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We performed first-principles calculations based on the density functional theory (DFT) to study the sensing and static dielectric properties (within a weak field regime) of arsenic trisulfide (As2S3) nanosheets toward selected volatile organic compounds (VOCs) such as methanal, ethanal, and propanal. Our rigorous simulations reported on the VOCs adsorption on pristine, vacancy-induced, and heteroatom substituted As2S3 sheets, and we further studied the corresponding dielectric constants to investigate the exotic sensing behavior. We found that certain vacancy defects and heteroatom substitution not only improved the binding energies of VOCs but also resulted in significant changes in the dielectric constants before and after the adsorption. Measurable changes in the electronic properties calculated through the density of states and band structure calculations of pristine and defective As2S3 sheets upon the exposure of VOCs reinforced the efficient sensing characteristics of the As2S3. Furthermore, we used statistical thermodynamic analysis to investigate the VOCs sensing behavior under various pressure and temperature conditions. We strongly believe that our findings can simplify the understanding of the complex sensing mechanism and further help the synthesis of As2S3-based nanosensors toward VOCs.

Arsenic trisulfide (As2S3) has been found to be an excellent glass former at high temperature and pressure. However, there is still some scarcity for the elastic and phonon behavior of the orpiment phase. By using the Dreiding force field of the geometry optimization computations, we investigated the elastic constants, mechanical moduli, and the phonon dispersion of orpiment As2S3 under the pressure from 0 to 5 GPa. Some results of the elastic parameters of orpiment-As2S3 at 0 GPa are consistent with the experimental data. The phonon dispersions for orpiment As2S3 under pressure are also reasonable with previous calculations.

An acousto-Optic Modulator (AOM) formed by an Arsenic Trisulfide (As $_2$ S $_3$ ) Mach–Zehnder interferometer (MZI), operating in a push-pull configuration and placed inside a surface acoustic wave (SAW) cavity on a Y-cut Lithium Niobate (LN) wafer is demonstrated. This is the first demonstration of such acousto-optic (AO) modulator in this As $_2$ S $_3$ -LN hybrid platform. In this approach, the high index contrast of As $_2$ S $_3$ waveguides is exploited to attain a high optical confinement. Additionally, the placement of the photonic MZI inside the SAW cavity enhances the AO interaction due to the high quality factor (Q) of the SAW resonator. An analytical expression that describes such enhancement as a function of the elasto-optic (EO) coefficient of As $_2$ S $_3$ is derived in conjunction with COMSOL finite element methods to describe strain in the SAW cavity. By fitting this expression to experimental data, the EO coefficient ( $p_{11}$ and $p_{12}$ , where $p_{11} \approx p_{12}$ ) for As $_2$ S $_3$ is extracted to be 0.29 at the wavelength of 1550 nm. This is the first time that the EO coefficient of thin film As $_2$ S $_3$ is experimentally derived.

Evolution of free-volume atomic scale structure under crystal-to-glass transition was re-examined in arsenic trisulfide As2S3 in glassy and crystalline state, employing mutually correlated positron annihilation lifetime studies treated in a framework of two-state simple positron trapping model. In crystalline state represented by mineral orpiment As2S3 supplied from Wanshan mine (China), the trapping rate is restricted to ~1.14 ns−1, associated with 0.240 ns defect-free bulk and 0.402 ns defect-specific lifetimes due to free volumes stabilized preferentially within inter-layer spaces. The positron trapping rate is notably enhanced to ~1.51 ns−1 in glassy state presented by melt-quenched As2S3, the positron traps being smaller with decreased bulk (0.278 ns) and defect (0.380 ns) lifetimes due to nanostructurized free volumes stabilized within corrugated quasi-layers. In general, vitrification in As2S3 produces depressing and time-enhancing trend in the recorded PAL spectra peaks. The ratio of bulk positron lifetimes for glassy and crystalline states serving as criterion of vitrification completeness reaches 1.16, meaning that some additional volume is available for annihilation in a glass. The ratio of mean positron lifetimes approaching 1.12 reflects a degree of realized crystal-to-glass transformation. Vitrification-related changes in As2S3 can be imagined as fragmentation of existing free-volume voids due to crumpling of intrinsic inter-layer spaces.

