Cost Effective Sol-gel Technique Research Articles

Environmentally benign fouling release metallosurfactant coatings; evaluation of surface properties, leaching rate, biocorrosion resistance and durability

Biofouling is the biggest issue that impair the success of marine infrastructure. The biofilm forming aerobic bacteria Pseudomonas aeruginosa present in sea water causes considerable environmental and economic losses by initiating microbially induced corrosion. Concerning the importance of fouling release coatings, we are aimed to fabricate non-toxic metallosurfactants (MS) coating on carbon steel to mitigate growth and adhesion of biofilm and consequent corrosive reactions on its surface. As the toxic ion release from fouling-release metallic coatings have deleterious effect on the aquatic eco-system therefore the MS coatings with slow release of metal ions can be a greener approach in this field. Here, we report the surface modification of CS with self-assembly of a series of MS viz. MC42H76N2Cl4, where M = Co, Ni and Cu. The MS under study is a complex of an anti-corrosive surfactant ligand cetyl pyridinium chloride (CPC) and transition metal salts in a stoichiometry of 2:1 (CPC: M). For surface modification, a cost-effective sol–gel technique was adopted. The coatings were characterized by Fourier Transform Infra-Red Spectroscopy (FT-IR), Atomic force microscopy (AFM), Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The chemical composition of coatings reveals the presence of anti-bacterial metal ions present in mixed oxidation state causing the variable rate of their leaching in sea water media (M1942). The quantification of metal ions leached from metallosurfactant coating after immersing in M1942 media was done using inductively coupled plasma-mass spectrometry (ICP-MS). The ICP-MS data shows 19.86 ng/mL release of Cu ions from coating after 21 days of immersion which advocates its slow-release nature. The corrosion activities of sea water salts and marine bacteria Pseudomonas aeruginosa on bare and modified CS substrates was extensively studied by employing standard electrochemical tests like potentiodynamic and potentiostatic polarisation, Electrochemical Impedance Spectroscopy (EIS). The potentiodynamic polarisation test shows the coatings exhibit corrosion inhibition efficiency up to 93.5%. The coatings remained intact even after polarisation at +0.7 V in sea water media. Atomic force microscopy (AFM) and Scanning Electron Microscopy (SEM) was conducted to check corrosion morphology and biofilm characteristics. The DEAD/LIVE test of biofilm displays a higher ratio of dead bacteria on modified surface as compared to bare which demonstrate the antibacterial character of coatings. The results obtained from various corrosion tests reveal this strategy can be used to develop long term and eco-friendly anti-fouling coatings.

Structural Analysis and Hydrophilic Behavior of Co3O4 Thin Film for Enhanced Photocatalytic Activity under Visible Light with Hole Scavengers

This research presents a cost-effective sol-gel technique to produce a uniform and highlyeffective Co3O4 thin film on glass substrates with a withdrawal speed of 5 m/s. The surface morphologyand roughness of the film were analyzed, and it demonstrated a thickness of 177 nm and band gap of 2.0eV. Under solar irradiation, the thin film exhibited remarkable photocatalytic degradation efficacy, with ahigh efficiency of 78% for blue methylene (BM). The 3D surface topography scan indicated significantroughness at 54.7 nm. Hole-scavengers such as H2O2, EDTA, and Octan-1 were found to enhance BMdegradation. The study highlights the potential of the Co3O4 thin film for treating various organiccontaminants in wastewater from diverse sources under solar irradiation.

Development of a Reliable Zinc Oxide Thin-Film-Based Ammonia Gas Sensor

In this work, a simple ZnO thin-film-based ammonia gas sensor fabricated via a straightforward and cost-effective sol-gel technique has been demonstrated. The as-prepared device was found to be extremely sensitive toward ammonia gas and has shown a high response of 13.5% at concentrations as low as 10 ppm at an optimal temperature of 180 °C (much lower than the threshold value of 25 ppm). The device response was observed to be linear up to 70 ppm ammonia concentration with a response of 51% corresponding to it. The simplicity, repeatability, low production cost, and high efficiency have made the device a potential candidate for various future applications, especially in industries where ammonia sensing is critical.

Structural and magnetic properties of DyCrTiO5 nanoparticles

The compounds with the general chemical formula RCrTiO5 (R = rare-earth ions) has an orthorhombic crystal structure having Pbam space group. However, there are limited work carried out on this group of materials, primarily in bulk to explore their structural and magnetic properties. The exploration of structural and magnetic properties of RCrTiO5 compounds in the nano dimension has not been reported to date. This report focuses on the synthesis of DyCrTiO5 nanoparticles using a simple, time saving and cost-effective sol–gel technique to investigate the role of size on structural as well as magnetic properties. The synthesized sample is calcined at 800 °C for three hours. The crystal structure is confirmed from the Le-Bail profile fitting of the x-ray diffraction (XRD) pattern. The DyCrTiO5 nanoparticles are crystallized in an orthorhombic structure with lattice parameters, a, b, c of 7.321 ± 0.001, 8.644 ± 0.002 and 5.840 ± 0.001 Å, respectively. The average particle size is found to be 53 ± 3 nm from transmission electron microscopy (TEM). From the temperature-dependent magnetization measurement, the obtained Néel temperature (TN) is 147 ± 2 K. In contrast to the bulk form, DyCrTiO5 nanoparticles do not show spin reorientation (SR) which is observed below 37 K or the magnetic compensation because of the dominating contribution of Dy3+ moment. In addition, the irreversibility in magnetization is suppressed when measured as a function of temperature in the heating and cooling cycle of the measurement with increasing the probing magnetic field. This indicates a feature similar to kinetic arrest. In isothermal magnetization measurements, exchange bias effect is observed because of interaction between the uncompensated spins on the surface of the nanoparticles.

