Bath pH Research Articles

Electroless nickel underlayer deposited between copper filler and silicon substrate: effect of bath pH

ABSTRACT This research proposed intermediate materials between Cu filler and Si wafer to reduce the coefficient of thermal expansion (CTE) mismatch in the through silicon via (TSV) structure. The proposed material is Ni underlayer because it has CTE value between Cu and SiO2 which is 13 ppm/°C (Cu = 17 ppm/°C, SiO2 = 0.6 ppm/°C). The deposition process of nickel underlayer was conducted using electroless deposition process at various pH value (4.5, 5.5 and 6.5) of plating bath and deposition time (20, 40 and 60 minutes). The deposition behaviour was studied through surface and cross-sectional analysis under scanning electron microscopy (SEM). The Ni thickness was measured using cross-sectional analysis under SEM. The chemical composition of Ni deposits was measured using energy dispersive spectroscopy equipped on SEM. The performance test analysis was conducted using Standard ASTM D3359 (Cross Hatch Tape-Test) for coating adhesion test and 4-Point Probe Test for resistivity measurement. It was found that the optimum pH of the Ni bath is 6.5 due to high stability of plating bath to form uniform Ni deposited on silicon wafer. These optimum coating parameters showed homogeneous and uniform distribution of Nickel deposited on the surface of silicon with excellent adhesion properties for all pH value.

Fabrication of a laminated felt-like electromagnetic shielding material based on nickel-coated cellulose fibers via self-foaming effect in electroless plating process

Sustainable low-cost cellulose-based electronics has exhibited brighter prospects. In this study, a laminated felt-like electromagnetic shielding material was prepared by using cellulose paper as the matrix through the self-foaming effect in electroless nickel plating process in which an efficient palladium-free activation was conducted that alkaline sodium borohydride (NaBH4) reduced nickel ions into nickel cluster to initiate the plating process. NaOH concentration in NaBH4 solution, pH of the plating bath and the plating time affected the thickness, metal deposition and surface resistance of the electromagnetic shielding material. By understanding the morphology, inner structure, chemical component and thermal stability, the pH in the plating solution is a key for the preparation. When the pH was 8.51, the electromagnetic shielding effective reached 65 dB in the frequency ranges of 9 kHz to 1.5 GHz, which could shield more than 99.99% electromagnetic radiation. This work offers a novel and feasible path to develop functional cellulose-based materials.

Chemical Bath Deposition of Copper Sulfide on Functionalized SAMs: An Unusual Selectivity Mechanism.

We have investigated the chemical bath deposition (CBD) of CuS using thioacetamide on functionalized self-assembled monolayers (SAMs) using scanning electron and optical microscopies, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. For all SAMs studied, the amount of CuS deposited is strongly dependent on the bath pH and can be attributed to the interaction of the SAM terminal groups with the chalcogenide ions present in solution. For -CH3-terminated SAMs, there is a steady increase in the amount of CuS deposited with an increase in the bath pH because there is an increase in the concentration of chalcogenide ion. However, for -OH- and -COOH-terminated SAMs, we observe that the maximum amount of CuS is deposited at pH 10. We attribute this behavior to a competition between the repulsion of the chalcogenide ions by the negatively charged SAM terminal groups and an increase in the chalcogenide ion concentration with an increase in the bath pH. Using the interaction of the chalcogenide ions with the different SAM terminal functional groups, we demonstrate that CuS can be selectively deposited on the -CH3-terminated areas of patterned -OH/-CH3- and -COOH/-CH3-terminated SAMs.

Optimization of Dyeing Process of Cotton Fabric with Cochineal Dye

The objective of this research is to optimize the dyeing parameters for cotton fabric with natural dyestuff extracted from Dactylopius coccus. In order to obtain purple hue, the influence of dyeing process conditions i.e. dye bath pH, concentration of dyestuff, and the addition of electrolyte has been studied. Additionally, potassium aluminium sulfate dodecahydrate and iron (II) sulfate heptahydrate were used as mordants on cotton fabrics in order to obtain coloration of specific purple hue. Colorimetric data and fastness properties of the dyed samples have been analyzed. Results indicate that the dyeing parameters as well as pre-treatment has a significant influence on the obtained purple shades and fastness properties.

