Effect Of Sulfur Doping Research Articles

Sulfur-doped carbon dots and g-C3N4 composite with thermally activated delayed fluorescence for white-light illumination and anticounterfeiting

Long-lived afterglow materials have attracted considerable interest in the fields of information security and illumination. Herein, a novel carbon dot (CD)-based thermally activated delayed fluorescence (TADF) material was synthesized by embedding sulfur-doped CDs (SCDs) into a graphitic carbon nitride matrix. The formation of covalent bonds between the matrix and SCDs enhances the stabilization of the triplet state in the composite, effectively suppressing nonradiative transitions. This stabilization, coupled with the effects of sulfur doping and covalent bonding, reduces the singlet–triplet splitting energy in the composite, thereby facilitating reverse intersystem crossing and resulting in TADF emission. This composite material has been successfully employed in the development of three types of CD-based white light–emitting diodes (WLEDs) excited by blue light. These WLEDs exhibit color temperatures of 7641, 5590, and 3215 K, with CIE coordinates of (0.30, 0.29), (0.33, 0.30), and (0.42, 0.40), respectively. The corresponding values of the color rendering index are recorded as 81.86, 90.13, and 75.07. In addition, this research provides a brief demonstration of the potential of the composite in information encryption and visible-light encryption applications. Furthermore, this study contributes to the advancement of CD utilization in the WLED field, promoting the development of next-generation CD-based WLEDs with exceptional properties.

MoO3 with the Synergistic Effect of Sulfur Doping and Oxygen Vacancies: The Influence of S Doping on the Structure, Morphology, and Optoelectronic Properties.

Molybdenum trioxide (MoO3) is an attractive semiconductor. Thus, bandgap engineering toward photoelectronic applications is appealing yet not well studied. Here, we report the incorporation of sulfur atoms into MoO3, using sulfur powder as a source of sulfur, via a self-developed hydrothermal synthesis approach. The formation of Mo-S bonds in the MoO3 material with the synergistic effect of sulfur doping and oxygen vacancies (designated as S-MoO3-x) is confirmed using Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). The bandgap is tuned from 2.68 eV to 2.57 eV upon sulfur doping, as confirmed by UV-VIS DRS spectra. Some MoS2 phase is identified with sulfur doping by referring to the photoluminescence (PL) spectra and electrochemical impedance spectroscopy (EIS), allowing significantly improved charge carrier separation and electron transfer efficiency. Therefore, the as-prepared S-MoO3-x delivers a sensitive photocurrent response and splendid cycling stability. This study on the synergistic effect of sulfur doping and oxygen vacancies provides key insights into the impact of doping strategies on MoO3 performance, paving new pathways for its optimization and development in relevant fields.

Effect of sulfur doping on the photocatalytic performance of sputtered BiVO4 thin films

BiVO4 thin films doped with various concentrations of sulfur were fabricated using RF sputtering followed by post-deposition sulfurization. The incorporation of sulfur in the samples was calculated to be approximately 8–11 at% from the S2s peak in their X-ray photoelectron spectra. The optical bandgap of sulfur-doped BiVO4 was generally smaller than that of the undoped sample. BiVO4 films doped with ∼8 at% sulfur showed the highest photoelectrochemical performance compared to the undoped sample. Almost similar minority-carrier lifetimes in undoped and low sulfur-doped BiVO4, measured by time resolve photoluminescence, suggest that the crystal qualities in terms of the recombination properties are roughly the same for both cases. Thus, although further investigation may be necessary, the improved photocurrent in 8 at% sulfur-doped BiVO4 in our study can roughly be attributed to the decrease in the bandgap, which facilitates more photoexcited carriers to contribute to the photoelectrochemical reaction. A further increase in sulfur doping above 10 at% distorted the BiVO4 local crystal structure, inducing defects, thus resulting in a lower photocurrent.

