Electron Trapping Sites Research Articles

Structural and optical properties of Ce-stabilized tetragonal phase and intense blue emission of monoclinic phase in ZrO2 nanoparticles

Structural and optical properties of Ce-stabilized tetragonal zirconium dioxide (ZrO2) and intense blue emission of monoclinic ZrO2 are presented in this paper. Nanoparticles of ZrO2 in the stabilized tetragonal and monoclinic phases have been prepared by the solution combustion method. X-ray diffraction studies and Rietveld refinement of the diffraction pattern show the stabilization of ZrO2 in the tetragonal phase (t-ZrO2) with Ce doping. It is the host-dopant ionic size mismatch that leads to lattice distortion and hence the t-ZrO2 stabilized phase. Raman modes confirm the phase transformation from the monoclinic to a tetragonal phase of ZrO2. The presence of oxygen vacancies and surface states in the samples play a role in altering the optical band gap. The dopant Ce-ions create defects/oxygen vacancies, which act as the trapping sites for electrons and holes/the donor and vacancy-related impurity levels. It is transition between these levels or between delocalized conduction bands that lead to band gap reduction. Photoluminescence studies reveal the presence of structural phase transformation dependent emission bands. The monoclinic phase (m-ZrO2) exhibits an intense blue emission originating from the asymmetric and unusual oxygen coordination of Zr in the m-ZrO2. The chromaticity coordinates indicate that the prepared material and adopted strategies are suitable in the field of optoelectronic application.

Theoretical studies on intrinsic electron traps in amorphous tantalum pentoxide

Charge traps in amorphous tantalum pentoxide (Ta2O5) can degrade electrical performance of electronic devices. An earlier study shows that a local region consisting of several interconnected [TaOn] polyhedrons can act as an electron trapping site in Ta2O5 cell, indicating polymer-like intrinsic electron traps (IETs). With first-principle calculations, in conjunction with molecular dynamic calculations, this work investigates the one-electron trapping behaviours of Ta2O5 in detail, including atomic configurations and electronic properties. Stable states of Ta2O5 cells with an extra electron demonstrate the existence of point-like IETs, such as a single [TaO6] polyhedron. An electron trapping at an IET can produce an electron state typically hundreds of meV below the conductive band minimum. The concentration of IETs is found to decrease exponentially with decreasing energy, and the total concentration is suggested to be of the order of 1020cm-3.

Theoretical Study on Photocatalytic Reduction of CO2 on Anatase/Rutile Mixed-Phase TiO2.

The construction of anatase/rutile heterojunctions in TiO2 is an effective way of improving the CO2 photoreduction activity. Yet, the origin of the superior photocatalytic performance is still unclear. To solve this issue, the band edges between anatase and rutile phases were theoretically determined based on the three-phase atomic model of (112)A/II/(101)R, and simultaneously the CO2 reduction processes were meticulously investigated. Our calculations show that photogenerated holes can move readily from anatase to rutile via the thin intermediated II phase, while photoelectrons flowing in the opposite direction may be impeded due to the electron trapping sites at the II phase. However, the large potential drop across the anatase/rutile interface and the strong built-in electric field can provide an effective driving force for photoelectrons' migration to anatase. In addition, the II phase can better enhance the solar light utilization of (112)A/(100)II, including a wide light response range and an intensive optical absorption coefficient. Meanwhile, the mixed-phase TiO2 possesses negligible hydrogenation energy (CO2 to COOH*) and lower rate-limiting energy (HCOOH* to HCO*), which greatly facilitate CH3OH generation. The efficient charge separation, strengthened light absorption, and facile CO2 reduction successfully demonstrate that the anatase/rutile mixed-phase TiO2 is an efficient photocatalyst utilized for CO2 conversion.

Gamma-Irradiation-Induced Electrical Characteristic Variations in MoS2 Field-Effect Transistors with Buried Local Back-Gate Structure.