Effect of Processing Parameters on the Thermal and Electrical Properties of Electroless Nickel-Phosphorus Plated Carbon Fiber Heating Elements

Carbon fibers (CFs) were plated with nickel-phosphorus (Ni-P) using an electroless plating process. The effects of the process parameters such as heat treatment temperature, heat treatment time, and the pH of the plating bath on electroless Ni-P plating were investigated. The structure, elemental composition, and thermal and electrical properties of Ni-P plated CFs (MCF) were characterized by X-ray diffraction (XRD), a four-probe volume resistivity tester, and an infrared thermal imaging camera, respectively. The XRD indicated the presence of amorphous and crystalline phases of Ni and Ni-P. The MCF were able to perform at high temperatures because of their higher thermal conductivity. A heat treatment temperature of 300 °C, a heat treatment time of 4 h, and a pH of 8.5 were found to be optimum for obtaining MCF with desirable thermal and electrical properties.

Effect of an acidic environment on a glass fibre reinforced polymer grid

The article deals with the effect of an acidic environment on the mechanical properties of a Glass Fibre Reinforced Polymer (GFRP) grid. GFRP composites are prone to the absorption of surrounding media which are either of a liquid or gaseous state, and this may result in the degradation of their mechanical properties. The effect of an acidic environment is examined on specimens cut from a GFRP grid. The specimens were stored in an acidic bath (pH scale 2 – 2.5) for a period of 0 (reference specimen), 1000, 2000 and 6000 hours. The temperature of the acidic bath was 60°C. The specimens were then tested using three‒point bending and the interlamination shear strength test. During the tests, the load and deformation of the specimens were monitored and flexural strength instead and modulus of elasticity were determined. The characteristics of the specimens exposed to the acidic environment were compared with those of the reference specimen. The experiment demonstrated the effect an acidic environment can have on the properties of GFRP material.

Simplified two-electrode electrochemical growth and characterization of Cd1−xZnxS thin films: Influence of electrolytic bath pH

Cd1−xZnxS thin films were prepared from an aqueous electrolytic solution using a simple low-cost two-electrode electrodeposition technique. Effect of pH on physico-chemical properties was studied at three different pH values of 1.8, 2.7 and 3.6. It was found as the pH is raised, intensity of the X-ray diffraction peaks of the films decreased gradually. Raman measurement also showed similar observation a decrease in intensity of peaks as pH is raised. Compositional characterization shows that more Zn is incorporated into the CdS lattice as pH increases and on the other hand deposition rate decreases due to formation of more OH− ions in the bath. SEM measurement reveals that the variation of pH significantly influences surface morphology of the films. The optical band gap ranges from 2.43 eV to 2.50 eV which indicate that, electrodeposited Cd1−xZnxS thin films can be used as good window/buffer layer for solar cell application in place of CdS.

Some Properties of Electron Beam-Irradiated Sheep Wool Linked to Cr(III) Sorption.

We examined the characteristics of an electron beam irradiated wool with an absorbed dose of (21–410) kGy in comparison with natural wool with respect to the determination of the isoelectric point (IEP), zero charge point (ZCP), mechanism of Cr(III) sorption from higher concentrated solutions, and the modelling of the wool-Cr(III) interaction. The data of ZPC and IEP differed between natural and irradiated samples. Increasing the dose shifted the pH of ZPC from 6.85 for natural wool to 6.20 for the highest dosed wool, while the natural wool IEP moved very little, from pH = 3.35 to 3.40 for all of the irradiated samples. The sorption experiments were performed in a pH bath set at 3.40, and the determination of the residual Cr(III) in the bath was performed by VIS spectrometry under optimized conditions. The resulting sorptivity showed a monotonically rising trend with increasing Cr(III) concentration in the bath. Lower doses, unlike higher doses, showed better sorptivity than the natural wool. FTIR data indicated the formation of complex chromite salts of carboxylates and cysteinates. Crosslinks via ligands coming from different keratin chains were predicted, preferably on the surface of the fibers, but to a degree that did not yet inhibit the diffusion of Cr(III)-cations into the fiber volume. We also present a concept of a complex octahedral structure.

