Ultraviolet Photoelectron Spectroscopy Research Articles

Bridging Electrochemistry and Ultrahigh Vacuum: "Unburying" the Electrode-Electrolyte Interface.

ConspectusElectrochemistry has a central role in addressing the societal issues of our time, including the United Nations' Sustainable Development Goals (SDGs) and beyond. At a more basic level, however, elucidating the nature of electrode-electrolyte interfaces is an ongoing challenge due to many reasons, but one obvious reason is the fact that the electrode-electrolyte interface is buried by a thick liquid electrolyte layer. This fact would seem to preclude, by default, the use of many traditional characterization techniques in ultrahigh vacuum surface science due to their incompatibility with liquids. However, combined UHV-EC (ultrahigh vacuum-electrochemistry) approaches are an active area of research and provide a means of bridging the liquid environment of electrochemistry to UHV-based techniques. In short, UHV-EC approaches are able to remove the bulk electrolyte layer by performing electrochemistry in the liquid environment of electrochemistry followed by sample removal (referred to as emersion), evacuation, and then transfer into vacuum for analysis.Through this Account, we highlight our group's activities using UHV-EC to bridge electrochemistry with UHV-based X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS) and scanning tunneling microscopy (STM). We provide a background and overview of the UHV-EC setup, and through illustrative examples, we convey what sorts of insights and information can be obtained. One notable advance is the use of ferrocene-terminated self-assembled monolayers as a spectroscopic molecular probe, allowing the electrochemical response to be correlated with the potential-dependent electronic and chemical state of the electrode-monolayer-electrolyte interfacial region. With XPS/UPS, we have been able to probe changes in the oxidation state, valence structure, and also the so-called potential drop across the interfacial region. In related work, we have also spectroscopically probed changes in the surface composition and screening of the surface charge of oxygen-terminated boron-doped diamond electrodes emersed from high-pH solutions. Finally, we will give readers a glimpse into our recent progress regarding real-space visualizations of electrodes following electrochemistry and emersion using UHV-based STM. We begin by demonstrating the ability to visualize large-scale morphology changes, including electrochemically induced graphite exfoliation and the surface reconstruction of Au surfaces. Taking this further, we show that in certain instances atomically resolved specifically adsorbed anions on metal electrodes can be imaged. In all, we anticipate that this Account will stimulate readers to advance UHV-EC approaches further, as there is a need to improve our understanding concerning the guidelines that determine applicable electrochemical systems and how to exploit promising extensions to other UHV methods.

Unveiling the mechanism and performance of electrocatalytic hydrodechlorination of chlorinated PPCPs by electron-rich palladium electrode modulated through PANI-rGO interlayer

In order to simultaneously achieve higher dispersion, smaller particle size, and better catalytic performance of Pd, a Pd/Polyaniline-reduced graphene oxide/Nickel foam (Pd/PANI-rGO/NF) electrode is synthesized by introducing conductive PANI-rGO interlayer for electrocatalytic hydrodechlorination (ECH) of typical chlorinated pharmaceuticals and personal care products (PPCPs). 99.3% diclofenac (DCF) and 94.6% clofibric acid (CA) are removed by this electrode within 180 min and the results of risk assessment show that the toxicities of the two typical chlorinated PPCPs are significantly reduced in the aqueous environment. The electrode is characterized and analyzed. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) results indicate that the introduction of PANI-rGO effectively enhances the dispersion of Pd and reduces the size of Pd particle. Meanwhile, the combined analyses of X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and density functional theory (DFT) calculation suggest that electron transfer occurs between the PANI-rGO interlayer and Pd, leading to the formation of electron-rich Pd. Cyclic voltammetry (CV) curve indicates that the PANI-rGO interlayer improves the yield of active adsorbed hydrogen (H*ads). Therefore, the catalytic activities of Pd particles are synergistically improved. This work can provide a beneficial choice for the effective treatment of typical chlorinated PPCPs in the water environment.

