Indium Sulfide Research Articles

Promotion of Photocatalytic Lignin Models Cβ–O Bond Cleavage by Cr-Doped Zinc Indium Sulfide in Alkaline Solvent

Photocatalytic valorization of lignin to aromatic monomers by cleaving the Cβ–O bond is a promising approach for the utilization of biomass resources. Herein, we achieved nearly 100% conversion of the model compound 2-phenoxy-1-phenylethanol (PP-ol), and the selectivity of phenol and acetophenone reached 96 and 95%, respectively, using water and Cr-doped ZnIn2S4 (CZIS) as the hydrogen source and photocatalyst, respectively. Density functional theory calculations showed that Cr present on the CZIS surface can provide appropriate free energy for the target reaction intermediate, reducing the uphill ΔG for cleaving the Cβ–O ether bond reaction of the Cα radical (Cα•) intermediate to form acetophenone and phenol (from 2.15 to −0.81 eV), which facilitate the photocatalytic PP-ol conversion. In addition, controlling the competitive hydrogen evolution on the photocatalyst surface by adjusting the alkalinity of the reaction solvent is also a key factor to improve the photocatalytic performance.

Influence of La3+ doping on nebulizer spray pyrolysed In2S3 thin film for enhanced photodetector performance

In recent years, the photodetectors gained much attention due to their wide range of applications and fabrication of high-performance, cost-effective devices using environmentally friendly material is always challenging. In this work we report the fabrication of Lanthanum -doped indium sulfide thin films (In2S3:La) using a low-cost nebulizer spray pyrolysis method. La-doping concentration is varied from 0 to 5 wt% and the effect of doping on the properties of In2S3 thin films are investigated using X-ray diffraction (XRD), energy dispersive x-ray analysis (EDX), field emission scanning electron microscope (FESEM), UV–Vis spectroscopy, photoluminescence spectra. Incorporation of 3 wt% of La3+ in In2S3 lattice has substantially improved the crystallinity, surface morphology and optical properties of the thin films suitable for the device fabrication. Moderate doping of La3+ in the crystal lattice of β-In2S3 led to a red-shift in the absorption edge, which benefited utilization of wider light spectrum. Photodetectors are fabricated using In2S3:La (0–5 wt%) films and photodetector performance parameters are evaluated using I-V characteristics and current–time characterization. The In2S3 film with 3% La dopant concentration showed high photodetector performance with estimated detectivity (D*), photoresponsivity (R), and external quantum efficiency (EQE) of 1.11 × 1011 Jones, 5.05 × 10-1 AW−1, 118% respectively. For the same sample, the rise and fall time calculated from transient photo-response analysis is found to be 0.4 s and 0.3 s respectively. These optimally doped In2S3:La 3wt% thin film samples could be useful for the fabrication of photosensor based optoelectronic devices.

Photocatalytic H2O2 Generation over Microsphere Carbon-Assisted Hierarchical Indium Sulfide Nanoflakes via a Two-Step One-Electron Pathway

The increasing demand for an alternative to traditional fuel has motivated intensive research and drawn more attention. H2O2 has emerged as an alternative due to its high capabilities, relatively safer nature as a fuel, and ease of transportation. The photocatalytic method is adopted to generate H2O2 using sustainable light energy to achieve an entire green system for a completely environmentally friendly process. Herein, the synthesized microsphere carbon-assisted hierarchical two-dimensional (2D) indium sulfide (In2S3) nanoflakes have been characterized thoroughly by various techniques such as X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectra (DRS), photoluminescence (PL), and electron paramagnetic resonance (EPR). The photocatalytic performance of the In2S3-based photocatalysts can be promoted with the carbon layer assisting in facilitating the transfer of the photogenerated electrons and narrowing their band gaps. Optimized In2S3 successfully yielded 31.2 mM g-1 h-1 in the photocatalytic oxygen reduction reaction (ORR) process. Based on the results of different radical trapping experiments and different reaction conditions, the catalytic ORR process is proposed to be a two-step one-electron pathway.

