorescence is excellently reproduced by the superposition of the phosphorescence emissions of the donor molecule phenothiazine  and the acceptor molecule dibenzothiophene‐S,S‐dioxide , with a shift of just 0.03 eV, showing that the lowest triplet state in DPTZ‐DBTO2 is a local triplet state (3LE), which carries clear contributions from both the triplet of the donor, 3D, and the triplet of the acceptor, 3A. This is due to the near orthogonality between the D and A fragments in DPTZ‐DBTO2 which decreases the electronic coupling between the two units. However, despite 3A and 3D having different phosphorescence lifetimes , the 3LE phosphorescence of DPTZ‐DBTO2 shows a single exponential decay without any change of the profile of the emission spectra over time  is identified by its well‐resolved phosphorescence at low temperature in both solution and solid films, Figure 3LE state is measured at the first vibronic peak as 2.58 eV.The me Figure3c. TheDPTZ‐DBTO2 phosphorescence is not compatible with two independent triplet states (3D and 3A) emitting simultaneously, and so here we observe phosphorescence from the unique lowest triplet excited state, which is of local character, (3LE). In zeonex the emission from 1CT appears slightly redshifted, due to the larger dielectric constant of zeonex, compared with MCH, a tail around 450 nm is also observed, due to a weak contribution from 1LE (1D and 1A) emissions. As is seen, in MCH the 1CT state is just 0.03 eV above 3LE.Simultaneous emission from two triplet states has been reported before in other compounds, suggesting that Kasha's rule for internal conversion is not fully obeyed in these cases.EST energy, a strong TADF contribution to the overall emission is observed in DPTZ‐DBTO2. For example, upon degassing in MCH, the luminescence of DPTZ‐DBTO2, increases ≈12 times , and the fluorescence yield, ΦF, increases from 0.03 ± 0.01 to 0.3 ± 0.1. Oxygen very effectively quenches any triplet population but does not affect singlet states, thus in aerated solution only “prompt” 1CT emission is observed. The emission spectra obtained in aerated and degassed MCH solutions match each other exactly; showing that TADF  and prompt fluorescence (PF) come from the same 1CT state. The (dominant) TADF contribution to the overall DPTZ‐DBTO2 emission is directly determined by comparing the emission in aerated and degassed solutions. In MCH, the recycled tripletsDPTZ‐DBTO2 fluorescence.Due to the vanishing ΔDPTZ‐DBTO2 in MCH solution, again giving clear indication that both emissions come from the same excited state (1CT), . The intramolecular origin of the delayed fluorescence (TADF) is confirmed by the strictly linear dependence of TADF with laser excitation intensity, and therefore, the origin of the delayed emission is unambiguously assigned to a thermally assisted mechanism, not triplet–triplet annihilation . This is also true for DPTZ‐DBTO2 in the solid state . The DPTZ‐DBTO2 luminescence decay, followed over a time interval spanning eight decades, shows two clear exponential components, Figure 1CT fluorescence, and a second regime decaying with a 5.5 μs time constant, assigned to the TADF decay (DF). A 10.3 TADF/PF ratio  is determined from the time resolved decay. This is in excellent agreement with the TADF/PF ratio determined from steady‐state oxygen dependent experiments.An excellent spectral match is also obtained between the steady state and delayed fluorescence (TADF) spectra of 1CT (prompt and delayed) fluorescence, and a long‐lived and resolved emission, observed only at low temperatures, assigned to the phosphorescence from the local triplet state (3LE).Time resolved, area normalized, emission spectra, obtained at 290 and 100 K, are shown in Figure kISCS>>kF+kICS and kRISC>>kPH+kISCT. In most cases, it is also observed that kISCS>>kRISC and kISCT>>kPH. Interconversion of the singlet and triplet emissive states then occurs many times before photon emission or nonradiative decay can take place.DPTZ‐DBTO2 in MCH, and the yield of excited singlet states formed via reverse intersystem crossing, ΦST, can be assumed to be close to 1. The triplet yield, ΦT, is thus determined directly from the 10.3 DF/PF ratio as 91 ± 2%.] Using the prompt luminescence lifetime, τF = 15.2 ± 0.9 ns, the intersystem crossing rate between the 1CT and local excited triplet states (3LE), kISCS=ΦTτF=(5.9 ± 0.3) × 107s−1 is also determined.For strong TADF to occur, the following inequalities must hold  × 107s−1, and the rate of internal conversion kICS=(0.51 ± 0.01) × 107s−1, are determined.Using the fluorescence quantum yield (PLQY) of the prompt 3LE to 1CT is determined from the TADF decay time, τTADF=5.48 ± 0.3 μs, and the amplitude ratio of the DF and PF decays obtained in Figure kRISC=IDFIPF 1τTADF=(1.9 ± 0.1) × 106s−1. Moreover, for small singlet–triplet ΔEST energy splitting, the two isoenergetic intersystem crossing rate constants, kISCS and kRISC0, Figure ΔEST=−kBTln(kRISCkRISC0) giving ΔEST = 0.08 ± 0.01 eV, in excellent agreement with the energy gap between the 1CT and 3LE states, ≈0.03 eV, estimated from the 1CT fluorescence and 3LE phosphorescence  ≈ 2.43 eV), Figure 3LE energy is not significantly altered because this is a state with no charge transfer character, being a local excitonic triplet state. Therefore, in toluene the 1CT state lies below the local triplet, 3LE, and the energy gap between these two states increases to ≈0.15 eV. This simple change has significant implications in the RISC mechanism, and explains why the TADF contribution to the overall emission is so strongly affected by the polarity of the host. In MCH the TADF contributes 91% to the overall emission, while in toluene the TADF contribution is around 67%. A similar conclusion is drawn from the time resolved emission decays in both solvents, Figure DPTZ‐DBTO2.In toluene solution, due to the higher polarity of this solvent, the DPTZ‐DBTO2, SOC is not operative between the 1CT and 3CT states, because the orbitals involved in both states are the same and thus the matrix element vanishes, 〈1CT|HSOC|3CT〉=0. This process is thus formerly forbidden for the HOMO perpendicular to LUMO and no change in spatial orbital would occur upon interconverting between these two states, and so no orbital angular momentum change, as required for a spin flip, could occur.1CT state and an energetically close local triplet state, the 3LE state in this case, via a spin orbit charge transfer ISC process, (SOCT), as this spin flip transition couples to a change in orbital angular momentum (much like an n‐π* transition), concomitant with the measured high ISC rate.DPTZ‐DBTO2, the ISC due to SOCT involves the 1CT and 3LE states, and thus achieving a very small energy gap between 3LE and 1CT is key for efficient thermally activated RISC. Consequently, for most well stabilized D‐A CT states, TADF is mediated between the 1CT and an energetically close local triplet state, 3LE.Basically, there are two mechanisms for interconversion between singlet and triplet states: spin orbit coupling (SOC) and hyperfine coupling (HFC). However, in systems where the D‐A electron coupling is weak, i.e., the CT character is strong, as it is in D‐A systems where the D‐A dihedral angle is close to 90°, as in 1CT to 3CT and back,3CT to 3LE. However, ISC due to weak hyperfine interactions can only occur when the exchange energy, i.e., approximately the energy difference between 1CT and 3CT states, is smaller than the typical hyperfine energy of a large organic system, typically 1 to 20 μeV. For intramolecular charge transfer states of twisted conformation between the D and A chromophores, HFC between 1CT and 3CT might be operative, because the energy separation between 1CT and 3CT states of highly twisted D‐A molecules might be of this magnitude, but as can be seen from Figure DPTZ‐DBTO2, the pronounced decrease in the TADF contribution in toluene when compared with MCH, indicates that the RISC mechanism is (at least) strongly dominated by SOCT between 1CT and 3LE.Hyperfine coupling can, in principle, interconvert 3LE state is populated directly from 1CT due to SOCT, and perhaps by HFC from 1CT to 3CT followed by IC between 3CT and 3LE. RISC then occurs from 3LE to 1CT to originate TADF. In toluene, however, where the energy ordering is reversed, see Figure 1CT to 3LE, followed by IC from 3LE to the 3CT, and HFC, occurring from 1CT to 3CT, populate the underlying 3CT state, instead of 3LE. TADF has then to be driven by RISC from 3CT and 1CT. So, in this case, if HFC were to give efficient spin interconversion within the charge transfer manifold of DPTZ‐DBTO2, no decrease in TADF contribution would be observed, since the entire triplet population arriving at 3CT would be converted back to 1CT. However, we observe a significant decrease in TADF contribution in toluene, which means that a far larger percentage of the triplet states are lost, and that can only be due to the smaller efficiency of the HFC mechanism between 1CT and 3CT. This result is easy to rationalize, given the fact that the HFC mechanism is efficient only for very small (<20 μeV) energy separations between 1CT and 3CT states. Therefore, we can assume that HFC is not operative at all, and then the drop in TADF contribution observed in toluene, is easily explained by the fact that the SOCT between 1CT and 3LE is an activated process in toluene, and since the energy gap between 1CT and 3LE is larger in toluene (ΔEST = 0.15 eV), compared with 0.03 eV in MCH, the TADF contribution will decrease, as the Boltzmann term is much smaller, but more initial prompt 1CT should be observed, as the longer PF decay time indicates in Figure 3LE has an additional fast decay channel open to it; as well as decaying directly to the ground state and ISC to feed 1CT, it may deactivate to the 3CT state by IC, which is not present in MCH. This process accelerates the decay of the 3LE state and so may explain