The impact of radiation on MoS2-based devices is an important factor in the utilization of two-dimensional semiconductor-based technology in radiation-sensitive environments. In this study, the effects of gamma irradiation on the electrical variations in MoS2 field-effect transistors with buried local back-gate structures were investigated, and their related effects on Al2O3 gate dielectrics and MoS2/Al2O3 interfaces were also analyzed. The transfer and output characteristics were analyzed before and after irradiation. The current levels decreased by 15.7% under an exposure of 3 kGy. Additionally, positive shifts in the threshold voltages of 0.50, 0.99, and 1.15 V were observed under irradiations of 1, 2, and 3 kGy, respectively, compared to the non-irradiated devices. This behavior is attributable to the comprehensive effects of hole accumulation in the Al2O3 dielectric interface near the MoS2 side and the formation of electron trapping sites at the interface, which increased the electron tunneling at the MoS2 channel/dielectric interface.

ZnO/NiO coaxial heterojunction nanofibers with oxygen vacancies for efficient photocatalytic Congo red degradation and hydrogen peroxide production

Vacancy engineering is a highly efficient approach to enhancing photocatalytic activity. This research presents an innovative development of ZnO/NiO coaxial heterojunction nanofibers (ZN1/1) and ZnO/NiO coaxial heterojunction nanofibers with engineered oxygen vacancies (OVs-ZN1/1) via electrospinning and annealing. Detailed characterization of the nanofiber microstructure was conducted using scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The OVs-ZN1/1 nanofibers demonstrated outstanding and unprecedented photocatalytic performance, achieving a 99 % degradation rate of Congo red dye (CR) under simulated solar light in just 45 min, with a good degradation coefficient of 0.091 min−1. Remarkably, the nanofibers’ photocatalytic activity remained a high level even after five cycles. Moreover, the photocatalytic H2O2 yield of OVs-ZN1/1 increased 20 times as much as that of ZN1/1. Experiments and mechanism analysis indicate that oxygen vacancy, as the electron trapping site of photoexcitation, accelerates the charge separation and transfer at the interface, thus promoting the adsorption and activation of target molecules. This study highlights the novel and superior performance of photochemical catalysts achieved through the strategic incorporation of oxygen vacancies and heterojunctions.

Defect and doping engineering mediated M-D-MIL(Fe)/Cu-C3N4 heterojunction with dual active centers for efficient tetracycline hydrochloride removal

It is essential to explore Fe-MOFs catalysts containing both multiple active sites and rapid charge separation for improving photo-Fenton performance. Herein, a defect and doping engineering mediated M-D-MIL(Fe)/Cu-C3N4 heterojunction with dual active centers was prepared and its removal performance was investigated against tetracycline hydrochloride. Characterization confirms that: (1) The ligand vacancies in M-D-MIL(Fe) can expose plenty of coordinatively unsaturated metal sites (Fe CUS), which enhance the Lewis acidity and optimize the adsorption of H2O2. Meanwhile, the built-in dual redox centers (Fe3+/Fe2+ and Cu+/Cu2+) can synergistically promote the activation of H2O2. (2) The ligand vacancies in M-D-MIL(Fe) and copper ion in C3N4 as electron trapping sites can optimize the carrier separation of single-component materials. Furthermore, the composites exhibit a suitable energy band structure, an oriented built-in electric field, and tight interfacial contacts, all of which collectively create an optimal pathway and driving force for the efficient transport of photoinduced charges. This, in turn, accelerates the Fe3+/Fe2+ redox cycle. Finally, M-D-MIL(Fe)/Cu-C3N4 demonstrates excellent photo-Fenton performance at low H2O2 concentrations (5 mM), with a kinetic rate (k) of 0.035 min⁻¹, which is 14.58, 18.42, 1.94, and 15.21 times higher than those of MIL-100(Fe), C3N4, M-D-MIL(Fe), and Cu-C3N4, respectively. The study presents an innovative idea with potential applications in environmental restoration.