Heterostructure engineering of NiO foam /In2S3 film for high-performance ethylene glycol gas sensors

Ethylene glycol, widely used as antifreeze for planes and motor cars, is odorless and harmful to humans; thus, high-performance ethylene glycol gas sensors are highly demanded. Herein, a type-II heterostructure of p-type nickel oxide foam/ n-type indium sulfide (NIS) was prepared for ethylene glycol gas sensing. The assembled NIS sensor exhibits a unique response (Rg/Ra=180.39) to 100 ppm ethylene glycol at a low temperature of 150 ℃ and a fast response/ recovery time (11.43 s/ 6.16 s), as well as excellent repeatability and long-term stability. The excellent gas-sensitive performance of the NIS sensors can be attributed to the formation of p-NiO/n-In2S3 heterojunctions resulting in a large change in the potential barrier, which leads to an increased sensing response. These results suggest that elaborate heterostructure engineering of NiO can potentially achieve highly sensitive ethylene glycol gas sensors.

Elucidating the local structure of V substitutes in In2S3 as potential intermediate band material by x-ray absorption spectroscopy and first principles calculations

Vanadium doped indium sulphide, In2S3:V, is studied as a potential absorber material for intermediate band (IB) solar cells. Based on electronic considerations, it is usually assumed that V occupies octahedrally coordinated In sites, although geometrical considerations would favour tetrahedral In sites. In this study, we therefore combined experimental x-ray diffraction and x-ray absorption spectroscopy with ab initio theoretical calculations of both and phase to elucidate the incorporation of V in In2S3:V thin films grown with different V content and different growth temperatures. Comparing shape and position of the measured and calculated x-ray absorption edge of V, comparing experimentally determined and calculated V–S bond lengths, and evaluating the calculated heat of solution of V on different lattice sites all indicate that V is incorporated on octahedral rather than tetrahedral sites in the In2S3 matrix. For this material system, the electronic benefit of octahedral coordination thus outweighs the mechanical stress of the associated lattice relaxation. Finally, we studied the electronic structure of V-substituted - using hybrid density functional calculations and find that for a concentration of 1.9 at %, V on octahedrally coordinated In sites forms an empty IB isolated from valence band and conduction band (CB). By increasing the V content to 3.8 at %, however, the gap between IB and CB closes, which results in a reduction of the band gap. This differs from the electronic structure calculated for -:V and clearly demonstrates that both crystal structure and V incorporation site affect the resulting electronic material properties.

Insights into the photovoltaic properties of indium sulfide as an electron transport material in perovskite solar cells

According to recent reports, planar structure-based organometallic perovskite solar cells (OPSCs) have achieved remarkable power conversion efficiency (PCE), making them very competitive with the more traditional silicon photovoltaics. A complete understanding of OPSCs and their individual parts is still necessary for further enhancement in PCE. In this work, indium sulfide (In2S3)-based planar heterojunction OPSCs were proposed and simulated with the SCAPS (a Solar Cell Capacitance Simulator)-1D programme. Initially, OPSC performance was calibrated with the experimentally fabricated architecture (FTO/In2S3/MAPbI3/Spiro-OMeTAD/Au) to evaluate the optimum parameters of each layer. The numerical calculations showed a significant dependence of PCE on the thickness and defect density of the MAPbI3 absorber material. The results showed that as the perovskite layer thickness increased, the PCE improved gradually but subsequently reached a maximum at thicknesses greater than 500 nm. Moreover, parameters involving the series resistance as well as the shunt resistance were recognized to affect the performance of the OPSC. Most importantly, a champion PCE of over 20% was yielded under the optimistic simulation conditions. Overall, the OPSC performed better between 20 and 30 °C, and its efficiency rapidly decreases above that temperature.