Doping carbon electrodes with sulfur achieves reversible sodium ion storage

We present a combination of experiments and theory to study the effect of sulfur doping in hard carbons anodes for sodium-ion batteries. Hard carbons are synthesised through a two step process: hydrothermal carbonisation followed by pyrolysis of a biomass-derived carbon precursor. Subsequent sulfur doping is introduced via chemical-vapour deposition. The resulting sulfur-doped hard carbon shows enhanced sodium storage capacity with respect to the pristine material, with significantly improved cycling reversibility. Atomistic first principles simulations give insight into this behaviour, revealing that sulfur chemisorbed onto the hard carbon increases the sodium adsorption energies and facilitates sodium desorption. This mechanism would increase reversible Na storage, confirming our experimental observations and opening a pathway towards more efficient Na-ion batteries.

Bandgap Reduction and Enhanced Photoelectrochemical Water Electrolysis of Sulfur-doped CuBi2O4 Photocathode

As interest in hydrogen energy grows, eco-friendly methods of producing hydrogen are being explored. CuBi2O4 is one of the p-type semiconductor cathode materials that can be used for photoelectrochemical hydrogen production via environment-friendly water electrolysis. CuBi2O4 has a bandgap of 1.5 – 1.8 eV which allows it to photogenerate electrons and holes from the absorption of visible light. This study investigated the effect of sulfur doping on the bandgap and photoelectrochemical water reduction properties of CuBi2O4. Sulfur-doped CuBi2O4 thin films were electrochemically synthesized using a nitrate-based precursor solution with thiourea. This was followed by two-step annealing in an Ar atmosphere, which effectively prevented the oxidation of sulfur. Sulfur doping up to 0.1 at% led to the expansion of the lattice volume of the CuBi2O4. The bandgap was reduced from 1.9 eV to 1.5 eV with increasing doping concentration, which resulted in the enhancement of photoelectrochemical current density by ~240%. X-ray photoelectron spectroscopy showed that sulfur-doping reduced oxygen vacancies with increasing doping concentration, confirming that the enhanced photoelectrochemical properties resulted from the reduction in bandgap, not from any extrinsic factor such as oxygen vacancies. Further studies of sulfur-doped CuBi2O4 to improve surface coverage are expected to lead to a more promising photoelectrochemical cathode material.

硫掺杂对析氧反应催化剂表面重构的影响

硫掺杂对析氧反应催化剂表面重构的影响

Electronic structures and optical spectra of KDP crystals with Sp doping defects: a first-principles study.

In order to further clarify the effect of sulfur doping on the laser damage threshold of potassium dihydrogen phosphate (KDP), the properties of sulfur substituting for phosphorus doping defects (SP) in KDP crystals with paraelectric (PE) and ferroelectric (PE) phases are studied in this article. More accurate defect transition levels were obtained by band edge correction, and the band edge corrected values were 1.28 eV and 1.88 eV for the PE and FE phases, respectively. The defect formation energies with four different defect charges (0, +1, +2, and-1) were obtained using the finite size correction scheme. The stable defect charge states were (+2 charge state) (+1 charge state) and (-1 charge state) in turn when the Fermi level moved from the valence band maximum (VBM) to the conduction band minimum (CBM). Moreover, by considering the electron-phonon coupling, the optical absorption and emission spectra were obtained. The absorption peak for the state of the PE phase at 4.63 eV was close to the experimental value. We predicted that the absorption peak at 4.50 eV belongs to the state with the FE phase. The emission peaks at 0.10 eV and 1.36 eV were related to the PE and FE phases, accordingly. The absorption may affect the application of S-KDP crystals and reduce the laser damage threshold.

Effect of sulfur doping of zinc-imidazole coordination polymer (ZnIm CP) as a novel photocatalyst for degradation of ionic dyes

Zinc-Imidazole coordination polymer (ZnImCP) was simply synthesized hydrothermally at relatively low temperature (70 °C) from zinc acetate and imidazole. ZnImCP was treated by sulfide solution to produce sulfur-doped samples (S-ZnImCPs). Structures of the synthesized ZnImCP and S-ZnImCPs were characterized through FTIR, PXRD, and, Raman, SEM/EDX, N2-BET, UV–VIS DRS, and pHpzc analyses. The photocatalytic performances of pristine CP and sulfur modified CPs under visible and ultra-violet irradiations for degrading the cationic methylene blue (MB) and the anionic methyl orange (MO) were investigated considering different initial pH values 4, 7 and 10. Under visible light, the results indicate that these CPs display considerable photocatalytic degradation towards the cationic MB for the initial pH 4 and 7 where degradation increases with sulfur content. While under ultra-violet, results indicate considerable photocatalytic degradation towards both dyes for the initial pH 7 and 10 where degradation increases with sulfur content which indicates the gainful of non-metal dopping. The buffering nature of CPs and the type of radiation considering determined band-gap values effectively influence the degradation mechanisms.

