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The development of photothermal agents for antibacterial applications has become increasingly attractive. An exciting area for these materials is in the food industry where such materials can be applied to prevent microbial contamination, as an environment-friendly alternative to chemical disinfectants. However, for such applications, there is a need for low-cost photocatalytic materials with easy synthesis procedures and long-term stability. In this regard, copper sulfide (CuS) nanomaterials have gained vast attention for their large antimicrobial response, driven primarily by the photothermal effect resulting from their uniform absorption in the NIR range. However, an important factor for a successful application is the level of the light-to-heat conversion capability of the specific CuS nanomaterial, which highly impacts on the antimicrobial response. Here, different synthesis procedures were investigated to synthesize a variety of CuS particles with distinct sizes and shapes, to demonstrate the large variation in antimicrobial response. The antibacterial activity of the particles was demonstrated on the bacterium Escherichia coli (E. coli) by irradiation with a regular IR lamp, to simultaneously investigate light absorption under a relatively low irradiation power. The results reveal that the light absorption of the CuS particles vary greatly and thus also so does the antibacterial effect. In conclusion, the difference in antimicrobial effect can not only be ascribed to size and morphology, but it is also influenced by crystal size and phase composition.

Clean chemical fuels such as molecular hydrogen are promising eco-friendly alternatives to CO2-emitting fossil fuels ; hydrogen can be generated using solar-driven photoelectrochemical water splitting with an efficient semiconductor photoelectrode. However, to optimize the process and reduce costs, exploring new materials and photoelectrode structures, as well as understanding their fundamental characteristics and impact on energy conversion, is crucial. Sulfide-based semiconductors such as CuS and ZnS have gained interest due to their earth abundance, non-toxicity, and suitable band gaps, but have limitations such as rapid recombination of photoexcited charge carriers and susceptibility to (photo)corrosion for CuS, and a wide band gap for ZnS. This thesis explores various approaches, such as varying synthesis conditions for the deposition of CuS thin films, forming CuS-ZnS mixtures, and doping, to improve the performance of both semiconductors. Firstly, CuxS thin films were synthesized using pulsed laser deposition. The deposition conditions such as substrate temperature and background gas pressure were varied to analyze their impact on structural and optoelectronic properties. Substrate temperature had a more significant effect on film growth than background gas pressure, and the highest temperature used (500°C) yielded the best performance with a reduced band gap and higher photocurrent density. However, poor stability was observed. To enhance the stability and overall performance of CuS, mixed films of CuS-ZnS were synthesized; they showed better optoelectronic properties and enhanced photoelectrode performance compared to films of CuS and ZnS on their own. Computational studies using DFT were also used to investigate the CuS-ZnS mixtures, which confirmed the enhanced charge separation as well as reduced band gaps compared to bulk CuS and ZnS. Altering the thickness of the ZnS layer also affected both stability and band gap, attributed to changes in interfacial

Copper sulfide shows some unique physico-chemical properties that make it appealing as a cathode active material (CAM) for solid-state batteries (SSBs). The most peculiar feature of the electrode reaction is the reversible formation of µm-sized Cu crystals during cycling, despite its large theoretical volume change (75%). Here, the dynamic microstructural evolution of CuS cathodes in SSBs is studied using in situ synchrotron X-ray tomography. The formation of µm-sized Cu within the CAM particles can be clearly followed. This process is accompanied by crack formation that can be prevented by increasing the stack pressure from 26 to 40 MPa. Both the Cu inclusions and cracks show a preferential orientation perpendicular to the cell stack pressure, which can be a result of a z-oriented expansion of the CAM particles during lithiation. In addition, cycling leads to a z-oriented reversible displacement of the cathode pellet, which is linked to the plating/stripping of the Li counter electrode. The pronounced structural changes cause pressure changes of up to 6 MPa within the cell, as determined by operando stack pressure measurements. Reasons for the reversibility of the electrode reaction are discussed and are attributed to the favorable combination of soft materials., China Scholarship Council http://dx.doi.org/10.13039/501100004543, NASEBER, KAROFEST, Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347, Deutsches Elektronen‐Synchrotron http://dx.doi.org/10.13039/501100001647, Peer Reviewed

The electrocatalytic reduction of CO2 to produce sustainable fuels and chemicals is attracting great attention. Cu-based catalysts can lead to the production of a range of different molecules, and interestingly the product selectivity strongly depends on the preparation history, although it is not fully understood yet why. We report a novel strategy that allowed us to prepare Cu nanoparticle on carbon catalysts with similar morphologies, but prepared by in-situ reduction of either supported CuS, Cu2S or CuO nanoparticles. For the first time the evolution of the Cu species was followed under CO2 and H+ reduction conditions using in-situ X-ray absorption spectroscopy. Excellent electrochemical contact between the Cu-based nanoparticles, the carbon support and the carbon-paper substrate was observed, resulting in metallic Cu as the predominant phase under typical electrochemical CO2 reduction conditions. Even covering less than 4% of the H2 producing carbon support with Cu-sulfide derived nanoparticles allowed to steer the selectivity to a maximum of 12% Faradaic efficiency for the production of formate. Clear differences between the catalysts derived from CuS, Cu2S or CuO nanoparticles were observed, which was ascribed to the presence of residual sulfur in the catalysts.

Copper chalcogenides are outstanding thermoelectric materials for applications in the medium-high temperature range. Among different chalcogenides, while CuSe is characterized by higher thermoelectric figures of merit, CuS provides advantages in terms of low cost and element abundance. In the present work, we investigate the effect of different dopants to enhance the CuS performance and also its thermal stability. Among the tested options, Pb-doped CuS shows the highest improvement in stability against sulfur volatilization. Additionally, Pb incorporation allows tuning charge carrier concentration, which enables a significant improvement of the power factor. We demonstrate here that the introduction of an optimal additive amount of just 0.3% results in a threefold increase of the power factor in the middle-temperature range (500–800 K) and a record dimensionless thermoelectric figure of merit above 2 at 880 K.