Emission tuning of AgInS2-based core/shell semiconductor quantum dots with type-II and quasi-type-II band alignments

Here, silver indium sulfide (AgInS2)/gallium selenide core/shell quantum dots (QDs) were developed to exhibit red band-edge emission. Previously, we developed AgInS2/gallium sulfide core/shell QDs, which exhibited yellow band-edge photoluminescence (PL). Upon the gallium selenide shell growth, the PL spectra redshifted by more than 100 nm owing to an indirect transition between the core and shell (called the type-II characteristic). After the posttreatment with HCl, the PL wavelength was further redshifted by the formation of Ag–In–S–Se alloyed cores with a narrow bandgap, and the PL intensity increased because of the formation of a quasi-type-II band alignment. In addition, the PL wavelength could be tuned between deep-red and yellow by varying the S/(S + Se) ratio in the Ga–S–Se ternary shells. Based on the long lifetime of the QDs with the alloyed shells, it was suggested that the electronic structure of these alloyed shell QDs is the full type II.

One-pot synthesis of CIS nano-particles and their EMI shielding studies

EMI Shielding behaviour of copper indium sulphide (CIS) nanoparticles synthesized by single-step method is presented. 1-Octadecene and oleic acid both play important role in the synthesis, however, presence of oleylamine leads to formation of phase pure CIS as confirmed by XRD. It is observed that incorporation of silver nanoparticles in 1:1 amount with respect to CIS, dramatically enhanced the shielding efficiency from about −3 dB to about −13.5 dB (average) of the CIS/PVA (0.5:1 w/w) composite in X-band. This is possibly the first study of CIS for EMI application.

Hydrogen Peroxide Production with High Solar to Chemical Conversion (0.16%) and Efficient Water Purification Using Carbon Quantum Dots-Modified Indium Sulfide

Photocatalytic production of hydrogen peroxide (H2O2) is the need of the hour for green synthesis and sustainability. Herein, we designed hierarchical carbon quantum dots (CQDs)-supported β-indium sulfide (β-In2S3) nanoflakes as an efficient catalyst for H2O2 generation via a two-electron oxygen reduction reaction. The composite material exhibited a high H2O2 production rate of 634 μM h–1, a solar-to-chemical conversion (SCC) efficiency of 0.16%, a high forward rate constant of ∼19 μM min–1, and a low H2O2 dissociation constant of ∼0.004 min–1, all of which are significantly higher than those of pure β-In2S3. Moreover, this material also manifested good water remediation photocatalytic performance by way of removal of 93% chromium(VI), 58% nickel(II), and 94% rhodamine B in 2 h. The apparent rate constant for chromium(VI) reduction of the composite was 0.023 min–1, which is 10-fold higher than that of the pure material. β-In2S3-CQDs exhibited superior results, which can be attributed to their large electrochemical surface area, good light harnessing ability, upconverted photoluminescence, and the ability to act as an electron reservoir preventing recombination.

Surface modification of organic hybrid indium sulfide via silver ion decoration with enhanced photocatalytic activity for degrading organic dyes and antibiotics

Crystalline organic hybrid metal chalcogenides have exhibited effective photocatalytic degradation ability for organic pollutants. However, few strategies have been applied to enhance its inherent photocatalytic degradation activity. Here, we used an organic hybrid indium sulfide [In8S13(S)1/2(SH)][In4S6(S3)1/2(SH)](TMDPH2)5 (HCF-1) (TMDP = 4,4′-trimethylenedipiperidine) as pristine material, by immersing HCF-1 into AgNO3 solution, the surface of HCF-1 crystal was decorated by Ag+ ions via electrostatic interaction. Compared with the pristine HCF-1, the as-modified Ag@HCF-1 exhibited enhanced photocatalytic degradation performance for organic dyes (RhB and MO) and antibiotics (TC and ENR). The decoration of Ag+ ions on the surface of HCF-1 can broaden the range of light absorption, and promote the separation of photo-generated carriers, and thus boost the photocatalytic activity. In addition, photocatalytic mechanism was studied by free radical capture experiments, which proved the dominant roles of h+ and •O2− in the degradation process.