Large area matrix of MXene/MoSe2 nanohybrid-based flexible piezoresistive pressure sensors for artificial e-skin application

In this study, a MoSe2/Ti3C2Tx nanohybrid-based fabricated flexible physical sensor demonstrates an elevated pressure sensitivity of 14.70 kPa−1 and a highly robust nature withstanding up to ∼2500 cycles. The fabricated pressure sensor's underlying transduction mechanism is elucidated by exploiting the inherent piezoresistive effect and the variation of the Schottky barrier height unveiled by the MoSe2/Ti3C2Tx interface with the assistance of comprehensive band structures that are appreciated by ultraviolet photoelectron spectroscopy. Also, sensors were employed as a 7 × 7 sensor matrix with a large area for tactile sensing and incorporated onto the volunteer hand to determine the artificial skin application.

Thermally Evaporated CsPbCl3 Perovskite on Si/SiO2 with Wide Spectrum Photoresponse from Ultraviolet (UV) to Near-Infrared (NIR)

CsPbCl3 metal halide perovskite photodetectors (PDs) are prepared via thermal evaporation and 75 °C in situ annealing on Si/SiO2 substrates, and their photoresponse as well as the morphology, structure, and photophysical properties are investigated. Wide spectrum photoresponse ranging from 350 to 980 nm has been achieved with optimal responsivity (R) of 2364, 3766, and 268 A/W at wavelengths (λ) of 420, 680, and 980 nm, respectively. Such photoresponse behavior can be attributed to the parallel photoresponse from both CsPbCl3 and Si based on the UPS (ultraviolet photoelectron spectrometry) and XPS (X-ray photoelectron spectroscopy) results. Yb3+ doped CsPbCl3 PDs with the photosensing layer structure of CsPbCl3 (50 nm)/YbCl3 (30 nm)/CsPbCl3 (50 nm) have been prepared, and it was found that Yb3+ dopant is capable of realizing obviously shorter exciton lifetime at 420 nm, lower trap density, as well as remarkably higher carrier mobility due to the combined effects of energy transfer from CsPbCl3 to Yb3+ and defect passivation from Yb3+, leading to remarkable improvement of the photoresponse performance with optimal R (2709, 6340 and 3573A/W), noise equivalent power (NEP) (5.64 × 10–7, 2.51 × 10–7, and 4.38 × 10–7 W), and specific detectivity (D*) (1.84 × 1011, 3.24 × 1011, and 1.5 × 1011 cm Hz1/2 W–1) compared to those of pristine CsPbCl3 at λ of 420, 720, and 980 nm, respectively. Especially at the NIR λ of 980 nm, 10-fold higher R is achieved after Yb3+ incorporation. The upconversion processing of Yb3+ can also be responsible for the enhanced wide spectrum photoresponse of Yb3+ doped CsPbCl3. Our study provides a practical way to realize wide spectrum perovskite PDs by simply connecting the perovskite to Si substrates by the Au electrodes.

Effects of different elements on the passivation behaviour of Fe-based metallic glasses in the NaCl solution

The passivation and microstructure of Fe-based metallic glasses (MGs) with different contents of essential elements in 3.5 wt% NaCl solution were investigated by electrochemical techniques such as potentiodynamic polarization (PDP), potentiostatic polarization (PSP) and Mott-Schottky (MS) as well as surficial stability analysis including X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). At the low passive potential region, the strongly Cr-enriched passive film on Fe48Cr15Mo14C15B6Y2 (Cr15Mo14) generates a higher resistance than that of Fe63Cr8Mo3.5C4B4Ni5P10Si2.5 (Cr8Mo3.5) with a Fe-rich film. As the potential increases, the enhanced hydration, e.g., Cr2O3 converted to Cr(OH)3, causes a film degradation of Cr15Mo14, while the stable Si-oxide is increasingly enriched and maintains the high film protection of Cr8Mo3.5. Consequently, the corrosion resistance of Cr8Mo3.5 becomes better than that of Cr15Mo14 at the high passive potential region.

Enhanced electron channel via the interfacial heterotropic electric field in dual S-scheme g-C3N4/WO3/ZnS photocatalyst for year-round antibiotic degradation under sunlight