Employing ultraviolet light to enhance the removal of As(V) by sulfide (S(-II)) from strongly acidic wastewater is a potential method. However, we found the arsenic trisulfide (As2S3) and elemental sulfur (S8) particles formed in this method not only vastly hinder light transmission in the wastewater but also undergo light-induced redissolution, leading to a decrease in removal rate and efficiency of As(V). Herein, As(V) removal by sulfide from strongly acidic wastewater was performed in a modified photochemical reactor to weaken the effect of the formed particles on As(V) removal. It was found that in this study, the formed particles could be efficiently removed from the photoreactor by three operations, i.e. circulation-filtration, septum setting, and lamp sleeve cleaning. The removal of As(V) was approximately 11-fold faster than that without three operations, saving 90.9% of the reaction time and 89.4% of energy consumption. The removal efficiency of As(V) also increased through weakening the light-induced redissolution of the formed particles. This study facilitates the practical application of the UV light promoted As(V) removal technology and also provides a new method to lessen the light-blocking effect in the particle-forming photochemical reaction systems.

During the laboratory tests the conditions of arsenic removal from acidic waste solutions of metallurgical enterprise in the form of arsenic trisulfide were determined. The technology based on the reduction of pentavalent arsenic to trivalent state with sodium pyrosulfite solution and following arsenic trisulfide precipitation from acidic solution after treatment with sodium sulfide solution was proposed. The arsenic removal proceeds with mechanical stirring, dosing the calculated amounts of reagents and collecting emissions of hydrogen sulfide. With such treatment, about 95% of arsenic, which was in the initial solution, passes into the precipitate. An enlarged laboratory experiment was carried out and the precipitate with 42.6% of arsenic and 46.9% of sulfur was obtained. The precipitate yield was ∼25.7 kg (dry weight) out of 1 m3 of the initial arsenic containing solution. Keywords: arsenic, arsenic trisulfide, acidic waste solutions, sodium sulfide, sodium pyrosulfite

The overall decrease in the quality of mineral raw materials, combined with the use of arsenic-containing ores, results in large amounts of various intermediate products containing this highly toxic element. The use of hydrometallurgical technologies for these materials is complicated by the formation of multicomponent solutions and the difficulty of separating copper from arsenic. Previously, for the selective separation of As from copper&ndash, arsenic intermediates a leaching method in the presence of Cu(II) ions was proposed. This paper describes the investigation of the kinetics of arsenic sulfide-containing materials leaching by copper sulfate solution. The cakes after leaching of arsenic trisulfide with a solution of copper sulfate were described using methods such as X-ray diffraction spectrometry (XRD), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy analysis (EDS). The effect of temperature (70&ndash, 90 &deg, C), the initial concentration of CuSO4 (0.23&ndash, 0.28 M) and the time on the As recovery into the solution was studied. The process temperature has the greatest effect on the kinetics, while an increase in copper concentration from 0.23 to 0.28 M effects an increase in As transfer into solution from 93.2% to 97.8% for 120 min of leaching. However, the shrinking core model that best fits the kinetic data suggests that the process occurs by the intra-diffusion mode with the average activation energy of 44.9 kJ/mol. Using the time-to-a-given-fraction kinetics analysis, it was determined that the leaching mechanism does not change during the reaction. The semi-empirical expression describing the reaction rate under the studied conditions can be written as follows: 1/3ln(1 &minus, X) + [(1 &minus, X) &minus, 1/3 &minus, 1] = 4,560,000Cu3.61e&minus, 44900/RT t.

Arsenic trisulfide (As2S3), in both amorphous and crystalline form, is a significant arsenic-containing compound naturally occurring in mine waste rock or generated as metallurgical waste. It is typically unstable in the enviroment, especially under alkaline and oxidizing conditions, which is a significant barrier to fixation of arsenic present in metallurgical waste streams in the form of arsenic trisulfide. Our previous study has shown the effect of different factors on the kinetics and mechanisms of arsenic and sulfur release from amorphous As2S3. To assess the effect of crystallinity on the stability of arsenic trisulfide, a series of laboratory leaching tests were performed with crystalline orpiment under fully controlled conditions. The experimental results showed that the release of arsenic and sulfur increased with pH, dissolved oxygen concentration, and temperature, but the release rates were much slower than those of amorphous arsenic trisulfude. The speciation analyses indicated that arsenic was present in the leachates as arsenite, which was subsequently oxidized to arsenate to different extents; thiosulfate was the main soluble sulfur species, which was converted to sulfate via oxidation and disproportionation pathways. The kinetic modeling suggested that the arsenic release process is a mixed-control reaction, in which the surface chemical reaction and the diffusion of dissolved oxygen through a product layer control the arsenic release rate. The solid surface characterization supported the presence of an arsenic-deficient phase enriched in elemental sulfur on the solid surfaces. The product layer acted as a barrier to the diffusion of reagents, as evidenced by the leaching being sensitive to the removal of elemental sulfur.