Copper chalcogenides are outstanding thermoelectric materials for applications in the medium-high temperature range. Among different chalcogenides, while Cu2-xSe is characterized by higher thermoelectric figures of merit, Cu2-xS provides advantages in terms of low cost and element abundance. In the present work, we investigate the effect of different dopants to enhance the Cu2-xS performance and also its thermal stability. Among the tested options, Pb-doped Cu2-xS shows the highest improvement in stability against sulfur volatilization. Additionally, Pb incorporation allows tuning charge carrier concentration, which enables a significant improvement of the power factor. We demonstrate here that the introduction of an optimal additive amount of just 0.3% results in a threefold increase of the power factor in the middle-temperature range (500–800 K) and a record dimensionless thermoelectric figure of merit above 2 at 880 K., Peer Reviewed, Postprint (author's final draft)

Cu2–xS has become one of the most promising thermoelectric materials for application in the middle-high temperature range. Its advantages include the abundance, low cost, and safety of its elements and a high performance at relatively elevated temperatures. However, stability issues limit its operation current and temperature, thus calling for the optimization of the material performance in the middle temperature range. Here, we present a synthetic protocol for large scale production of covellite CuS nanoparticles at ambient temperature and atmosphere, and using water as a solvent. The crystal phase and stoichiometry of the particles are afterward tuned through an annealing process at a moderate temperature under inert or reducing atmosphere. While annealing under argon results in Cu1.8S nanopowder with a rhombohedral crystal phase, annealing in an atmosphere containing hydrogen leads to tetragonal Cu1.96S. High temperature X-ray diffraction analysis shows the material annealed in argon to transform to the cubic phase at ca. 400 K, while the material annealed in the presence of hydrogen undergoes two phase transitions, first to hexagonal and then to the cubic structure. The annealing atmosphere, temperature, and time allow adjustment of the density of copper vacancies and thus tuning of the charge carrier concentration and material transport properties. In this direction, the material annealed under Ar is characterized by higher electrical conductivities but lower Seebeck coefficients than the material annealed in the presence of hydrogen. By optimizing the charge carrier concentration through the annealing time, Cu2–xS with record figures of merit in the middle temperature range, up to 1.41 at 710 K, is obtained. We finally demonstrate that this strategy, based on a low-cost and scalable solution synthesis process, is also suitable for the production of high performance Cu2–xS layers using high throughput and cost-effective printing technologies., Peer Reviewed, Postprint (author's final draft)

Copper sulfide describes a group of chemical compounds consisting of copper and sulfur that can exist in various compositions. The properties of copper sulfide depend on the composition, size and shape of the material, making it an interesting candidate for various applications, including catalysis. The first part of this thesis describes several methods to prepare copper sulfide nanoparticles. Colloidal copper sulfide (hetero)nanocrystals as well as supported copper sulfide nanoparticles were prepared with good control over size, shape and composition. In addition, the methods resulted in copper sulfide nanoparticles suitable for catalytic applications by for example, removing bulky organic ligands from the particle surface to make the surface accessible for reactants, or by preparing nanoparticles anchored on a support material to improve their stability and handling. The second part of the thesis focusses on the applications of copper sulfide nanoparticles in photo- and electrocatalysis. From our findings, Cu2-xS nanoparticles are not very promising photocatalysts. However, their use in electrochemical CO2 reduction led to interesting results. Even though the copper sulfide nanoparticles reduce to metallic copper under typical CO2 and H+ reduction conditions, residual sulfur in the catalysts steered the product selectivity to formate.

The electrocatalytic reduction of CO2 to produce sustainable fuels and chemicals is attracting great attention. Cu-based catalysts can lead to the production of a range of different molecules, and interestingly the product selectivity strongly depends on the preparation history, although it is not fully understood yet why. We report a novel strategy that allowed us to prepare Cu nanoparticle on carbon catalysts with similar morphologies, but prepared by in-situ reduction of either supported CuS, Cu2S or CuO nanoparticles. For the first time the evolution of the Cu species was followed under CO2 and H+ reduction conditions using in-situ X-ray absorption spectroscopy. Excellent electrochemical contact between the Cu-based nanoparticles, the carbon support and the carbon-paper substrate was observed, resulting in metallic Cu as the predominant phase under typical electrochemical CO2 reduction conditions. Even covering less than 4% of the H2 producing carbon support with Cu-sulfide derived nanoparticles allowed to steer the selectivity to a maximum of 12% Faradaic efficiency for the production of formate. Clear differences between the catalysts derived from CuS, Cu2S or CuO nanoparticles were observed, which was ascribed to the presence of residual sulfur in the catalysts., ChemE/Materials for Energy Conversion and Storage

Nanoscale cation exchange (CE) has resulted in colloidal nanomaterials that are unattainable by direct synthesis methods. Aliovalent CE is complex and synthetically challenging because the exchange of an unequal number of host and guest cations is required to maintain charge balance. An approach to control aliovalent CE reactions is the use of a single reactant to both supply the guest cation and extract the host cation. Here, we study the application of GaCl3-L complexes [L = trioctylphosphine (TOP), triphenylphosphite (TPP), diphenylphosphine (DPP)] as reactants in the exchange of Cu+ for Ga3+ in Cu2-xS nanocrystals. We find that noncomplexed GaCl3 etches the nanocrystals by S2- extraction, whereas GaCl3-TOP is unreactive. Successful exchange of Cu+ for Ga3+ is only possible when GaCl3 is complexed with either TPP or DPP. This is attributed to the pivotal role of the Cu2-xS-GaCl3-L activated complex that forms at the surface of the nanocrystal at the onset of the CE reaction, which must be such that simultaneous Ga3+ insertion and Cu+ extraction can occur. This requisite is only met if GaCl3 is bound to a phosphine ligand, with a moderate bond strength, to allow facile dissociation of the complex at the nanocrystal surface. The general validity of this mechanism is demonstrated by using GaCl3-DPP to convert CuInS2 into (Cu,Ga,In)S2 nanocrystals, which increases the photoluminescence quantum yield 10-fold, while blue-shifting the photoluminescence into the NIR biological window. This highlights the general applicability of the mechanistic insights provided by our work.

In this paper, the effect of the cupric and chloride ions concentrations on copper dissolution from chalcopyrite concentrate was studied in acidified media. Variables included three different concentrations of Cu2+ (0.5, 1.5, and 2.5 g L−1), four different concentrations of Cl− (0, 5, 7, and 10 g L−1), two different pH values of 1 and 2, and a constant temperature of 60 °C. Results indicated that addition of Cl− to the system improves copper extractions, especially at higher concentrations of Cu2+. Initial copper concentrations in the leaching solution did not significantly affect the copper extraction when Cl− was not present. Better copper extractions were obtained at pH 1 as compared with pH 2. As the Cu2+ and Cl− concentrations were increased, higher values of redox potential were obtained. According to the formation constants of the chloro-complexes, the predominant species in the Cu2+/Cl− system in the studied interval were CuCl+ and Cu2+. Using a model of copper speciation in the experimental range predicted for a single copper concentration with increasing Cl− concentration, the Cu2+ concentration decreased significantly while the concentration of the chloro-complex species CuCl+ increased. In the leached residue, evidence of sulfur formation was found using SEM and corroborated by XRD analysis. When chloride is present in the medium, the amounts of copper and iron in the residue decrease, confirming a positive effect of chloride on the extraction of copper from concentrate for the studied conditions., Validerad;2019;Nivå 2;2019-10-18 (svasva)

