Band Positions Research Articles

Insight into the Rate-Determining Step in Photocatalytic Z-Scheme Overall Water Splitting by Employing A Series of Perovskite RTaON2 (R = Pr, Nd, Sm, and Gd) as Model Photocatalysts.

Photocatalysis is an intricate process that involves a multitude of physical and chemical factors operating across diverse temporal and spatial scales. Identifying the dominant factors that influence photocatalyst performance is one of the central challenges in the field. Here, we synthesized a series of perovskite RTaON2 semiconductors with different A-site rare earth atoms (R = Pr, Nd, Sm, and Gd) as model photocatalysts to discuss the influence of the A-site modulation on their local structures as well as both physical and chemical properties and to get insight into the rate-determining step in photocatalytic Z-scheme overall water splitting (OWS). It is interesting to find that, with a decreasing ionic radius of the A-site cations, the RTaON2 compounds exhibit continuous blue shift of light absorption and a concomitant reduction in the lifetime of photogenerated carriers, revealing a significant influence of A-site atoms on the light absorption and charge separation processes. On the other hand, the A-site atomic substitution was revealed to significantly modulate the valence band positions as well as surface oxidation kinetics. By employing the Pt-modified RTaON2 as H2-evolving photocatalysts, the activity of photocatalytic Z-scheme OWS for hydrogen production on them is found to be determined by its surface oxidation process instead of light absorption or charge separation. Our results give the first experimental demonstration of the rate-determining step during the photocatalytic Z-scheme OWS processes, as should be instructive for the design and development of other efficient solar-to-chemical energy conversion systems.

A novel 0D/3D Z-Scheme heterojunction ZnS/MIL-88(A) with significantly boosted photocatalytic activity toward tetracycline

Coupling two different photocatalytic materials to construct a heterojunction is a preferable strategy for obtaining the composite photocatalyst with high activity. Herein, a novel 0D/3D Z-scheme heterostructure ZnS/MIL-88(A) was constructed by anchoring 0D ZnS nanoparticles on the surface of the 3D MIL-88(A). The prepared ZnS/MIL-88(A) was characterized by using FT-IR, XRD, SEM, UV–vis and XPS. The photodegradation of tetracycline (TC) was conducted under the irradiation of visible light to evaluate the photocatalytic performance of ZnS/MIL-88(A). The creation of the Z-scheme heterostructure between ZnS and MIL-88(A) enables ZnS/MIL-88(A) to exhibit excellent visible-light absorption ability and dramatically boost separation and transfer of the photo-induced charge carriers. Compared with MIL-88(A), ZnS/MIL-88(A) shows prominently enhanced photocatalytic activity toward tetracycline, achieving a TC degradation rate of 94 %. The highest photodegradation rate constant (0.02083 min−1) of TC by ZnS/MIL-88(A) is 7.77 and 12.33 folds as large as those by MIL-88(A) and ZnS, respectively. After five cycles of reuse, ZnS/MIL-88(A) shows only a slightly decreased TC removal rate, presenting excellent photo-stability. Furthermore, the Z-scheme interfacial charge migration mode and the photocatalytic mechanism of ZnS/MIL-88(A) were discussed according to the band position as well as the identification result of the active species. The radicals ·O2− and ·OH generated in photocatalysis serve as major reactive species to decompose TC. This work provides a new way for designing efficient composite photocatalysts.

Additive engineering for Sb2S3 indoor photovoltaics with efficiency exceeding 17%