The results of high-resolution x-ray reflectivity study of nano-dimensionally thin arsenic trisulfide (As2S3) glass films reveal surface roughness anisotropy upon prolonged irradiation with polarized 436 nm blue light. The anisotropy correlates with the photoinduced anisotropy and LC photoalignment observed on these thin films. However, the As2S3 film's thickness reduces drastically during the reflectivity experiments, and ambient oxygen and moisture penetrate the film and create a second altered thin layer on top of a thicker film of As2S3. The results confirm the viability of As2S3 films for non-contact LC photoalignment material but suggests the need for further process optimization to reduce the films' degeneration to increase their effectiveness.

The accumulation of arsenic in solid, liquid and gaseous waste of metallurgical production is an acute problem. Deposition of arsenic by sodium hydrosulfide is an effective and fast method of arsenic removal from solutions. The paper proposes a reactor design procedure for extraction of As (III) using the sulfide technology from washing solutions for wet gas scrubbing in sulfuric acid production. The paper takes into consideration the optimum parameters for removal of arsenic from solutions: the specific consumption of sulfide sulfur per1 kgof arsenic, the concentration of As (III) ions in the solution, the rate of sodium hydrosulfide feeding into the solution, and the hydrodynamic regime of the reactor. The obtained results are useful for design of experimental-industrial reactors used in dearsenication of solutions.

We study, both theoretically and experimentally, tunable metasurfaces supporting sharp Fano-resonances inspired by optical bound states in the continuum. We explore the use of arsenic trisulfide (a photosensitive chalcogenide glass) having optical properties which can be finely tuned by light absorption at the post-fabrication stage. We select the resonant wavelength of the metasurface corresponding to the energy below the arsenic trisulfide bandgap, and experimentally control the resonance spectral position via exposure to the light of energies above the bandgap., 7 pages, 5 figures

An efficient vertical grating coupler design for arsenic trisulfide (As2S3) on silicon dioxide (SiO2) on lithium niobate (LN) is proposed, fabricated, and experimentally verified. We report 4 dB coupling efficiency per grating for vertical fiber coupling at a wavelength of 1550 nm with a 3 dB bandwidth of 40 nm using an aluminum reflector mirror between the LN and SiO2 interface. This coupler is the first step towards the demonstration of high-performance integrated photonic devices, which would simultaneously benefit from the acousto-optic properties of As2S3 and electro-optic and acoustic properties of LN. This hybrid platform is deemed to impact a broad range of applications such as imaging, ranging, and inertial sensing.

The Geothermal fluids were disturbed by volcanic gas sulfide deposit reactions which form by reaction of metal(s) with H2S. this sulfate acid is one of the most corrosive compounds in the steam which lead the pitting, stress corrosion cracking and other corrosion mechanisms. An optical microscope, XRF dan X-ray diffraction is used to observe the sediment samples that came from stationary blades. The results show that it mainly consists of 89.7%wt iron sulfide (FeS) and 10.3%wt arsenic trisulfide (As2S3). This phase is toxic by inhalation and ingestion. Downstream steam pipeline treatment is required to reduce sulfide carried away into steam turbines such as scrubbing or washing steam. For this reason, special handling is needed for the toxic waste resulting from washing.

Infrared optical fibers are used in numerous applications in various industries. Knowledge of the radiative properties of optical fiber materials is important for the design and analysis of the processes in which the fibers are used. An experimental method for measuring the spectral absorption coefficient of infrared optical fibers using FTIR spectroscopy is presented. Blackbody radiation from a calibration source at different temperatures is transmitted through an optical fiber into an FTIR spectrometer. A mathematical model of the radiative heat transfer in the fiber is used to develop a linear spectral instrument response function relating the radiative energy from the calibration source to the output signal of the detection system. The spectral absorption coefficient of an infrared optical fiber is estimated from the ratio of the slopes of the instrument response functions for fibers of differing length. The method is used to estimate the room-temperature spectral absorption coefficient of infrared optical fibers made of arsenic trisulfide chalcogenide glass, ZBLAN glass, and indium fluoride glass.