Ce-TiO2 nanoparticles with surface-confined Ce3+/Ce4+ redox pairs for rapid sunlight-driven elimination of organic contaminants from water

Industrial discharge of organic pollutants poses a severe threat to human health and aquatic life. Elimination of these pollutants from drinking and wastewater is imperative for a sustainable environment. To address this issue, pure and Ce3+-doped TiO2 nanoparticles are designed with stable tetragonal (anatase) lattices by a low-temperature sol–gel process. The spectroscopic and structural analyses reveal the formation of TiO2 and Ce-TiO2 nanocrystals with controlled crystallite size (3–6 nm), high surface areas, and varying surface chemistry. The effect of calcination (thermal (Δ) treatment at 450 °C) on the structure and photocatalytic performance of ΔTiO2 and ΔCe-TiO2 nanoparticles is also investigated. Simultaneous photocatalysis experiments over a 90-min exposure to natural sunlight show 240 % and 191 % improved elimination of methylene blue (MB), an organic pollutant, by Ce-TiO2 and ΔCe-TiO2 nanoparticles compared to their pure TiO2 analogs. Also, Ce-TiO2 and ΔCe-TiO2 nanoparticles exhibit 326 % and 229 % faster kinetics for the photocatalytic elimination of MB primarily due to the surface-confinement of Ce3+ in Ce-TiO2 nanocrystals, where Ce3+ ions play a dual role as reducing agent for adsorbed oxygen species and electron trap sites via Ce3+/Ce4+ interconversion. The mechanism of photocatalytic redox reactions is discussed. The study elaborates on the role of Ce-TiO2 nanoparticles as an effective photocatalyst for the elimination of organic pollutants in wastewater.

Fe vacancies in FeOCl enhanced reactive oxygen species generation for photocatalytic elimination of emerging pollutants

Reactive oxygen species (ROS) play an important role when using semiconductor photocatalysts in water remediation. Nonetheless, the insufficient conduction band potentials, as well as the limited mobility and quick recombination of charge carriers, often inhibit the ROS generation by many pristine photocatalysts. Here, we prepared FeOCl with tunable Fe-vacancy concentrations by using a NaCl-assisted thermal decomposition method. The defective FeOCl exhibited significantly higher rates of degradation and mineralization for organic pollutants compared to the non-defective FeOCl. This superior performance is attributed to the much faster superoxide (O2•−) and singlet oxygen (1O2) generation. Based on the experimental data and DFT simulations, Fe vacancies serve as electron trapping sites, leading to enhanced carrier lifetime and mobility, and can also reduce the conduction band potential of FeOCl, hence facilitating the formation of ROS. This study provides useful insights for developing cation-defected inorganic semiconductors and for improving the efficiency of O2 activation in photocatalysis.

Plasma-assisted annealing of Pt-doped rutile TiO2 nanoparticles for enhanced decomposition and bacterial inactivation under general lighting

Enhanced photocatalytic activity of rutile-based TiO2 materials under general lighting is practically desired. O2 plasma-assisted annealing (PAA) effects on Pt-doped rutile TiO2 nanoparticles were clarified along with its visible-light-driven photocatalytic activity enhancement. The PAA-treated samples were mainly analyzed using optical spectroscopy and x-ray photoelectron spectroscopy (XPS). The photocatalytic activity was assessed by decomposing methylene blue dye and inactivating Bacillus subtilis under general lighting. The PAA treatment changed the O 1s, Ti 2p, and Pt 4f spectra of XPS from those of the pristine sample. This change indicated that the PAA treatment introduced more oxygen deficiency or oxygen vacancies and more oxygen groups adsorbed on the surface. The introduced oxygen vacancies and adsorbed oxygen groups would change the band structure, which primarily narrowed the bandgap energy or broadened the valence band edge, increased the number of electron-trapping sites from the shallow to midgap levels, and enhanced the upward band-bending at the surface. The PAA-induced change in the band structure enhanced the decomposition and bacterial inactivation because it facilitated the separation and concentration of photoexcited carriers. The findings provide a new perspective on enhancing the photocatalytic activities of rutile-based TiO2 nanoparticles under general lighting.