a faster TADF decay in toluene as it is observed in Figure 3LE and 1CT increases.Even assuming that HFC may be operative, and then in MCH, the underlying 1CT state and the local triplet state, in this case 3LE, is key to achieving TADF with high efficiency. Therefore, the design of new TADF emitters should target minimizing the energy gap between the emissive 1CT state and any underlying local triplet states, instead of trying to minimize the gap between the 1CT and 3CT. However, the restriction imposed by the D–A molecular geometry in order to obtain efficient TADF emission, shows that even if 1CT and 3LE are almost degenerate RISC is only possible if the D–A relative orientation is allowed to rock about perfect orthogonality. We believe this rationale will open novel strategies to design TADF emitters. It should be noted that it is not really important whether the 3LE is above or below the 1CT state, providing there is a local triplet excited state in the proximity of the 1CT state, i.e., with an energy separation that is less than the width of the Boltzmann distribution, so thermally activated ISC between the two states can be efficient. However, the mechanism sustaining the intersystem crossing is important here. Since SOCT is not active between 1CT and 3CT states, the intersystem crossing between these two states can only occur by hyperfine coupling, and this mechanism is only active for very small energies (less than a few μeV). Therefore, it is vital that a local triplet state exists in the proximity of 1CT state so that intersystem crossing by SOCT can occur to support efficient TADF.This leads to the conclusion that the energy difference between the emissive −2m concentration, as a small band on the foot of the donor ππ* absorption edge, having an extinction coefficient, ε ≅ 102m−1 cm−1, concomitant with a very low transition dipole moment. Measurements of phenothiazine at the same concentrations reveal no such band and so it arises as a direct result of the coupling with the acceptor unit in DPTZ‐DBTO2, . Aggregation effects were shown not to be the cause of this new band.Direct CT absorption is also observed in solution, at 10Figure1CT state, with identical spectra to those observed when directly exciting the donor of DPTZ‐DBTO2. However, as the excitation wavelength was increased to excite more preferentially this new transition, the emission intensity also increased, Figure DPTZ‐DBTO2, and it is very weak we ascribe it to a direct CT absorption band, which avoids the population of 1LE excitonic states. Importantly, this indicates that nonradiative decay from 1LE presents a significant loss mechanism when the donor 1LE state is optically excited, and that by avoiding this far higher PLQY can be achieved, see Figure The new band was found to show a blueshift with increasing solvent polarity, indicative of the transition having nπ* character. This is shown in 2.3DPTZ‐DBTO2 emission retains the same CT character observed in MCH and toluene solutions. The luminescence spectrum appears broad and devoid of any structure, peaking at 560 nm. Again the 1CT fluorescence is observed to be strongly oxygen dependent even in solid film. The triplet yield is determined from these measurements in good agreement with the previous determinations in MCH as 81 ± 5%.When dispersed in a solid zeonex matrix the DPTZ‐DBTO2 shows a striking contribution from 3LE phosphorescence, causing the peak and onset of the emission to effectively blueshift from 560 to 525 nm, even at RT, see Figure1CT state peaks at 560 nm. When degassed the emission peak blueshifts to 525 nm and the intensity significantly increases due to the contribution of both TADF and 3LE‐phosphorescence. RT‐phosphorescence has been previously observed in our other D–A–D materials. Phosphorescence from 3LE is even more clearly observed at low temperature, Figure 1CT state rapidly decays in the μs time range, leaving behind the long‐lived and blueshifted 3LE phosphorescence, showing a longer lifetime (80 ms) than the 1CT emission, which again is in excellent agreement with that of phosphorescence from N‐substituted phenothiazines,3LE state has predominantly 3(nπ*) characterNoticeably, in zeonex the room temperature oxygen‐free spectrum of 1LE state in DPTZ‐DBTO2 is also observed at early times following excitation in solid matrix, decaying in 6 ns, and matching the phenothiazine fluorescence (1D), . These observations are of crucial importance, because they fundamentally show that the 1LE decay to the ground state and ISC to the 3LE states is able to compete with the population of the 1CT state, which can be attributed to the near perpendicular D‐A structure of the DPTZ‐DBTO2 molecule and the rigid environment.Fluorescence emission from the DPTZ‐DBTO2 films in zeonex is again confirmed by the strictly linear dependence of the delayed fluorescence integral with excitation intensity . Moreover, the temperature dependence of the DPTZ‐DBTO2 delayed fluorescence, , shows a pronounced increase of the emission intensity with temperature from 20 to 250 K, but remains practically constant above 250 K, due to the very small 1CT–3LE energy barrier, determined as 0.02 eV in excellent agreement with singlet–triplet energy gap.The intramolecular TADF origin of the delayed fluorescence observed in DPTZ‐DBTO2 dispersed in zeonex, the emission decay is more complex than that observed in solution due to the presence of short‐lived 1LE fluorescence and long‐lived 3LE phosphorescence that overlap with the 1CT emission, see FigureDespite the small energy barrier for triplet harvesting that is observed for 1CT state strongly mixed with 1LE fluorescence. This emission progressively shifts to longer wavelengths, from 512 to 560 nm (2.21 eV), due to the growing contribution of the 1CT emission, decaying with a 30 ns time constant. The delayed fluorescence, also from the 1CT state, decays with a time constant of 1.5 μs, the emission peak being observed at 560 nm up to a delay time of ≈400 ns. It then progressively shifts back to shorter wavelengths, due to the growing contribution of the underlying 3LE phosphorescence. For delay times in the μs time range, the delayed emission maximum is at 540 nm (2.29 eV), and at late times, into the ms time range, the emission peaks at 512 nm, closely matching the peak of the 3LE phosphorescence.In a zeonex matrix the prompt emission is described by two decay regimes, a fast component of around 3.3 ns, corresponding to a blueshifted emission peaking at ≈512 nm (2.42 eV), which we assign to the fluorescence emission of the DPTZ‐DBTO2 in solvent‐free rigid matrix can be understood from the basic equation governing electron transfer, KET = 4π2/hVDA2 [FCWD],[[qv: 13a]] where VDA is the electronic D–A coupling, which has been minimized in DPTZ‐DBTO2 by the near‐orthogonality of the D and A fragments, and the FCWD is the Frank–Condon weighted density of states, the measure of the total spatial overlap of all D and A vibrational modes. In the case of DPTZ‐DBTO2 where D and A are nearly perpendicular, only out‐of‐plane modes can thus couple to enable state crossing, also causing the FCWD to be rather small. Thus, in rigid matrix one can see that the initial intramolecular electron transfer will be extremely slow. This is why at very early times 1D emission from the donor phenothiazine fragment is observed in rigid medium .This behavior of DPTZ‐DBTO2 excited at 355 nm when dispersed in a 4,4‐bis(9‐carbazolyl)‐1,1‐biphenyl (CBP) matrix follow a similar trend to that seen for DPTZ‐DBTO2 dispersed in zeonex films, . From these measurements we are able to fully describe the DPTZ‐DBTO2 excited state dynamics: Upon optical excitation of the phenothiazine donor (1LE), and depending on the environment, the 1CT state is formed by relatively fast (in solution), or slower (in solid films), electron transfer. In the solid state, initial fluorescence from the 1LE state is clearly observed. Intersystem crossing from 1LE to 3LE occurs in competition with the population of the 1CT state, which emits at 560 nm. Equilibrium between 1CT and 3LE states is achieved through the recycling of CT singlet and triplet states, via intersystem crossing and thermally assisted reverse intersystem crossing, yielding the long‐lived thermally assisted delayed fluorescence from 1CT. At late times phosphorescence from 3LE is observed.The excited state dynamics of 2.4FigureDPTZ‐DBTO2 as the emitter in CBP host (architecture: ITO/NPB (40 nm)/10% DPTZ‐DBTO2:CBP (20 nm)/TPBi (60 nm)/LiF/Al), where NPB is N,N′‐Di(1‐naphthyl)‐N,N′‐diphenyl‐‐4,4′‐diamine, give excellent performance with EQE of 18.8% . Roll‐off is seen at high brightness, consistent with many other TADF devices utilizing simple emitter layer architectures,[[qv: 1a]][[qv: 1b]] decreasing the EQE value to 16.2% at 100 cd m−2 and 11.7% at 1000 cd m−2.S,S‐dioxide acceptor, −3.0 eV , so electron injection will occur onto the decoupled A unit not the phenothiazine. Therefore, charges will be injected directly into the donor fragment HOMO and acceptor fragment LUMO of DPTZ‐DBTO2. Thus excited state formation from charge recombination directly generates the CT charge transfer states, not the unrelaxed local singlet and triplet states. This is well documented in previous work on interfacial exciplex devices1CT state. We also note that the DPTZ‐DBTO2 emitter is also within a rigid CBP matrix which may also help to give a high PLQY. All 3CT states formed on charge recombination will rapidly internally convert to a near isoenergetic 3LE state; probably this is why the 3CT state can never be resolved spectroscopically, however, these triplet states are then recycled by RISC to the 1CT state and emit TADF.In devices, whereas the hole injection onto the HOMO of the donor is energetically favorable, the phenothiazine LUMO level is far too shallow, <−1.9 eV (from our measurements) compared to that of the dibenzothiophene‐31CT