In this paper, the effect of the cupric and chloride ions concentrations on copper dissolution from chalcopyrite concentrate was studied in acidified media. Variables included three different concentrations of Cu2+ (0.5, 1.5, and 2.5 g L−1), four different concentrations of Cl− (0, 5, 7, and 10 g L−1), two different pH values of 1 and 2, and a constant temperature of 60 °C. Results indicated that addition of Cl− to the system improves copper extractions, especially at higher concentrations of Cu2+. Initial copper concentrations in the leaching solution did not significantly affect the copper extraction when Cl− was not present. Better copper extractions were obtained at pH 1 as compared with pH 2. As the Cu2+ and Cl− concentrations were increased, higher values of redox potential were obtained. According to the formation constants of the chloro-complexes, the predominant species in the Cu2+/Cl− system in the studied interval were CuCl+ and Cu2+. Using a model of copper speciation in the experimental range predicted for a single copper concentration with increasing Cl− concentration, the Cu2+ concentration decreased significantly while the concentration of the chloro-complex species CuCl+ increased. In the leached residue, evidence of sulfur formation was found using SEM and corroborated by XRD analysis. When chloride is present in the medium, the amounts of copper and iron in the residue decrease, confirming a positive effect of chloride on the extraction of copper from concentrate for the studied conditions., Validerad;2019;Nivå 2;2019-10-18 (svasva)

Copper sulfide has been regarded as a promising thermoelectric material with relatively high thermoelectric performance and abundant resource. Large-scale synthesis and low-cost production of high-performance thermoelectric materials are keys to widespread application of thermoelectric technology. Here, Cu2-xS particles encapsulated in a thin carbon shell are fabricated by a scalable wet chemical method (19.7 g/batch). The synthesized particles go through the crystal-phase transition from orthorhombic to tetragonal during high-temperature annealing and sintering. After the phase transition, electrical conductivity of this composite (Cu2-xS@C) increases by approximately 50% compared to that of the pure Cu2-xS sample, and can be attibuted to an increase in carrier concentration. Phonon scattering interface formation and superionic phase of Cu2-xS@C results in very low lattice thermal conductivity of 0.22 W m-1 K-1, and maximum thermoelectric figure of merit (ZT) of 1.04 at 773 K, which is excellent for thermoelectric performance in pure-phase copper sulfide produced via chemical synthesis. This discovery sets the stage for the use of facile wet chemical synthesis methods for large-scale transition-metal chalcogenide thermoelectric material production.

Lithium-sulfur (Li-S) batteries are promising energy storage systems due to their large theoretical energy density of 2600 Wh kg(-1) and cost effectiveness. However, the severe shuttle effect of soluble lithium polysulfide intermediates (LiPSs) and sluggish redox kinetics during the cycling process cause low sulfur utilization, rapid capacity fading, and a low coulombic efficiency. Here, a 3D copper, nitrogen co-doped hierarchically porous graphitic carbon network developed through a freeze-drying method (denoted as 3D Cu@NC-F) is prepared, and it possesses strong chemical absorption and electrocatalytic conversion activity for LiPSs as highly efficient sulfur host materials in Li-S batteries. The porous carbon network consisting of 2D cross-linked ultrathin carbon nanosheets provides void space to accommodate volumetric expansion upon lithiation, while the Cu, N-doping effect plays a critical role for the confinement of polysulfides through chemical bonding. In addition, after sulfuration of Cu@NC-F network, the in situ grown copper sulfide (CuxS) embedded within CuxS@NC/S-F composite catalyzes LiPSs conversion during reversible cycling, resulting in low polarization and fast redox reaction kinetics. At a current density of 0.1 C, the CuxS@NC/S-F composites' electrode exhibits an initial capacity of 1432 mAh g(-1) and maintains 1169 mAh g(-1) after 120 cycles, with a coulombic efficiency of nearly 100%.

Lithium-sulfur (Li-S) batteries are promising energy storage systems due to their large theoretical energy density of 2600 Wh kg(-1) and cost effectiveness. However, the severe shuttle effect of soluble lithium polysulfide intermediates (LiPSs) and sluggish redox kinetics during the cycling process cause low sulfur utilization, rapid capacity fading, and a low coulombic efficiency. Here, a 3D copper, nitrogen co-doped hierarchically porous graphitic carbon network developed through a freeze-drying method (denoted as 3D Cu@NC-F) is prepared, and it possesses strong chemical absorption and electrocatalytic conversion activity for LiPSs as highly efficient sulfur host materials in Li-S batteries. The porous carbon network consisting of 2D cross-linked ultrathin carbon nanosheets provides void space to accommodate volumetric expansion upon lithiation, while the Cu, N-doping effect plays a critical role for the confinement of polysulfides through chemical bonding. In addition, after sulfuration of Cu@NC-F network, the in situ grown copper sulfide (CuxS) embedded within CuxS@NC/S-F composite catalyzes LiPSs conversion during reversible cycling, resulting in low polarization and fast redox reaction kinetics. At a current density of 0.1 C, the CuxS@NC/S-F composites' electrode exhibits an initial capacity of 1432 mAh g(-1) and maintains 1169 mAh g(-1) after 120 cycles, with a coulombic efficiency of nearly 100%.

Lithium-sulfur (Li-S) batteries are promising energy storage systems due to their large theoretical energy density of 2600 Wh kg(-1) and cost effectiveness. However, the severe shuttle effect of soluble lithium polysulfide intermediates (LiPSs) and sluggish redox kinetics during the cycling process cause low sulfur utilization, rapid capacity fading, and a low coulombic efficiency. Here, a 3D copper, nitrogen co-doped hierarchically porous graphitic carbon network developed through a freeze-drying method (denoted as 3D Cu@NC-F) is prepared, and it possesses strong chemical absorption and electrocatalytic conversion activity for LiPSs as highly efficient sulfur host materials in Li-S batteries. The porous carbon network consisting of 2D cross-linked ultrathin carbon nanosheets provides void space to accommodate volumetric expansion upon lithiation, while the Cu, N-doping effect plays a critical role for the confinement of polysulfides through chemical bonding. In addition, after sulfuration of Cu@NC-F network, the in situ grown copper sulfide (CuxS) embedded within CuxS@NC/S-F composite catalyzes LiPSs conversion during reversible cycling, resulting in low polarization and fast redox reaction kinetics. At a current density of 0.1 C, the CuxS@NC/S-F composites' electrode exhibits an initial capacity of 1432 mAh g(-1) and maintains 1169 mAh g(-1) after 120 cycles, with a coulombic efficiency of nearly 100%.

Inkjet-printing of metal nanoparticles is a particularly promising technique for the fabrication and modification of surfaces with a multifunctional nature. Recently copper sulfide nanoparticles (CuS NPs) have attracted wide interest due to a range of valuable properties including long term stability, photo-thermal activity, ease of synthesis and low cost. In the present study, printed CuS patterns were successfully fabricated on latex coated paper substrates and characterized by means of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV–Vis-NIR spectroscopy, and grazing incidence X-ray diffraction (GID). The resulted patterns displayed pronounced photo-thermal effect under Near Infrared Irradiation (NIR) even with relatively low laser power. Finally, by utilizing an automated real-time imaging platform it was possible to verify that the CuS printed film was not cytotoxic to human dermal fibroblast cells (HDF). The pronounced photo-thermal properties and nontoxic nature of these printed low-cost flexible CuS films make them promising candidates for fabrication of devices with localized photo-thermal effect suitable for biomedical applications

This paper presents experimental findings of the effect of temperature on corrosive sulfur formation in transformers. To conduct the experimental study, new transformer oil was randomly selected and heated at 40, 60, 80, 120, and 150 degrees C temperature for 72 hours each along with copper strips wrapped with insulation paper and immersed in oil in accordance with IEC-62535 standard test covered conductor deposition (CCD). The oil, copper strips, and the insulation paper samples were evaluated using gas chromatography-sulfur chemiluminescence detector (GC-SCD), X-ray fluorescence spectroscopy (XRF), inductively coupled plasma optical emission spectrometry (ICP), and scanning electron microscopy (SEM) tests after 72 hours exposure at each temperature. The values so obtained, were analyzed and effect of temperature on various parameters was studied individually and as well as collectively. It was found that temperature plays an important role on corrosive sulfur formation process inside the transformers and hence the temperature of the oil should be kept within the allowed operating ranges for avoiding unforeseen failures.