Effect of pH Condition on Natural Indigo (Indigofera tinctoria) Reduction by Yeast (Saccharomyces cerevisiae)

Ultimate goal of this research is to develop an efficient microbial system for indigo reduction by using yeast (Saccharomyces cerevisiae). For this purpose, we investigated the effect of pH condition on natural indigo (Indigofera tinctoria) reduction by yeast. We also checked the viability of yeast at high pH condition by observing yeast cell in the indigo reduction bath with an optical microscope. The pH of indigo reduction bath was initially set from 10.2 to 12.0 with the buffer solution. The pH value dropped drastically up to 5.5–6.5 at the initial stage of reduction. After adjusting pH once within 1–2 days, we measured some parameters related to reducing power such as the color yield (K/S value) of ramie fabric dyed with the supernatant of bath, the oxidation/reduction potential (ORP), and the pH values changed. When the initial pH was set at lower than 11 (10.2, 10.7), the baths adjusted to pH 11 showed better reducing power than the baths of pH other than 11. And also, when the initial pH was set higher than 11 (11.3 and 12.0), the baths adjusted to pH 11 showed better reducing power than the baths of pH other than 11. It took 5–11 days to reach the maximum dye uptake after the initiation of reduction, and, during the corresponding time, the ORP was from -563 to -599 mV. All the initial and the adjusted pH values were not maintained but decreased continuously, and the maximum dye uptake reached at pH 9.17-9.43. The initial and the adjusted pH greatly affected the indigo reducing power, and the highest color yield was obtained with indigo reduction bath of initial pH 10.7. When the pH of the bath was adjusted to pH 11.0, the maximum reducing power was obtained most efficiently. Also, for the pH adjustment, use of sodium hydroxide showed higher reducing power than use of calcium hydroxide.

Effect of current density and alkaline pH on morphology and properties of electroplated Sn

The purpose of this research is to examine the effect of plating current density as well as bath pH on the morphology and solderability of Pb‐free pure Sn, plated from alkaline baths on copper substrates. Pure Sn coatings were prepared from a plating electrolyte composed of sodium stannate, sodium hydroxide, and sorbitol as an additive. The bath pH was changed from 9 to 14 and the plating current density was varied from 5–25 mA cm−2. The solderability of the Sn platings was estimated by spread ratio measurement according to JIS-Z-3197 standard. The obtained coatings were polycrystalline having a tetragonal β-Sn structure. The deposits were spongy and porous at pH ≈ 9–10. As the bath pH was increased from 11–13, the film growth improved, the best crystallinity of film was obtained at pH 13 and a current density of 15–20 mA cm−2. The coatings possess optimum microhardness and spreadability at a current density of 15 mA cm−2 and bath pH ∼12–13. It is shown that the optimization of current density and bath pH is necessary for the better strength and solderability of Sn coatings when alkaline baths are employed.

A NOVEL METHOD FOR PRODUCING NANOSTRUCTURED CdSe THIN FILM

In this study, we produced Cadmium selenide (CdSe) crystalline thin film on commercial glass substrates via chemical bath deposition. Transmittance, absorbance, refractive index and optical bandgap of thin films were examined by UV/vis spectrum. XRD revealed a hexagonal form. The pH level of the baths in which CdSe thin films were deposited varied and optical and structural properties of the resulting thin films were analyzed. SEM analysis was used for surface analysis. Some features of the films were supposed to change with pH and these properties were investigated by testing different pH levels, which were 8, 9, 10 and 11. The variation of the optical bandgap changed between 1.60 and 1.75[Formula: see text]eV, according to the pH of deposition bath. Film thickness varied from 60[Formula: see text]nm to 93[Formula: see text]nm, with the variation of deposition bath’s pH. Moreover, it has been found that refractive index values were also changed with film thickness; these were calculated as 2.28, 2.19, 2.22 and 2.36 for 93.27, 60.97, 61.09 and 60.18[Formula: see text]nm, respectively. Dielectric constant also varied with refractive index, taking values 0.85, 0.75, 0.78, 0.93 for refractive indexes 2.28, 2.19, 2.22 and 2.36, respectively.