Widespread and persistent presence of antibiotic contaminants in natural aquatic environments has aroused all mankind concern due to their potential threat to human health. Photocatalysis represents a promising means to remediate polluted waters with the simple assistance of solar energy. In this context, the feasibility of treating antibiotic contaminated water with g-C3N4/WO3/ZnS dual S-scheme heterojunction driven by interfacial heterotropic electric field was investigated under year-round climate conditions. The optimum composite (5-CWZ) could degrade >85% of tetracycline within 1 h of summer sunlight and 1.5 h of winter sunlight irradiation. The results of electron spin resonance (ESR), chemical trapping experiment, High performance liquid chromatography mass spectrometry (HPLC-MS), ultraviolet photoelectron spectroscopy (UPS) and density functional theory (DFT) calculation reflected that in-situ anchoring of WO3 and ZnS on the surface of g-C3N4 facilitates the formation of interfacial heterotropic electric field which were effective towards low-resistance charge carrier channelization, resulting sufficient •O2–, h+, •OH species evolving for attacking the active atoms of contaminants with high Fukui index. Furthermore, the retention of superior photocatalytic properties in complex actual water matrices together with the non-toxicity of both 5-CWZ photocatalyst and treated TC solution proved by Pisum sativum bud radicle elongation and bacterial (E. coli and B. subtilis) cultivation further demonstrated the feasibility of the 5-CWZ to treat antibiotics in real water under irradiation of solar light.

Synthesis of Z-type spherical B-g-C3N4/Bi2WO6 heterojunctions for enhanced rhodamine B degradation

A spherical B-g-C3N4/Bi2WO6 heterojunction photocatalyst was synthesized using the hydrothermal coprecipitation method. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible diffuse reflectance spectroscopy (DRS) showed that B-g-C3N4 was uniformly dispersed on the Bi2WO6 surface through a strong chemical bond, reducing the energy bandgap of Bi2WO6. The outcomes of the experiment regarding the photocatalytic degradation of rhodamine B (RhB) demonstrated a notable enhancement in the degradation rate for the 1:3 BCN/BWO composite. Specifically, the degradation rate was found to be 76 times greater than that of B-g-C3N4 and 7 times higher than that of Bi2WO6. Furthermore, a photocatalytic degradation mechanism was proposed based on the results of ultraviolet photoelectron spectroscopy (UPS) and free radical capture experiments. The direct Z-type B-g-C3N4/Bi2WO6 heterojunction structure promotes the effective separation of photogenerated carriers and enhances their oxidation-reduction ability.

Interface-Engineered Organic Near-Infrared Photodetector for Imaging Applications.

We report a high-speed low dark current near-infrared (NIR) organic photodetector (OPD) on a silicon substrate with amorphous indium gallium zinc oxide (a-IGZO) as the electron transport layer (ETL). In-depth understanding of the origin of dark current is obtained using an elaborate set of characterization techniques, including temperature-dependent current-voltage measurements, current-based deep-level transient spectroscopy (Q-DLTS), and transient photovoltage decay measurements. These characterization results are complemented by energy band structures deduced from ultraviolet photoelectron spectroscopy. The presence of trap states and a strong dependency of activation energy on the applied reverse bias voltage point to a dark current mechanism based on trap-assisted field-enhanced thermal emission (Poole-Frenkel emission). We significantly reduce this emission by introducing a thin interfacial layer between the donor: acceptor blend and the a-IGZO ETL and obtain a dark current as low as 125 pA/cm2 at an applied reverse bias of -1 V. Thanks to the use of high-mobility metal-oxide transport layers, a fast photo response time of 639 ns (rise) and 1497 ns (fall) is achieved, which, to the best of our knowledge, is among the fastest reported for NIR OPDs. Finally, we present an imager integrating the NIR OPD on a complementary metal oxide semiconductor read-out circuit, demonstrating the significance of the improved dark current characteristics in capturing high-quality sample images with this technology.

Spectral Signatures of a Negative Polaron in a Doped Polymer Semiconductor: Energy Levels and Hubbard U Interactions.

The modern picture of negative charge carriers on conjugated polymers invokes the formation of a singly occupied (spin-up/spin-down) level within the polymer gap and a corresponding unoccupied level above the polymer conduction band edge. The energy splitting between these sublevels is related to on-site Coulomb interactions between electrons, commonly termed Hubbard U. However, spectral evidence for both sublevels and experimental access to the U value is still missing. Here, we provide evidence by n-doping the polymer P(NDI2OD-T2) with [RhCp*Cp]2, [N-DMBI]2, and cesium. Changes in the electronic structure after doping are studied with ultraviolet photoelectron and low-energy inverse photoemission spectroscopies (UPS, LEIPES). UPS data show an additional density of states (DOS) in the former empty polymer gap while LEIPES data show an additional DOS above the conduction band edge. These DOS are assigned to the singly occupied and unoccupied sublevels, allowing determination of a U value of ∼1 eV.