and the underlying local triplet state, 3LE, is the dominant ISC mechanism in DPTZ‐DBTO2. It is crucial to design the correct CT geometry into the ground state of the emitter, thereby guaranteeing that CT formation always occurs even in a nonpolar rigid matrix or device host, and that an underlying local triplet excited state, nearly degenerate with the emissive 1CT state, exists to facilitate TADF, and that this energy gap is the true barrier to RISC.This investigation has focused on a TADF emitter with D–A–D subunits with near orthogonal orientation to study the interplay between the excited states localized on the D and A subunits and the CT excited states in the TADF mechanism. We have established that SOCT between 1CT state is clearly observed in DPTZ‐DBTO2, showing that initial photoexcitation to the donor singlet state introduces a major nonradiative loss channel. However, in OLEDs, charge recombination into the HOMO of the donor and LUMO of the acceptor that directly forms CT states on the emitter, avoids this loss associated with the local excitonic states, thereby giving rise to higher device efficiencies, along with the rigidity of the matrix which will also minimize nonradiative decay.Weak, direct absorption to the DPTZ‐DBTO2 devices. Despite the fact that some of these emitters may share common photophysics with DPTZ‐DBTO2, reasons for low device EQEs can be numerous, including material purity, device fabrication, ordering of energy levels, etc., and it is in general difficult to establish definite reasons to explain the observation of lower EQE in devices fabricated with other, even if similar, molecular structures. However, from this work it is clear that the precise ordering and energy splitting between 1CT and 3LE states in DPTZ‐DBTO2 and the D–A molecular geometry are critical in order to avoid fully rigid and orthogonal geometry between D–A moieties.Other TADF emitters with near perpendicular D‐A structure have been reported recently with slightly different molecular structures.4−5–10−2m range, and samples were degassed using 5 freeze/thaw cycles. DPTZ‐DBTO2/zeonex films were prepared by spin coating with DPTZ‐DBTO2:zeonex ratio of (1:20 w/w). DPTZ‐DBTO2/CBP films were prepared by coevaporation. Absorption and emission spectra were collected using a UV‐3600 double beam spectrophotometer (Shimadzu), and a Fluorolog fluorescence spectrometer (Jobin Yvon). Phosphorescence, prompt fluorescence, and delayed emission (DF) spectra and decays were recorded using nanosecond gated luminescence and lifetime measurements (from 400 ps to 1 s) using either a high energy pulsed Nd:YAG laser emitting at 355 nm (EKSPLA) or a N2 laser emitting at 337 nm. Emission was focused onto a spectrograph and detected on a sensitive gated iCCD camera (Stanford Computer Optics) having subnanosecond resolution. PF/DF time resolved measurements were performed by exponentially increasing gate and delay times; details can be found elsewhere.Solution measurements used concentrations in the 10tio of 1: w/w. DPT−2 and ITO thickness of 100 nm. The OLED devices had a pixel size of 2 × 1.5 mm. The small molecule and cathode layers were thermally evaporated using the Kurt J. Lesker Spectros II deposition apparatus at 10−6 mbar. All organic materials and aluminum were deposited at a rate of 1 Å s−1, the DPTZ‐DBTO2:CBP layer was deposited by coevaporation: 0.2 Å s−1 for DPTZ‐DBTO2 and 2 Å s−1 for CBP; the LiF layer was deposited at 0.1 Å s−1.OLED devices were fabricated using precleaned indium‐tin‐oxide (ITO) coated glass substrates purchased from Ossila with a sheet resistance of 20 Ω cmAs a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors.SupplementaryClick here for additional data file.


HA glycoproteins of these viruses showed sequence changes previously associated with alterations in receptor‐binding properties. To address how these changes influence virus propagation, viruses were isolated and propagated in conventional MDCK cells and MDCK‐SIAT1 cells, cells with enhanced expression of the human receptor for the virus, and analysed at each passage.Two new subclades of influenza A(H3N2) viruses became prominent during the 2014‐2015 Northern Hemisphere influenza season. The MDCK cells and MDCK‐SIAT1 cells. Alterations in receptor recognition associated with passage of virus were examined by haemagglutination assays using red blood cells from guinea pigs, turkeys and humans. Microneutralisation assays were performed to determine how passage‐acquired amino acid substitutions and polymorphisms affected virus antigenicity.Gene sequence analysis was undertaken as virus was passaged in conventional MDCK‐SIAT1 cells more efficiently than conventional MDCK cells. Viruses of both the 3C.2a and 3C.3a subclades showed greater sequence change on passage in conventional MDCK cells than in MDCK‐SIAT1 cells, with amino acid substitutions being seen in both HA and NA glycoproteins. However, virus passage in MDCK‐SIAT1 cells at low inoculum dilutions showed reducing infectivity on continued passage.Viruses were able to infect MDCK‐SIAT1 cell line to maintain faithful replication of the virus, and at an appropriate multiplicity of infection to retain infectivity.Current H3N2 viruses should be cultured in the  Over their nearly 50‐year history in humans, H3N2 viruses have also altered their receptor‐binding properties viruses Associated with the progressive changes in receptor binding are changes in the abilities of circulating viruses to infect cells in culture. Viruses isolated after 2001 display decreased ratios of infection of conventional Madin Darby canine kidney (MDCK) cells in comparison with MDCK‐SIAT1 cells, cells modified to express a higher density of α2,6 human receptorsSince their first detection in late March 2014, two new H3N2 virus variants established themselves rapidly and became the predominant virus subtype circulating in North America and Europe during the 2014‐2015 Northern Hemisphere winter seasonIn the light of the reversion at residue 225 of HA1, to that of viruses in circulation in humans from 2002 to 2004, it seemed possible that the recognition of receptor by the 3C.2a and 3C.3a viruses had altered. Notably, changes in receptor recognition can affect the efficiency of virus propagation in cell culture22.12. G418 sulphate  (1 mg/mL) was added to the culture medium for propagating MDCK‐SIAT1 cells.MDCK‐SIAT1 cells, stably expressing human CMP‐N‐acetylneuraminate:β‐galactoside α‐2,6‐sialyltransferase2.2The clinical specimens used in this study were collected during the 2013‐2014 influenza season and provided by the WHO National Influenza Centres in Hong Kong SAR, China, and Buenos Aires, Argentina.2.32 for 72 hour. Further passages were performed using 200 μL inocula of cell culture supernatant per well, both undiluted and at higher dilution, from the previous passage.Hundred microlitres per well of clinical specimens were inoculated in parallel on confluent cell monolayers of MDCK‐parent or MDCK‐SIAT1 cells in 24‐well tissue culture plates and incubated at room temperature for 1 hour, and then, 1 mL of DMEM supplemented with 2 μg/mL TPCK‐treated trypsin (Sigma Cat no T1426) was added. Cultures were incubated at 34°C with 5% (v/v) CO2.4HAA were performed according to standard methods2.5Sialidase activity of each virus was measured using 2′‐(4‐methylumbelliferyl)‐α‐D‐N‐acetyl neuraminic acid 2.6Following RT‐PCR, nucleotide sequences of HA and NA genes were determined by Sanger dideoxynucleotide sequencing using ABI prism BigDye terminator cycle sequencing kits (Cat. No. 4336774) and an ABI 3730XL DNA analyser. Primer sequences are available on request. Next‐generation sequencing (NGS) was performed using a MBT‐universal 3 primer approach2.7These were performed as described previously33.1Clinical specimens were inoculated onto conventional MDCK cells or MDCK‐SIAT1 cells, and viruses were passaged twice further in each cell line. The HA and NA gene sequences of viruses in the clinical specimens were determined by both Sanger and deep sequencing methods, and viruses from each tissue culture passage were sequenced using Sanger sequencing. The results of Sanger sequencing are summarised in Table In contrast, for six of seven clinical specimens in subclade 3C.2a, NGS data showed increased variation in the HA gene encoding amino acids at positions 158‐160 of HA1, notably so at residue 160 . On passBoth subclade 3C.3a and 3C.2a viruses showed polymorphism at NA positions 148 or 151 after three passages in conventional MDCK cells (four of five subclade 3C.3a and eight of nine subclade 3C.2a viruses), but no similar polymorphism in the NA was detected in viruses propagated in MDCK‐SIAT1 cells  had acquired polymorphism in the NA gene and was able to agglutinate RBCs through its NA, infected MDCK cells more efficiently than the other two 3C.3a subclade viruses examined, A/Switzerland/9715293/2013 and A/Norway/466/2014, neither of which showed evidence of NA‐mediated agglutination of RBCs.3.4As a significant proportion of the subclade 3C.2a viruses were unable to bind to RBCs from a variety of species, MN assays were used for the antigenic characterisation of viruses in the two newly emerged subclades. The majority of tested subclade 3C.2a (53 of 58) and all eight subclade 3C.3a viruses were recognised poorly by a ferret antiserum raised against A/Victoria/361/2011 at titres ≥fourfold lower than for the homologous virus  at titres within twofold of the titre with the homologous virus. This antiserum also recognised most subclade 3C.2a viruses with an intact HA1 158‐160 glycosylation motif  at neutralisation titres within twofold of that with the homologous virus. Those 3C.2a viruses that had lost or were polymorphic at the glycosylation motif showed somewhat poorer recognition, with 54% of viruses being recognised at titres within twofold of the titre of the antiserum with the homologous virus (14 