Mesoporous sulfur-modified metal oxide cathodes for efficient electro-Fenton systems

Development of cathode materials with high activity, stability, and wide operating pH range is crucial for electro-Fenton reactions. Herein, mesoporous sulfur-modified metal oxides were coated onto stainless steel meshes and applied as a cathode to promote in-situ generation of H2O2 for electro-Fenton processes. Different mesoporous metal oxides with and without sulfur-modification were synthesized using Fe, Ni, and Zn precursors to investigate the effect of sulfur doping. Among them, sulfur doped Fe2O3 showed the best electrocatalytic performance, and it was attributed to several factors such as large specific surface area, high-efficiency oxygen reduction reaction activity, and enhanced electron/charge transfer. The effect of operational parameters such as applied voltage, catalyst dosage, initial pH, initial concentration of phenol, and electrolyte concentration on the catalytic performance was investigated in terms of degradation efficiencies and rate constants. The results indicate that for high concentration 100 ppm phenol solution, 78% removal efficiency with a rate constant of 0.186 h−1 was achieved with sulfur-doped Fe2O3 on stainless steel mesh electrode under optimal conditions in 8 h. This cathode worked effectively in a wide pH range (3–10) due to its pH self-control ability and exhibited superior stability and reusability with insignificant deterioration in the catalytic activity. This study offers an alternative approach to fabricate electrocatalysts with low-cost sulfur-doped metal oxides for electro-Fenton systems.

Sulfur-doped NiCo carbonate hydroxide with surface sulfate groups for highly enhanced electro-oxidation of urea

NiCo-based hydroxides are promising catalysts for urea oxidation reaction. To further enhance their catalytic performance, the combined effect of nonmetal heteroatom doping and surface functional groups on their catalytic behaviors deserves to be evaluated. Herein, as a proof of concept, both the sulfur-doped NiCo(OH)2CO3 with surface sulfate groups (SS-NiCo) and the surface-sulfated NiCo(OH)2CO3 (S-NiCo) are synthesized by hydrothermal method. The effect of sulfur doping and surface sulfate treatment on the morphology, crystal structure, electronic structure and electrochemical properties is comprehensively studied. It is found that both the incorporation of sulfur into the crystal structure and the introduction of surface sulfate groups can tune the electronic structure and thus promotes the intrinsic activity of the NiCo(OH)2CO3. Additionally, the surface sulfate groups can effectively reduce the series resistance and thus enhance the charge transfer/reaction kinetics. The optimized SS-NiCo catalyst delivers a current density of 100 mA cm−2 at 1.34 V vs RHE, which is much smaller than those of the S-NiCo (1.38 V) and the pristine NiCo(OH)2CO3 (1.43 V). In addition, the SS-NiCo catalyst shows good performance in the urea-assisted water electrolysis for hydrogen production.

Unraveling the effect of sulfur doping into electronic and optical performance of monoclinic hafnium dioxide (m-HfO2: S): an (DFT + U) insights report

Unraveling the effect of sulfur doping into electronic and optical performance of monoclinic hafnium dioxide (m-HfO2: S): an (DFT + U) insights report

Effects of Sulfur Doping and Temperature on the Energy Bandgap of ZnO Nanoparticles and Their Antibacterial Activities.