Indoor photovoltaics (IPVs) have attracted increasing attention for sustainably powering Internet of Things (IoT) electronics. Sb2S3 is a promising IPV candidate material with a bandgap of ~1.75 eV, which is near the optimal value for indoor energy harvesting. However, the performance of Sb2S3 solar cells is limited by nonradiative recombination, which is dependent on the quality of the absorber films. Additive engineering is an effective strategy to fine tune the properties of solution-processed films. This work shows that the addition of monoethanolamine (MEA) into the precursor solution allows the nucleation and growth of Sb2S3 films to be controlled, enabling the deposition of high-quality Sb2S3 absorbers with reduced grain boundary density, optimized band positions, and increased carrier concentration. Complemented with computations, it is revealed that the incorporation of MEA leads to a more efficient and energetically favorable deposition for enhanced heterogeneous nucleation on the substrate, which increases the grain size and accelerates the deposition rate of Sb2S3 films. Due to suppressed carrier recombination and improved charge-carrier transport in Sb2S3 absorber films, the MEA-modulated Sb2S3 solar cell yields a power conversion efficiency (PCE) of 7.22% under AM1.5 G illumination, and an IPV PCE of 17.55% under 1000 lux white light emitting diode (WLED) illumination, which is the highest yet reported for Sb2S3 IPVs. Furthermore, we construct high performance large-area Sb2S3 IPV minimodules to power IoT wireless sensors, and realize the long-term continuous recording of environmental parameters under WLED illumination in an office. This work highlights the great prospect of Sb2S3 photovoltaics for indoor energy harvesting.

Prediction of soil heavy metal content around mine tailings using multiple methods combined with transformed hyperspectral reflectance data

The extensive accumulation of tailings can potentially cause heavy metal contamination in the surrounding farmland soil. Accurately predicting the spatial distribution of heavy metals in farmland soil is crucial for assessing the potential environmental hazards of tailings.This study focuses on the spatial distribution and the quantitative prediction of heavy metals (chromium (Cr), vanadium (V), and copper (Cu)) in soils surrounding mine tailings using advanced spectral data analysis and multiple prediction models. The original hyperspectral reflectance data were processed using first-order differential (FD), second-order differential (SD), reciprocal logarithmic (LR), and continuum removal (CR) transformations to highlight the positions of characteristic bands. Multiple linear regression (MLR), stepwise linear regression (SLR), partial least squares regression (PLSR), random forest (RF), and back propagation artificial neural network (BP-ANN) models were used to establish inversion models for Cr, V, and Cu based on bands with high correlation coefficients. The performance of the inversion models was evaluated using the coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), and residual predictive deviation (RPD). The results indicate that the raw hyperspectral data from the measured soil exhibit a weak response to heavy metal content in the study area. However, applying FD, SD, and CR transformations significantly enhances the sensitivity of soil spectral data to heavy metal concentrations, facilitating subsequent modeling. Among these, the SD transformation is particularly beneficial for modeling the Cr and Cu elements in the soil. For the V element, the FD transformation yields data that are more suitable for modeling. Regarding the inversion models based on the measured spectral data, the BP-ANN model exhibited the best predictive performance. Specifically, when combined with SD spectral data, the BP-ANN achieved the highest predictive accuracy for Cu content (R² = 0.85, RPD = 2.12). The RF model demonstrated the next best performance, with its optimal inversion model also utilizing SD spectral data for predicting Cu content (R² = 0.76, RPD = 1.90). On the other hand, the MLR model exhibited the poorest performance and is unsuitable for predicting heavy metal content in the region using the measured spectral data. This study highlights the potential of spectral data in environmental monitoring and provides a technical reference for the inversion assessment and regulation of heavy metals in farmlands surrounding tailing sites.

Local Structure and Optical Studies of Mn2+ Doped L-histidine-4- nitrophenolate 4-nitrophenol Single Crystal

Background: The zero-field splitting parameters of Mn2+ doped L-histidine-4- nitrophenolate 4-nitrophenol single crystals are evaluated Methods: The superposition model and perturbation theory are used to obtain zero-field splitting parameters for Mn2+ ion-doped LHPP single crystals. The optical spectra of the system are computed using the crystal field parameters from the superposition model as input into the crystal field analysis program. Results: The evaluated zero field splitting parameters are in good match with the experimental values when local distortion is taken into account. The experimental finding that the Mn2+ ion enters the L-histidine-4-nitrophenolate 4-nitrophenol lattice at the interstitial position is supported by the theoretical result. Conclusion: It is found that the calculated and experimental band positions agree fairly well. Thus, the theoretical study supports the experimental observation.

Anion-Driven Bandgap Tuning of AgIn(SxSe1-x)2 Quantum Dots.