Arsenic trisulfide (As2S3) is known as one of the possible precipitates in arsenic removal from metallurgical waste streams. The advantage of precipitation in the form of arsenic trisulfide is its high arsenic content (up to 61% theoretically). However, arsenic trisulfide is unstable, especially under alkaline and oxidizing conditions, which is a significant barrier to arsenic fixation in the form of arsenic trisulfide. To further understand its stability, a series of laboratory leaching tests were performed under fully-controlled conditions to quantify the effect of pH, dissolved oxygen concentration, and temperature on the total arsenic and sulfur released. The experimental results show that the release rate of arsenic and sulfur increased with pH, the dissolved oxygen concentration, and temperature. In less alkaline conditions, the aqueous arsenic to sulfur ratio by weight was higher than the stoichiometric value of 1.6 in the solid As2S3, suggesting the formation of secondary phases or precipitates enriched in sulfur. The rate law derived from the kinetic modeling suggests that the rate-limiting step in the arsenic release process is the surface chemical reaction.

Arsenic removal from metallurgical waste streams in the form of arsenic trisulfide (As2S3) is promising due to its high arsenic content. However, the major barrier to widely implementing the sulfidization process is the stability of arsenic trisulfide. Our previous study has shown that the release rate of arsenic and sulfur increased with pH, the dissolved oxygen concentration, and temperature. The rate-limiting step was proposed to be surface chemical reaction based on the magnitude of the reaction orders and the activation energy. To further support the proposed mechanism, we analyzed aqueous arsenic and sulfur speciation and examined the changes in the solid surface properties during leaching. The speciation analyses indicate that arsenic was initially released in the form of arsenite, which was subsequently oxidized to arsenate. The extent of oxidation increased with pH, the dissolved oxygen concentration, and temperature. Thiosulfate was the predominant dissolved sulfur species, which was subsequently converted to sulfate via two different pathways. The oxidation pathway was favored at pH higher than 8. The disproportionation pathway was favored at pH 8 and below, where elemental sulfur was generated and precipitated out of solution as a solid. The SEM/EDX and XRD analyses of the solid residues confirmed the formation of elemental sulfur on the solid surfaces at pH 8 but not at pH 9. The formation of elemental sulfur reduced the sulfur concentration in the leachates, resulting in the aqueous As/S ratio being higher than the stoichiometric value in the As2S3 structure. The elemental sulfur produced did not act as a barrier to diffusion of reactants, as evidenced by the leaching being insensitive to the removal of elemental sulfur.

A bright and photostable near-infrared (NIR) emitting quantum dot (QD) glass was prepared. The solidification of PbS/CdS core/shell QD-layered double hydroxide (LDH) composites in an arsenic trisulfide glass matrix for >200 h under continuous ultraviolet irradiation produced a photostable NIR-emitting glass. The QD-LDH glass could be successfully applied to optical fibers for down-conversion and can be used for promising potential applications such as optical fiber amplifiers.

The nature of intrinsic phase separation initiated under different homogenization routes is studied in arsenic trisulfide As2S3 glass using Raman scattering spectroscopy. It is shown that As2S3 glass prepared within conventional melt-quenching route is subjected to essential phase separation dependent on the homogenization of elemental constituents sealed in evacuated ampoules. Under condition of low-temperature homogenization at 450–550 °С, chemical interaction due to limited solubility of liquid S in solid As results in structurally intrinsic As- and S-rich phases with high content of homoatomic As–As and S–S bonds, respectively, which are “wrong” from the point of As2S3 stoichiometry This process can be essentially facilitated with more rapid heating and greater amount of initial elemental ingredients taken for synthesis. During prolonged homogenization of this intrinsically-decomposed melt (such as lasting 2 days in a rocking furnace), these products are partially separated giving main glassy phase enriched on As in the form of realgar- and dimorphite-type molecules, isolated As–As bonds in a glassy network and volatilized S-rich phase, which condenses on the walls of ampoules. If such melt is insufficiently homogenized as under 6-h heating at 500 °C with only 2-h rocking, the coordination disordering is maintained in the ultimate glass. This provides that volatilized S-rich phase does not form, and all decomposition products are stabilized in glassy state as quasi-tetrahedral units and compensating homoatomic As–As bonds.