Self-driven electron enrichment of ultrafine PdAu nanoparticles for electrochemical CO2 reduction: High applicability of work function as an activity descriptor

Highly coupled metal/dopant-incorporated carbon dyads provide a possibility to modulate the electron density of metallic materials by forming a rectifying interface, thus showing an enhanced activity in electrochemical CO2 reduction reaction (ECRR). However, understanding the promotion effects of dopants for ECRR is limited to the prediction by theoretical interpretation and case-by-case studies. Herein, we report the direct experimental evidence that the work function, regulated by single structural factor-dopant contents, is significantly correlated to the ECRR reaction activity and kinetics. We prepared a series of PdAu/NxC electrocatalysts composed of ultrafine (∼5.7 nm) PdAu bimetallic nanoparticles and tailorable N-doped carbon supports. The wide range of the amount of N dopants allowed the modification of the band gap of the carbon easily. Using ultraviolet photoelectron spectroscopy (UPS) measurements, we demonstrate that the reactivity and kinetics trends of the PdAu/NxC in the ECRR can be intrinsically correlated with the work function of the catalysts. PdAu/N7.50C electrocatalyst with the highest N contents displays a 100% CO2-to-CO conversion and high conversion efficiency over a wide potential window, superior over other reported PdAu catalysts. This work provides a novel way to boost ECRR performance by deliberately lowering the work function of the metal/carbon electrocatalysts through the enhancement by dopants.

Semiconductor Heterostructure (SFT–SnO2) Electrolyte with Enhanced Ionic Conduction for Ceramic Fuel Cells

Electronic conduction inhibition, heterostructure construction, constituting built-in electric field (BIEF), and the generation of an energetically more active region in the lattice and at the interface are ways to increase the ionic conductivity (σi) of electrolyte materials for ceramic fuel cells (CFCs). The conduction of ions and stoppage of e– conductivity are of utmost importance in semiconductor-based electrolytes. Type-II heterojunction can be synthesized to improve fuel cell performance by increasing ionic conductivity. SFT (SrFe0.3Ti0.7O3)–SnO2 p–n heterojunction was produced by combining p-type SFT and n-type SnO2 semiconductors. The resulting SFT–SnO2 heterostructure unveiled a high ionic conductivity of 0.18 S/cm and an open-circuit voltage (OCV) of 1.04 V, contributing to a remarkable power output of 805 mW/cm2 at a low operating temperature of 520 °C. High ionic conductivity and efficient fuel cell performance are attributed to a synergistic interaction between the SFT/SnO2 heterojunction and BIEF. Heterojunction production between SFT and SnO2 was confirmed by numerous characterization techniques (X-ray diffractometer (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), UV–visible, ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS)). The SFT/SnO2 junction valence band deviation and energy band structure were also validated. Our research shows that the constructed heterostructure SFT–SnO2 is an effective and efficient electrolyte material for future fuel cell technology.

Charge transfer and electronic relaxation effects in the photoemission of EMIM-DCA ionic liquid vapor

Ultraviolet photoelectron spectroscopy (UPS) measurements of EMIM-DCA vapors have been conducted. Density functional theory (DFT), Møller–Plesset perturbation theory (MP2) and many-body perturbation theory calculations (GW) have been used to interpret the experimentally measured spectra. The vapor of ionic liquids normally consists of isolated ion-pairs and the corresponding photoemission spectra should reflect the electronic binding energies of the molecular orbitals. The UPS spectra have revealed that many photolines are shifted when compared to ab initio calculation results. The hybrid DFT functionals, which performed very good in the description of the UPS spectra of many other ionic liquid vapors have shortcomings in the EMIM-DCA case. The MP2 calculation and the quasiparticle GW approach are shown to offer a better description of the experimental UPS spectra. The charge distribution analysis showed that there seems to be a favorable charge transfer from the cation to the anion upon ionization. The new data provides strong support to the argument that in some cases DFT still has difficulties in the modeling of IL ion-pairs.

Constructing Type-II and S-Scheme Heterojunctions of Cu2O@Cu4(SO4)(OH)6·H2O Polyhedra by In Situ Etching Cu2O with Different Exposed Facets for Enhanced Photocatalytic Sterilization and Degradation Performance.