Metal oxide nanoparticles (MO-NPs) are presently an area of intense scientific research, attributable to their wide variety of potential applications in biomedical, optical, and electronic fields. MO-NPs such as zinc oxide nanoparticles (ZnO-NPs) and others have a very high surface-area-to-volume ratio and are excellent catalysts. MO-NPs could also cause unexpected effects in living cells because their sizes are similar to important biological molecules, or parts of them, or because they could pass through barriers that block the passage of larger particles. However, undoped MO-NPs like ZnO-NPs are chemically pure, have a higher optical bandgap energy, exhibit electron–hole recombination, lack visible light absorption, and have poor antibacterial activities. To overcome these drawbacks and further outspread the use of ZnO-NPs in nanomedicine, doping seems to represent a promising solution. In this paper, the effects of temperature and sulfur doping concentration on the bandgap energy of ZnO nanoparticles are investigated. Characterizations of the synthesized ZnO-NPs using zinc acetate dihydrate as a precursor by a sol–gel method were done by using X-ray diffraction, ultraviolet–visible spectroscopy, and Fourier transform infrared spectroscopy. A comparative study was carried out to investigate the antibacterial activity of ZnO nanoparticles prepared at different temperatures and different concentrations of sulfur-doped ZnO nanoparticles against Staphylococcus aureus bacteria. Experimental results showed that the bandgap energy decreased from 3.34 to 3.27 eV and from 3.06 to 2.98 eV with increasing temperature and doping concentration. The antibacterial activity of doped ZnO nanoparticles was also tested and was found to be much better than that of bare ZnO nanoparticles.

Uncovering sulfur doping effect in MnO2 nanosheets as an efficient cathode for aqueous zinc ion battery

Manganese-based oxides are considered potential cathode materials for rechargeable aqueous zinc ion batteries (RAZIBs). However, structural instability and sluggish reaction kinetics are major limitations restricting their available capacity and cycle stability. Herein, sulfur doped MnO2 (S-MnO2) nanosheets is proposed as a high performance cathode for Zn-ion batteries, featuring large discharge capacity, high rate performance and long cycle life. Electrochemical measurements show a specific discharge capacity of 324 mAh g−1 at a current density of 200 mA g−1 and 205 mAh g−1 at a current density of 2000 mA g−1, which is 1.1 and 5.8 folds higher than that of pristine MnO2. The ex-situ X ray diffraction/absorption, electrochemical analysis and theoretical studies reveal that the doped sulfur atoms in oxygen sites with lower electronegativity can improve intrinsic electronic conductivity of MnO2 and weaken the electrostatic interactions with multivalent Zn2+cations, thus accelerating reaction kinetics. Moreover, sulfur doping induced amorphous surface with rich oxygen defects contributing to extra Zn storage sites with pseudocapacitve behavior. This study shines a new light on the anionic doping strategy in metal oxides for Zn ions storage and can be expanded to other cathode materials design for energy storage applications.

Bifunctional Catalyst Derived from Sulfur-Doped VMoOx Nanolayer Shelled Co Nanosheets for Efficient Water Splitting

A novel sulfur-doped vanadium-molybdenum oxide nanolayer shelling over two-dimensional cobalt nanosheets (2D Co@S-VMoOx NSs) was synthesized via a facile approach. The formation of such a unique 2D core@shell structure together with unusual sulfur doping effect increased the electrochemically active surface area and provided excellent electric conductivity, thereby boosting the activities for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). As a result, only low overpotentials of 73 and 274 mV were required to achieve a current response of 10 mA cm-2 toward HER and OER, respectively. Using the 2D Co@S-VMoOx NSs on nickel foam as both cathode and anode electrode, the fabricated electrolyzer showed superior performance with a small cell voltage of 1.55 V at 10 mA cm-2 and excellent stability. These results suggested that the 2D Co@S-VMoOx NSs material might be a potential bifunctional catalyst for green hydrogen production via electrochemical water splitting.

Sulfur Doping versus Hierarchical Pore Structure: The Dominating Effect on the Fe–N–C Site Density, Activity, and Selectivity in Oxygen Reduction Reaction Electrocatalysis