Sustainable Membrane Production through Polyelectrolyte Complexation Induced Aqueous Phase Separation

AbstractNonsolvent induced phase separation (NIPS) is the most common approach to produce polymeric membranes. Unfortunately, NIPS relies heavily on aprotic organic solvents like N‐methyl‐pyrrolidone. These solvents are unsustainable, repro‐toxic for humans and are therefore becoming increasingly restricted within the European Union. A new and sustainable method, aqueous phase separation (APS), is reported that eliminates the use of organic solvents. A homogeneous solution of two polyelectrolytes, the strong polyanion poly(sodium 4‐styrenesulfonate) (PSS) and the weak polycation poly(allylamine hydrochloride) (PAH), is prepared at high pH, where PAH is uncharged. Immersing a film of this solution in a low pH bath charges the PAH and results in a controlled precipitation, forming a porous water‐insoluble polyelectrolyte complex, a membrane. Pore sizes can be tuned from micrometers to just a few nanometers, and even to dense films, simply by tuning the polyelectrolyte concentrations, molecular weights, and by changing the salinity of the bath. This leads to excellent examples of microfiltration, ultrafiltration, and nanofiltration membranes. Polyelectrolyte complexation induced APS is a viable and sustainable approach to membrane production that provides excellent control over membrane properties and even allows new types of separations.

Preparation of Polyvinyl Alcohol/Ninhydrin Blend Nanomembranes by Needleless Electrospinning and Their Application in Latent Finger Mark Detection

Finger mark identification, which is one of the biological recognition methods, has a history of more than 100 years. In this study, polyvinyl alcohol (PVA)/ninhydrin blend nanomembranes were prepared using needleless electrospinning and applied in latent finger mark detection. The morphology and structure of the PVA/ninhydrin nanomembranes were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The results showed that the preferable composition for the best spinnability of the complex solution was 86.9 g/L PVA and 76.1 g/L ninhydrin, using water as solvent. The ninhydrin was uniformly dispersed in the PVA/ninhydrin nanomembranes in the amorphous regions. There was a small amount of hydrogen bonds between the PVA and ninhydrin. The addition of ninhydrin did not affect the crystal structure of PVA. When subjected to hot steam of a weak acidic water bath (pH = 6), the PVA/ninhydrin nanomembranes completely displayed the latent invisible finger marks left on glass or ceramic surfaces in purple within 3–5 min of the steam exposure, which were easily observed by the naked eyes. The purple finger marks on the nanomembranes were due to the reaction of ninhydrin with amino acids in sweat released from the fingers. Both chemical cross-linking and physical adhesion of the membrane to the surface occurred in the area of the finger mark regions. Physical adhesion also developed in the regions without finger marks. Therefore, finger marks identification using electrospun PVA/ninhydrin nanomembranes is simple, rapid, harmless, and sensitive, and does not need large instruments or any type of liquid chemical reagent.

Influence of Organic Additive Benzene Sulfamide on the Magnetic Behavior of Electrodeposited CoMnP Thin Film Alloys

Electro deposition of CoMnP thin films was carried out for different concentrations of organic additive Benzene sulfamide at a constant bath pH value and for various current density. Magnetic properties such as coercivity, saturation magnetization and the surface morphology were investigated for electrodeposited CoMnP thin films. The characteristics of the CoMnP thin films were found to attain enhanced values, because of the variation in the concentration of the bath solution. The Scanning Electron Microscope (SEM) micrographs of the CoMnP thin films for various bath compositions and additive concentration exhibited different micro cracks. From the X-ray diffraction pattern, structure of the CoMnP alloy films was analyzed and it was found to be Hesagonal Close Packed (HCP) structures with the dominant microstructure and all the co-deposited thin films were found to exhibit Nano crystalline structure. The magnetic properties of the specimens were characterized using Vibrating Sample Magnetometer (VSM). Adhesion and hardness of the electroplated films influenced by organic additive Benzene Sulfamide were also investigated. The magnetic properties were highly influenced by the addition of the organic additive Benzene Sulfamide for various bath composition and bath conditions. Under best condition involving addition of 0.2 M of NaH2PO2 and 2 g/L of Benzene Sulfamide acid at current density 5 mA/cm2 and time of deposition 60 Minutes, the thickness of the film was found to be 4.6 micrometer with coercivity 1500 Oe.