Accurate tuning of the electronic and photophysical properties of quantum dots is required to maximize the light conversion efficiencies in semiconductor-assisted processes. Herein, we report a facile synthetic procedure for AgIn(SxSe1-x)2 quantum dots with S content (x) ranging from 1 to 0. This simple approach allowed us to tune the bandgap (2.6-1.9 eV) and extend the absorption of AgIn(SxSe1-x)2 quantum dots to lower photon energies (near-IR) while maintaining a small QD size (∼5 nm). Ultraviolet spectroscopy studies revealed that the change in the bandgap is modulated by the electronic shifts in both the valence band and the conduction band positions. The negative overall charge of the as-synthesized quantum dots enabled us to make films of quantum dots on mesoscopic TiO2. Excited state studies of the AgIn(SxSe1-x)2 quantum dot films demonstrated a fast charge injection to TiO2, and the electron transfer rate constant was found to be 1.5-3.5 × 1011 s-1. The results of this work present AgIn(SxSe1-x)2 quantum dots synthesized by the one-step method as a potential candidate for designing light-harvesting assemblies.

Photoluminescence and Raman spectroscopy of Ce3+ doped Y3Al5O12 single crystalline films grown onto Y3Al5O12 and Lu3Al5O12 substrates

Raman spectroscopy, high spectral resolution luminescence, and X-ray diffraction techniques were employed to study two Ce3+ doped Y3Al5O12 single crystalline films grown by liquid phase epitaxy method onto Y3Al5O12 and Lu3Al5O12 single crystal substrates. Optical spectra were obtained with a micrometer step along the cross-sections of epitaxial structures, allowing excellent differentiation of the film, the transition layer, and the substrate of each sample. X-ray measurements demonstrate the mismatch between the lattice constants of the Y3Al5O12:Ce3+ film and its Lu3Al5O12 substrate, an effect related to different compositions. Consequently, the film grown onto Lu3Al5O12 exhibits higher residual stresses than its counterpart grown onto Y3Al5O12. This was confirmed by a mutual comparison of the Raman bands positions of the films. The luminescence spectra of both samples consist mainly of cerium 5d-4f emission, the intensity of which allows for additional study of epitaxial cross section and estimation of the size of transition layer.

Optimizing the thermal stability of Tb3+-based phosphor through intervalence charge transfer compensation and charge transfer band edge red-shift

Thermal quenching (TQ) limits the large-scale practical application of most luminescent materials, so the investigation on thermal quenching phenomenon of phosphors has emerged as a prominent research area, garnering significant attention in academic circles. The thermal quenching performance is closely related to the charge transfer band (CTB) and intervalence charge transfer (IVCT) band. Herein, we study the correlation between CTB edge red-shift, IVCT band position and the thermal stability of Tb3+-based lithium tantalate phosphors, aiming to regulate the thermal quenching performance. The results show that totally anomalous thermal quenching (TATQ) was found to exist in LiTaO3:xTb3+ phosphors during the process of temperature rising, and the whole CTB edge absorption showed a red-shift and enhance with increasing temperature. Based on this characteristic phenomenon, under the excitation of CTB edge (270 nm), the phosphor exhibits obvious antithermal quenching. In addition, the existence of the Tb3+-Ta5+ IVCT band can be used as a compensation channel for Tb3+ 5D3 → 5D4 transition, which makes the phosphor produce stronger antithermal quenching performance. Accordingly, the co-regulation of the CTB edge red-shift and IVCT compensation effect was proposed. Modulation of Tb3+ concentration revealed that during thermal activation (λem = 547 nm), LiTaO3:0.005Tb3+ luminescence integral intensity (423 K) reaches 255.6% of the initial intensity, phosphor achieves the most excellent performance. The maximum absolute sensitivity (Sa) and relative sensitivity (Sr) for temperature sensing scheme based on the intensity ratio of excitation spectrum CTB and CTB-IVCT reaches 0.996%@523 K and 0.927%@523 K, respectively. The co-regulation strategy of thermal activation-induced CTB edge red-shift and IVCT compensation channel provides a promising research idea for developing Tb3+-based antithermal quenching luminescent materials.

