CFTS-3/In2S3/SnO2:F heterojunction structure as eco-friendly photocatalytic candidate for removing organic pollutants

In this paper, quaternary chalcogenide Cu₂FeSnS₄ (CFTS) thin films were synthesized by spray pyrolysis using multilayer deposition technique in which the number (N) of sequential deposition runs (DR) is N = 1, 2, 3 and 4. The delivered volume in each sample is (N × 300 ml). Correspondingly, samples are named CFTS-N. Chemical composition, morphological, structural, optical and electrical properties were characterized using dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, spectrophotometer and Hall Effect measurements. XRD and Raman spectroscopy show a purer phase and better crystalline quality of CFTS-3 than other films. Average particle size increases with DR and reaches a maximum value of about 60 nm for N = 3. Optical results show high absorption coefficient value about 10⁵ cm⁻¹ in visible range, with an optical band gap of about 1.47 eV. Electrical resistivity of CFTS-3 equals to 5.82 10⁻³ Ω cm which is the lowest value of these four samples. We have investigated the photocatalysis activity of various thin films by measuring the degradation of methylene blue (MB) and Rhodamine (RhB) as pollutant dyes. In particular we have compared the candidates: CFTS-3/SnO₂:F, CFTS-3/In₂S₃ and CFTS-3/In₂S₃/SnO₂:F. Under sun light irradiation, CFTS-3/In₂S₃/SnO₂:F heterojunction exhibits the best photodegradation rate (96%) of MB dye.     

Preparation of Ga<Subscript>2</Subscript>Se<Subscript>3</Subscript> thin films by sol–gel technique

In this study we describe the preparation of Ga₂Se₃ semiconductor compound thin films by sol–gel method for different crystal formation temperatures. The films were characterized by X-ray diffraction analyses (XRD), UV–visible spectrometer, and scanning electron microscope (SEM). The XRD spectrum showed that the formation of Ga₂Se₃ crystals were between 743 and 823 K. The thin film crystals that were formed at 773 K corresponded to the β phase and the preferred crystal structure was monoclinic. The value of band gap from optical absorption spectra for the Ga₂Se₃ thin films was estimated to be about E _g ~ 2.56 eV. The thickness of the one-coat Ga₂Se₃ thin films, which was measured by a Spectroscopic Ellipsometer, was about ~200 nm. The average grain sizes of scattered particles were within the limits between 200 and 500 nm.     

Novel Electroless Deposition of Cu<Subscript>3</Subscript>Se<Subscript>2</Subscript> Film on Silicon Substrate by a Simple Galvanic Displacement Process

A novel electroless deposition method for depositing highly uniform adhesive thin films of copper selenide (Cu₃Se₂) on silicon substrates from aqueous solutions is described. The deposition is carried out by two coupled galvanic reactions in a single deposition bath containing copper cations, hydrogen fluoride, and selenous acid: the galvanic deposition of copper on silicon and the subsequent galvanic reaction between the deposited copper with selenous acid in the deposition bath. The powder X-ray diffraction and scanning electron microscopy are used to characterize and examine the deposited films.     

Optical constants,dispersion energy parameters and dielectric properties of ultra-smooth nanocrystalline BiVO4 thin films prepared by rf-magnetron sputtering

BiVO₄ thin films have been prepared through radio frequency (rf) magnetron sputtering of a pre-fabricated BiVO₄ target on ITO coated glass (ITO-glass) substrate and bare glass substrates. BiVO₄ target material was prepared through solid-state reaction method by heating Bi₂O₃ and V₂O₅ mixture at 800 °C for 8 h. The films were characterized by X-ray diffraction, UV–Vis spectroscopy, LCR meter, field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. BiVO₄ thin films deposited on the ITO-glass substrate are much smoother compared to the thin films prepared on bare glass substrate. The rms surface roughness calculated from the AFM images comes out to be 0.74 nm and 4.2 nm for the films deposited on the ITO-glass substrate and bare glass substrate for the deposition time 150 min respectively. Optical constants and energy dispersion parameters of these extra-smooth BiVO₄ thin films have been investigated in detail. Dielectric properties of the BiVO₄ thin films on ITO-glass substrate were also investigated. The frequency dependence of dielectric constant of the BiVO₄ thin films has been measured in the frequency range from 20 Hz to 2 MHz. It was found that the dielectric constant increased from 145 to 343 at 20 Hz as the film thickness increased from 90 nm to 145 nm (deposition time increased from 60 min to 150 min). It shows higher dielectric constant compared to the literature value of BiVO₄.     