The effect of electroless bath pH on the surface properties of one-dimensional Ni–P nanomaterials

In this research, the one-dimensional Ni–P nanomaterials was formed on alumina substrate. The effect of electroless bath pH on the surface properties of one-dimensional Ni–P nanostructures was investigated. For evaluation of morphological properties and chemical composition of deposits, scanning electron microscopy (SEM) analysis, which coupled with energy disperse spectroscopy (EDS) were used. Two-step anodization for alumina substrate was selected as the best sample for producing the one-dimensional Ni–P nanomaterials. The electroless coating was carried out at different pH = 4.5, 5.5 and 6.5 values. The results showed that in all samples, due to the high Ni–P deposition rate, the Ni–P nanomaterials does not fill the entire channel path. By increasing the pH value, the one-dimensional nanomaterials were changed from nanowire to nanotube type. Also, by increasing the pH value, despite increasing the length of Ni–P nanomaterials, but the compactness of this material was reduced. So, the optimum pH value for producing the one-dimensional Ni–P materials was 4.5. On the other hand, by reducing the pH value, the crystallinity degree of Ni–P deposits was increased. The pH content trends along the nanomaterials length were indicated that the phosphorus content toward the bottom of channel was increased.

Extraction of phenolic components from an Aloe vera (Aloe barbadensis Miller) crop and their potential as antimicrobials and textile dyes

The present work focuses on the use of solid and agricultural residues from Aloe vera crops, as a source of antimicrobial agents and textile dyes. The roots from an A. vera plantation post-harvest were extracted with ethyl acetate, purified and phytochemically characterized to obtain five metabolites: aloesaponarin-I (1), deoxyerythrolaccin (2), lacaic acid D methyl ester (3), aloesaponarin-II (4), and aloesaponol-I (5). Acid hydrolysis of the solid industrial residue gave aloe-emodin (6) as the main product with a good yield. All of the components were tested for the first time against phytopathogenic bacteria strains, and deoxyerythrolaccin and lacaic acid D methyl ester were active against Xanthomonas campestris with MIC values of 46.86 and 93.75 μg/mL, respectively. Aloesaponarin-I and aloe-emodin, the main products, were tested as dyes for polyester fabrics using different mordants and pH bath conditions. The colour of each material was investigated in terms of the CIELAB L*, a* and b* values, and the colour fastness to light and washing was investigated according to the Mexican standard methods (NMX-A-074-INNTEX-2005; NMX-A-105-B02-INNTEX-2010). Aloesaponarin-I dyed polyester bright yellow but the final colour was very sensitive to the pH of the dye bath. Aloe-emodin dyed polyester deep yellow, and the fabrics showed good colour fastness to light and to domestic laundering. This study provides evidence that the phenolic components obtained from agricultural residues of the aloe industry can be useful organic alternatives as antimicrobial agents and textile dyes.

Variation in chemical bath pH and the corresponding precursor concentration for optimizing the optical, structural and morphological properties of ZnO thin films

In the present study, ZnO thin films were deposited by chemical bath deposition carried out by selective correlation of varying (i) pH values at fixed concentration and (ii) concentration of the precursors at fixed pH. The selective correlations were done by using the characterization tools like X-ray diffraction, scanning electron microscopy, transmittance, refractive index, dielectric constant, Fourier-transform infrared spectroscopy and IV measurements. Transmittance was found to increase from 57 to 87% on varying the pH from basic side (10.8) to acidic side (pH 6.8) with a blue shift in band gap. The nature and morphology of the deposited films were found to be dependent on pH as well as concentration. Acidic pH 5.0 was found to be most suitable for deposition of highly transparent film with low absorption coefficient, refractive index and dielectric constant. On the other hand, nearly complete coverage of the substrate and high purity was observed in the ZnO thin films which was deposited by taking equal 100 mM concentration of Zn(NO3) and HMTA precursors at a fixed pH 5.0 as desired, sheet resistance was also found to increase on the acidic pH side which is useful in case of buffer layer solar cell application. These studies lay a foundation stone for understanding the optical and morphological parameters by selectively correlating the pH and concentration variation at the same time.

Electrochemically Enhanced Processes for Leather Tanning

Leather production involves several operations where the tanning plays the major role in improving the durability of leather products by forming durable linkages between the tanning agents and the collagen. Different agents are used, but the most important is chromium. However, nowadays there is a growing demand for a cleaner, but still effective alternative for production processes. In the traditional tanning process, the penetration of these agents inside the leather is governed by diffusion based on a concentration gradient. In this study, a new tanning approach is proposed, taking advantage of the intensification effects of an applied electric field, within two electrodes in solution, on the tanning method [1]. An improvement in the efficiency is observed due to the positive charge acquired by the agents (Cr, Ti, Zr and Fe) complexes in tanning solutions and the possibility to control the bath pH by exploiting the side reactions at the two electrodes. The new electrochemically intensified tanning technique shows better performances than the standard one, resulting in a larger agent uptake in the same amount of time, leading to a shorter process time. The intensification of the tanning process will be justified in light of a simulation model of the involved phenomena. Enhanced chrome tanning process, Patent Pending