Construction of g-C3N4-based donor-acceptor conjugated copolymer for photocatalytic selective oxidation of biomass-derived 5-hydroxymethylfurfural under visible light

Donor-acceptor structure porous nanosheets CNSA-x (x denotes the amount of salicylic acid) were prepared by co-thermal condensation polymerization of aromatic compound salicylic acid (SA) and prepolymer melamine. A variety of characterization methods have been used to thoroughly analyze the morphology, structure, optical and electrical features of the synthesized catalysts. It turned out that the introduction of SA promotes the formation of pore structure and an enhanced specific surface area, which resulted in more reactive sites. Moreover, the introduction of SA improves light absorption capacity and effectively adjusts the valence band position. Meanwhile, it also extends the delocalization system, thereby promoting the migration and separation of photogenerated electron-hole pairs. The catalyst exhibited high performance and stability in the photocatalytic oxidation of 5-hydroxymethylfurfural (HMF) under the synergies of these advantages. Additionally, the elucidation of active reaction species and proposed reaction mechanism enriched the understanding of the catalytic process.

Synthesis of CdS QDs/NH2-Nb2O5 via electrostatic self-assembly method for highly efficient photocatalytic removal of NO and synchronous inhibition of NO2

A two-step electrostatic self-assembly method was used to first graft –NH2 groups onto the Nb2O5 followed by loading of CdS QDs onto the NH2-Nb2O5 to obtain CdS/NH2-Nb2O5. The performance of the samples under visible light was evaluated under simulated conditions of 25 °C and varying relative humidity (RHs). The results showed that with the increase of RH, the NO removal efficiency by CdS/NH2-Nb2O5 increased first and then decreased, reaching the maximum NO removal efficiency when RH = 50 %. The selectivity of NO2 on CdS/NH2-Nb2O5 (9.01 %) was significantly lower compared to that of Nb2O5 (24.44 %) and NH2-Nb2O5 (19.72 %). The introduction of –NH2 groups and CdS QDs significantly enhanced visible light absorption and improved the separation efficiency of photogenerated charge carriers. In-situ DRIFTS analysis revealed that Cd2+ served as an additional active site for NO adsorption. Furthermore, CdS had a relatively negative conduction band position, which was conducive to the generation of O2–, further inhibiting the generation of NO2. This work provides a new approach to the design and preparation of catalysts for photocatalytic oxidation of NO.

Enhanced Oxalic Acid Electroreduction Selectivity toward Glyoxylic Acid on Ti3+‐Self‐Doped TiO2 Nanotube Arrays

AbstractElectroreduction of oxalic acid (OX) to glyoxylic acid (GO) is an extremely important and promising application in organic electrosynthesis. Pb cathodes, which exhibits good selectivity, need to be replace due to the severe deactivation and harmful to the environment. Herein, self‐doped titanium dioxide nanotube arrays (H‐TiO2NTs‐2) are synthesized as an alternative cathode for OX electroreduction to GO. Benefiting from two‐step anodization, the synthesized nanotube arrays are highly ordered with oriented openings. The ordered structure promotes the mass transfer of both OX and GO to ensure efficiently providing OX reactants for the diffusion‐controlled OX electroreduction and removal of GO products from the electrode to prevent the over‐reduction to glycolic acid. Additionally, the electroreduction treatment introduces more Ti3+ active sites and modulates the conduction band position of H‐TiO2NTs‐2, thereby enhancing the reduction driving force. Owing to the unique structural advantages, the Faraday efficiency of generating GO from OX reaches up to 81.3 % in an oxalic acid saturated electrolyte at 20 °C with a current density of 1500 A m−2. This designed H‐TiO2NTs‐2 holds broad application prospects in OX electroreduction.