The construction of type-II or S-scheme heterojunctions can effectively accelerate the directional migration of charge carriers and inhibit the recombination of electron-hole pairs to improve the catalytic performance of the composite catalyst; therefore, the construction and formation mechanism of a heterojunction are worth further investigation. Herein, Cu2O@Cu4(SO4)(OH)6·H2O core-shell polyhedral heterojunctions were fabricated via in situ etching Cu2O with octahedral, cuboctahedral, and cubic shapes by sodium thiosulfate (Na2S2O3). Cu2O@Cu4(SO4)(OH)6·H2O polyhedral heterojunctions demonstrated obviously enhanced sterilization and degradation performance than the corresponding single Cu2O polyhedra and Cu4(SO4)(OH)6·H2O. When Cu2O with a different morphology contacts with Cu4(SO4)(OH)6·H2O, a built-in electric field is established at the interface due to the difference in Fermi level (Ef); meanwhile, the direction of band bending and the band alignment are determined. These lead to the different migration pathways of electrons and holes, and thereby, a type-II or S-scheme heterojunction is constructed. The results showed that octahedral o-Cu2O@Cu4(SO4)(OH)6·H2O is an S-scheme heterojunction; however, cuboctahedral co-Cu2O@Cu4(SO4)(OH)6·H2O and cubic c-Cu2O@Cu4(SO4)(OH)6·H2O are type-II heterojunctions. By means of X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), diffuse reflectance spectra (DRS), and Mott-Schottky analyses, the band alignments, Fermi levels, and band offsets (ΔECB, ΔEVB) of Cu2O@Cu4(SO4)(OH)6·H2O polyhedral heterojunctions were estimated; the results indicated that the catalytic ability of the composite catalyst is determined by the type of heterojunction and the sizes of band offsets. Cubic c-Cu2O@Cu4(SO4)(OH)6·H2O has the strongest driving force (namely, biggest band offsets) to accelerate charge migration and effectively separate charge carriers, so it exhibits the strongest catalytic bactericidal and degrading abilities.

Highly Efficient ITO-Free Quantum-Dot Light Emitting Diodes via Solution-Processed PEDOT:PSS Semitransparent Electrode.

We present a study on the potential use of sulfuric acid-treated poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as a viable alternative to indium tin oxide (ITO) electrodes in quantum dot light-emitting diodes (QLEDs). ITO, despite its high conductivity and transparency, is known for its disadvantages of being brittle, fragile, and expensive. Furthermore, due to the high hole injection barrier of quantum dots, the need for electrodes with a higher work function is becoming more significant. In this report, we present solution-processed, sulfuric acid-treated PEDOT:PSS electrodes for highly efficient QLEDs. The high work function of the PEDOT:PSS electrodes improved the performance of the QLEDs by facilitating hole injection. We demonstrated the recrystallization and conductivity enhancement of PEDOT:PSS upon sulfuric acid treatment using X-ray photoelectron spectroscopy and Hall measurement. Ultraviolet photoelectron spectroscopy (UPS) analysis of QLEDs showed that sulfuric acid-treated PEDOT:PSS exhibited a higher work function than ITO. The maximum current efficiency and external quantum efficiency based on the PEDOT:PSS electrode QLEDs were measured as 46.53 cd/A and 11.01%, which were three times greater than ITO electrode QLEDs. These findings suggest that PEDOT:PSS can serve as a promising replacement for ITO electrodes in the development of ITO-free QLED devices.

Improving the Performance of Layer-by-Layer Processed Organic Solar Cells via Introducing a Wide-Bandgap Dopant into the Upper Acceptor Layer.

The layer-by-layer (LbL) solution-processed organic solar cells (OSCs) are conductive to achieve vertical phase separation, tunable donor-acceptor (D/A) interfaces, and favorable charge-transport pathways. In this work, a wide-bandgap component poly(9-vinylcarbazole) (PVK) is added to the upper electron acceptor layer to improve the performance of LbL-processed OSCs. Results show that the PVK component can adjust the film morphology, dope the electron acceptor, increase the electron concentration, and improve charge transport. Such n-type doping is verified by Seebeck coefficient measurement, ultraviolet photoelectron spectroscopy, and electron paramagnetic resonance characterization. In addition, the fluorescence intensity and exciton lifetime of the PVK-doped acceptor film are increased, thus being beneficial for exciton diffusion to the D/A interface. Therefore, the power conversion efficiency (PCE) of LbL OSCs increases when 2.50 wt.% PVK is employed in the electron acceptor layer of commonly-used high-efficiency system and a maximum value of 19.05% can be achieved. The role of PVK played in the active layer is different from those of additives and ternary components reported previously, so the results provide an alternative way to enhance the device performance of LbL-processed OSCs.