Electrodeposition of Copper Selenide onto Mo Electrode in Tartaric Acid Solution

Results are presented of a study of the electrochemical behavior of copper(II) and selenium(IV) ions and their joint reduction on a molybdenum electrode by cyclic voltammetry in a tartaric acid electrolyte. The potentiostatic deposition was used to obtain copper selenide deposits on Mo plates. The diffraction and energydispersive analyses demonstrated that a Cu_2?xSe compound is formed with an admixture of the CuSe phase. A suggestion is made that the process of underpotential reduction affects the formation of copper selenide. Copper selenide films were deposited at a potential of ?0.6 V in the course of 30 min with a thickness of 0.43 μm and high adhesion to the substrate. At potentials in this range, an additional amount of the deposit may be formed due to the chemical reaction between Cu⁺ and Se^2? ions. The p-type conduction was determined for films electrodeposited at various potentials.     

Deposition conditions,composition, and structure of chemically deposited In<Subscript>2</Subscript>Se<Subscript>3</Subscript> films

In₂Se₃ films up to 300 nm thick have been obtained for the first time by hydrochemical deposition on glass, glass ceramic, and molybdenum substrates in the In(NO₃)₃–C₄O₆H₆–CSeN₂H₄ system with the use of selenourea as a chalcogenizing agent. The phase and element composition and morphological features of layers obtained at 353 and 363 K have been studied by X-ray photoelectron spectroscopy, energy-dispersive electron probe X-ray microanalysis, and scanning electron microscopy. The optical band gap width has been determined.     

Investigation of optical properties of amorphous Ge15Se85-xCux thin films using spectroscopic ellipsometry

Different compositions of amorphous Ge₁₅Se_85-xCu_x thin films were deposited onto glass substrates by the thermal evaporation technique. Their amorphous structural characteristics were studied by X-ray diffraction (XRD). The optical constants (n, k) of amorphous Ge₁₅Se_85-xCu_x thin films were obtained by fitting the ellipsometric parameters (ψ and Δ) data for the first time using three layers model system in the wavelength range 300–1100 nm. It was found that the refractive index, n, increases with the increase of Cu content. The possible optical transition in these films is found to be indirect transitions. The optical energy gap decreases linearly from 1.83 to 1.44 eV with increasing the Cu. The experimental transmittances spectrum can be simulated using the thickness and optical constants modeled by spectroscopic ellipsometry model.     

离子液体电沉积CuIn_xGa_(1-x)Se_2薄膜(英文)

采用循环伏安法(CV)对离子液体Reline中三元CuCl2+InCl3+SeCl4体系和四元CuCl2+InCl3+GaCl3+SeCl4体系的电化学行为进行了研究。研究表明,In3+并入三元CIS(Cu-In-Se)薄膜体系和Ga3+并入四元CIGS(Cu-In-Ga-Se)薄膜体系均有两种途径:一是发生共沉积,二是直接还原。利用电感耦合等离子体发射光谱(ICP)和扫描电镜(SEM)对沉积电势、镀液温度和主盐浓度对CIGS薄膜组成、镀层表面形貌的影响进行了测试,结果表明通过工艺参数的选择可以控制Ga/(Ga+In)和CIGS薄膜组成并得到化学计量比为Cu1.00In0.78Ga0.27Se2.13的薄膜。     

The effect of different gas atmospheres on the structure,morphology and photoluminescence properties of pulsed laser deposited Y3(Al,Ga)5O12:Ce3+ nano thin films

Luminescent properties of Y₃(Al,Ga)₅O₁₂:Ce³⁺ phosphor powder and thin films were obtained. The phosphor powder was used as target material for Pulsed Laser Deposition (PLD) of the thin films in the presence of different background gases. Excitation peaks for the powder were obtained at 439, 349, 225 and 189 nm and emission peaks at 512 and 565 nm. X-ray diffraction indicated that better crystallization took place for films deposited in a 20 mTorr O₂ atmosphere. Atomic force microscope revealed an RMS value of 0.7 nm, 2.5 nm and 4.8 nm for the films deposited in vacuum, O₂ and Ar atmospheres, respectively. The highest PL intensity was observed for films deposited in the O₂ atmosphere. A slight shift in the wavelength of the PL spectra was obtained for the thin films due to a change in the crystal field. The thickness of the films varied from 120 nm to 270 nm with films deposited in vacuum having the thin layer and those in Ar having the thick layer. The stoichiometry of the powder was maintained in the film during the deposition as confirmed by Rutherford backscattering spectroscopy.     