This dissertation examines solar cell absorber materials that have the potential to replace silicon in solar cells, including several copper-based sulfides and perovskites. Earth-abundant absorbers such as these become even more cost-effective when used in a nanostructured solar cell. Atomic layer deposition (ALD) and chemical vapor deposition (CVD) deposit highly conformal films and hence are important tools for developing extremely thin absorber solar cells with scalability. Thus, the primary deposition techniques used for this work are the vacuum-based ALD and CVD. The primary characterization technique used is extended X-ray absorption fine structure (EXAFS), which has the ability to probe the local environment about different atoms, and can also give very precise ratios of elements using their fluorescence peaks.The work on copper-based sulfides focused on examining the local structure of ZnS, ZnS/Cu_2S, and Cu_2SnS_3 composite films prepared with ALD and CVD. Individual thin films of Zinc Sulfide (ZnS) and Copper (I) Sulfide (Cu_2S) formed very successfully via ALD and resemble bulk structure. Yet multi-layer films of ZnS/Cu_2S, prepared using a wide range of parameters, produce films that are predominantly either ZnS or Cu_2S, with the other material being highly disordered. This can be attributed to the crystal structure mismatch of ZnS and Cu_xS, making ALD with these precursors unsuitable for a CuZnS alloy. Another copper-based material, Cu_2SnS_3, has a stable structure with good electrical and optical absorption properties. Composite films of Cu_2SnS_3 were made using CVD layers of Cu_2S and SnS_2 with an anneal step. The results highlight the importance of stoichiometry and phase control in copper-based ternary and quaternary materials.Cu_2ZnSnS_4 (CZTS) has many desirable properties for a solar cell absorber, but the structures formed within the material remain difficult to characterize. This work investigates the local structure about the metal atoms

High-resolution photoelectron spectroscopy is used to study the chemical composition at the rubber-brass adhesive interface and to elucidate mechanisms of strong adhesion and adhesion-degradation processes. A layer composed of CuxS (x ≈ 2) and CuS is formed as an adhesive agent. The CuxS/CuS ratio is higher at the bonding front than in the bulk of the adhesive layer. Thermal aging leads to the reduction of the CuxS/CuS ratio and the adhesion force. These results suggest the important role that CuxS (x ≈ 2) plays in adhesion, High-resolution photoelectron spectroscopy is used to study the chemical composition at the rubber-brass adhesive interface and to elucidate mechanisms of strong adhesion and adhesion-degradation processes. A layer composed of CuxS (x ≈ 2) and CuS is formed as an adhesive agent. The CuxS/CuS ratio is higher at the bonding front than in the bulk of the adhesive layer. Thermal aging leads to the reduction of the CuxS/CuS ratio and the adhesion force. These results suggest the important role that CuxS (x ≈ 2) plays in adhesion

This dissertation examines solar cell absorber materials that have the potential to replace silicon in solar cells, including several copper-based sulfides and perovskites. Earth-abundant absorbers such as these become even more cost-effective when used in a nanostructured solar cell. Atomic layer deposition (ALD) and chemical vapor deposition (CVD) deposit highly conformal films and hence are important tools for developing extremely thin absorber solar cells with scalability. Thus, the primary deposition techniques used for this work are the vacuum-based ALD and CVD. The primary characterization technique used is extended X-ray absorption fine structure (EXAFS), which has the ability to probe the local environment about different atoms, and can also give very precise ratios of elements using their fluorescence peaks.The work on copper-based sulfides focused on examining the local structure of ZnS, ZnS/Cu_2S, and Cu_2SnS_3 composite films prepared with ALD and CVD. Individual thin films of Zinc Sulfide (ZnS) and Copper (I) Sulfide (Cu_2S) formed very successfully via ALD and resemble bulk structure. Yet multi-layer films of ZnS/Cu_2S, prepared using a wide range of parameters, produce films that are predominantly either ZnS or Cu_2S, with the other material being highly disordered. This can be attributed to the crystal structure mismatch of ZnS and Cu_xS, making ALD with these precursors unsuitable for a CuZnS alloy. Another copper-based material, Cu_2SnS_3, has a stable structure with good electrical and optical absorption properties. Composite films of Cu_2SnS_3 were made using CVD layers of Cu_2S and SnS_2 with an anneal step. The results highlight the importance of stoichiometry and phase control in copper-based ternary and quaternary materials.Cu_2ZnSnS_4 (CZTS) has many desirable properties for a solar cell absorber, but the structures formed within the material remain difficult to characterize. This work investigates the local structure about the metal atoms

The study presents the results of experimental investigation of finding out the maximum acceptable concentrations of DBDS, sulfur mercaptan, and optimal concentration of passivator for safe and prolonged operation of power transformers in the local environmental conditions of Saudi Arabia. For experimental investigation of optimal concentrations of DBDS and sulfur mercaptan, new oil free of sulfur compounds was acquired. Four specimens of this were spiked with different concentrations of DBDS and another four with free sulfur mercaptan RSH concentrations. The covered conductor deposition (CCD) tests were performed in accordance with IEC 62535 method on all the specimens. Next, to study the effect of passivator concentrations and temperatures on corrosive sulfur formation, 10 specimens from new oil were spiked with different concentrations of BTA and Irgamet 39. Copper strips were immersed in these specimens and the vials containing the oil and the copper strips were subjected to different temperature from 50 to 150 degrees C for 24 hours in the oven. The experimental results indicated that the concentration of DBDS should always be <4 ppm and sulfur mercaptan < 1 ppm in the new oils before putting in to the service. Based on the effectiveness of the passivators, BTA was found to be effective with 50 ppm concentration at 150 degrees C compared to Irgamet 39 which was effective only with 150 ppm concentration.