of 26). Sequencing of the analysed viruses showed that two‐thirds of those recognised at reduced titre (titres ≥fourfold reduced compared to homologous titre) had additional substitutions in HA1, such as Q197R, R261Q, N171K and S114T, that may account for low reactivity irrespective of any loss or polymorphism at the HA1 158‐160 glycosylation motif.In contrast, a ferret antiserum raised against a cell culture‐propagated subclade 3C.2a virus, A/Hong Kong/7295/2014, recognised all the 3C.2a viruses very well, whether or not they encoded the HA1 158‐160 glycosylation motif, but most subclade 3C.3a viruses tested  were recognised at titres ≥fourfold lower than the titre with the homologous virus , in MN assays (Table Taken together, these results indicate that loss or polymorphism of the HA1 158‐160 glycosylation motif in subclade 3C.2a viruses had only a minor effect on the antigenic properties of the viruses whether analysed by antisera raised against the 3C.3a reference virus A/Switzerland/9715293/2013 or against reference subclade 3C.2a viruses with or without the 158‐160 glycosylation motif. Moreover, these results indicate that viruses in both newly emerged subclades are antigenically different from viruses previously in circulation and, while there is some antigenic similarity between viruses in the two subclades, groups of viruses designated by subclades 3C.3a and 3C.2a are not antigenically identical to one another.3.5During the course of the MN assays, it was observed that when undiluted culture supernatant from a previous passage was used as inoculum in MDCK‐SIAT1 cells, many viruses produced subpopulations that gave very small plaques despite the presence of significant NA activity in the passage supernatant. Small plaques might be indicative of abortive infection of the cells. To investigate this possibility, a subset of viruses were analysed in detail as they were serially passaged at varying virus dilutions.Figure In the light of the falling titres on passage of viruses in MDCK‐SIAT1 cells, a comparison of the yield of virus propagated at higher dilutions of inocula in MDCK‐SIAT1 cells is shown in Figure −2 to 6×10−2 retained faithful virus replication (Next, to examine whether serial propagation of virus at high dilution affected the virus sequence polymorphism that might emerge, with particular reference to the HA1 158‐160 glycosylation motif acquired by the 3C.2a viruses, samples of culture supernatant at each passage at the two dilutions were examined by Sanger sequence analysis . Very lilication .4The common features of viruses in two newly emerged H3N2 HA subclades, 3C.2a and 3C.3a, are changes in the glycosylation and receptor‐binding sites of HA. In comparison with the previously circulating A/Victoria/361/2011‐like and A/Texas/50/2012‐like viruses, HAs in both subclades have an HA1 N225D substitution, located in the 220 loop of the receptor‐binding pocket, and changes at HA1 position 159 located in antigenic site B adjacent to the receptor‐binding pocket. Our previous studyWe have shown here that propagation of the new H3N2 viruses in conventional MDCK cells continues to promote NA‐mediated agglutination of RBCs in a significant number of viruses from subclades 3C.2a and 3C.3a. Consistent with NA‐mediated agglutination of RBCs, sequence analysis of four of five viruses in subclade 3C.3a showed polymorphism at residue 151 of the NA while eight of nine 3C.2a viruses examined in detail showed either substitution or polymorphism at residues 148 or 151 of the NA, these changes being associated with NA‐mediated agglutination of RBCsWe observed loss of the glycosylation motif at HA1 158‐160 in subclade 3C.2a viruses in four of the eight HA sequences at passage 3 when viruses were propagated in conventional MDCK cells but, importantly, similar changes were not observed in viruses propagated in MDCK‐SIAT1 cells. Glycosylation was stable in subclade 3C.3a viruses in both cell lines.To examine the antigenic relationships between viruses in the two new subclades, and the influence of HA and NA amino acid substitutions and polymorphism acquired during culture, we used MN assaysIn the light of the observation of the loss of the HA1 158‐160 glycosylation motif during culture in conventional MDCK cells, we asked whether this might be reflected in antigenic analysis of circulating viruses. For this, we used three antisera raised against viruses in genetic group 3C.2a that had either retained, or had lost, or was polymorphic for this glycosylation motif, and analysed examples of viruses from subclade 3C.2a, propagated in cell culture, that had similar motif compositions. From MN assay results, we concluded that antisera raised against the three reference viruses generally recognised test viruses with the three motif compositions similarly and that the antigenic properties of viruses that had acquired polymorphism at HA1 158‐160 are similar to those with an intact glycosylation motif at this site. It is noteworthy that the virus recommended as the prototype for use in influenza vaccines for the 2016 Southern Hemisphere and 2016‐2017 Northern Hemisphere seasons, A/Hong Kong/4801/2014, had lost its HA1 158‐160 glycosylation motif during adaptation to propagation in hens’ eggs.The observations made here support recommending continued use of the MDCK‐SIAT1 cell line for propagation of current H3N2 viruses, although this is not free of problems. In MN assays, in some cases, we observed virus plaques of very small size and as virus was passaged in the MDCK‐SIAT1 cell line, infectivity was progressively lost although infectivity could be maintained by passage at lower MOI Figure . HoweverTo sum up, from the perspective of avoiding the selection of polymorphic or mutant viruses, whether mutated in the HA gene and/or the NA gene, we conclude that the current H3N2 viruses in subclades 3C.2a and 3C.3a remain more faithfully propagated in the MDCK‐SIAT1 cell line than in conventional MDCK cells. This is despite amino acid substitutions in the vicinity of the receptor‐binding site, notably at residue 225, which might have overcome the poor efficiency of H3N2 viruses circulating since 2005 to infect conventional MDCK cells Click here for additional data file. Click here for additional data file. Click here for additional data file.


Fe3O4 NPs below 20 nm have stable single domains (SSD), which can be oriented by magnetic field application. Dispersion of Fe3O4 NPs in silicon dioxide (SiO2) matrix allows local SSD response with uniaxial anisotropy and orientation to easy axis, 90° <001> or 180° <111>. A successful, easy methodology to produce Fe3O4 NPs (6–17 nm) has been used with the Stöber modification. NPs were embedded in amorphous and biocompatible SiO2 matrix by mechanical stirring in citrate and tetraethyl orthosilicate (TEOS). Fe3O4 NPs dispersion was sampled in the range of 2–12 h to observe the SiO2 matrix formation as time function. TEM characterization identified optimal conditions at 4 h stirring for separation of SSD Fe3O4 in SiO2 matrix. Low magnetization (Ms) of 0.001 emu and a coercivity (Hc) of 24.75 Oe indicate that the embedded SSD Fe3O4 in amorphous SiO2 reduces the Ms by a diamagnetic barrier. Magnetic force microscopy (MFM) showed SSD Fe3O4 of 1.2 nm on average embedded in SiO2 matrix with uniaxial anisotropy response according to Fe3+ and Fe2+ electron spin coupling and rotation by intrinsic Neél contribution.Currently, superparamagnetic functionalized systems of magnetite (Fe The systems based on superparamagnetic NPs behaviour have either biological or technological potential applications. Fe3O4 NPs have been extensively studied due to their interesting properties, which allow their evaluation and potential application as catalytic agents13, gas sensors14, water treatment agents15, environmental remediation agents18 magnetic resonance contrast agents19, ferrofluids20, data storage devices21, and electronic devices22. Superparamagnetic Fe3O4 NPs with SSD have crystal anisotropy in the order 1.1, which allows easy reorientation and energy exchange to generate magnetic hyperthermia in presence of a magnetic field AC23. However, avoiding Fe3O4 NPs agglomeration due to interactions between neighbours is a challenge for biological applications. One alternative is separating the Fe3O4 SSD considerable distances by embedding them in a negatively charged, amorphous SiO2 matrix24. This method allows a local response orientation of SSD to be obtained, according to Majetich S. A. et al.; if neighbouring superparamagnetic particles with a low anisotropy are coupled by exchange or dipolar interactions, their optimal separation for the maximum coercivity will allow the configuration of individually addressable SSD25. The local interactions will be the same, if the Fe3O4 particle size is similar. Then, SSD will have coherent rotation and contribute to the effective energy exchange by hyperthermia.The addressable Fe26. For this reason, different investigations have developed different methods to stabilize Fe3O4 NPs while preserving the main SSD properties29. V Reichel et. al. showed that the magnetic properties of magnetite are dependent on Néel relaxation. These depend on the particle size, morphology and interparticle interactions as well as the temperature and time-scale of the measurement in Fe3O4 NPs (9 ± 3 nm)30. The SiO2 media can be used to give Fe3O4 NPs specific accumulation in organs or tissues through bio-functionalization35 because it is an interaction-capable surface with ligands related to biological molecules.Current implementation of these systems depends on the superparamagnetic particle size (<20 nm) and SSD anisotropy, which directly influence the stability, dissipated energy and magnetic properties as function of time, such as the magnetic susceptibility and coercive field3O4 NPs with SiO2 can be achieved by using citrate as a dispersing agent. The polymerization time