(Invited) Characteristics of GaN/High-k Capacitors Under Positive Bias Stress

Vertical GaN-based trench gate metal-oxide-semiconductor field-effect transistors (MOSFETs) have been widely investigated to suppress leakage currents for applications associated with high power and high frequency. Various materials with high dielectric constant (High-k) such as Al2O3, HfO2, AlSiO x , HfSiO x , and HfAlOx have been studied as gate insulator to obtain high gm value of GaN MOSFET [1-6]. The structure of High-k gate insulator and interface between GaN and High-k is well known to affect characteristics of GaN MOS capacitor. An amorphous HfAlOx film could be fabricated by forming (HfO2)/(Al2O3) nanolaminate films via plasma-enhanced atomic layer deposition and post-deposition annealing at 800°C. Al2O3 and HfAlOx gate insulators with an amorphous structure found to exhibit superior fundamental electrical properties including no frequency dispersion, a high breakdown voltage and a low interface state density [3,5,6]. However, reliability characteristics under high voltage sweep and positive bias stress (PBS) conditions are not currently well understood.In this paper, we investigate flatband voltage (Vfb) shift of the Al2O3 and HfAlOx capacitors by varying effective electric field (Eeff) from Vfb under PBS. We also compare Vfb shift behavior among Al2O3, HfAlOx and reported High-k gate insulators.Here, to understand influence of the thermal budget at 800°C on electrical property, two n-GaN/Al2O3(10nm)/Pt MOS capacitors were prepared: One was fabricated by thermal budget at 300°C (AlO). The other was fabricated by the same capacitor fabrication process, with the GaN substrate annealed at 800°C before Al2O3 film deposition (Pre800C-AlO). To examine interface properties of the n-GaN/HfAlOx, n-GaN/interfacial layer (IL)/HfAlOx(10nm)/Pt capacitor with a 0.5nm-thick-Al2O3-IL (AlO/HfAlO) and a 0.5nm-thick-HfO2-IL (HfO/HfAlO) and without IL (HfAlO) were prepared.All High-k gate insulators had an amorphous structure. The k-values of Al2O3 and HfAlOx gate insulators estimated from C-V measurement were 8 and 17.2, respectively [3,6]. All capacitors exhibited the smooth J-Eeff properties due to an amorphous structure regardless of the 800°C pre-annealing of the GaN substrate and IL of HfAlOx case. All capacitors also exhibited no frequency dispersion in the range of 1k-1MHz. However, the Pre800C-AlO capacitor showed a large hump due to the electrical defects in the C-V curve. The Vfb shift behavior of the capacitor was examined by varing Eeff from Vfb of PBS. The Eeff was estimated from the applied voltage divided by capacitanc equivalent thickness. The Eeff from Vfb of Al2O3 and HfAlOx capacitors were varied from 4.1-8.7 and 6.5-15.4MVcm-1, respectively. The stress time was varied from 0 to 300s . The sweep voltage range of C-V measurement for obtaining Vfb in each stress time was always applied smaller than the PBS voltage. The positive Vfb shift was observed in all capacitors after PBS, indicating the presence of some electron trapping sites. The positive Vfb increased siginificantly up to a stress time of 10s, gradually increased up to 200s, and saturated above 200s in all Eeff from Vfb regions. The positive Vfb value of all capacitors reached to around 0.2V when the Eeff from Vfb was applied to 6.5MVcm-1 at 300s. Above 6.5MVcm-1, different Vfb shift profiles were observed for two Al2O3 and three HfAlOx capacitors. The positive Vfb value of the Al2O3 capacitors increased drastically to 0.5V as the Eeff from Vfb increased from 6.5 to 8.7MVcm-1. Furthermore, the Pre800C-AlO capacitor became larger Vfb shift than the AlO capacitor because the Pre800C-AlO capacitor is due to the introduction of some defects on the GaN surface by pre-annealing at 800°C. On the other hand, for the HfAlO, AlO/HfAlO and HfO/HfAlO capacitors, the positive Vfb shift value was suppressed to 0.3V even when the Eeff from Vfb was applied to 15.4 MVcm-1. Furthermore the Vfb shift showed similar behavior regardless of Al2O3- and HfO2-IL. Based on these experimental data, we conclude that the HfAlOx capacitors have a high reliability under PBS condition.This work was supported by the MEXT Program for Creation of Innovative Core Technology for Power Electronics Grant Number JPJ009777. This work was supported in part by JSPS KAKENHI Grant No. JP20H02189.[1] J. T. Asubar et al., J. Appl. Phys. 129, 121102 (2021). [2] Y. Ando et al., Appl. Phys. Lett. 117, 102102 (2020). [3] K. Yuge et al., Semicond. Sci. Technol. 34, 034001 (2019). [4] D. Kikuta et al., Appl. Phys. Express 13, 026504 (2020). [5] T. Nabatame et al., Appl. Phys. Express 12, 011009 (2019). [6] T. Nabatame et al., ECS Trans. 104 113 (2021).