As an earth-abundant p-type semiconductor, copper sulfide (Cu2S) is an attractive material for application in photovoltaic devices. However, it suffers from a minority carrier diffusion length that is less than the length required for complete light absorption. Core-shell nanowires and nanorods have the potential to alleviate this difficulty because they decouple the length scales of light absorption and charge collection. To achieve this geometry using Cu2S, cation exchange was applied to an array of CdS nanorods to produce well-defined CdS-Cu2S core-shell nanorods. Previous work has demonstrated single-nanowire photovoltaic devices from this material system, but in this work, the cation exchange chemistry has been applied to nanorod arrays to produce ensemble-level devices with microscale sizes. The core-shell nanorod array devices show power conversion efficiencies of up to 3.8%. In addition, these devices are stable when measured in air after nearly one month of storage in a desiccator. These results are a first step in the development of large-area nanostructured Cu2S-based photovoltaics that can be processed from solution.

Copper sulfide nanowires/reduced graphene oxide (CuSNWs/rGO) nanocompsites are successfully synthesized via a facile one-pot and template-free solution method in a dimethyl sulfoxide (DMSO)-ethyl glycol (EG) mixed solvent. It is noteworthy that the precursor plays a crucial role in the formation of the nanocomposites structure. SEM, TEM, XRD, IR and Raman spectroscopy are used to investigate the morphological and structural evolution of CuSNWs/rGO nanocomposites. The as-fabricated CuSNWs/rGO nanocompsites show remarkably improved Li-storage performance, excellent cycling stability as well as high-rate capability compared with pristine CuS nanowires. It obtains a reversible capacity of 620 mAh g(-1) at 0.5C (1C = 560 mA g(-1)) after 100 cycles and 320 mAh g(-1) at a high current rate of 4C even after 430 cycles. The excellent lithium storage performance is ascribed to the synergistic effect between CuS nanowires and rGO nanosheets. The as-formed CuSNWs/rGO nanocomposites can effectively accommodate large volume changes, supply a 2D conducting network and trap the polysulfides generated during the conversion reaction of CuS.

Copper sulfide nanowires/reduced graphene oxide (CuSNWs/rGO) nanocompsites are successfully synthesized via a facile one-pot and template-free solution method in a dimethyl sulfoxide (DMSO)-ethyl glycol (EG) mixed solvent. It is noteworthy that the precursor plays a crucial role in the formation of the nanocomposites structure. SEM, TEM, XRD, IR and Raman spectroscopy are used to investigate the morphological and structural evolution of CuSNWs/rGO nanocomposites. The as-fabricated CuSNWs/rGO nanocompsites show remarkably improved Li-storage performance, excellent cycling stability as well as high-rate capability compared with pristine CuS nanowires. It obtains a reversible capacity of 620 mAh g(-1) at 0.5C (1C = 560 mA g(-1)) after 100 cycles and 320 mAh g(-1) at a high current rate of 4C even after 430 cycles. The excellent lithium storage performance is ascribed to the synergistic effect between CuS nanowires and rGO nanosheets. The as-formed CuSNWs/rGO nanocomposites can effectively accommodate large volume changes, supply a 2D conducting network and trap the polysulfides generated during the conversion reaction of CuS.

As an earth-abundant p-type semiconductor, copper sulfide (Cu2S) is an attractive material for application in photovoltaic devices. However, it suffers from a minority carrier diffusion length that is less than the length required for complete light absorption. Core-shell nanowires and nanorods have the potential to alleviate this difficulty because they decouple the length scales of light absorption and charge collection. To achieve this geometry using Cu2S, cation exchange was applied to an array of CdS nanorods to produce well-defined CdS-Cu2S core-shell nanorods. Previous work has demonstrated single-nanowire photovoltaic devices from this material system, but in this work, the cation exchange chemistry has been applied to nanorod arrays to produce ensemble-level devices with microscale sizes. The core-shell nanorod array devices show power conversion efficiencies of up to 3.8%. In addition, these devices are stable when measured in air after nearly one month of storage in a desiccator. These results are a first step in the development of large-area nanostructured Cu2S-based photovoltaics that can be processed from solution.

Novel copper sulfide (CuS) nanowire bundles with a diameter of about 6 nm and a length up to several micrometers are successfully synthesized by a template- and surfactant-free method in a dimethyl sulfoxide (DMSO)-ethyl glycol (EG) mixed solvent. The resulting CuS nanowire bundles are used as a cathode material in lithium-ion batteries and exhibit a large capacity and excellent cycling stability and rate capability. The unique structure of the CuS nanowire bundles is responsible for their excellent electrochemical performance. © 2014 Elsevier B.V. All rights reserved.

Nature has the ability to mineralize and build intricate nanostructures of inorganic materials with a very high precision. Various bio-molecules can mineralize and control the morphology and composition of inorganic materials at ambient conditions. Inspired by nature, this work focuses on utilizing the M13 virus, a filamentous phage, 880 nm in length and 6 nm in diameter, for mineralizing copper sulfide and copper oxide semiconductor nanomaterials. The various coat proteins of the virus can easily be modified to express different peptides with specific affinity to various inorganic materials. A phage-display technique was utilized to identify a copper sulfide binding peptide expressed on the entire pVIII coat protein of the virus. This modified phage was used for synthesizing copper sulfide nanoparticles along the length of the template. To increase the yield and coverage of the mineralized material on the phage-templates, non-specific electrostatic interactions between a negatively charged phage (E3) and positively charged copper ions were utilized to synthesize copper sulfide at ambient conditions. The mineralized material coated the phage template and was identified to be cubic Cu1.8S, a non-stoichiometric phase of the copper sulfide material system. The material showed strong optical absorption below 800 nm due to band-to-band transitions and localized surface plasmon resonance (LSPR) peaks in the infrared region. The LSPR peaks increased in absorption and the electrical resistance of the materials decreased with time indicating an increase in the number of free carriers in the material due to exposure at ambient conditions. The free carrier increase was attributed to a compositional change on the surface of the material. The synthesized Cu1.8S was utilized to fabricate NH3 gas sensors. These gas sensors showed a high response to NH3 gas which may be attributed to the large surface-to-volume ratio of the viral-templated nanomaterials. Finally, utilizing the non

Nature has the ability to mineralize and build intricate nanostructures of inorganic materials with a very high precision. Various bio-molecules can mineralize and control the morphology and composition of inorganic materials at ambient conditions. Inspired by nature, this work focuses on utilizing the M13 virus, a filamentous phage, 880 nm in length and 6 nm in diameter, for mineralizing copper sulfide and copper oxide semiconductor nanomaterials. The various coat proteins of the virus can easily be modified to express different peptides with specific affinity to various inorganic materials. A phage-display technique was utilized to identify a copper sulfide binding peptide expressed on the entire pVIII coat protein of the virus. This modified phage was used for synthesizing copper sulfide nanoparticles along the length of the template. To increase the yield and coverage of the mineralized material on the phage-templates, non-specific electrostatic interactions between a negatively charged phage (E3) and positively charged copper ions were utilized to synthesize copper sulfide at ambient conditions. The mineralized material coated the phage template and was identified to be cubic Cu1.8S, a non-stoichiometric phase of the copper sulfide material system. The material showed strong optical absorption below 800 nm due to band-to-band transitions and localized surface plasmon resonance (LSPR) peaks in the infrared region. The LSPR peaks increased in absorption and the electrical resistance of the materials decreased with time indicating an increase in the number of free carriers in the material due to exposure at ambient conditions. The free carrier increase was attributed to a compositional change on the surface of the material. The synthesized Cu1.8S was utilized to fabricate NH3 gas sensors. These gas sensors showed a high response to NH3 gas which may be attributed to the large surface-to-volume ratio of the viral-templated nanomaterials. Finally, utilizing the non

Novel copper sulfide (CuS) nanowire bundles with a diameter of about 6 nm and a length up to several micrometers are successfully synthesized by a template- and surfactant-free method in a dimethyl sulfoxide (DMSO)-ethyl glycol (EG) mixed solvent. The resulting CuS nanowire bundles are used as a cathode material in lithium-ion batteries and exhibit a large capacity and excellent cycling stability and rate capability. The unique structure of the CuS nanowire bundles is responsible for their excellent electrochemical performance. © 2014 Elsevier B.V. All rights reserved.