Nitrogen doping has been always regarded as one of the major factors responsible for the increased catalytic activity of Fe–N–C catalysts in the oxygen reduction reaction, and recently, sulfur has emerged as a co-doping element capable of increasing the catalytic activity even more because of electronic effects, which modify the d-band center of the Fe–N–C catalysts or because of its capability to increase the Fe–Nx site density (SD). Herein, we investigate in detail the effect of sulfur doping of carbon support on the Fe–Nx site formation and on the textural properties (micro- and mesopore surface area and volume) in the resulting Fe–N–C catalysts. The Fe–N–C catalysts were prepared from mesoporous carbon with tunable sulfur doping (0–16 wt %), which was achieved by the modulation of the relative amount of sucrose/dibenzothiophene precursors. The carbon with the highest sulfur content was also activated through steam treatment at 800 °C for different durations, which allowed us to modulate the carbon pore volume and surface area (1296–1726 m2 g–1). The resulting catalysts were tested in O2-saturated 0.5 M H2SO4 electrolyte, and the site density (SD) was determined using the NO-stripping technique. Here, we demonstrate that sulfur doping has a porogenic effect increasing the microporosity of the carbon support, and it also facilitates the nitrogen fixation on the carbon support as well as the formation of Fe–Nx sites. It was found that the Fe–N–C catalytic activity [E1/2 ranges between 0.609 and 0.731 V vs reversible hydrogen electrode (RHE)] does not directly depend on sulfur content, but rather on the microporous surface and therefore any electronic effect appears not to be determinant as confirmed by X-ray photoemission spectroscopy (XPS). The graph reporting Fe–Nx SD versus sulfur content assumes a volcano-like shape, where the maximum value is obtained for a sulfur/iron ratio close to 18, i.e., a too high or too low sulfur doping has a detrimental effect on Fe–Nx formation. However, it was highlighted that the increase of Fe–Nx SD is a necessary but not sufficient condition for increasing the catalytic activity of the material, unless the textural properties are also optimized, i.e., there must be an optimized hierarchical porosity that facilitates the mass transport to the active sites.

Chalcogenide Dopant-Induced Lattice Expansion in Cobalt Vanadium Oxide Nanosheets for Enhanced Supercapacitor Performance

We explore the effect of sulfur doping in Co3V2O8 on the electrochemical performance of supercapacitors in terms of enhanced lattice spacing, electrochemical surface area (ECSA), electronic conductivity, and density of states. The sulfur-doped Co3V2O8 (S-Co3V2O8) nanosheets were grown in situ as a binder-free synthesis on nickel foam by the hydrothermal method. The electrochemical performance was analyzed in an aqueous alkaline electrolyte where the S-Co3V2O8 electrode exhibited a specific capacity of 410 mAh/g at 2 A/g with enhanced rate capability and capacity retention of 94.2% at 5 A/g specific currents after 4000 cycles, whereas the undoped Co3V2O8 electrode exhibited a specific capacity of 337.8 mAh/g at 2 A/g. The high capacity of S-Co3V2O8 is attributed to the enhanced ECSA (by ∼45%) and improved electrical conductivity (by ∼22%) upon doping with sulfur. Furthermore, these results corroborated with density functional theory results. The calculations suggest an increase in lattice parameters and the introduction of additional density of states near the valence-band edge due to the doping of sulfur, resulting in a decrease in charge-transfer resistance. An asymmetric supercapacitor was fabricated, using S-Co3V2O8 nanosheets as the cathode and activated carbon as the anode, which shows a high specific capacity (or capacitance) value of 485 mAh/g, an energy density of 36.4 W h/kg, and a power density of 740 W/kg at 2 A/g with 98.4% specific capacity retention after 4000 consecutive charge–discharge cycles. Furthermore, the analysis was extended in a nonaqueous medium for Li-ion storage where S-Co3V2O8 exhibits a specific capacity of 994 mA h/g and a specific energy density of 828 W h/kg at 1 A/g making it a promising candidate for future high-energy storage systems. The concept of doping is extended to other chalcogenide (e.g., selenium) doping (Se-Co3V2O8), which also shows improved device performance and makes this a versatile approach for high-performance devices.