Pushing the heterometal doping limit while preserving long-lived charge separation in a Ti-based MOF photocatalyst

This study explores the nature, dynamics, and reactivity of the photo-induced charge separated excited state in a Fe3+-doped titanium-based metal organic framework (MOF), xFeMIL125-NH2, as a function of iron concentration. The MOF is synthesized with doping levels x = 0.5, 1 and 2 Fe node sites per octameric Ti-oxo cluster and characterized by powder x-ray diffraction, UV-vis diffuse reflectance, atomic absorption, and steady state Fe K-edge X-ray absorption spectroscopy. For each doping level, time-resolved X-ray transient absorption spectroscopy studies confirm the electron trap site role of the Fe sites in the excited state. Time scan data reveal multiexponential decay kinetics for the charge recombination processes which extend into the microsecond range for all three concentrations. A series of dye photodegradation studies, based on the oxidative decomposition of Rhodamine B, demonstrates the reactivity of the charge separated excited state and the photocatalytic capacity of these MOF materials compared to traditional heterometal-doped semiconductor photocatalysts.

Modeling Dynamic Evolution of Oxygen Vacancies in Solid Oxide Materials

SOEC is a promising H2 generation technology for mitigating climate change. Novel material design and optimization strategies, such as oxygen vacancy chemistries, can enhance SOEC efficiency. In this study, Monte Carlo-ReaxFF and eReaxFF simulations were used to study oxygen vacancies (Ov) and electron migration in BZY20 solid oxide material. Our results shows that Ov migrate towards the surface, increasing surface Ov concentration by 10%. Yttrium restricts electron mobility and functions as an electron trapping site, while Zr accelerates electron mobility and migration. These insights could improve solid-state electrolytes’ electrochemical performance in renewable energy applications.

Tröger's base derived 3D-porous aromatic frameworks with efficient exciton dissociation and well-defined reactive site for near-unity selectivity of CO2 photo-conversion