Three routes to more efficient photovoltaics using conformal Cu2S, organic luminescent films, and nanocrystalline PbSe films are outlined below. Properties of these materials are investigated experimentally and numerically in separate studies. In the first study, chemical vapor deposition (CVD) processes were used to fabricate Cu2S using hydrogen sulfide and the metal-organic precursor, KI5. The alternating exposure of mesoporous TiO2 and planar ZnO to the two precursors resulted in films that penetrated porous structures and deposited at a constant rate of 0.08nm/cycle over the temperature range 150C-400C. Sheet resistance and optical absorption measurements suggest the presence of a metallic copper-poor phase of less than 100nm thick forming at the Cu2S/substrate boundary.In a separate study, organic films doped with luminescent dyes were placed above CdTe/CdS solar cells to convert high energy photons to lower energies, better matched to the CdTe/CdS quantum efficiency peak. Efficiency improvements of up to 8.5% were obtained after optimizing dye concentration, dye chemistry, and the host material. Long-term stability tests show that the organic films are stable for at least 5000 hours under 1 sun illumination provided that the dye is encapsulated in an oxygen and water free environment.Finally, a Monte Carlo model was developed to simulate electron and hole transport in nanocrystalline PbSe films. Transport is carried out as a series of thermally activated tunneling events between neighboring sites on a cubic lattice. Each site, representing an individual nanocrystal, is assigned a size-dependent electronic structure, and the effects of crystal size, charging, inter-crystal coupling, and energetic disorder on electron and hole mobilities/conductivities are investigated. Results of simulated field effect measurements confirm that electron mobilities and conductivities increase by an order of magnitude when the average nanocrystal diameter is increased in the 3-5n

Three routes to more efficient photovoltaics using conformal Cu2S, organic luminescent films, and nanocrystalline PbSe films are outlined below. Properties of these materials are investigated experimentally and numerically in separate studies. In the first study, chemical vapor deposition (CVD) processes were used to fabricate Cu2S using hydrogen sulfide and the metal-organic precursor, KI5. The alternating exposure of mesoporous TiO2 and planar ZnO to the two precursors resulted in films that penetrated porous structures and deposited at a constant rate of 0.08nm/cycle over the temperature range 150C-400C. Sheet resistance and optical absorption measurements suggest the presence of a metallic copper-poor phase of less than 100nm thick forming at the Cu2S/substrate boundary.In a separate study, organic films doped with luminescent dyes were placed above CdTe/CdS solar cells to convert high energy photons to lower energies, better matched to the CdTe/CdS quantum efficiency peak. Efficiency improvements of up to 8.5% were obtained after optimizing dye concentration, dye chemistry, and the host material. Long-term stability tests show that the organic films are stable for at least 5000 hours under 1 sun illumination provided that the dye is encapsulated in an oxygen and water free environment.Finally, a Monte Carlo model was developed to simulate electron and hole transport in nanocrystalline PbSe films. Transport is carried out as a series of thermally activated tunneling events between neighboring sites on a cubic lattice. Each site, representing an individual nanocrystal, is assigned a size-dependent electronic structure, and the effects of crystal size, charging, inter-crystal coupling, and energetic disorder on electron and hole mobilities/conductivities are investigated. Results of simulated field effect measurements confirm that electron mobilities and conductivities increase by an order of magnitude when the average nanocrystal diameter is increased in the 3-5n

In this dissertation, fine control over the morphology and composition of a nanostructured semiconductor thin film is demonstrated at a degree not previously possible. While such control is beneficial in a variety of optical and electrical devices, this research was performed from the perspective of photovoltaics.A new architecture is presented for low cost and high conversion efficiency photovoltaics, utilizing self-assembled nanocrystals. A method is introduced for vertically aligning nanorods using a controlled-evaporation self-assembly technique, enabling the uniform alignment of nanorods on a square-centimeter substrate. Such meso-scale assembly and optimization required the development of a morphology quantification technique. The technique presented here utilizes grazing incidence x-ray diffraction to assemble a quantitative pole figure, or nanorod orientation histogram, and can be used with any thin film. After nanorod assembly, an asymmetric electrical junction (required for photovoltaic operation) is achieved in each rod using a cation exchange technique, which can be performed reliably and reversibly on-chip. This results in a film comprising a massively parallel array of single-crystal nanodiodes. Electrical measurements of these films show rectified behavior and reveal a photocurrent upon illumination of the aligned and cation-exchanged films. Finally, the stability of the Cu2S phase is investigated as a function of nanocrystal size. The low chalcocite to high chalcocite solid-solid crystallographic phase transition is found to occur at temperatures depressed 60 Kelvin below the bulk phase transition temperature.The research summarized in this dissertation describes a set of synthetic and analytical techniques that enable nanoscopic control of morphology and composition in device-scale semiconductor thin films. Such control may be leveraged to precisely manipulate the flow of charge carriers in optoelectronic devices. Due to the simple wet chemical proc

Quantum confinement of electronic wavefunctions in semiconductor quantum dots (QDs) yields discrete atom-like and tunable electronic levels, thereby allowing the engineering of excitation and emission spectra. Metal nanoparticles, on the other hand, display strong resonant interactions with light from localized surface plasmon resonance (LSPR) oscillations of free carriers, resulting in enhanced and geometrically tunable absorption and scattering resonances. The complementary attributes of these nanostructures lends strong interest toward integration into hybrid nanostructures to explore enhanced properties or the emergence of unique attributes arising from their interaction. However, the physicochemical interface between the two components can be limiting for energy transfer and synergistic coupling within such a hybrid nanostructure. Therefore, it is advantageous to realize both attributes, i.e., LSPRs and quantum confinement within the same nanostructure. Here, we describe well-defined LSPRs arising from p-type carriers in vacancy-doped semiconductor quantum dots. This opens up possibilities for light harvesting, non-linear optics, optical sensing and manipulation of solid-state processes in single nanocrystals.