3D self-assembled indium sulfide nanoreactor for in-situ surface covalent functionalization: Towards high-performance room-temperature NO2 sensing

Thiol functionalization of two-dimensional (2D) metal sulfides has been demonstrated as an effective approach to enhance the sensing performances. However, most thiol functionalization is realized by multiple-step approaches in liquid medium and depends on the dispersity of 2D materials. Here, we utilize a three-dimensional (3D) In2S3 nano-porous structure that self-assembled from 2D components as the nanoreactor, in which the surface-absorbed thiol molecules from the chemical residues of the nanoreactor are used for the in-situ covalent functionalization. Such functionalization is realized by facile heat the nanoreactor at 100 °C, leading to the recombing sulfur vacancies with thiol-terminated groups. The NO2 sensing performances of such functionalized nanoreactor are investigated at room temperature, in which In2S3-100 exhibits a response magnitude of 21.5 towards 10 ppm NO2 with full reversibility, high selectivity, and excellent repeatability. Such high-performance gas sensors can be attributed to the additional electrons that transferring from the functional group into the host, thus significantly modifying the electronic band structure. This work provides a guideline for the facile in-situ functionalization of metal sulfides and an efficient strategy for the high performances gas sensors without external stimulus.

Single-Particle Dynamics of ZnS Shelling Induced Replenishment of Carrier Diffusion for Individual Emission Centers in CuInS2 Quantum Dots.

Insights into blinking and photoactivation of aqueous copper indium sulfide (CIS) quantum dots have been obtained using fluorescence correlation spectroscopy (FCS) and fluorescence lifetime correlation spectroscopy (FLCS). An unusual excitation wavelength-dependence of photoactivation/photocorrosion is manifested in an increase in the initial correlation amplitude G(0) for λex = 532 nm, but a decrease for λex = 405 nm. This has been rationalized in terms of different contributions from surface-assisted recombination in the two cases. Blinking times obtained from the autocorrelation functions (ACFs) of the 100-200 ns lifetime component (core Cu-mediated recombination) are almost unaffected by shelling, but those from the ACF for the 10-30 ns lifetime (surface states) increase significantly. Absence of cross-correlation between the two recombinative states of bare CIS QDs and the emergence of an anticorrelation with the introduction of the ZnS shell are observed, indicating the diffusive nature of the two states for CIS-ZnS. The diffusion is inhibited in bare CIS QDs due to the preponderance of surface states.

Defect-driven electroless deposition and activation of platinum sites on ZnIn2S4 nanosheets for accelerated kinetics of photocatalytic hydrogen production

The role of defects introduced into photocatalysts has been controversial, as some claim they serve as electron-trapping sites for improving the photogenerated charge separation, while others argue they act as exciton recombination centers to shorten the lifetime and mean free path of photocarriers. In the current study, we show the defect sites introduced into Zinc indium sulfide (ZIS) function as a double-bladed sword: on one hand, they act as recombination centers to impede photogenerated electron-hole separation in bulk ZIS; on the other hand, they drive electroless deposition and activation of the Pt co-catalyst through strong electronic coupling and thereby drastically enhance photocatalytic hydrogen production. As such, the defect-rich ZIS with a moderate Pt loading manifests the best hydrogen evolution rate of 15.56 mmol h−1 g−1 with a superb Pt-based TOF of 2334 h−1, apart from a high TON of 99610 in 92 h, which are among the best reported in literature for chalcogenide-based photocatalysts. Comprehensive microscopic, spectroscopic and photoelectrochemical characterizations unveil that the intimate coupling between the ZIS vacancy sites and deposited Pt atoms/clusters not only promotes photoexcited electron-hole separation, but also modulates local charge polarization to leverage the intrinsic activity of the co-catalyst.

Visible light active ZnIn2S4/g-C3N4 heterostructure nanocomposite photoelectrode for efficient photoelectrochemical water splitting activity

Hexagonal zinc indium sulfide coupled g-C3N4 (H-ZnIn2S4/g-C3N4) nanocomposites were synthesized using chemisorption method and its performance towards photoelectrochemical water splitting activity was studied. The H-ZnIn2S4/g-C3N4 (H-ZIS/CN) nanocomposites exhibited ∼ 1.9 times enhanced photoelectrochemical performance as compared to the H-ZnIn2S4. The enhancement in the PEC water splitting activity of H-ZIS/CN nanocomposite is ascribed to the formation of type-II heterojunction which resulted in improved separation of photogenerated charge carriers and faster transfer of charges at the photoelectrode/electrolyte interface. The electrochemical impedance study and Mott-Schottky supported these results. Moreover, during photoelectrochemical reactions, H-ZIS/CN nanocomposites showed tremendous stability under visible light. A potential mechanism of the enhanced photoelectrochemical activity of H-ZIS/CN nanocomposites was proposed and endorsed by the PEC results. This study demonstrates that establishing a heterostructure system by coupling a ternary chalcogenide semiconductor with a conducting polymer is an effective strategy for PEC water splitting applications.