The overall photocatalytic conversion of CO2 and H2O to fuel and O2 is challenging. In this study, a series of three-dimensional Tröger's base-derived porous aromatic frameworks (3D-X-TB-PAFs (X = TEPE, TEPM, SPF)) featuring designated reaction sites and unique charge transfer properties were developed. The incorporation of V-shaped Tröger's base (TB) units and aromatic alkynes imparts the polymers with permanent porosity, additional photon scattering cross-sections, and enhanced CO2 adsorption/activation capabilities. Density functional theory calculations and optoelectronic measurements revealed the formation of intramolecular built-in polarization and electron-trap sites induced by TB, which modulated charge separation and customized reaction sites in collaboration with 3D networks. In addition, product allocation during the photoreduction of CO2 was regulated by the photooxidation of H2O. Among the as-prepared 3D-PAFs, the most efficient electron transport channel was demonstrated by the TEPE-TB-PAF with fully conjugated TEPE-T. In the absence of cocatalysts and sacrificial agents, TEPE-TB-PAF exhibits a competitive CO formation rate (194.50 μmol g−1 h−1) with near-unity selectivity (99.74%). Significantly, the low energy barrier for CO desorption and the high energy barrier for *CHO formation contribute to the high efficiency of TEPE-TB-PAF, as demonstrated by computational exploration and in situ diffuse reflectance infrared Fourier transform spectra. This work offers efficient building blocks for the synthesis of multifunctional organic photocatalysts and groundbreaking insights into the simultaneous enhancement of photocatalytic reactivity and selectivity.

In situ fluorine migration in ZIF-67/F-TiO2 Z-type heterojunction and its photocatalytic degradation mechanism of tetracycline hydrochloride

The advancement of photocatalytic technology depends on the creation of effective photocatalysts. In this research, a series of ZIF-67/F-TiO2 composite catalysts with various ZIF-67 content were made using a straightforward hydrothermal approach, and their photocatalytic performance was examined. The analysis of element content and crystal structure of the composites showed that F element in TiOF2/TiO2 migrated during the hydrothermal process, resulting in F-TiO2 with special surface fluorine. The existence of special surface fluorine can act as electron trapping sites to promote oxygen adsorption and accelerate the hole migration to the surface of TiO2, to achieve better electron hole separation efficiency and enhance photocatalytic activity. Density functional theory (DFT) calculations verified the formation of heterojunction. Tetracycline hydrochloride (TCH) was broken down by ZIF-67/F-TiO2 composites with different mass ratios under simulated sunlight to determine their photocatalytic effectiveness. The results indicated that ZIF-67/F-TiO2 composite photocatalyst with 10 % ZIF-67 content had the highest removal efficiency (87 %) of tetracycline hydrochloride (20 mg/L) within 1 h. The following are the causes of the increased photocatalytic activity of ZIF-67/F-TiO2 composites: More electron capture sites are made available by the surface F produced by in situ F migration, which also encourages photogenerated electron-hole separation. A Z-type heterojunction, on the other hand, lengthens the lifetime of photogenerated carriers. This study introduces a fresh idea: F-TiO2 with special surface fluorine was prepared by in situ F migration, and the photocatalytic degradation of wastewater containing tetracycline hydrochloride by F-TiO2 composites was investigated.

2D Ultrathin Iron Doped Bismuth Oxychloride Nanosheets with Rich Oxygen Vacancies for Enhanced Sonodynamic Therapy.

Sonodynamic therapy (SDT) combines ultrasound and sonosensitizers to produce toxic reactive oxygen species (ROS) for cancer cell killing. Due to the high penetration depth of ultrasound (US), SDT breaks the depth penetration barrier of conventional photodynamic therapy for the treatment of deeply seated tumors. A key point to enhance the therapeutic efficiency of SDT is the development of novel sonosensitizers with promoted ability for ROS production. Herein, ultrathin Fe-doped bismuth oxychloride nanosheets with rich oxygen vacancies and bovine serum albumin coating on surface are designed as piezoelectric sonosensitizers (BOC-Fe NSs) for enhanced SDT. The oxygen vacancies of BOC-Fe NSs provide electron trapping sites to promote the separation of e- -h+ from the band structure, which facilitates the ROS production under the ultrasonic waves. The piezoelectric BOC-Fe NSs create a built-in field and the bending bands, further accelerating the ROS generation with US irradiation. Furthermore, BOC-Fe NSs can induce ROS generation by a Fenton reaction catalyzed by Fe ion with endogenous H2 O2 in tumor tissues for chemodynamic therapy. The as-prepared BOC-Fe NSs efficiently inhibited breast cancer cell growth in both in vitro and in vivo tests. The successfully development of BOC-Fe NSs provides a new nano-sonosensitiser option for enhanced SDT for cancer therapy.