The synthesis of Bi2MoO6 with metallic and nonmetallic vacancies for degradation of LVF in visible light

Defect engineering advantages include regulating the band structure of photocatalytic materials, inhibiting the recombination of photoelectron-hole pairs, and promoting the conversion of photogenerated electrons into active radicals. In this paper, bismuth molybdate (Bi2MoO6) photocatalysts with double vacancies (VBi-O-BMO) were prepared by solvothermal and ionic eutectic solvent methods. EPR, TEM, and XPS results confirmed the successful construction of oxygen and bismuth vacancies on Bi2MoO6. The photocatalytic performance of the prepared catalysts was investigated by photodegradation of levofloxacin hydrochloride (LVF) under visible light. The double vacancies markedly enhanced the photocatalytic properties of Bi2MoO6, with the photodegradation rate of VBi-O-BMO reaching 88.36 % for 40 mg/L LVF within 60 min. Kinetic studies have demonstrated that the reaction rate constant of VBi-O-BMO can reach 0.0351 min−1, which is 3.2 times higher than that of bulk-BMO. This can be attributed to the favorable synergistic effect of oxygen and bismuth double vacancies. VO not only captures oxygen and electrons, facilitating the generation of superoxide radicals (O2−), but also elevates the conduction band position and boosts the reduction capability of Bi2MoO6. VBi not only captures photogenerated holes (h+) to directly impact LVF degradation, but also promotes interfacial charge transfer and inhibits the recombination of electron-hole pairs. Furthermore, the intermediates and degradation pathways of LVF photodegradation were surmised based on the LC-MS analysis. The reaction mechanism of LVF photodegradation by VBi-O-BMO was elucidated through the application of the free radical pathway. This study demonstrates a methodology for the creation of double vacancies in catalysts and the significant potential of VBi-O-BMO for the remediation of antibiotic residues in water under visible light.

The significant role of Z-scheme band alignment at the heterojunction for the enhanced photocatalytic H2 production in TiO2/BiNbO4/rGO nanocomposite

An efficient ternary TiO2/BiNbO4/rGO nanocomposite was prepared by a simple wet impregnation process. PXRD confirmed the tetragonal and orthorhombic crystalline natures of titanium dioxide (TiO2) and bismuth niobate (BiNbO4) respectively. The loading of BiNbO4 and reduced graphene oxide (rGO) shifted the light absorption of TiO2 to a longer wavelength from 400 to 430 nm. The suitable conduction band position of BiNbO4 facilitated a favourable band alignment to suppress the electron/hole (e−/h+) recombination in TiO2 via the Z scheme mechanism at the heterojunction. The excited electrons at the CB of TiO2 were easily transported via the fast electron accepting and conducting rGO matrix for the surface redox reactions with the improved charge transfer efficiency, which was confirmed by EIS and PL studies respectively. BiNbO4 and rGO synergistically improved the specific surface area and solar light absorption. EPR analysis confirmed the presence of increased oxygen vacancies at the heterojunction. Hence, the ternary TiO2/BiNbO4/rGO nanocomposite demonstrated an enhanced hydrogen evolution (8910 μ mol h−1 gcat−1) than bare TiO2 (4820 μ mol h−1 gcat−1), bare BiNbO4 (950 μ mol h−1 gcat−1) and TiO2/BiNbO4 (6730 μ mol h−1 gcat−1) under direct solar light. The optimum of 1 wt % BiNbO4 and rGO loaded TiO2 nanocomposite produced twice the H2 production than the bare TiO2. This also further confirms that rGO played a major role during the photocatalytic process by highlighting the potential of metal oxides combined with carbon material as an efficient photocatalyst which prominently enhances the H2 evolution.

Sulfur vacancies-engineered CaIn2S4 microspheres for enhanced photocatalytic organic pollutant and antibiotic removal

It is an interesting research topic on construction of defect- rich structures to enhance the performance of photocatalysts. In this study, CaIn2S4 photocatalyst containing sulfur vacancy was successfully synthesized using a straightforward solvothermal method. The sulfur vacancy concentration in CaIn2S4 was controlled by adjusting the amount of thioacetamide added during preparation. Among the prepared samples, CaIn2S4-10 sample with excellent photocatalytic performance exhibits superior degradation efficiency (98.2 %) within 50 minutes when the initial methyl orange (MO) concentration was 20 mg/L. Similarly, it shows the highest degradation performance (94 %) against the antibiotic tetracycline hydrochloride (TCH) (20 mg/L). The phase structure, surface element composition, optical properties and other characteristics of the prepared samples were systematically investigated. The findings demonstrate that the CaIn2S4-10 sample exhibits a decreased band gap width and a negatively shifted conduction band position, which enhances its reduction ability and improves its photocatalytic activity.