This brief review summarizes some results of studies concerning the effect of modification (doping with amphoteric elements, laser and electron-beam irradiation) on the physico-structural and optical properties of chalcogenide glasses and the possibility of using doped arsenic trisulphide to create multilayer composite structures for the recording of holographic optical elements.

Chalcogenide glasses have a variety of unique optical properties due to the intrinsic structural flexibility and bonds metastability. They are desirable materials for many applications, such as infrared communication sensors, holographic grating, optical imaging, and ultrafast nonlinear optic devices. Here, we introduce a novel electron-beam evaporation process to deposit the good quality arsenic trisulfide (As2S3) films and then the As2S3 films were used to fabricate the As2S3 waveguides with three approaches. The first method is photoresist lift-off. Because of the restriction of thermal budget of photoresist, the As2S3 film must be deposited at the room temperature. The second one is the silicon dioxide lift-off process on sapphire substrates, in which the As2S3 film could be evaporated at a high temperature (>180 °C) for better film quality. The third one is the plasma etching process with a metal protective thin layer in the pattern development process.

PbS and PbS/CdS core/shell colloidal quantum dots (QDs) were mixed with As2S3 glass powders to prepare solid composite materials. PbS QDs showed an absorption band centered at a wavelength of λ = 1478 nm and a photoluminescence (PL) band centered at λ = 1547 nm. PbS/CdS core/shell QDs had higher PL intensity than did bare PbS QDs. Solid composites made by mixing QDs and As2S3 glass powders showed clear PL bands at λ = 1385 nm. Optical fibers of As2S3 glass can be prepared from these composite materials if appropriate scale-up technology is realized.

Because the toxicity of arsenic is well known, arsenic-containing compounds have frequently been ingested for suicidal purposes. We report a case of attempted suicide by massive ingestion of arsenic trisulfide, an arsenic mineral of low solubility, which resulted in minimal symptoms.An asymptomatic 57-year-old man presented to an Emergency Department 13h after his reported ingestion of approximately 84g of arsenic contained in a mineral specimen of orpiment (arsenic trisulfide) that had been crushed and mixed with an alcoholic beverage and food. His only symptom before presentation was nausea. Physical examination was unremarkable, and diagnostic tests included a normal electrolyte panel, a normal serum lactate, and a normal electrocardiogram. An abdominal radiograph revealed hyper-dense material scattered throughout the large intestine. As per the recommendations of the regional poison center, the patient was managed with whole bowel irrigation with a polyethylene glycol solution, maintenance intravenous hydration, and observation on a telemetry unit. Chelation was not performed. A spot urine specimen collected 12h after admission contained 1490μg of total arsenic per liter (background range50μg per liter). The patient remained asymptomatic throughout his hospital course. Follow-up studies revealed a diminution in both intra-abdominal radiopacities and urine arsenic concentration. X-ray diffraction analysis of the specimen confirmed its identity as arsenic trisulfide.Our experience demonstrates that massive ingestion of a poorly soluble inorganic arsenic compound can be successfully managed with gastrointestinal decontamination alone without chelation, provided that the patient remains asymptomatic during close clinical monitoring.

A hybrid annealed proton exchange (APE) waveguide with a vertically integrated arsenic trisulfide (As2S3) waveguide on a lithium niobate (LiNbO3) substrate is used to create an optical phased array (OPA) that allows for the non-mechanical steering of 1550 nm light on an integrated optic platform. The high electro-optic coefficient of the x-cut y-propagating LiNbO3 (r33 = 30.8 pm/V) is utilized by electrode structures fabricated on the LiNbO3 substrate to create a low-power, lowloss beam steering with high-speed bandwidths, capable of 10 GHz and larger as demonstrated by commercial LiNbO3 modulators. The As2S3 waveguide is introduced because of its high refractive index, which leads to a highly confined optical mode. Design and fabrication are presented for a large full width steering angle of 34°, representing an order of magnitude improvement over low-confinement, diffused LiNbO3 waveguides and two orders of magnitude improvement over other reported LiNbO3 OPAs.