Low-Temperature Photoluminescence Dynamics Reveal the Mechanism of Light Emission by Colloidal CuInS2 Quantum Dots

Copper indium sulfide colloidal quantum dots are in focus of the nanocrystal community as their optical properties make them exciting candidates for applications in bioimaging and biosensing, solar cells, luminescent solar concentrators, and lighting. However, fulfilling this application potential is hampered by poor understanding of the mechanism of light emission by these dots. In this work, we study temperature and magnetic field dependent photoluminescence (PL) dynamics and spin dynamics at cryogenic temperatures. We cast our experimental observations against two prevailing models of PL in CuInS2 quantum dots: an excitonic mechanism and a free-to-bound mechanism, in which a delocalized electron recombines with a hole localized at a copper ion. We unambiguously show that the PL occurs as the result of the free-to-bound mechanism.

Functionalized Regulation of Metal Defects in ln2S3 of p-n Homojunctions.

The introduction of metal vacancies into n-type semiconductors could efficiently construct intimate contact interface p-n homojunctions to accelerate the separation of photogenerated carriers. In this work, a cationic surfactant occupancy method was developed to synthesize an indium-vacancy (VIn)-enriched p-n amorphous/crystal homojunction of indium sulfide (A/C-IS) for sodium lignosulfonate (SL) degradation. The amount of VIn in the A/C-IS could be regulated by varying the content of added cetyltrimethylammonium bromide (CTAB). Meanwhile, the steric hindrance of CTAB produced mesopores and macropores, providing transfer channels for SL. The degradation rates of A/C-IS to SL were 8.3 and 20.9 times higher than those of crystalline In2S3 and commercial photocatalyst (P25), respectively. The presence of unsaturated dangling bonds formed by VIn reduced the formation energy of superoxide radicals (•O2-). In addition, the inner electric field between the intimate contact interface p-n A/C-IS promoted the migration of electron-hole pairs. A reasonable degradation pathway of SL by A/C-IS was proposed based on the above mechanism. Moreover, the proposed method could also be applicable for the preparation of p-n homojunctions with metal vacancies from other sulfides.

Fabrication and immobilization of heteropoly acids (HPAs) and hexadecyl trimethyl ammonium bromide (CTAB) co-modified ternary zinc indium sulfide (ZnIn2S4): Capture photogenerated electrons and pollutant molecules by co-photocatalyst for enhancing the photocatalytic ability

In this article, a series of HPAs, including phosphotungstic acid (H3PW12O40), silicotungstic acid (H4SiW12O40), phosphomolybdic acid (H3PMo12O40), and hexadecyl trimethyl ammonium bromide (CTAB) co-modified ZnIn2S4 photocatalysts (HPAs/CTAB@ZnIn2S4) were successfully fabricated for the first time by a simple one-pot hydrothermal strategy. As a photogenerated electron capture tool, HPAs and CTAB can capture photogenerated electrons by W 5d (or Mo 4d) unsaturated electron orbitals and quaternary ammonium groups (–N+), thus improving the photogenerated carrier (e––h+) separation efficiency of the main photocatalyst ZnIn2S4. As a pollutant molecule capture tool, HPAs and CTAB can capture pollutant molecules to the surface of photocatalyst through acid-base interaction and hydrogen bonding, so that the target pollutants can be efficiently degraded in the environment of high concentration hydroxyl radicals (·OH). In order to improve the engineering application value of as-prepared photocatalyst, we also successfully fabricated immobilized photocatalyst (H3PMo12O40/CTAB@ZnIn2S4@CC) by using clay ceramsite (CC) as a carrier. The photocatalytic activity of immobilized H3PMo12O40/CTAB@ZnIn2S4@CC is higher than that of H3PMo12O40/CTAB@ZnIn2S4 due to the trapping effect of CC carrier on photons.