Analysis of a thermal correction method for infrared spectroscopy : preparation for the future observations of the Martian moons Phobos and Deimos with the MIRS instrument

Abstract The MIRS infrared spectrometer is part of the scientific payload of JAXA’s Martian Moon eXploration (MMX) mission. From the reflected sunlight by the planetary surfaces, MIRS will provide information on the Mars atmosphere and the mineralogy and chemistry of its moons. Spectra carried out by the instrument (0.9-3.6 µm) include the thermal emission from the surface, which needs to be modeled and removed to extract the compositional information. In this study, to find an efficient and rapid way to thermally correct infrared data, we developed a simple thermal emission correction based on black body fits, and quantify its relative error. To test the method, we generated synthetic spectra of Phobos by using a thermophysical model. We found that the method can produce reflectance spectra with only a few percent errors, although some under-correction of the thermal contribution is observed. Compositional information may still be retrieved through the position of absorption bands, despite the thermal emission correction can leave some uncertainties in its strength. We conclude that the method could be used for a first and quick analysis for interpretation of the MIRS data. We also applied our thermal correction methodology to real CRISM observations of Phobos. The method looks reliable with a satisfactory removal of the thermal contribution, confirms the presence of an absorption band centered around 2.8 µm, and reveals an apparent absorption at 3.2 µm. However, we are not able to confirm the reality of the 3.2 µm band at this stage, because of the presence of an artifact in CRISM data.

Biogenic fabrication of NiO-ZnO-CaO ternary nanocomposite using Azadirachta Indica (Neem) leaves extract with proficient photocatalytic degradation of rhodamine B dye

In the current study, a ternary nanocomposite (NiO–ZnO–CaO) was successfully synthesized through the co-precipitation method using Azadirachta Indica (neem) leaves extract as green approach. The characterization of prepared nanocomposite was conducted using FT-IR, XRD, SEM and EDS to determine the metal oxides absorption bands, structural properties, elemental composition, and surface morphology of the nanocomposite. FT-IR analysis revealed characteristic vibrational peaks at 621, 684, and 721 cm−1, corresponding to Ni-O, Zn-O, and Ca-O bond vibrations, respectively. XRD patterns showed distinct diffraction peaks, indicative of the hexagonal structure of ZnO and the cubic structures of NiO and CaO. EDS analysis confirmed the presence of calcium, nickel, zinc, and oxygen with weight percentages of 9.2%, 14.4%, 15.1%, and 20.9%, respectively. SEM images displayed an irregular cube like morphology with noticeable clustering within the nanocomposite. The ternary nanocomposite was employed as photocatalyst and exhibited degradation efficiency (97%) against rhodamine B dye under 180 min of irradiation time. The kinetic studies of dye on the photocatalyst surface were accurately explained by a first-order kinetics model, with all R2 > 95, signifying a strong correlation between time and dye concentration. The potocatalytic degradation mechanism of ternary nanocomposite was proposed based on band positions of of NiO, ZnO and CaO forming double type II heterojunction. Furthermore, species trapping experiments employing different scavengers were carried out, revealing the active participation of OH● and O2●─ radicals in the degradation mechanism.

Investigating Hydrated Silica in Syrtis Major, Mars: Implications for the Longevity of Water–Rock Interaction

AbstractWe use the crystallinity of hydrated silica, represented by the 1.4 μm absorption position in orbiter spectroscopic data, as a proxy for the longevity of water–rock interaction in the Syrtis Major region. Geological maps and crater size–frequency distribution analyses are employed to contextualize mineral detections and estimate surface ages. Hydrated silica is detected within two distinct geological units: a younger “volcanic terrain” (vt) unit (∼2.4 Ga) and an older “highland terrain” (ht) unit (3.5–3.7 Ga). Hydrated silica in the vt unit typically has a band position <1.41 μm, consistent with amorphous opal‐A, suggesting these younger terrains have experienced limited interaction with water. In contrast, hydrated silica in the older highlands typically has a band position >1.41 μm, indicating opal‐CT, suggesting that these deposits have had more time to interact with water, while also producing accessory minerals such as kaolinite and Fe/Mg phyllosilicates.