Determination of the phase diagrams for the nanocrystalline forms of materials is crucial for our understanding of nanostructures and the design of functional materials using nanoscale building blocks. The ability to study such transformations in nanomaterials with controlled shape offers further insight into transition mechanisms and the influence of particular facets. Here we present an investigation of the size-dependent, temperature-induced solid-solid phase transition in copper sulfide nanorods from low- to high-chalcocite. We find the transition temperature to be substantially reduced, with the high chalcocite phase appearing in the smallest nanocrystals at temperatures so low that they are typical of photovoltaic operation. Size dependence in phase trans- formations suggests the possibility of accessing morphologies that are not found in bulk solids at ambient conditions. These other- wise-inaccessible crystal phases could enable higher-performing materials in a range of applications, including sensing, switching, lighting, and photovoltaics.

Quantum confinement of electronic wavefunctions in semiconductor quantum dots (QDs) yields discrete atom-like and tunable electronic levels, thereby allowing the engineering of excitation and emission spectra. Metal nanoparticles, on the other hand, display strong resonant interactions with light from localized surface plasmon resonance (LSPR) oscillations of free carriers, resulting in enhanced and geometrically tunable absorption and scattering resonances. The complementary attributes of these nanostructures lends strong interest toward integration into hybrid nanostructures to explore enhanced properties or the emergence of unique attributes arising from their interaction. However, the physicochemical interface between the two components can be limiting for energy transfer and synergistic coupling within such a hybrid nanostructure. Therefore, it is advantageous to realize both attributes, i.e., LSPRs and quantum confinement within the same nanostructure. Here, we describe well-defined LSPRs arising from p-type carriers in vacancy-doped semiconductor quantum dots. This opens up possibilities for light harvesting, non-linear optics, optical sensing and manipulation of solid-state processes in single nanocrystals.

Determination of the phase diagrams for the nanocrystalline forms of materials is crucial for our understanding of nanostructures and the design of functional materials using nanoscale building blocks. The ability to study such transformations in nanomaterials with controlled shape offers further insight into transition mechanisms and the influence of particular facets. Here we present an investigation of the size-dependent, temperature-induced solid-solid phase transition in copper sulfide nanorods from low- to high-chalcocite. We find the transition temperature to be substantially reduced, with the high chalcocite phase appearing in the smallest nanocrystals at temperatures so low that they are typical of photovoltaic operation. Size dependence in phase trans- formations suggests the possibility of accessing morphologies that are not found in bulk solids at ambient conditions. These other- wise-inaccessible crystal phases could enable higher-performing materials in a range of applications, including sensing, switching, lighting, and photovoltaics.

In this dissertation, fine control over the morphology and composition of a nanostructured semiconductor thin film is demonstrated at a degree not previously possible. While such control is beneficial in a variety of optical and electrical devices, this research was performed from the perspective of photovoltaics.A new architecture is presented for low cost and high conversion efficiency photovoltaics, utilizing self-assembled nanocrystals. A method is introduced for vertically aligning nanorods using a controlled-evaporation self-assembly technique, enabling the uniform alignment of nanorods on a square-centimeter substrate. Such meso-scale assembly and optimization required the development of a morphology quantification technique. The technique presented here utilizes grazing incidence x-ray diffraction to assemble a quantitative pole figure, or nanorod orientation histogram, and can be used with any thin film. After nanorod assembly, an asymmetric electrical junction (required for photovoltaic operation) is achieved in each rod using a cation exchange technique, which can be performed reliably and reversibly on-chip. This results in a film comprising a massively parallel array of single-crystal nanodiodes. Electrical measurements of these films show rectified behavior and reveal a photocurrent upon illumination of the aligned and cation-exchanged films. Finally, the stability of the Cu2S phase is investigated as a function of nanocrystal size. The low chalcocite to high chalcocite solid-solid crystallographic phase transition is found to occur at temperatures depressed 60 Kelvin below the bulk phase transition temperature.The research summarized in this dissertation describes a set of synthetic and analytical techniques that enable nanoscopic control of morphology and composition in device-scale semiconductor thin films. Such control may be leveraged to precisely manipulate the flow of charge carriers in optoelectronic devices. Due to the simple wet chemical proc

Copper is widely known as a very important material due to its applications in our daily life, such as electrical devices and heating appliances. It is not so common knowledge that copper is not found in its metallic form, but mixed with other metals and elements like sulphur and oxygen. The process to obtain pure copper nowadays implies a strong impact on the environment. Regarding copper sulphides, its reduction to metallic copper is based in the oxidation of the ore products which forms sulphur dioxide (SO2), amongst others. Although SO2 is sent to sulphuric acid production, there are still emissions to the environment. Since the reduction of contaminant emissions has become of a primary concern, several alternatives have been studied to replace the current process. One of the alternatives that is gaining strength is the leaching or bioleaching, where poor ores are treated with solvents (chemical leaching) or with bacteria (bioleaching). The advantages of this process is that low pressures and temperatures are needed, but long times are required. However, a high pressure and temperature version exists to reduce the leaching retention time. Another option is the so – called mechanochemical reactions. These are based in applying high energy by grinding and milling a small amount of the sample. The main disadvantages are that the reaction is slow and small amounts can be treated at a time. This choice is taken where tiny particle size is required, since copper of nano size can be prepared. In addition, it is used as a pre – treatment for the leaching/bioleaching process, because the milling activates the reactivity of the solid and shortens the leaching times. The process that has attracted more attention is the reduction with hydrogen (H2) gas. If feasible, a similar system as it exists nowadays could be adapted to the H2 flow. Regarding the particular case of copper sulphides, several authors have already investigated the reaction. Among their conclusions, the rea, Outgoing

Size- and shape-controlled nanocrystal growth is intensely researched for applications including electro-optic, catalytic, and medical devices. Chemical transformations such as cation exchange overcome the limitation of traditional colloidal synthesis, where the nanocrystal shape often reflects the inherent symmetry of the underlying lattice. Here we show that nanocrystals, with established synthetic protocols for high monodispersity, can be templates for independent composition control. Specifically, controlled interconversion between wurtzite CdS, chalcocite Cu2S, and rock salt PbS occurs while preserving the anisotropic dimensions unique to the as-synthesized materials. Sequential exchange reactions between the three sulfide compositions are driven by the disparate solubilites of the metal ion exchange pair in specific coordinating molecules. Starting with CdS, highly anisotropic PbS nanorods are created, which serve as an important material for studying strong 2-dimensional quantum confinement, as well as for optoelectronic applications. Furthermore, interesting nanoheterostructures of CdS|PbS are obtained by precise control over ion insertion and removal.