Tailoring the Electron Trapping Effect of a Biocompatible Triboelectric Hydrogel by Graphene Oxide Incorporation towards Self-Powered Medical Electronics.

Triboelectric nanogenerators (TENGs) are associated with several drawbacks that limit their application in the biomedical field, including toxicity, thrombogenicity, and poor performance in the presence of fluids. By proposing the use of a hemo/biocompatible hydrogel, poly(2-hydroxyethyl methacrylate) (pHEMA), this study bypasses these barriers. In contact-separation mode, using polytetrafluoroethylene (PTFE) as a reference, pHEMA generates an output of 100.0 V, under an open circuit, 4.7 μA, and 0.68 W/m2 for an internal resistance of 10 MΩ. Our findings unveil that graphene oxide (GO) can be used to tune pHEMA's triboelectric properties in a concentration-dependent manner. At the lowest measured concentration (0.2% GO), the generated outputs increase to 194.5 V, 5.3 μA, and 1.28 W/m2 due to the observed increase in pHEMA's surface roughness, which expands the contact area. Triboelectric performance starts to decrease as GO concentration increases, plateauing at 11% volumetric, where the output is 51 V, 1.76 μA, and 0.17 W/m2 less than pHEMA's. Increases in internal resistance, from 14 ΩM to greater than 470 ΩM, ζ-potential, from -7.3 to -0.4 mV, and open-circuit characteristic charge decay periods, from 90 to 120 ms, are all observed in conjunction with this phenomenon, which points to GO function as an electron trapping site in pHEMA's matrix. All of the composites can charge a 10 μF capacitor in 200 s, producing a voltage between 0.25 and 3.5 V and allowing the operation of at least 20 LEDs. The triboelectric output was largely steady throughout the 3.33 h durability test. Voltage decreases by 38% due to contact-separation frequency, whereas current increases by 77%. In terms of pressure, it appears to have little effect on voltage but boosts current output by 42%. Finally, pHEMA and pHEMA/GO extracts were cytocompatible toward fibroblasts. According to these results, pHEMA has a significant potential to function as a biomaterial to create bio/hemocompatible TENGs and GO to precisely control its triboelectric outputs.

0D/2D/1D Ag@Ni(OH)2/La(OH)3 heterojunction with semi-coherent interface derived from perovskite La1-xAgxNiO3 self-assembling with g-C3N4 for boosting photocatalytic hydrogen evolution

Interfacial electron transfer plays an important role in the boosting photoactivity of heterojunction under sunlight irradiation. Here, the lattice oxygen migration etching Ag-doped perovskite induced self-assembly ternary heterojunction 0D/2D/1D Ag@Ni(OH)2/La(OH)3 via hydrothermal treatment. The LaNiO3 controlled self-assembled into Ni(OH)2/La(OH)3 heterojunctions at the interface and constructed a semi-coherent interface. Furthermore, it became reinforced quaternary heterojunction 0D/2D/1D/2D Ag@Ni(OH)2/La(OH)3/g-C3N4 by electrostatic self-assembly with g-C3N4. The novel constructed Z-scheme heterojunction Ag@Ni(OH)2/La(OH)3/g-C3N4 promotes the effective separation of photogenerated carriers. The semi-coherent interface between Ni(OH)2/La(OH)3 promotes the transfer of photogenerated carriers. At the same time, the silver nanoparticles on Ni(OH)2 nanosheets act as electron trapping sites to further improve the photocatalytic performance. In this way, the synthesized photoexcited quaternary heterojunction Ag@Ni(OH)2/La(OH)3/g-C3N4 showed an outstanding hydrogen production rate from photocatalytic water splitting (the yield of hydrogen was 1633 μmol/g/h) under simulated sunlight. It is comparable to many g–C3N4–based photocatalysts known at present.