of SiO2 was considered in the range of 2–12 h. However, Fe3O4 functionalization and interaction media barriers with organic products can reduce Ms. The magnetic response will depend on the volume, particle form and SSD population density in the system36. Rotation SSD Fe3O4 will depend on the intrinsic structure defined Néel interactions and magnetic moment distribution per volume unit by the easy axis crystal orientation, <100> or <111> and the coercivity terms, which are crucial for SSD uniaxial response37. The routes to control the dispersion Fe3O4 NPs embedded in SiO2 help to consolidate well defined the local SSD and their magnetic interactions. Superparamagnetic Fe3O4 NPs dispersions in an inorganic matrix allow the creation of a functional target or hyperthermia generators with potential applications in nanomedicine39.Successful stabilization of Fe3O4 NPs is the ion relation ½ Fe+2: Fe+3 by co-precipitation and the additional dispersion reaction by Stöber route. These ions were dispersed with citrate and TEOS to produce Fe3O4 in an amorphous SiO2 matrix according to the methodology described by L. Yang et al.40 with some modifications.The key to obtaining Fe3O4 NPs with a cubic inverse spinel structure, forming a close packing fcc (a = 8.396 Å)41, Fig. 2+ and trivalent Fe3+ occupying octahedral sites and a double-exchange mechanism, while Fe3+ tetrahedral sites form an antiferromagnetic response, Fig. 42.XRD results show the main crystalline reflections of Fe2 matrix and the Fe3O4 NPs, which do not lose their crystalline quality. Wide diffraction peaks from the Fe3O4 NPs are observed in an amorphous curve for the entire stirring range of 2–12 h. The fluorescence increased and the intensities decreased for each reflection in the patterns corresponding to the Fe3O4 NPs embedded in the SiO2 matrix. This is attributed to the confinement of the Fe3O4 NPs inside the amorphous SiO2 matrix.The spectra  16.49 nm and 8.360 Å at 2 h, (b) 15.37 nm and 8.3641 Å at 4 h, (c) 16.92 nm and 8,3619 Å at 8 h, and (d) 17.07 nm and 8.3614 Å. The lattice parameters showed small distotions as Fe3O4@γ-Fe2O3 by surface NPs oxidation.Additionally, wide peaks are related to the nanometric particle size. Some changes in the NPs size were observed as a function of the reaction time, Fig. 3O4 NPs in the SiO2 matrix can be observed. Characteristic iron-oxygen bond (Fe-O) signals at approximately 585 cm−1 are in the five spectra. Crystalline Fe3O4 is conserved after the embedding process. Also, it is possible to identify the SiO2 contributions in Fig. −1 is observed. There are also two interactions of interest at 1113 cm−1, which is attributed to the Si-O-Si bonds, and another at 986 cm−1, which is due to the Si-OH groups from the matrix. These interactions slightly increased in intensity with the reaction time, which promoted the SiO2 layer thickness. No additional linkage interactions were observed for the functional groups characteristic of citrate and the stabilizing agents used during the experiment. These were completely removed during the particle washing step. This indicates that the reaction parameters, such as the concentration of the solutions and the reaction times, allow the dispersed particles to be obtained without adsorbed citrate molecules on the surface of the Fe3O4 NPs.The FT-IR spectra of different samples are presented in Fig. 3O4 NPs embedded in SiO2 matrix as a function of time are shown in Fig. 3O4 NPs at 2 h, Fig. 3O4 structure with a low amorphous contribution from SiO2. (2) Good dispersion of individual Fe3O4 NPs at 4 h, Fig. 2 contributes a negative charge between the NPs to form individual SSD, Fig. 3O4 NPs and the amorphous matrix of SiO2. The crystalline Fe3O4 structure diffracted in the planes (220), (311) and (440). (3) The regions of agglomerated Fe3O4 NPs plus SSD dispersed for 8 h of stirring, Fig. 3O4 NPs with diffraction planes in (311) and (440)44. The agglomerates increased in size. (4) Agglomerates plus isolated SSD were obtained in the SiO2 matrix after 12 h of stirring, Fig. 3O4, which are very similar in intensity to those in Fig. 2 formed at 4 h stirring is a negatively charged film that confines the SSD as individual entities. As the agitation time is increased to 8–12 h, the dynamic movement increases the coalitions between NPs and their interactions. As consequence, the attraction between NPs increases the agglomeration with a long agitation time.TEM results for Fe3O4 NPs lies in their superparamagnetic properties, uniaxial anisotropy, particle size and form. Typically, bulk Fe3O4 has a Ms of 91 emu/g, and its inner structure forms multidomains with magnetic anisotropic axial ratios larger than 546. In superparamagnetic NPs, the magnetic anisotropic energy barrier is reduced and allows the rotation of SSD from a spin-up state to spin-down state to readily rotate the magnetic spin direction on the easy axis47. The magnetization from Fe3O4 NPs embedded in a SiO2 matrix shows superparamagnetic, closed hysteresis loops48. As the particle size of Fe3O4 decreased below the superparamagnetic diameter, Ms decreases as well, and the magnetic fluctuation leads to a small Hc near zero with a low remanence at 300 K49. Samples as a function of the stirring time were Ms = 0.0015 emu, Hc = 26.480 Oe at 2 h; Ms = 0.0010 emu, Hc = 24.000 Oe at 4 h; Ms = 0.0013 emu, Hc = 24.800 Oe at 8 h; and Ms = 0.0015 emu, Hc = 25.570 Oe at 12 h, Fig. 3O4 NPs SSD embedded in the SiO2 matrix at 4 h of stirring. These parameters and the particle size are directly related to the descending Hc value as follows: (a) agglomerations of NPs 11.70 nm on average at 2 h; (b) fragmentation and dispersion of 5.64 nm NPs with distances from 5.54 to 29.21 nm as individual SSD in SiO2 at 4 h; (c) aggregates of 15.45 nm NPs on average and individual 4.47 nm NPs on average separated by 3.54 nm to 6.00 nm in SiO2 at 8 h; and (d) 13.7 nm average agglomerates and 6.02 nm NPs on average separated by distances 5.20 nm to 6.43 nm in SiO2 at 12 h. Coherent results were obtained by Ms and Hc with 4 h of stirring. This means that individual SSD have uniaxial anisotropy and are addressable by the separation between the NPs, Fig. s and Hc increase due to the major volume contribution from the neighbouring interactions and thermal fluctuations. The diamagnetic SiO2 barrier around the Fe3O4 NPs reduces Ms. However, separation between the monodispersed NPs maintains the Hc as local SSD. These effects can also be observed in encapsulated Fe3O4 NPs with organic chains. Some organic coating media have important roles due their permeability, specificity and individual drive of the magnetic domains that can be accumulated in tumours50. The integration of SSD as functionalized systems at optimal distances and relatively high Hc values would increase the hyperthermia efficiency by magnetic field AC excitation in the frequency range 100 kHz–500 MHz51.The main challenge in potential applications of Fe3O4 NPs distribution embedded in the SiO2 matrix were observed by atomic force microscopy. The 3D images show the differences in the dispersed nanoparticles according the stirring time for 4 and 12 h. Figure 2 matrix, Fig. Fe48. SSD are NPs that can be aligned in parallel by exchanging forces of the electron spins from applied magnetic field. Inner magnetic structure Fe3O4 SSD with Fe+3 and Fe+2 electron spin coupling respond uniaxially because magneto-crystalline anisotropy forces tend to align in a preferred direction based on the easy axis. For superparamagnetic sizes, the relative magnitude of the boundary energy becomes larger than the magnetostatic energy. At a critical size, the spin direction can be oriented by exchange interactions in the SSD37. MFM 3D images showed surface of NPs by magnetization H↑ and demagnetization H = 0 effects from Fe3O4 SSD embedded in the SiO2 matrix. The magnetic interaction at the tip in the lift mode shows the disorder from the intrinsic structure at H = 0. Under the saturation measurement conditions H~1200  Oe for the Co-Ni tip, the SSD uniaxial orientation of the magnet is shown with the domains oriented at 90° for the majority n↑ and minority n ↓ states with H↑48. Finally, domain disorder is observed by demagnetization under the initial conditions H = 0. When the magnetic field AC is applied to these systems, the magnetic domains will fluctuate with local vibrations and will transform this energy into thermal energy. The orientation was observed in a non-continuous media with local SSD interactions at 4 h of stirring, Fig. MFM shows the magnetic moment density per volume unit. The 3D images are generated by the interaction of magnetic tip polarization, which is normal with respect to the NPs surface, and sensing of the attractive and repulsive states3O4 NPs, which are defined by Neél interactions, Fig. θ (deg) and domains oriented in the normal direction, 90°, with average domain sizes of 1.2 nm and uniaxial anisotropy from main crystalline direction37. The anisotropy energy is given by Ea = KVsin2θ, where K is a typical constant of the material, V is the volume of the particle, θ is the angle between the magnetization and the easy axis. The local response of Fe3O4 NPs showed magnetic domains with an average size of 1.2 nm surrounded by the SiO2 matrix with stirring for 4 h. The profile defines the parallel interactions of the uniaxial response, Fig. 3O4 NPs in SiO2 matrix with 12 h of stirring show well-defined interactions in the same direction as the sum of local interactions with similar magnetic domains in the range of 1.2 nm, Fig. 3O4 SSD in the SiO2 matrix show a local response of addressable superparamagnetic behaviour, which is mainly governed by particle size and shape of Fe3O4 cores in a monodispersion at magnetic field saturation. The degree axis in the profiles shows the deflection propensity in attraction and repulsion generated by H↑, and these values can change based on the roughness