This work reports a detailed study of the processing and photo-patterning of two chalcogenide glasses (ChGs) − arsenic trisulfide (As2S3) and a new composition of germanium-doped arsenic triselenide Ge5(As2Se3)95 − as well as their use for creating functional optical structures. ChGs are materials with excellent infrared (IR) transparency, large index of refraction, low coefficient of thermal expansion, and low change in refractive index with temperature. These features make them well suited for a wide range of commercial and industrial applications including detectors, sensors, photonics, and acousto-optics. Photo-patternable films of As2S3 and Ge5(As2Se3)95 were prepared by thermally depositing the ChGs onto silicon substrates. For some As2S3 samples, an anti-reflection layer of arsenic triselenide (As2Se3) was first added to mitigate the effects of standing-wave interference during laser patterning. The ChG films were photo-patterned by multi-photon lithography (MPL) and then chemically etched to remove the unexposed material, leaving free-standing structures that were negative-tone replicas of the photo-pattern in networked-solid ChG. The chemical composition and refractive index of the unexposed and photo-exposed materials were examined using Raman spectroscopy and near-IR ellipsometry. Nano-structured arrays were photo-patterned and the resulting nano-structure morphology and chemical composition were characterized and correlated with the film compositions, conditions of thermal deposition, patterned irradiation, and etch processing. Photo-patterned Ge5(As2Se3)95 was found to be more resistant than As2S3 toward degradation by formation of surface oxides.

We demonstrate compensation for the spherical aberration due to the refractive index mismatch that occurs when a laser beam is focused into a thick arsenic trisulfide (As $$_2$$ S $$_3$$ ) film with a high numerical aperture objective. The effects of the aberration at different focal depths on the point spread function have been calculated numerically and the axial response method shown to be a useful measure for compensating the spherical aberration. We show that with the addition of adaptive optics based on a spatial light modulator, the aberration can be significantly reduced, resulting in an increase in peak intensity by a factor of 2.4 and a decrease in axial elongation by a factor of 2.2.

A new configuration consisting of an arsenic trisulfide (As2S3) channel waveguide on top of an erbium (Er)-doped titanium-diffused x-cut lithium niobate (Er:Ti:LiNbO3) waveguide has been investigated by simultaneous analytical expressions, numerical simulations, and experimentation. Both simulation and experimental results have shown that this structure can enhance the optical gain, as predicted by the analytical expressions. An As2S3 channel waveguide has been fabricated on top of a conventional Er:Ti:LiNbO3 waveguide, where the higher refractive index As2S3 waveguide is used to pull the optical mode toward the substrate surface where the higher Er concentration yields an improved propagation gain. The relationship between the gain and As2S3 layer thickness has been evaluated, and the optimal As2S3 thickness was found by simulation and experimentation. Side integration was applied to reduce the extrapropagation loss caused by the titanium diffusion bump. The propagation gain has been improved from 1.1 to 2 dB/cm.

This study investigates the feasibility of a precipitation process for the removal of arsenic from highly alkaline enargite leaching solutions in the Cu3AsS4–NaHS–NaOH system and regeneration of the leaching reagents. The main objective was to reduce elemental sulfur and subsequently oxidize arsenite (As (III)) to arsenate (As (V)) for the formation and precipitation of Na3AsS4. First, solutions with over 35 g/L As were prepared with either arsenic trisulfide (As2S3) or enargite (Cu3AsS4) in the NaHS–NaOH system. These solutions were conditioned at 90 °C followed by addition of elemental sulfur and fast cooling to 30 °C for precipitate formation. The effect of elemental sulfur addition (sulfur/arsenic ratio), NaHS and NaOH concentrations and times for conditioning and precipitation were evaluated, as well as the recirculation of the mother liquor containing arsenic with leach reagents. The results showed that conditioning solution with high arsenic concentration at 90 °C in NaHS (100–250 g/L) and NaOH (50–100 g/L), and sulfur addition at 1/2 wt of arsenic in solution for 1–2 h followed by fast cooling to 30 °C and conditioning for 3–5 h reduced arsenic concentration in solution by over 60%. Characterization by XRD showed Na3AsS4 as the dominant phase. Starting solutions prepared from As2S3 and Cu3AsS4 produced similar results. The recirculation of process filtrates for re-use in enargite leaching continued to give reproducible leaching results.

An investigation of the various parameters controlling the response of rapidly-fabricated As2S3 SERS substrates has been undertaken. As2S3 is an infrared-transmitting chalcogenide glass which is also photosensitive; it can be used to fabricate micro- and nano-structures as well as guide light. The substrates were optimised for interference angle, As2S3 thickness and metal type and thickness. Maximum enhancement factors are greater than 2.4 × 10 3 at a wavelength of 1064 nm.