Reaction Mechanism Analysis of Zn Electrodeposition Process in Acidic Sulphate Bath Using Potentiodynamic Polarization Technique

Zinc (Zn) metal is commonly known as a sacrificial anode, and is widely used as corrosion protection coating for ferrous materials. Electrodeposition of Zn is a popular method of coating substrates and it can be performed in acidic or alkaline conditions [1]. Zn electrodeposition is a two electron multi step reaction, and it is accompanied by hydrogen evolution reaction in acidic conditions. Hydrogen bubble formation during Zn deposition can affect mass transport of different species in the electrolyte bath [2]. In addition, mass transfer of cations can limit the reaction rate at typical deposition conditions. Zn electrodeposition process has been modeled in the literature [3-6].The models employ either a single step simple electron transfer reaction with mass transfer effects or multi-step reactions which neglect mass transfer limitations. In this work, we present experimental results of Zn electrodeposition in aqueous acidic sulphate solution, and propose a model to explain the observed results. The model (Figure 1a) involves a multi step mechanism with diffusional mass transfer effects, Hydrogen evolution reaction (HER) occurring in parallel with the Zn electrodeposition process. All the electrochemical experiments were carried out using a Zn rotating disk electrode (rde) in a conventional three electrode cell and conducted with IVIUMSTAT electrochemical workstation. Pt mesh was used as the counter electrode and Hg/Hg2SO4 (saturated K2SO4) was used as the reference electrode. The kinetics and mass transfer effects of the process were studied by potentiodynamic polarization (PDP) technique. PDP experiments were performed as a function of Zn salt concentration, electrolyte bath pH and electrode rotational speed. The concentration of Zn salt was varied from 0.01 M to 1 M. The electrolyte bath pH was varied from 2 to 4. The electrode rotational speed was varied from 400 to 1600 rpm to characterize mass transfer effects during the process. A supporting electrolyte (Na2SO4) at 1 M concentration was used to reduce the effects of solution resistance. A few experiments were also conducted without Zn salt (blank solution at pH 2) to quantify the Hydrogen evolution on Zn rde. Figure 1b shows the PDP curves obtained for blank solution at pH 2 and different rotational speeds to quantify the hydrogen evolution rate alone. Figure 1c shows the PDP curves of Zn electrodeposition process at pH 2 and different rotational speeds. As expected, the current magnitude increases with an increase in cathodic bias, and saturates at large cathodic potentials. The saturation current increases with an increase in electrode rotational speed. Reaction mechanism analysis was employed to describe the deposition mechanism of Zn in acidic sulphate baths. Several multi step mechanisms were evaluated to model the polarization data acquired in kinetic limited regime. A seven step mechanism [4] as mentioned in figure 1a involving three deposition steps and Volmer Heyrovsky (VH) steps for hydrogen evolution reaction was found to be the best mechanism in the kinetic limited regime. Further analysis on mechanistic investigation to include mass transfer effects during the Zn electrodeposition is in progress.

Chemical bath pH influence on the structural, morphological and optical properties of zinc sulphide thin film prepared from acidic baths

Zinc sulphide (ZnS) thin films were prepared on glass substrate by using solution growth method from acidic chemical bath. The effect of bath pH on the physical and chemical properties of ZnS thin films were established well. The synthesized thin films were characterized by different techniques to study how bath pH affects the nature of the ZnS thin films. The XRD study established that the prepared ZnS thin films had a cubic crystal structure. The XRD results further showed that the diffraction peaks around 28.7° and 48.1° enhanced as the bath pH increased. The SEM study confirmed that the bath pH play significant role on the nature of the surface morphology of ZnS thin film deposited in acidic chemical bath. The EDS study confirmed the presence of the constituent elements Zn and S. This measurement also shows that the prepared ZnS thin films were in a good stoichiometric ratio (Zn/S). The optical band gap of the prepared thin films found in the range of 3.24 eV to 3.89 eV as the bath pH decreased from 4.86 to 4. Irrespective of bath pH, all the deposited ZnS thin films exhibited a strong PL emission in red region, however, the intensity of the PL emissions were varied with bath pH.