topography and H↑ intensity to form field lines between the tip and sample. The differences in the tip deflections from the SSD were −33.1°–(−39.1°) = 6.0° at 4 h of stirring, Figs. Zoom was performed under the saturation conditions H↑ to show the uniaxial behaviour. Parallel stripes from attractive and repulsive interactions define the magnetic domains. The exchange forces of the parallel alignment are result of the internal magnetic structure in Fe3O4 NPs with close hysteresis loop. However, the superparamagnetic single-domains response of Fe3O4 NPs is maintained by local response SSD as agglomeration phenomena is reduced in the case of SiO2 matrix due to its permeability47. According to Dave S., R. Dave and G. Xiaohu, the formation of the domain walls is a process driven by the balance between the magnetostatic energy as a function of the particle size52.Tipically Hc decreases as a function of particle size in Fe3O4 NPs by stabilizing them in SiO2 as a function of the stirring time without altering their crystalline features.The synthesis strategy presented is a fast and effective option to avoid the agglomeration phenomenon of Fec is maintained in individual Fe3O4 SSD with uniaxial behaviour at 4 h of stirring. MFM showed SSD and that local NPs in the SiO2 matrix have similar responses as the NPs concentration increases. However, Ms is reduced by the distance between the NPs among the SiO2 matrix, and this depends on the permeability of the media. Neél interactions produce local fluctuations and energy transference from reorientable SSD by magnetic fields at high frequencies. The challenge is to control the Fe3O4 SSD as individuals in organic media to increase the response velocity and effective magnetic excitation to produce hyperthermia.The H3O4 NPs embedded in a SiO2 matrix are candidates as functional groups or specific organic linkers for cancer cell interactions and hyperthermia therapy. The development of dispersed SSD is mandatory to improve biological applications.Fe2, 98%), iron chloride III (97%), a tetramethyl ammonium solution , tetraethyl orthosilicate , a 28% ammonium hydroxide solution (NH4OH) and absolute ethyl alcohol (C2H5OH) were all from Sigma-Aldrich and used as received without any purification.For the synthesis, hydrochloric acid (HCl) , deionized water , iron chloride II  was prepared to dissolve the precursor salts of the Fe+2  and Fe+3 ions .The formation of nanostructured magnetite through a co-precipitation method2 was added. Another 25 mL of the solution was used to dissolve 6.99 g of FeCl3, and both solutions were kept under magnetic stirring for 1 h. Then, both solutions were mixed in a round-bottom, three-necked flask and bubbled with Ar for 5 min to remove any dissolved oxygen in the solution. The resultant solutions were stirred at 500 rpm and heated to 70 °C. Once the temperature stabilized, 21 mL of tetramethylammonium hydroxide was added dropwise, providing an alkaline environment for the formation of the magnetite. The solution turned black, which was an indication that iron oxide formed in the solution. After 40 min, the stirring and heating were stopped, and the mixture was allowed to cool to room temperature. The nanoparticles were washed with water and precipitated with the aid of a magnet until the pH of the dispersion was equal to 7. Once the nanoparticles were dispersed in water, they were freeze-dried for 12 h to obtain the magnetite powder.After the acidic solution was prepared, 6.25 mL was taken, and 2.52 g of FeCl3O4 NPs powder (0.02 g) was taken and mixed with the same amount of citrate in an aqueous solution (250 mL) and mechanically stirred at 500 rpm for 1 h. Citrate was used as a dispersal agent to avoid agglomeration of the nanostructures prior to the formation of the SiO2 matrix.The Fe2 precursor solution was prepared as follows: 10 mL of water, 50 mL of ethanol, 5 mL of ammonium hydroxide and 0.2 mL of TEOS were mixed by magnetic stirring for 10 min. After that, the solution of magnetite and citrate was mixed with the SiO2 precursor solution. To modify the thickness of the SiO2 coating, the mixture reacted for 2, 4, 8 and 12 h under mechanical stirring at 500 rpm. Once the different times passed, the particles were washed with ethanol and precipitated with the help of a magnet. They were dried at room temperature, and the powder was characterized.Then, the SiO3O4 NPs dispersal in the SiO2 matrix and the magnetic properties of the magnetite under different stirring conditions.The analysis of the material allowed determination of the optimal reaction time conditions to reduce the agglomeration in the citrate suspension. Additionally, these samples were processed by the Stöber method to embed the magnetite NPs in the matrix of silicon dioxide. This is an easy methodology to reduce agglomeration and to improve the Feθ with a copper source of 1.5424 Å and wavelength to define Fe3O4/SiO2 structures. PowderCell Software was used to analyse experimental diffractograms from XRD54. Their dispersion and particle sizes were observed by JEOL-JEM 2010 transmission electron microscope, TEM, with a LaB6 filament at an acceleration voltage of 200 kV. The functional groups of silicon and magnetite were examined with an FT-IR spectrophotometer, NICOLET 6700. The magnetic response was determined using a MPMS3 Magnetometer SQUID of Quantum Design with a sensitivity of 5 × 10−8 emu.To determine the properties of the nanostructures, different characterization techniques were used: RIGAKU Smart Lab X-ray diffractometer, XRD, was used in the Bragg-Brentano configuration with 0.02 steps in the range from 25 to 70°, 2 Magnetic force microscopy (MFM) was performed with a scanning probe microscope (SPM) JEOL JSPM 5200 multimodes. The samples were dispersed in carbon adhesive tape over the holder. An ultra-sharp silicon cantilever NSC14/Co-Cr/15 micro-mesh was exposed to a strong neodymium magnet. The voltage and lift conditions were defined according to the magnetic surface interactions of the sample with the tip lift output [0.030–0.1 V].Supplementary Information


The remarkable improvement of surface quality shows a higher first cycle Coulombic efficiency (≈95%), a significantly enhanced cycling performance, and a better rate capability in electrochemical measurements. A combined study of Raman spectroscopy and inductive coupled plasma emission spectroscopy reveals that the evolution of Li4Ti5O12 surface in a water‐based hydrothermal environment is a hydrolysis–recrystallization process, which can introduce a new phase of anatase‐TiO2. While, with a small amount of Na2S (0.004 mol L−1 at least), the spinel‐Li4Ti5O12 phase is maintained without a second phase. During this process, the alkaline environment created by Na2S and the surface adsorption of the sulfur‐containing group (HS− or S2−) can suppress the recrystallization of anatase‐TiO2 and renew the particle surfaces. This finding gives a better understanding of the surface–property relationship on Li4Ti5O12 and guidance on preparation and modification of electrode material other than coating or doping.Through a facile sodium sulfide (Na Over the past few decades, LIBs with carbonaceous anodes have dominated the portable power market.4Ti5O12 (LTO) is attractive to scale up and make high performance and cheap static energy storage viable. Unlike the carbonaceous anode, LTO has a higher Li‐insertion voltage (≈1.5 V vs Li+/Li),To develop advanced LIBs that will meet the requirements of large‐scale energy storage, a series of materials have been investigated as alternative anode materials. Among the candidates, spinel Li2 g−1), and shortens the ion and electron diffusion lengths.However, the commercially available micrometer‐sized LTO particles have not achieved the outstanding performance that may be expected from the promising material properties. The low intrinsic electronic and ionic conductivity is considered as the main reason. Two main strategies were proposed to improve the conductivity. One strategy is to fabricate a nano‐ or porous structure, which enlarges the specific surface area over 200 m0 m2 g−1,2S). The modified LTO particles possess a higher first cycle Coulombic efficiency (≈95%), a significantly enhanced cycling performance, and a better rate capability, making this approach effective and promising for application in LIB technology. The modification process was systematically investigated and based on our results we propose the following mechanism: Under the hydrothermal environment of water, the LTO particles experienced a hydrolysis‐recrystallization process, which introduces anatase‐TiO2 at the LTO surface. Benefiting from the alkaline environment created by Na2S and the surface adsorption of the sulfur‐containing group (HS− or S2−), the hydrolysis of LTO is reduced. At the same time, the recrystallization of anatase‐TiO2 is suppressed entirely. Thus, the LTO phase is protected while the amorphous phase and impurity ions are removed by the hydrolysis. The surface reconstruction mechanism and the corresponding surface structure–electrochemical performance relationship were characterized by Raman, inductive coupled plasma emission spectrometer (ICP) and cyclic voltammetry (CV) tests. This finding gives guidance to electrode material preparation and modification strategies. Furthermore, the proposed approach is facile and easy to scale up and can be combined with other treatments, such as coating or doping, for improving the performance of micro‐ or nanosized LTO electrode materials.Here, we propose a different strategy to improve the LTO performance, focusing on the improvement of the quality of the LTO surface and staying within the boundary condition of the low cost and facile modification methods based on the available LIB manufacturing technology. Large‐scale production of LTO introduces surface defects, for example, an amorphous layer or the presence of impurity ions. In this work, for the first time, we describe a simple surface modification mechanism to prepare LTO particles with pure, clean, and nondefective surfaces through simple hydrothermal treatment with aqueous solution of sodium sulfide , which is a prerequisite for a large volumetric energy density. After modification with Na2S solution, the size and morphology of LTO particles do not change noticeable. However, through high‐resolution transmission electron microscopy (HR‐TEM), it is observed that the very thin (about 10 nm) outermost amorphous layer on the pristine LTO surface was totally removed . The results show that the surface modification significantly improved the reversibility of lithium intercalation and deintercalation. This is supported by comparing the voltage during the initial stages of Li‐ion insertion between the first and the second cycle as indicated in Figure +) during the initial discharge, in which the electrolyte decomposed on the graphite surface and then formed a SEI, consuming cyclable lithium, lowering the Coulombic efficiency, and making obvious voltage deviation.