A S-scheme heterojunction Fe-doped TiO2/SnO2 with rich oxygen vacancies for photo-Fenton degradation of Rhodamine B under visible light illumination

The photo-Fenton process serves as a highly efficient approach for removing contaminants from wastewater. In this study, we developed a Fe-doped TiO2/SnO2 heterojunction catalyst to enhance the efficiency of photo-Fenton catalytic activity under visible light. To investigate the physical properties of the catalysts, various characterization techniques were utilized, including XRD, SEM, TEM, HR-TEM, UV-VIS, PL, and XPS. The 7% mol Fe-doped TiO2/SnO2-OVs (TFS-7) heterostructure exhibited the highest rate constant of 17.03 × 10−3 min−1; 8.4 and 2.1 times higher than the individual components. This enhanced performance is mainly attributed to the rapid migration of photoinduced electrons to Fe3+ and the subsequent generation of Fe2+, which improved electron transfer capacity and facilitated the rapid production of hydroxyl radicals (•OH) through the reaction between Fe2+ and H2O2. We proposed a S-scheme mechanism for the Fe-doped TiO2/SnO2-OVs catalyst based on the analysis of reactive species trapping experiments, photoluminescence (PL) spectra, ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT). These findings offer not only a straightforward approach for synthesizing highly active photocatalysts for the degradation of RhB dye, but also a framework for the construction of heterostructure photocatalysts.

Interdigitated electrodes-based Au-MoS2 hybrid gas sensor for sensing toxic CO and NH3 gases at room temperature

In the quest to create effective sensors that operate at room temperature, consume less power and maintain their stability over time for detecting toxic gases in the environment, molybdenum disulfide (MoS2) and MoS2-based hybrids have emerged as potent materials. In this context, the current work describes the fabrication of Au-MoS2 hybrid gas sensor fabricated on gold interdigitated electrodes (GIEs) for sensing harmful CO and NH3 gases at room temperature. The GIEs-based Au-MoS2 hybrid sensors are fabricated by decorating MoS2 nanoflowers (MNF) with varying size of Au nanoparticles using an inert gas evaporation technique. It is observed that by varying the size of Au nanoparticles, the crystallinity gets modified, as confirmed by x-ray diffraction and Micro-Raman spectroscopy (μRS). The gas sensing measurements revealed that the best sensing response is found from the Au-MoS2 hybrid (with an average particle size of 10 nm). This particular hybrid shows a 79% response to CO exposure and a 69% response to NH3 exposure. The measurements are about 3.5 and 5 times higher than the bare MoS2 when exposed to CO and NH3 at room temperature, respectively. This enhancement in sensing response is attributed to the modified interfacial interaction between the Au nanoparticles and MNF gets improved, which leads to the formation of a Schottky barrier, as confirmed using x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy analysis. This enables the development of efficient gas sensors that respond quickly to changes in the gas around them.

Designing of graphene oxide-induced p-NiO/n-MoO3 heterostructures for improved photocatalytic activity through plasmon-enhanced S-scheme mechanism and its biological and electrochemical performance.