Efficient planar mixed-cation perovskite photovoltaics with low-temperature-processed indium sulfide as electron transport material

Electron transport materials(ETMs) are crucial for efficient transport of photocarriers from the perovskites to the cathode in perovskite solar cells (PSCs). Although titanium dioxide (TiO2) is frequently employed as an ETM, PSC performance and applicability are hindered by its high-temperature manufacturing and limited electron mobility. In this work, a low-temperature solution-processable indium sulfide (In2S3) was incorporated into triple-cation perovskite solar cells to be an efficient ETM for the first time. After solvent-thermal synthesis of In2S3, followed by spin-coatingpreparation of In2S3 ETM, aPSC is constructed. The photoelectrical measurements show that the In2S3-based PSC has lower density of charge traps, higher conductivity, better electron transportation at the In2S3/perovskite interfaces, and a lower transfer resistance and carrier recombination. The PSC-based In2S3 yields a champion efficiency of 18.182%, and the PSC-based TiO2 gets an efficiency of 15.288%. Without encapsulation, the In2S3-based devices demonstrate increased stability in ambient environments. Our ETM layer and perovskite were made at low temperatures, which may open up new possibilities for solution-processed flexible electronics.

Enhanced Electrochemical Performance of Supercapacitors via Two-Dimensional Indium Sulfide Heterostructure on Carbon Nanotubes

This study reports on the synthesis and characterization of a novel electrode material for supercapacitor applications based on a clustered heterostructure of indium sulfide (In2S3) and single-walled carbon nanotubes (SWCNTs). The In2S3-SWCNT (INSC) sample was prepared using the facile successive ionic layer adsorption and reaction (SILAR) method and demonstrated a higher specific capacitance (258 Fg−1 at 1 Ag−1) compared to the bare indium sulfide (In2S3) electrode. The enhanced electrochemical performance is attributed to the synergistic effect between the In2S3 and SWCNTs, which improves electron transportation, catalytic nature, and specific capacitance. Moreover, the cyclic stability of the INSC electrode was significantly improved, retaining 96.8% of the initial capacitance after 3000 cycles. The high voltage holding capacity and high cyclic efficiency of the fabricated INSC-based supercapacitor devices suggest their potential for next-generation energy storage devices. Additionally, the INSC electrode-based supercapacitor devices exhibit excellent flexibility and bendability, retaining similar performance even at a bending angle of 180°, making them suitable for flexible energy storage applications.

Efficacious performance of photoactive electrode In:SnO2/Er2S3:In2S3 in a photoelectrochemical system

A transparent conductive electrode using Erbium sulphide and Indium sulphide composite for a photoelectrochemical cell was created from a single source precursor using spin coating. X-ray diffraction examination presented Er2S3-In2S3 in the composite with 56 nm crystallite size. Hexagonal structures were observed through SEM analysis. Er 4d, In 3d and S 2p core levels were detected by X-ray photoelectron spectroscopy. The composite displayed an optical band gap of 4.12 eV. Using cyclic voltammetry, linear sweep voltammetry, transient chronoamperometry (CA), and electrical impedance spectroscopy, electrical studies in a photoelectrochemical cell were measured. In every experiment, the electrode showed a markedly higher photocurrent density than in dark. A rise in the photoelectrode's specific capacitance in the presence of illumination was also noted across all scan rates. Specific capacitance was determined to have a maximum value under illumination of 421 Fg−1 as contrasted to 381 Fg−1 in the absence of a light source at 5 mVs−1. CA also presented a good photocurrent density of 27.6 mA. Nyquist plot presented the Rs to be 20.8 Ω of the cell and a conductivity of 4.22 × 10−5 Scm−1. An effective photoelectrode that can be employed in renewable energy systems was thus presented by the study.