Sulfur-doped triazine-conjugated microporous polymers for achieving the robust visible-light-driven hydrogen evolution

Conjugated microporous polymers (CMPs) have emerged in recent years as prospective materials for photocatalytic hydrogen production. The most common synthesis method for triazine is ionothermal synthesis at high temperatures (>350 °C), which also requires a large amount of ZnCl2, in which CF3SO3H-catalyzed method was invented to synthesize triphenyl triazine at room temperature. Herein, we reported the synthesis and characterization of two triazine-based conjugated micropores polymers photocatalysts at low temperature via polymerization of triphenyl triazine (TPT) with TPT and pyrene (Py). The TPT-based CMPs show excellent photocatalytic performance and a hydrogen evolution rate of 108.1 and 116.5 µmol h−1 under visible light for Py-TPT-CMP and TPT-TPT-CMP, respectively, but with low photocatalytic stability. In general, organic polymers add a small amount of platinum to efficiently produce H2 with high photocatalyst stability. To provide a new opportunity to overcome the low stability, a sulfur doping method using readily available sulfur (S8) has been proposed which was used here for the first time to achieve a highly photocatalyst stability development without the use of noble metals. The as-synthesized polymers after sulfur doped exhibit an enhanced photocatalytic stability which can keep the hydrogen production for a long period of time without loss in the photocatalytic efficiency. Furthermore, our triazine-based CMP materials have interest apparent quantum yield (AQY) values particularly for Py-TPT-CMP and TPT-TPT-CMP which exhibit AQY of 41.9 and 32.38%, respectively at 420 nm, these values are compatible with the highest AQY of organic photocatalysts up to date. This study makes a significant contribution forward for photocatalysis with polymers because it provides excellent HERs and AQYs for the sulfur-doped triazine-based CMPs with high thermal, chemical, and photo stabilities. As well as, this work could give researchers in the field a different opinion on the effect of sulfur-doping.

Effects of Sulfur Doping on Generalized Stacking Fault Energy of Indium Phosphide

Indium phosphide (InP) is one of the most important optoelectronic materials, while stacking faults (SFs), as planar defects, are usually inevitable during the growth of InP possibly due to the low SF energy. As n-type dopants, sulfur atoms are generally used to change the electron concentration of InP-based devices, whereas the effects of sulfur doping on SFs of InP have not been studied in detail. In this work, the generalized stacking fault (GSF) energies of pure and sulfur-doped InP have been investigated by gliding the layers successively in the framework of first principle calculations. The results reveal the stable SF energies of InP are low and extrinsic stacking fault could be seen as the twin embryos in pure InP. Sulfur doping could decrease the GSF energies dramatically due to the lower charge density along In-S bonds than along In-P bonds, which consequently enhances the ability of twinning locally. The preferential segregation of sulfur atoms on SFs or twin boundaries could further promote the thickening of microtwin in InP. These results are of great significance to the understanding of the formation of planar defects in n-type doped III–V compounds.

Conceptual DFT and TDDFT study on electronic structure and reactivity of pure and sulfur doped (CrO3)n (n = 1–10) clusters

Different isomers of (CrO3)n (n = 1–10) cluster units have been investigated using Density functional approach. Their stability and reactivity has been analyzed by plotting chemical potential and HOMO-LUMO gap as a function of cluster size. The CrO3, (CrO3)6 and (CrO3)9 are identified as the most reactive species. Reactivity of each atomic site in the cluster has been interpreted using local reactivity descriptors called Fukui Function plots. The clusters have been doped with sulfur by adding it as substitutional impurity, effect of sulfur doping has been understood by analyzing excitation energies and absorption wavelengths using time dependent-DFT(TDDFT) at CAM-B3LYP level of theory.

Photoluminescence-tunable carbon dots from synergy effect of sulfur doping and water engineering

Multiple-color-emissive carbon dots (CDs) is one of the hotspots due to its potential in multi-fields. However, the exploring of efficient synthetic strategies and emission mechanisms still remain challenging. Herein, we report a facile solvothermal route to prepare CDs with tunable photoluminescence (PL) from green to red via a novel PL-tuning strategy of sulfur doping and water engineering. By detailed characterizations and comparison, it is demonstrated that the S doping can significantly increase the content of graphitic nitrogen, resulting in the fluorescence shifting from green to yellow; on the other hand, water engineering is able to yield carboxyl group and enhance surface oxidation degree, which can further facilitate the PL shifting from yellow to red. Owning to multicolor emissions and S doping, the prepared PL-tunable CDs present versatility in various applications including fluorescent films, light-emitting diodes (LED), bioimaging probe and highly sensitive Fe3+ detector.