Theoretical studies on intrinsic electron traps in strained amorphous silica

Charge trapping in amorphous silica (a-SiO2) dielectric layer can degrade electrical performances of semiconductor devices. Earlier studies demonstrate that a SiO4 tetrahedra unit with a wide O-Si-O angle (≥132.0∘) can act as an electron trapping site in unstrained a-SiO2 cells. With first-principle calculations, in conjunction with molecular dynamic calculations, this work investigates the impacts of uniaxial tensile strain on one-electron trapping behaviors of a-SiO2, including atomic configurations and electronic properties. Stable states of strained a-SiO2 cells with an extra electron indicate that a SiO4 with a wide O-Si-O angle (≥132.0∘) and a long Si-O bond (≥1.660Å) making up the angle can act as a novel intrinsic electron tap. An electron trapping on this trap can generate a stable defect complex with two components: a negatively charged non-bridging oxygen hole center and a neutral oxygen vacancy with an unpaired electron.

Single-atomic-site platinum steers photogenerated charge carrier lifetime of hematite nanoflakes for photoelectrochemical water splitting

Although much effort has been devoted to improving photoelectrochemical water splitting of hematite (α-Fe2O3) due to its high theoretical solar-to-hydrogen conversion efficiency of 15.5%, the low applied bias photon-to-current efficiency remains a huge challenge for practical applications. Herein, we introduce single platinum atom sites coordination with oxygen atom (Pt-O/Pt-O-Fe) sites into single crystalline α-Fe2O3 nanoflakes photoanodes (SAs Pt:Fe2O3-Ov). The single-atom Pt doping of α-Fe2O3 can induce few electron trapping sites, enhance carrier separation capability, and boost charge transfer lifetime in the bulk structure as well as improve charge carrier injection efficiency at the semiconductor/electrolyte interface. Further introduction of surface oxygen vacancies can suppress charge carrier recombination and promote surface reaction kinetics, especially at low potential. Accordingly, the optimum SAs Pt:Fe2O3-Ov photoanode exhibits the photoelectrochemical performance of 3.65 and 5.30 mA cm−2 at 1.23 and 1.5 VRHE, respectively, with an applied bias photon-to-current efficiency of 0.68% for the hematite-based photoanodes. This study opens an avenue for designing highly efficient atomic-level engineering on single crystalline semiconductors for feasible photoelectrochemical applications.

Construction of TiO2-x Confined by Layered Iron Silicate toward Efficient Visible-Light-Driven Photocatalysis-Fenton Synergistic Removal of Organic Pollutants.

The photocatalysis-Fenton synergistic reaction has great potential for water purification but generally suffers from unsatisfactory electron transfer due to an undesirable interface structure. Herein, we developed a novel heterojunction of oxygen vacancy-rich TiO2-x confined in the layer space of a synthetic montmorillonite-like iron silicate (denoted as TiO2-x/FeMMT) that addresses the issue mentioned above. Two-dimensional layered montmorillonite-like silicates in heterojunctions as a support not only provided more active sites for the reaction but also induced oxygen vacancies in TiO2-x through interfacial effects to enhance the visible-light harvesting ability. Notably, such loading TiO2-x as an electron donor accelerated the Fe(III)/Fe(II) redox cycling and facilitated the effective activation of H2O2, while Fe(III) in the montmorillonite-like silicate as electron trap sites greatly improved the separation of photogenerated electron-hole pairs. More interestingly, the internal electric field and oxygen vacancies (Vo) existing at the interface realized the directional migration of photogenerated electrons and improved the energy band structure of the heterojunction, respectively. Eventually, the TiO2-x/FeMMT composites exhibited superior photocatalysis-Fenton performance toward degradation removal of phenol, dinotefuran (DIN), and sulfamethoxazole (SMX) under visible-light irradiation. This paves the way for the rational design of high-efficiency heterojunction catalysts based on layered silicates for environment-related applications.