Solid state studies on cobalt and copper tungstates nano materials

The cobalt and copper tungstates of the composition Co_1?xCu_xWO₄ (where x = 0.0, 0.3, 0.5, 0.7 and 1.0) were synthesized by co-precipitation method. The compounds were characterized by Thermogravimetric Differential Scanning Calorimeter, X-ray powder diffraction, Infrared spectroscopy, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The Rietveld refinements of X-ray powder diffraction data for the composition Cu_0.5Co_0.5WO₄ reveal the triclinic structure with Pī symmetry. The SEM and TEM studies of the compounds show average particle size in the range of 30–50 nm. The XPS studies confirmed the 2+ oxidation state of the Co and Cu, whereas W exists in 6+ state. The Diffuse reflectance Ultraviolet–visible spectroscopy illustrates band gaps of the compounds ranging from 2.95 to 2.79 eV. The CoWO₄ shows promising photoluminescence result exhibiting strong emission intensity at 468 nm.     

Multi-walled carbon nanotubes as electrode materials for electrochemical studies of organometallic compounds in organic solvent media

Abstract  

Films of vertically aligned multi-walled carbon nanotubes (MWCNT) were selectively synthesized on silicon dioxide substrate by catalytic chemical vapor deposition using either benzene or acetonitrile as carbon source and ferrocene (1% w/w) as catalyst. The MWCNT were extensively characterized by using scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and Raman spectroscopy. In order to examine the prospective application of the fabricated MWCNT films for the detection of electro-active compounds in organic solvent media, electrochemical studies of the oxidation of cobaltocene (CoCp₂) to cobaltocenium cation (CoCp₂⁺) (Cp = cyclopentadienyl anion) in acetonitrile were performed on these films. For this purpose, cyclic voltammetry and electrochemical impedance spectroscopy were employed. The electrochemical parameters for the CoCp₂^+/0 couple in acetonitrile were derived and compared with those obtained using a conventional glassy carbon electrode. The results demonstrate that the synthesized MWCNT films are promising electrode materials for the electrochemical detection of electro-active species in organic solvents. The MWCNT film formed upon decay of benzene has higher capacitance, less Warburg impedance, and less charge transfer resistance, and consequently it provides faster electron transfer kinetics.     

离子液体电沉积CuInxGa1-xSe2薄膜

采用循环伏安法(CV)对离子液体Reline中三元CuCl₂+InCl₃+SeCl₄体系和四元CuCl₂+InCl₃+GaCl₃+SeCl₄体系的电化学行为进行了研究。研究表明,In³⁺并入三元CIS(Cu-In-Se)薄膜体系和Ga³⁺并入四元CIGS(Cu-In-Ga-Se)薄膜体系均有两种途径：一是发生共沉积,二是直接还原。利用电感耦合等离子体发射光谱(ICP)和扫描电镜(SEM)对沉积电势、镀液温度和主盐浓度对CIGS薄膜组成、镀层表面形貌的影响进行了测试,结果表明通过工艺参数的选择可以控制Ga/(Ga+In)和CIGS薄膜组成并得到化学计量比为Cu_1.00In_0.78Ga_0.27Se_2.13的薄膜。     

Insight into the enhancement of photovoltaic properties of Ti-doped Copper(I) oxide via: Modified spray pyrolysis technique

For years, the human race has awaited a more convenient, greener, and largely efficient material for energy conversion and electronic applications. Cu₂O thin films produced by spray pyrolysis meet the economic viability and cost requirements, and it is widely assumed that they will lead to the production of functionally viable technologies. The spray pyrolysis method was used to added titanium into copper (I) oxide thin films with a deposition temperature of 200 °C and annealing for 2 h at 200 °C in this study. The Ti-doped Cu₂O's optical, surface morphology, and photovoltaic characteristics have all been thoroughly explored. The best characteristics were obtained at 3% Ti doped Cu₂O. The near-band emission of Ti-doped Cu₂O was moved from 385 nm to 400 nm. The bandgap was reduced from 2.35 to 1.98Ev at 3% Ti doped Cu₂O. As a result, Cu₂O (Ti)-based solar cells' short circuit current density and open circuit voltage were greatly improved. It has been demonstrated that adding Ti to p-CuO/n-Si solar cells enhances their photovoltaic performance.     