Size- and shape-controlled nanocrystal growth is intensely researched for applications including electro-optic, catalytic, and medical devices. Chemical transformations such as cation exchange overcome the limitation of traditional colloidal synthesis, where the nanocrystal shape often reflects the inherent symmetry of the underlying lattice. Here we show that nanocrystals, with established synthetic protocols for high monodispersity, can be templates for independent composition control. Specifically, controlled interconversion between wurtzite CdS, chalcocite Cu2S, and rock salt PbS occurs while preserving the anisotropic dimensions unique to the as-synthesized materials. Sequential exchange reactions between the three sulfide compositions are driven by the disparate solubilites of the metal ion exchange pair in specific coordinating molecules. Starting with CdS, highly anisotropic PbS nanorods are created, which serve as an important material for studying strong 2-dimensional quantum confinement, as well as for optoelectronic applications. Furthermore, interesting nanoheterostructures of CdS|PbS are obtained by precise control over ion insertion and removal.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Biomolecular and Physical Sciences, Science, Environment, Engineering and Technology, This thesis presents the results of an investigation into the nature of chemical bath deposition (CBD) of copper sulfide (CuxS) thin films and the processes involved in the deposition process. CBD copper sulfide thin films were deposited onto several different substrates including glass microscope slides, silicon wafers and gold and platinum electrodes. The resulting products were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and shown to be amorphous or poorly crystalline with a particulate appearance. The particle size was measured at ~200 nm for as-deposited samples and ~170 nm for samples that had been annealed in air at 150 °C. Annealing in air also increased the crystallinity of the samples and reduced the film thickness. Atomic force microscopy (AFM) and neutron reflectometry indicated the presence of considerable roughness at the film/air interface. This was considered to be due to the presence of precipitates that had loosely adhered to the film surface...

This thesis presents the results of an investigation into the nature of chemical bath deposition (CBD) of copper sulfide (CuxS) thin films and the processes involved in the deposition process. CBD copper sulfide thin films were deposited onto several different substrates including glass microscope slides, silicon wafers and gold and platinum electrodes. The resulting products were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and shown to be amorphous or poorly crystalline with a particulate appearance. The particle size was measured at ~200 nm for as-deposited samples and ~170 nm for samples that had been annealed in air at 150 °C. Annealing in air also increased the crystallinity of the samples and reduced the film thickness. Atomic force microscopy (AFM) and neutron reflectometry indicated the presence of considerable roughness at the film/air interface. This was considered to be due to the presence of precipitates that had loosely adhered to the film surface..., Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Biomolecular and Physical Sciences, Science, Environment, Engineering and Technology, Full Text

Thermodynamic stability of Cu2S sulfide in low carbon steels has been investigated using a CALPHAD type thermodynamic calculation method. Thermodynamic properties of the Cu-S binary and Fe-Cu-S ternary systems were critically assessed. By combining the newly assessed thermodynamic parameters to an existing thermodynamic database for steels, a thermodynamic description for low carbon steels involving sulfur and Cu could be obtained and be used to calculate phase equilibria and thermodynamic stability of precipitating phases such as AlN, MnS, and Cu2S. It was predicted that the Cu2S sulfide often observed in low carbon steels is actually a thermodynamically unstable phase and can precipitate when thermodynamic equilibrium state is not reached during steel making processes. Probable reasons and conditions for the formation of this unstable phase are discussed., QC 20100525

Photoelectrochernistry (PEC) of straight and isolated CU2S nanowires arrayed on a copper foil is studied. A cathodic photocurrent is observed, which increases with the increasing negative bias of the film electrode, conforming to the p-type semiconducting nature of CU2S. PEC studies on the core/sheath nanowires of Cu2S (Cu2S nanowires coated with other nanoparticles such as CdS, polypyrrole, and Au) have revealed distinctly different characteristics. Cu2S/CdS nanowires exhibit a slightly higher photocurrent response due to the charge transfer between the p-type Cu2S core and n-type CdS sheath, whereas the photocurrent response obtained for Cu2S/PPy nanowires is generally an order of magnitude smaller than that for pure Cu2S nanowires under the same bias voltage. For Cu2S/Au nanowires, however, Au nanoparticles can readily accept the photogenerated electrons from the conduction band of CU2S; this redirects the electron transfer pathway and results in the anodic photocurrent response. On the basis of these findings, different photocurrent generation mechanisms are proposed. (c) 2005 The Electrochemical Society. [DOI: 10. 1149/1.1859991] All rights reserved.

Photoelectrochernistry (PEC) of straight and isolated CU2S nanowires arrayed on a copper foil is studied. A cathodic photocurrent is observed, which increases with the increasing negative bias of the film electrode, conforming to the p-type semiconducting nature of CU2S. PEC studies on the core/sheath nanowires of Cu2S (Cu2S nanowires coated with other nanoparticles such as CdS, polypyrrole, and Au) have revealed distinctly different characteristics. Cu2S/CdS nanowires exhibit a slightly higher photocurrent response due to the charge transfer between the p-type Cu2S core and n-type CdS sheath, whereas the photocurrent response obtained for Cu2S/PPy nanowires is generally an order of magnitude smaller than that for pure Cu2S nanowires under the same bias voltage. For Cu2S/Au nanowires, however, Au nanoparticles can readily accept the photogenerated electrons from the conduction band of CU2S; this redirects the electron transfer pathway and results in the anodic photocurrent response. On the basis of these findings, different photocurrent generation mechanisms are proposed. (c) 2005 The Electrochemical Society. [DOI: 10. 1149/1.1859991] All rights reserved.

Photoelectrochernistry (PEC) of straight and isolated CU2S nanowires arrayed on a copper foil is studied. A cathodic photocurrent is observed, which increases with the increasing negative bias of the film electrode, conforming to the p-type semiconducting nature of CU2S. PEC studies on the core/sheath nanowires of Cu2S (Cu2S nanowires coated with other nanoparticles such as CdS, polypyrrole, and Au) have revealed distinctly different characteristics. Cu2S/CdS nanowires exhibit a slightly higher photocurrent response due to the charge transfer between the p-type Cu2S core and n-type CdS sheath, whereas the photocurrent response obtained for Cu2S/PPy nanowires is generally an order of magnitude smaller than that for pure Cu2S nanowires under the same bias voltage. For Cu2S/Au nanowires, however, Au nanoparticles can readily accept the photogenerated electrons from the conduction band of CU2S; this redirects the electron transfer pathway and results in the anodic photocurrent response. On the basis of these findings, different photocurrent generation mechanisms are proposed. (c) 2005 The Electrochemical Society. [DOI: 10. 1149/1.1859991] All rights reserved.

In this study, we developed a simple and facile synthesis method for producing CuS films at low temperatures. The method uses self-reducible complex inks comprising copper formate (Cuf) as the copper source and thioacetamide (TA) as both the sulfur source and complexing agent. The thermal properties of complex inks with different TA/Cuf ratios (0.5–2.0) were analyzed. The ink with a TA/Cuf ratio of 1 exhibited a significant decrease in the reduction temperature. The synthesis of a CuS film involved calcination of the ink at 140 °C; however, some residual Cuf was observed. Introducing hexanol to the ink, aimed at prolonging the liquid-phase reaction, yielded a pure CuS film that contained agglomerated particles. The thermal reduction pathway of Cuf to CuS was analyzed through thermogravimetric–mass spectrometric analysis, and the results revealed that the low-temperature synthesis was attributed to the formation of acetonitrile and formic acid during thermal decomposition of the ink.