+ insertion–extraction process occurs at 1.55 V (vs Li/Li+), far from the decomposition voltage of electrolyte and it is generally accepted that LTO surface cannot form a SEI film.+ between the electrolyte and the spinel LTO phase, which hinders the charge‐transfer process, which apparently becomes rate limiting at large currents. Although the rate performance does not achieve that of carbon‐coated LTO, nano/porous LTO, or other samples based on methods aiming at improving the conductivity,Coin‐type cells were assembled to evaluate the electrochemical properties of pristine LTO and modified LTO. Figure−1 Na2S) for 4, 8, and 12 h, in turn (black color). The Raman spectrum of the initial sample is fully assigned to the F2g mode of bending vibration δ(Ti–O), can be taken as a characteristic Raman fingerprint of LTO. After 4 h treatment, another group Raman bands appeared and the intensity of these bands increased with the extension of hydrothermal time. According to the theoretical calculation and the Raman result of standard sample of anatase‐TiO2 . Also, the most intense Raman band at 141 cm−1 corresponds to a characteristic Raman indicator of anatase‐TiO2. Herein, we define the intensity ratio of Raman bands at 141 and 231 cm−1 (I141/I231 or A/L) as the indicator of anatase‐TiO2 content. In other words, the higher the value of A/L, the higher the content of anatase‐TiO2. The Ti‐O bonds in anatase‐TiO2 possess large polarity which tends to react with trace water in electrolyte and form hydroxyl groups on the surface. The hydroxyl groups are Lewis‐acid sites which are considered to be able to initiate the decomposition of electrolyte solvent. Due to this high catalytic activity, anatase‐TiO2 is considered as an undesired phase and potentially triggers severe side reactions and gassing.−1 Na2S aqueous solution, the A/L value is always zero from 4 to 12 h, indicating that Na2S prevents the formation of anatase‐TiO2 phase on the LTO surface. Consistently, no X‐ray diffraction peaks of anatase‐TiO2 were observed . To verify this result, high resolution of synchrotron X‐ray was employed for the sample after 12 h treatment. From the synchrotron data, no anatase‐TiO2 phase can be found indicting the total inhibition of TiO2 phase . Furthermore, compared with the Raman signal of the pristine sample, a significant enhancement was observed in samples after Na2S‐assisted hydrothermal treatments  for 8 h , it is suggested that the anatase‐TiO2 phase can be inhibited when the Na2S concentration exceeds 0.004 mol L−1 resulting in a high‐quality LTO surface. Figure−1 Na2S) as a function of time. The data suggest that the dissolved amount of lithium always increases with time, while the soluble Ti first reaches a peak concentration at 4 h (0.26 mg L−1) after which it decreases to a relatively low level. Thus, combined with the Raman results, this infers that the surface evolution without Na2S includes two stages. In the first stage, the outmost layer of Li4Ti5O12 begins to hydrolyze, during which the amount of soluble Li and Ti experiences an increase. The hydrolytic process is shown in Equations 4Ti5O12 first transforms to TiO(OH)2 and the Li+ dissolves, subsequently some TiO(OH)2 transforms to dissolved TiO32− in water. In the second the stage, Li4Ti5O12 continues releasing the Li+ from the lattice, while TiO(OH)2 no longer hydrolyzes but transforms to anatase‐TiO2  and different concentrations of NaEquation . AdditioEquation . This ex2S was added to the solution, the hydrolysis‐recrystallization process was disturbed. It is directly proved by the ICP data  that both of the Li and Ti concentration increase, not reaching a maximum during the hydrothermal process. Based on our results, we propose the following surface reconstruction mechanism of LTO, depicted in Figure 2S manifests itself in two aspects. First, the alkaline environment created by Na2S may, to some extent, weaken the hydrolysis of Li4Ti5O12.2S is only about 70% of that without Na2S . The consequence is that in the presence of Na2S only the hydrolysis occurs which completely removes the amorphous layer including the impurity elements resulting in a pure, clean, and nondefective surface.This process can be described as the hydrolysis‐recrystallization process Figure c. When s−1 for five cycles. A pair of sharp and intense redox current peaks is observed at about 1.66 and 1.49 V on all the tested samples including the pristine LTO, the hydrothermal treated LTO with water, and with 0.008 mol L−1 Na2S aqueous solution. The peaks were due to the Li+ insertion and deinsertion in LTO.Figure2 phase.2S‐assisted hydrothermal treatment  exhibits the typical CV curve of LTO electrode at a scan rate of 0.1 mV st Figure e,f, no a34Ti5O12 anode materials existing of simple hydrothermal treatment with a Na2S aqueous solution. Based on the HR‐TEM, XPS, and Raman observations during the treatment, an ≈10 nm amorphous layer at the outmost layer of pristine Li4Ti5O12 was entirely removed resulting in clean and nondefective surfaces. The subsequent electrochemical measurements show that the modified Li4Ti5O12 spheres possess a higher Coulombic efficiency (94.9%) during the first cycle, a longer cycle life, and a better rate capability. It is interesting that the hydrothermal treatment with water results in anatase‐TiO2 on the Li4Ti5O12 surface, while the hydrothermal‐treated Li4Ti5O12 sample with the Na2S aqueous solution maintains a pure and high‐quality spinel‐Li4Ti5O12 phase. The surface reconstruction mechanism and chemical process were carefully investigated through a series of experiments with different concentration of Na2S aqueous solution and hydrothermal treatment time. The combined Raman and ICP analysis revealed that the interaction of water and Li4Ti5O12 particle is a hydrolysis‐recrystallization process, while with a proper amount of Na2S (0.004 mol L−1 at least), the recrystallization process can be totally hindered due to the adsorption of S2− or HS− ions. These findings shed new light on the importance of surface phenomena that need to be fully understood and ultimately controlled by developing practical methods for electrode material preparation and modification.In summary, a facile modification method was introduced for Li4Surface‐Modified Method: The LTO material used in this study was purchased from Ishihara Sangyo Kaisha Co. Ltd. (Japan). The LTO particles were modified using a simple hydrothermal procedure. Typically, 5 g of LTO and 0.16 g of Na2S•9H2O (Aldrich) were thoroughly mixed in 80 mL of water  at ambient temperature. Then the solution was transferred to a 100 mL Teflon‐lined stainless reactor and placed in an oven at 180 °C for 8 h. After that, the solution was centrifuged, collected, and taken to detect the concentration of soluble lithium and titanium by ICP tests (Agilent). Meanwhile, the white solid samples were collected by direct filtrating, washing with water, and then drying at 120 °C. To investigate the surface reconstruction process and mechanism, a series of analogous experiments were performed with 5 g LTO and different concentrations of Na2S (from 0 to 0.02 mol L−1) and different hydrothermal duration .Structural Characterization: The morphology and size of the LTO were characterized using a HITACHI S4800 scanning electron microscope (SEM). HR‐TEM was performed using a 300 kV field emission‐TEM . The phase and the crystallographic structure of the LTO were characterized by powder X‐ray diffraction using Cu Kα radiation (λ = 1.5418 Å) at the range of 10°–70° . Synchrotron X‐ray was also employed to detect the possible minor phase of anatase‐TiO2. The X‐ray diffraction data were obtained at beamline BL14B1 of the Shanghai Synchrotron Radiation Facility (SSRF) using X‐ray with a wavelength of 0.6896 Å. The detailed information about beamline BL14B1 can be found in ref. Electrochemical Characterization: Electrochemical tests were carried out using coin‐type cells (CR2032) assembled in an argon‐filled glove box. The working electrode was fabricated by casting the mixture of active material , super‐P , and poly(vinyl difluoride)  onto an aluminum foil. A polypropylene film  was used as a separator, and the pure metallic lithium foil was used as a counter electrode. The 1 m LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC)/diethyl carbonate (DEC) (1:1:1) solvent was employed as electrolyte. In our study, the loading mass of active materials is about 7.2 mg cm−2. The cycling and rate capability measurements of the assembled cells were carried out using a Land CT2001A system. The CV tests were performed using an electrochemical workstation . All the described cell tests were performed in the voltage range of 1.0−2.5 V (vs Li+/Li) at 25 °C.The authors declare no conflict of interest.SupplementaryClick here for additional data file.