Study of the optimal condition for electroplating of Bi2S3 thin films and their photoelectrochemical characteristics

Bismuth sulfide (Bi₂S₃) thin films were electrodeposited from non-aqueous dimethyl sulfoxide medium containing Bi(NO₃)₃ and thiourea as the precursor salts, triethanol amine as the complexing agent, and TritonX-100 as the surface active agent. The prepared films were subjected to rigorous experimentation in order to validate their potential candidature for solar cells. The films exhibited band gap energy of ∼1.3 eV and resistivity of the order of 2 × 10⁶ Ω cm at room temperature as was obtained from UV–Vis spectroscopy and four-probe measurements, respectively. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy dispersive analysis of X-ray were employed to reveal the morphology, structure, and chemical composition of the film matrix. The Bi₂S₃ films were found to be non-decomposable up to the temperature of 1,000 °C with the help of thermogravimetry–differential thermal analysis. The Nyquist and Mott–Schottky plots derived from electrochemical impedance spectroscopy measurements provided important information regarding electrical and semiconducting properties of the films. The n-type film with a donor density of the order of ∼10²³ m⁻³ displayed reasonable photoactivity under illumination and is recommended as a promising candidate for potential photoelectrochemical applications.     

High solar-light photocatalytic activity of using Cu3Se2/rGO nanocomposites synthesized by a green co-precipitation method

Current work presents a facile, cost-effective, and green method to synthesize copper selenide nanostructures and copper selenide/graphene nanocomposites. The products were synthesized by a co-precipitation method by glycine amino acid as a green surfactant and graphene oxide (GO) sheets as a graphene source. X-ray diffraction patterns (XRD) of the products indicated that the products were Cu₂Se₃ with tetragonal phase. Fourier transform infrared (FTIR) spectroscopy and the XRD patterns indicated that the GO sheets were changed into reduced GO (rGO) during the synthesis process. Scanning and transmission electron microscopy (SEM and TEM) images showed the nanoparticles (NPs) that were decorated on rGO sheets had the significantly smaller size in compared to the pristine NPs. UV-vis results revealed that, the absorption peak of the products were in the visible region with a band-gap value between 1.85 eV and 1.95 eV. Finally, the products were applied as photocatalytic materials to remove Methylene Blue (MB) dye under solar-light and visible-light irradiation conditions. It was observed; the rGO had a significant role in enhancing the photocatalytic performance of the products and Cu₂Se₃/rGO (15%) could degrade more than 91% and 73% of MB only during 1 h under solar-light and visible-light sources, respectively.     

Preparation and characterization of thin TiO2-films on gold/mica

Flat and highly (111) oriented gold and silver films were prepared by physical vapour deposition (PVD) using optimized deposition parameters. On these films, which were characterized with atomic force microscopy (AFM), scanning tunneling microscopy (STM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), titanium dioxide films were deposited by electron beam evaporation and dip coating. Dip coating from titanium tetraisopropoxide solutions resulted in films with different morphology and coverage depending on the alkoxide concentration (0.009 mol/L – 0.60 mol/L) and the post-treatment. Scanning electron microscopy (SEM) and AFM revealed that the deposited TiO₂ consists of amorphous, highly porous islands when the applied alkoxide concentration is high (0.05 mol/L – 0.6 mol/L). At higher temperatures these amorphous TiO₂ islands sintered significantly and crystallized to anatase. In contrast, transparent TiO₂ films were obtained from low concentrated alkoxide solutions (< 0.01 mol/L) which covered the whole substrate, similar to electron beam evaporated thin films. Sputter profiles with ion scattering spectroscopy (ISS) indicated that the film thickness is in the range of 2 nm when alkoxide solutions with a concentration of 9 mmol/L are used. The deposition of TiO₂ by electron beam evaporation normally resulted in significantly reduced TiO₂ films, completely oxidized ones were obtained when deposition was performed at elevated oxygen partial pressures (p(O₂) > 2 × 10^–5 mbar).     