A method for fabricating infrared-transmitting waveguides that yields low optical losses and strong confinement of light is presented. The method minimises the number of fabrication steps by exploiting the photosensitivity of arsenic trisulfide glass, using it both as a photoresist and as a waveguiding material. Controlled annealing/remelting of the waveguides minimises scattering due to fluctuations in refractive index at the interface between the waveguide and the surrounding medium, allowing low losses to be realised. Bends and Y-splitter structures have been realised, as well as the longest As(2)S(3) serpentine planar waveguides yet reported.

This work reports the processing and properties of a new chalcogenide glass film that can be photo-patterned by multiphoton lithography (MPL) with enhanced post-fabrication stability. Thermally evaporated germanium-doped arsenic selenide [Ge5(As2Se3)95] thin films were photo-patterned using the output of a mode-locked titanium:sapphire laser. The morphology, chemical structure, and optical properties of the material were studied before and after photo-patterning and compared for their long-term aging behavior and stability to previously investigated arsenic trisulfide (As2S3) films fabricated using similar MPL conditions. Relative to As2S3, thermally deposited Ge5(As2Se3)95 is found to offer higher photo-sensitivity and greater chemical stability after photo-patterning, as evidenced by lack of age-induced crystallization and reduced feature degradation over a four year aging period. These findings demonstrate the suitability of a new photo-patternable material for the creation of robust, long-lived functional infrared anti-reflective coatings and meta-optics.

The layered spiral microstructured optical fiber (LS-MOF) design allows higher nonlinearities than the most common microstructured optical fibers. Here, we have chosen a highly nonlinear glass for its composition, the arsenic trisulfide, and we have determined its dispersion and nonlinear characteristics. After adjusting the fiber’s parameters, we obtained a record value for the nonlinear parameter of 50.7[Formula: see text]W[Formula: see text]m[Formula: see text], at 1.550[Formula: see text][Formula: see text]m. We have simulated light propagation under these optimized circumstances, achieving a broad supercontinuum, extending from 500[Formula: see text]nm to 3900[Formula: see text]nm, in a very short distance: 0.3[Formula: see text]mm.

Arsenic trisulfide (As2S3) is a chalcogenide (ChG) material with excellent infrared (IR) transparency (620 nm to 11 μm), low phonon energies, and large nonlinear refractive indices. These properties directly relate to commercial and industrial applications including sensors, photonic waveguides, and acousto-optics. Multi-photon exposure can be used to photopattern thermally deposited As2S3 ChG glassy films of molecular clusters. Immersing the photo-patterned cross-linked material into a polar-solvent removes the unexposed material leaving behind a structure that is a negative-tone replica of the photo-pattern. Nano-structure arrays that were photo-patterned in single-layered As2S3 films through multi-photon direct laser writing (DLW) resulted in the production of nano-beads as a consequence of a standing wave effect. To overcome this effect, an anti-reflective (AR) layer of arsenic triselenide (As2Se3) was thermally deposited between the silicon substrate and the As2S3 layer, creating a multi-layered film. The chemical composition of the unexposed and photo-exposed multi-layered film was examined through Raman spectroscopy. Nano-structure arrays were photopatterned in the multi-layered film and the resulting structure, morphology, and chemical composition were characterized, compared to results from the single-layered film, and correlated with the conditions of the thermal deposition, patterned irradiation, and etch processing.