N-Aromatic Complexation in Tetraphenyl Porphyrin Iron (III)-Pyridine: Evidence of Spin-Flip via Gas-Phase Electronic Spectroscopy.

There is growing interest in the electronic properties of metalloporphyrins especially in relation to their interactions with other molecular species in their local environment. Here, UV-VIS laser photodissociation spectroscopy in vacuo has been applied to an iron-centred metalloporphyrin (FeTPP+) and its N-aromatic adduct with pyridine (py) to determine the electronic effect of complexation. Both the metalloporphyrin (FeTPP+) and pyridine adduct (FeTPP+⋅py) absorb strongly across the spectral region studied (652-302 nm: 1.91-4.10 eV). Notably, a large blue shift was observed for the dominant Soret band (41 nm) upon complexation (0.47 ± 0.02 eV), indicative of strong pyridine binding. Significant differences in the profiles (i.e. number and position of bands) of the electronic spectra are evident comparing FeTPP+ and FeTPP+⋅py. Time-dependent density functional theory calculations were used to assign the spectra, revealing that the FeIII spin-state flips from S = 3/2 to S = 5/2 upon complexation with pyridine. For FeTPP+, all bright spectral transitions are found to be π-π* in character, with electron density variously distributed across the porphyrin and/or its phenyl substituents. Similar electronic excitations are observed for FeTPP+⋅py, with an additional bright transition which involves charge transfer from the porphyrin to the pyridine moiety.

Nitrogen-doped ZnIn2S4 and TPA multi-dimensional synergistically enhance photocatalytic hydrogen production

To alleviate the environmental pollution and energy crisis caused by the excessive use of fossil fuels, photocatalytic water splitting to produce hydrogen is an important way to solve energy and environmental problems. Here, Nitrogen-doped ZnIn2S4 (N-ZIS) composite tungsten-based polyoxometalate (TPA) composites (denoted as N-ZIS/TPA) were synthesized by a one-step solvothermal method. The introduction of N3– instead of S2− in ZIS changes the internal electron arrangement of ZIS, improves the electronegativity of ZIS, and is conducive to the surface adsorption of positively charged H*. At the same time, the impurity energy level is generated at the valence band position, which narrows the band gap and broadens the light absorption range, thereby promoting photocatalytic hydrogen production. After compounding, due to the adjustable redox properties of TPA itself, the internal W6+ part is reduced to W4+, resulting in the coexistence of W6+ and W4+ in the composite material, which fully verifies the flow of interface electrons from N-ZIS to TPA. The close contact between N-ZIS and TPA and the built-in electric field’s driving force help achieve efficient interfacial charge transfer. At the same time, W6+/W4+ redox pairs were introduced to accelerate the separation of photogenerated electrons and holes. The photocatalytic hydrogen production rate of the best sample 1N-ZIS/TPA-15 is as high as 17345.53 μmol·g−1·h−1, which is 2.92 times that of N-ZIS (5940.08 μmol·g−1·h−1) and 8.03 times that of ZIS (2159.22 μmol·g−1·h−1). This study explores the design and construction of efficient s-type heterojunctions by adjusting the energy band position of ZnIn2S4 as a new strategy in the field of photocatalytic hydrogen production.

Multimode optical thermometry using CaWO4 emission band

Optical thermometry has emerged as a promising technique for remote temperature sensing in plenty of applications, where traditional contact methods are useless. To date, many sensing strategies have been developed and realized, but most of them are based on monitoring of the single temperature dependent parameter. Here, we report simple dual-center materials (Eu3+ and Sm3+-doped CaWO4) that provide multimode optical thermometry. In addition to standard ratiometric approach based on intensity ratio between host and lanthanide emission bands, spectral position and bandwidth of CaWO4 emission band were successfully utilized as temperature sensitive parameters for the first time. It was shown that multimode sensing leads to broadening of temperature working range and enhances reliability of thermal sensing. The best thermometric characteristics were achieved for CaWO4:Sm3+ sample: Sr = 1.29 % K−1@273–673 K and δT = 0.15 K.