Synthesis of Bi2Se3 thermoelectric nanosheets and nanotubes through hydrothermal co-reduction method

Bi₂Se₃ nanosheets and nanotubes were prepared by a hydrothermal co-reduction method at 150, 180, 200, and 210 °C. Bi₂Se₃ nanosheets, nanobelts and nanotubes were obtained. The Bi₂Se₃ nanoflakes are 50-500 nm in width and 2-5 nm in thickness. The Bi₂Se₃ nanotubes are 5-10 nm in diameter, 80-120 nm in length, and 1.3 nm in wall thickness. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and electron diffraction were employed to characterize the products. Experimental results showed that the nanosheets and the nanotubes are hexagonal in structure with a=4.1354 Å and c=27.4615 Å. A possible formation and crystal growth mechanism of Bi₂Se₃ nanostructures is proposed.     

Physical and chemical properties of silicon carbonitride nanocrystalline films

Nanocrystalline transparent films SiC_xN_y were obtained by plasma-enhanced chemical deposition within the temperature range 473–1173 K from low pressure gas phase from a mixture of hexamethyldisilazane vapor, ammonia, and helium. Physical chemical properties of the films obtained were studied by IR and Raman spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, scanning electron microscopy, high resolution transmission electron spectroscopy and synchrotron radiation powder diffaction. Voltage-capacity and voltage-current measurements were also made. The dependence of chemical and phase composition of the films on deposition conditions was determined, and the formation of approximately 2 nm sized spherical nanocrystals within the films was established. The nanocrystals are formed by a phase similar to usual α-Si₃N₄, with silicon atoms partially substituted by carbon ones.     

The effect of different substrate temperatures on the structure and luminescence properties of Y2O3:Bi3+ thin films

Y₂O₃:Bi³⁺ phosphor thin films were prepared by pulsed laser deposition in the presence of oxygen (O₂) gas. The microstructure and photoluminescence (PL) of these films were found to be highly dependent on the substrate temperature. X-ray diffraction analysis showed that the Y₂O₃:Bi³⁺ films transformed from amorphous to cubic and monoclinic phases when the substrate temperature was increased up to 600 °C. At the higher substrate temperature of 600 °C, the cubic phase became dominant. The crystallinity of the thin films, therefore, increased with increasing substrate temperatures. Surface morphology results obtained by atomic force microscopy showed a decrease in the surface roughness with an increase in substrate temperature. The increase in the PL intensities was attributed to the crystallinity improvement and surface roughness decrease. The main PL emission peak position of the thin films prepared at substrate temperatures of 450 °C and 600 °C showed a shift to shorter wavelengths of 460 and 480 nm respectively, if compared to the main PL peak position of the powder at 495 nm. The shift was attributed to a different Bi³⁺ ion environment in the monoclinic and cubic phases.     

Exploration of spray pyrolysis technique in preparation of absorber material CFATS: Unprecedented hydrophilic surface and antibacterial properties

In this study, we achieve the production of nontoxic Cu₂Fe_1-xAl_xSnS₄ films (x = 0, 0.25, 0.50, 0.75 and 1) by substituting Fe with Al atoms. Physical properties of the investigated films were studied using: Energy dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, spectrophotometer and drop shape analysis system (DSA). The formation of new quaternary Cu₃Al_0.6Sn₁S₆ (CATS) chalcogenide for x = 1 was proven from EDX study. Notably, the major diffraction peaks were located at 2θ = 28.34°, 47.43° and 55.93° which are respectively tagged as (1 1 2), (2 0 4), and (3 1 2) plans, confirming the stannite crystal structure of Cu₃Al_0.6Sn₁S₆ film. The morphological states show a nanofiber structure accompanied with voids and cavities for CATS films. Tauc-relation plot reveals direct energy bandgap, close to 1.52 eV, which proves the absorber film type of Cu₃Al_0.6Sn₁S₆. The effluent toxicity of the obtained thin films has been assessed using the inhibition of Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and indicated good antibacterial activity of the CATS/SnO₂:F heterojunction. The viability rates against S. aureus achieved 40 %, 31 % and 15% for SnO₂:F, Cu₃Al_0.6Sn₁S₆ films and CATS/SnO₂:F heterojunction. These results highlight the great antibacterial activity of coupled CATS/SnO₂:F. Therefore this research underscores the effectiveness of CATS/SnO₂:F surface which demonstrates self-disinfecting and self-cleaning with hydrophilicity and high antibacterial activity.