An environmentally benign, economically advantageous microwave hydrothermal approach is used in synthesis of desirably tailored graphene oxide-induced p-NiO/n-MoO3 (GNM) heterostructures. Various analytical techniques such XPS, XRD, UPS, EIS, and Mott-Schottky were conducted to comprehend complete morphology and functioning of the novel ternary heterostructure photocatalysts. Also, SEM and HR-TEM images were presented for better interpretation. The strategic plasmonic step scheme (S-scheme) charge migration approach was used to describe the effective charge recombination process. Hydroxyl and oxide active species were corollaries of the reactive radical-scavenging experiments and electron spin resonance. The work function has been confirmed using ultraviolet photoelectron spectroscopy (UPS), which assessed an electron transfer between NiO and MoO3, yielding work function values of 6.32eV and 5.26eV, respectively. The cell apoptosis of the HeLa cell line approves the material's biocompatibility. Cyclic voltammetry and electrochemical impedance spectroscopy reveal electrochemical performance of GNM heterostructures. We anticipate our results would pave the way for current and future applications. In order to ensure eco-restoration such photocatalyst which are eco and cost friendly are synthesized. Assessment of pollutant risks presents the impact of them on human and terrestrial and aquatic animals. Sustainability of material is acknowledge as they use solar light for photocatalysis and dye degradation, and hence can be green material. One such material for the treatment of wastewater, dye-infused waters, and industrial water has been tailored, which is capable of dye degradation, heavy metal, and other pollutant removal. Very importantly, the synthesized material is a biocompatible one.

Comparative investigation on defect-engineered Bi2S3-xSex for boosting photocatalytic Cr(VI) reduction and in-situ H2O2 generation: Mechanistic and kinetic studies

Heterogeneous photocatalysis has been demonstrated as a highly effective approach in addressing the difficulties encountered by conventional technologies in environmental remediation. Herein, for the first time, a novel hierarchical photocatalyst of selenium-doped Bi2S3 (Bi2S3-xSex) was successfully synthesized through a one-spot hydrothermal route followed by a vacancy engineering process (V-Bi2S3-xSex). The photocatalytic reduction of Cr(VI) and in-situ generation of hydrogen peroxide (H2O2) under simulated solar-light irradiation were performed to evaluate the catalytic activity of the as-prepared samples. The catalytic activity of as-prepared samples was evaluated toward the photocatalytic reduction of Cr(VI) and in-situ generation of H2O2 under simulated solar-light irradiation. Notably, V-Bi2S3-xSex (V-BSSe-5, as optimum sample) exhibited a photo-reduction of Cr(VI) at a rate of 97.04% during 150 min, which was 1.53- and 1.39-fold higher than those of pure Bi2S3 and Bi2Se3, respectively. Interestingly, the V-Bi2S3-xSex photocatalyst not only harvested more incident light in the UV–vis and near-infrared (NIR) regions but also supplied many active sites, improving the promotion of photo-generated charge-carriers, inhibiting charge recombination, and thus enhancing the photocatalytic activity. In addition, V-BSSe-5 showed greater photocatalytic efficiency for H2O2 generation, which was 15.69, 10.07, and 1.79 times higher than those of Bi2S3, Bi2Se3, and BSSe-5, respectively. The charge-carrier migration pathway and possible photocatalytic mechanisms were systematically discussed by assisting the electron spin resonance and ultraviolet photoelectron spectroscopy analyses. The findings of this study demonstrate that doping and defect engineering strategies have the potential to be a significant advancement in the development of visible- and NIR-light responsiveness photocatalysts, thereby providing a solution to current environmental and energy challenges.

Dynamic Distortions of Quasi-2D Ruddlesden–Popper Perovskites at Elevated Temperatures: Influence on Thermal and Electronic Properties

Ruddlesden–Popper hybrid halide perovskites are quasi-two-dimensional materials with a layered structure and structural dynamics that are determined by the interplay between the organic and inorganic layers. While their optical properties are governed by confinement effects, the atomistic origin of thermal and electronic properties of these materials is yet to be fully established. Here we combine computational and experimental techniques to study A2PbI4 (A = butylammonium (BA), phenethylammonium (PEA)) Ruddlesden–Popper perovskites and compare them with the quintessential perovskite CH3NH3PbI3. We use first-principles density functional theory, molecular dynamics simulations based on machine-learned interatomic potentials, thermal measurements, temperature-dependent Raman spectroscopy, and ultraviolet photoelectron spectroscopy to probe the thermal and electronic properties of these materials at elevated temperatures. Our molecular dynamics simulations demonstrate that dynamic fluctuations in the organic sublattice determine the bulk-average distortions of these materials at room temperature, explaining significant differences in their electronic density of states close to the Fermi level. Furthermore, by analyzing the organic layer dynamics in BA2PbI4 we provide a mechanistic explanation for the phase transition of this material at 274 K and observations from Raman measurements. Our results highlight the role of the organic interlayer for the electronic and thermal transport properties of Ruddlesden–Popper perovskites, paving the way for the design of new hybrid materials for tailored applications.