The effects of cations and anions on the simultaneous determination of metal ions do not exhibit significant interference, thereby demonstrating the selectivity of the electrode for simultaneous determination of Pb2+ and Cu2+. The same method was also used to determine Cu2+ in water samples.The use of nanomaterials, such as nanoparticles and nanotubes, for electrochemical detection of metal species has been investigated as a way of modifying electrodes by electrochemical stripping analysis. The present study develops a new methodology based on a comparative study of nanoparticles and nanotubes with differential pulse anodic stripping voltammetry (DPASV) and examines the simultaneous determination of copper and lead. The glassy carbon electrode modified by gold nanoparticles demonstrated increased sensitivity and decreased detection limits, among other improvements in analytical performance data. Under optimized conditions , the detection limits were 0.2279 and 0.3321 ppb, respectively, for determination of Pb Metal pollution has become a serious threat to living organisms. Cobalt, copper, iron, manganese, molybdenum, and zinc are examples of metal species that play an important role in living organisms. They are essential in small quantities for the operating metabolism but may be harmful at excessive levels. Even small doses of very toxic metals such as arsenic, cadmium, lead, and mercury can cause serious problems for the environment and human health. The accumulation of such metals in the human body can cause diseases and disorders of the nervous, immune, reproductive, and gastrointestinal systems –4.μg L−1. It is a general metabolic poison and enzyme inhibitor. It can cause mental retardation and brain damage in young children. Lead has the ability to replace calcium in bones to form sites for long-term replacement. Reduced academic performance and behavior problems such as aggression may be associated with blood lead levels  (L), as a new synthetic phosphorus ylide. The analytical performance of the proposed electrode has been examined using square wave voltammetry and low detection limits of 0.07 μg L−1 for Tl+, 0.09 μg L−1 for Pb2+, and 0.08 μg L−1 for Hg2+ were achieved /K4[Fe(CN)6] 10−3 M in 0.1 M KCl.All solutions were prepared with deionized water but aqueous stock solutions of Pb2 nanomaterials were dispersed in DMF .The multiwalled CNT and CNT/nanoAu-SiOThe materials and voltammetric cell were washed for 24 h with 10% nitric acid to minimize potential contamination.ϕ = 3 mm) was polished carefully with 0.3 μm alumina slurry, washed in deionized water and dried in air. Then a 1 μL aliquot of nanomaterial solution was dropped onto the surface of the cleaned electrode and the electrode was kept at 70°C for 10 min. For multiwalled CNT, ten 1 μL aliquots were dropped onto the surface of the electrode, for CNT/nanoAu-SiO2 ten aliquots (1 μL) of CNT/nanoAu-SiO2 and for CNT/nanoSiO2 five aliquots (1 μL) of CNT and five aliquots (1 μL) of nanoSiO2  as the working electrode and a platinum coil electrode (reference electrode + counterelectrode).Scanning Electrochemical Microscopy analysis of the GC/CNT, GC/CNT/Hg, GC/CNT/Bi, and GC/CNT/nanoAu-SiO4[Fe(CN)6]·3H2O) 0.1 M in KCl to check the electroactive area of the cleaned electrodes, sweeping the measurements from −0.2 to 0.6 V at 100 mV s−1 in 10 cycles (versus Ag/AgCl/Cl− 3 mol/L). A scan array with sweep in comb mode was performed with x distance 1000 μm, an increment of 10 μm, and y distance 1000 μm with 10 μm team increment and 100 ms wait.The electrochemical characteristics of the modified electrode surface were characterized using cyclic voltammetry (CV) with a standard solution of 5 mM (K3[Fe(CN)6]/K4[Fe(CN)6] solution to examine the electroactive area of the cleaned electrodes, sweeping measurements from −0.3 to 0.6 V (versus Ag/AgCl/Cl− 3 mol/L). The voltammograms of Pb2+ and Cu2+ ions were obtained by DPASV mode using two methods.The electrochemical characteristics of the modified electrode during the self-assembled process were characterized using cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV). Cyclic voltammetry used a standard KMethod 1. It is as follows: first film formation and then determining the metal ion.Film Formation. The electrochemical deposition of mercury and bismuth in the glassy carbon electrode was performed in an electrochemical cell with 10 mL of HgSO4 10−3 M and Bi (NO3)3 10−6 M swept from −1.0 V to −1.0 V for 300 s and 180 s, respectively, stirring and bubbling with argon gas. After this preconcentration step, the system was aborted.Metal Determination. The DPV was performed in an electrochemical cell with 10 mL of HCl 0.1 M, aliquots of Cu2+, and Pb2+ concentration from 1 to 5 ppb with electrodeposition at 0.8 V (versus Ag/AgCl/Cl− 3 mol/L) of 300 s and stirring and bubbling with argon gas. After this preconcentration step, the electrode was swept from −0.7 V to −0.3 V for Pb+2 and −0.45 V to −0.15 V for Cu2+ (anode region) with pulse amplitude 50 mV, pulse width 50 ms, and potential jump of 4 mV.Method 2. It is as follows: film formation and determination of the metal performed concurrently. The DPV measurements were taken in an electrochemical cell with 10 mL of HCl 0.1 M containing 3.4 × 10−6 M Hg2+ or Bi3+ 10−6 M, with aliquots of 1 to 5 ppb concentration Cu2+ and Pb2+ and electrode positioned at −0.8 V (versus Ag/AgCl/Cl− 3 mol/L) of 300 s for Hg2+, and Bi3+, and stirring and bubbling with argon gas. After this preconcentration step, the electrode was swept from 0.7 V to −0.3 V for Pb2+ and −0.45 V to −0.15 V for Cu2+ (anode region) with pulse amplitude 50 mV, pulse width 50 ms, and potential jump of 4 mV.The influence of other species on the copper and lead ions in the voltammetric response of the electrode with gold nanoparticles was investigated by evaluating of the iron, zinc, and copper at a concentration 10 times greater compared to the analyte for calcium, 100 times greater compared to sodium, and 1000 times greater compared to sulfate and carbonate.There is great interest in obtaining information on the surface of the electrodes under study, since the electrochemistry is based on surface processes. The application of SECM is important for obtaining images that contain information on the electrochemical activity of the material and, in this study, the chemical, electrochemical, kinetic, and topographical properties of the interfaces.Morphological analysis of the nanomaterial modified electrode surface has shown that these substrates have electroactivity that extends broadly across the surface of the electrodes, as can be seen in This explains the electroactive performance of the nanomaterials and the films deposited on the glassy carbon. Although the whole surface of the electrode is not electroactive with the films, the high current produces good results.2), and the metal films of mercury (Hg2+) and bismuth (Bi3+) to determine trace metal species, copper (Cu2+), and lead (Pb2+) was conducted using the differential pulse anodic stripping voltammetry technique (DPASV) following two methods: Method 1 and Method 2 (in line). Method 1 exhibits a redox signal, Ipa, directly proportional to the concentration of metal for all the electrode surfaces, as can be seen from the analytical calibration curves in The electrochemical study of glassy carbon and nanomaterials, carbon nanotube (CNT), gold nanoparticles (nanoAu) and silica nanoparticles .The analytical calibration curves for the electrodes used for analysis of Cu2+ is 10−3 mol/L in Method 1 and 3.4 × 10−6 mol/L in Method 2 and, in the case of Bi3+, 10−6 mol/L for both methods.The electrodes in Method 1 showed greater sensitivity than that in Method 2. It is thus important to note that the concentration of metals used for formation of the film is different for the different methods, as the concentration of Hg2 electrode exhibits a better analytical response using both methods, according to the analytical parameters examined. It is interesting to note the striking inclination of the line of this electrode (See 2) promoted an increase of the sensitivity (modified electrode).rode See . One of Studies have been conducted on the use of a chemically modified electrode (CME) and the performance of ASV is strongly affected by the electrode materials. 2+ and Pb2+ metal ions, the GC/NTC/nanoAu-SiO2 electrode performed well and also exhibited good electroactivity, according to morphological analysis of the electrode surface using Scanning Electrochemical Microscopy (SECM), in such a way that this electrode was used for simultaneous determination of the species under study.According to the electrochemical study to identify the best nanomaterial for determination of Cu2+ and Pb2+, like the individual determination, showed that the redox signal, Ipa, is directly proportional to the concentration of the metals. The signal profile is the same, being broader for Cu2+ and narrower for Pb2+.According to 2+, Zn2+, and Fe3+ at concentrations ten times greater than the concentration of analytes, Na+ and Ca2+ at concentrations one hundred times greater than the concentration of analytes, and SO42− and CO32− at concentrations one hundred times greater than the concentration of analytes.Interferences are substances that positively or negatively affect the size of the final measurement of quantitative analytical chemical method. The study of interferences was carried out under the same conditions of simultaneous analysis, with the following species used as possible interferences: CdEpa for Pb2+ and Cu2+ subtly shifts to a more cathodic potential in simultaneous determination, with values of −0.450 V and −0.252 V in presence of Cd2+, −0.433 V and −0.236 V in presence of Zn2+, −0,450 V and −0,256 V in presence of Fe3+, −0,413 V and −0,207 V in presence of Na+  −0,421 V and −0,227 V in presence of Ca2+, −0,450 V and −0,248 V in presence of SO42−, and −0,425 V and −0,240 V in presence of CO32−.The presence of interferences ions in the electroanalytical system in determination of the lead and copper ions does not significantly interfere, since the stripping signal for the two metals is directly proportional to the concentration and retains the characteristic feature, although 2+ ion to 1 ppb for Pb2+ and Cu2+.Lead and copper ions may thus be characterized and quantified without interference, since the oxidation signal for both metals does not vary significantly with the addition of 10 ppb interferent Zn2+ and Pb2+. Water sample analysis used the GC/CNT/nanoAu-SiO2 electrode under optimized conditions, HCl 0.1 mol L−1, and a preconcentration time of 300 s, for determination of the Cu2+ and Pb2+ species.The studies conducted to identify the best electrode and method were followed by optimization of the electroanalytical system and analysis of possible interferences for determination of CuμL, 75 μL, 100 μL, 125 μL, and 150 μL) in the analytical calibration curve of the Cu2+ and Pb2+ standard, determined under the same conditions as the sample analysis. The present study was unable to identify Pb2+ for reason of the absence of this metal ion in the sample.The concentrations of analyte in the sample were determined by replacing the current values of the aliquots added  and of metal films of mercury (Hg) and bismuth (Bi) in determination of trace metals lead (Pb) and copper (Cu) in an aqueous medium, using two methods, the common method and the in-line method.The present study investigated the electrochemical behavior of the nanomaterials carbon nanotube (CNT), nanogold (nanoAu), and nanosilica  investigation showed the response of the current to be proportional to the concentration in the system, according to the characteristic electroactive area of each electrode substrate.2 electrode performed the best in the analysis for determining Cu2+ and Pb2+ metals. This is very interesting, given the absence of a metal film.For the analytical parameters, linearity, sensitivity, repeatability, and linear band, nanoAu-SiO2+ and Cu2+ on the nanoAu-SiO2 electrode established as adequate for the metals shows an anodic peak potential that facilitates oxidation compared to the other electrodes. With the nanoAu-SiO2 electrode, the oxidation of Pb2+ showed a stripping signal at Epa = −0.514 V and that of Cu2+ at Epa = −0.295 V.Furthermore, the stripping of PbBoth of the methods used in this study may be applied, although the common method performs better for the determination of Pb and Cu metals with more sensitive results.The morphological characterization of the surface of the carbon nanotube electrodes with or without the mercury and bismuth film and of the nanogold explains the satisfactory electrochemical results, given the high degree of electroactivity that these exhibit in accordance with their electronic properties.The optimization of the electroanalytical system showed hydrochloric acid to be the best performing electrolyte and that the medium needs to be considerably acidic (pH 1) for arrangement of the species in free ions with a preconcentration time of 300 s to obtain a definite signal. The simultaneous determination of metals can successfully be based on the optimized system to obtain clearly separate and distinct oxidation signals.The ions used in this study to determine the behavior of the lead and copper species generally do not interfere with the oxidation signal of metals, since they are obtained cleanly in their stripping potential and with the characteristic feature of the stripping signal of copper and lead.