Amorphous arsenic trisulfide (As 2 S 3 ) and arsenic triselenide (As 2 Se 3 ) are among widely investigated amorphous materials due to its interesting electrical, optical and photoelectrical properties. In order to improve the physical properties and recording characteristics, and to extend the spectral range of photosensibility, a special interest represents the mixed amorphous materials, like (As 2 S 3 ):(As 2 Se3). Chalcogenide vitreous semiconductors (ChVS) of the As-S-Se system exhibit photostructural transformations with reversible and irreversible properties, and are promising materials as registration media for holography and optical information, for fabrication of diffractive elements, and other optoelectronic applications. Because many optoelectronic devices on amorphous semiconductors are based on the photoconductivity effect, special interests represent investigation of the stationary and non-stationary characteristics of photoconductivity. In this paper the experimental results of steady-state photoconductivity and holographic characteristics of amorphous (As4S 3 Se 3 ) 1-x :Sn x thin films are presented. It was shown that the photoconductivity spectra depend on the polarity on the top illuminated electrode and on the Sn concentration in the host glass. The photosensitivity of amorphous ((As4S 3 Se 3 ) 1-x :Sn x thin films is almost constant for all Sn-containing glasses. The Moss rule was used for determination of the optical forbidden gap E g from the photoconductivity spectra. It was demonstrated that the investigated amorphous films are sensitive to the light irradiation and can be used as effective registration media for holographic information. The relaxation of photodarkening in amorphous (As4S 3 Se 3 ) 1-x :Sn x thin films was investigated and was shown that the relaxation curves of transmittance T/T0 = f(t) can be described the stretch exponential function T(t)/T(0) = A0+Aexp[-(t-t0)/τ] (1-β) . The kinetics of diffraction efficiency growth η (t) was measured by registration of the laser intensity of the 1-st interference maximum versus time exposure. With increasing of Sn concentration in amorphous (As4S 3 Se 3 ) 1-x :Sn x thin films up to 6.0 at. % Sn, the diffraction efficiency η increases, than for higher concentrations of tin, decreases.

Silver sulfide nanocrystals and chalcogenide glasses (ChGs) are two distinct classes of semiconductor materials that have been exploited for new infrared technologies. Each one exhibits particular optoelectronic phenomena, which could be encompassed in a hybrid material. However, the integration of uniformly distributed crystalline phases within an amorphous matrix is not always an easy task. In this paper, we report a single step method to produce Ag2S nanocrystals (NCs) in arsenic trisulfide (As2S3) solution. The preparation is carried out at room temperature, using As2S3, AgCl and propylamine resulting in highly crystalline Ag2S nanoparticles in solution. These solutions are spin-coated on glass and silicon substrates to produce As2S3/Ag2S metamaterials for optoelectronics.

The reversible photoinduced change exhibited by amorphous chalcogenide glasses has been extensively studied recently, partly as an interesting subject for fundamental research in the field of disordered solids and partly due to potential applications in optoelectronics such as photoresists, optical memories, optoelectronic circuits, etc. The illumination of many amorphous chalcogenides changes their internal and/or surface structure while preserving their amorphous state. In this study, amorphous arsenic trisulfide (As2S3) thin film samples whose thickness is 5 µm were prepared on silicon wafers by thermal evaporation, and their thermal diffusivity and thermal conductivity were measured by photoacoustic spectroscopy and a 3? method, respectively. These measurements were repeated after illumination by an Ar+ laser beam whose photon energy E g is consistent with the energy band gap of As2S3. The results show that the thermal diffusivity and thermal conductivity increase by about 50% and 14–15%, respectively, by the photoinduced darkening, and this can be explained by the rearrangement of atoms and thermal expansion of the film.

In order to investigate the photo-induced thermal property changes in chalcogenide thin films, amorphous As2S3 thin film samples, whose thicknesses are 0.5, 1.0, 2.0, and 4.0 μm, were prepared on silicon wafers by thermal evaporation. Their thermal conductivity was measured by the 3ω method between room temperature and 100 °C. These measurements were repeated after the illumination of an Ar+ laser beam whose photon energy is consistent with the bandgap energy of As2S3, and repeated again for annealed films at 180 °C for 1 h. The result shows that the thermal conductivities of fresh films were 0.14 to 0.27 W·m−1·K−1; however, the values increase to 0.28–0.47 W·m−1·K−1 after illumination of the sample and decrease to 0.19–0.42 W·m−1·K−1 after annealing of the sample. These changes can be explained by the change in microstructure produced from the photo-darkening and thermal annealing.

Chalcogenide glasses are important in a range of optical applications because of their good infrared transmission and low phonon energy, as compared to the oxide glasses. These glasses are considered promising materials for the design of all optical high-speed elements, data processing (electronic switches, optical memories), solar cells, and waveguides. Such optical components are often used in ambient atmosphere. In this study, polished arsenic trisulfide (As2S3) samples were heated in a furnace at selected temperatures in ambient atmosphere. Subsequently, samples were characterized using x-ray photoelectron spectroscopy (XPS), micro-Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM) after each stage of environmental exposure oxidation to monitor any change in chemical structure and morphological patterns. Although heating produced a change in the surface roughness, no oxidation was observed.