Fabrication and characterization of mesoporous guar gum/NiWO4 nanocomposite for efficient adsorption of phloxine B and crystal violet from aqueous solution and evaluation of its antioxidant activity

Guar gum/nickel tungstate (GG/NiWO4) nanocomposite is prepared using simple and cost-effective sol-gel technique, while NiWO4 nanoparticles are formed by co-precipitation method. The nanocomposite is characterized by FTIR, XRD, BET, SEM-EDX and TEM techniques. The effectivity of GG/NiWO4 nanocomposite is investigated for the sequestration of phloxine B (PB) and crystal violet (CV) from wastewater. The effect of dose, agitation time, initial solution pH, and initial dyes concentration is appraised. The adsorption isotherm, kinetics and thermodynamic parameters are also studied. Langmuir isotherm and pseudo-second order models are best fitted to the equilibrium data. The thermodynamic parameters confirm that adsorption is spontaneous, exothermic and entropy-driven. An excellent desorption of PB and CV from the loaded adsorbent is acquired by utilizing either ethanol or acetone with a desorption ability in the range of 57.60%–91%. The antioxidant activities of synthesized nanocomposite are also studied.

Sol-gel derived high performance low-voltage thin film transistor

Sol-gel high-k metal oxide thin film transistors (TFTs) have fascinated huge interest due to their prospective applications in cost-effective, low operating voltage electronics such as sensors, radio frequency identification tags, portable electronics and backplane circuitry for flat panel display. In this work, we report a sol–gel synthesis procedure of γ-phase of lithium aluminates (γ-LiAlO2) which is a high-k material due to the ionic polarization of mobile Li+ of the crystal. This high-k dielectric has been successfully utilized as a gate insulator of a low voltage indium zinc oxide (IZO) TFT. The optimize device shows a moderate on/off ratio of 9 × 102 and electron mobility of 4 cm2 V−1 s−1 under 2.0 V operation. This γ-LiAlO2 dielectric has been synthesized by cost-effective sol–gel technique followed by annealing process at 700 °C.

Hierarchical nickel sulphide microstructures for controlled water disinfection and cold cathode emission

Hierarchical nickel sulphide microtubes were prepared by cost effective sol-gel technique with tuning of morphology and applied for photo-induced hazardous dye segregation and cold electron emission. The synthesized samples were characterized for crystalline phase, morphology and composition via X-ray diffractometry, electron microscopy and energy dispersive X-ray studies respectively. The band gaps were estimated from UV–vis data. The samples were found to be effective as a dye degrading agent under UV irradiation. The pollutant removal efficiency of the nickel sulphide (NS) microstructures was found to be governed by dimension and compositional parameters jointly. The sample showing highest degradation efficiency was found to degrade phenol effectively. Scavenger test was carried out to identify the active radicals involved in the catalysis process. To ensure long term action of the catalyst sample, recyclability of the same was investigated thoroughly. The NS microstructures also showed field emission behaviour which is reported for the first time. The growth of different shapes and hierarchical units of NS structures was correlated with stoichiometric alteration which may also be extended for synthesis of other nickel chalcogenides.

Modified nanostructured titania photocatalysts for aquatic disinfection applications

According to the SDG 6, everyone on earth should have access to safe and affordable drinking water. In sharing water-treatment technologies that leads to accomplishing this goal, it is imperative to devise ways of removing microbial contaminants such as E. coli from drinking water especially in resource-limited settings that lack centralized water supply systems. One of the approaches is bacterial disinfection of water at the point of use. In this study, the bactericidal effects of the photocatalysis of titanium dioxide-based nanoparticles under UV and visible light are explored.Pristine and silver doped nanostructured mesoporous titanium dioxide (Ag-TiO2, TiO2) particles with high specific surface area and average crystallite domain size of ∼ 7.0–7.5 nm were prepared using the simple and cost effective sol–gel technique followed by thermal treatment. The addition of Ag+ ions during the hydrolysis/condensation of the Ti(IV) molecular precursor led to homogeneous dispersion of the Ag+ cations on the titania matrix. The As-prepared nanoparticles were characterized using X-Ray Diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), thermogravimetry, Fourier Transform Infra-Red (FTIR), and Raman Spectroscopy. X-ray diffraction, FTIR and Raman spectroscopy confirmed that the crystalline structure of the TiO2 matrix corresponds to the anatase polymorph; however, the presence of the dopant led to an increase in the system disorder due to the rise in concentration of oxygen vacancies. The As-prepared nanoparticles were used for Escherichia coli (E. coli) inactivation under dark and UV–Visible light conditions. Under dark conditions, Ag doped titania and pristine titania resulted in ∼ 95% and ∼ 64% E. coli population inactivity while under light conditions, ∼99% and ∼ 97% degradation respectively were observed. Taken together, these results demonstrate that, the synthesized TiO2 nanoparticles have promising applications in the light mediated point of use inactivation of bacterial contaminants in water.

Preparation of Co and Ni doped ZnO nanoparticles served as encouraging nano-catalytic application

Nickel (Ni) and cobalt (Co) doped ZnO nanoparticles were prepared using simple and cost-effective sol-gel technique. Effects of various weight ratios (5, 10, 15 and 20) % of Co and Ni-doped into ZnO have been examined. The prepared undoped and doped nanoparticles (NPs) were characterized using XRD, SEM, FTIR, EDX and UV-Vis spectroscopy. By analyzing the catalysis potential of the samples under UV irradiation, the probable mechanism of particles was investigated. XRD results revealed that ZnO and doped ZnO have hexagonal wurtzite phase, the lattice strain and particle size were measured by Williamson and Hall plot. The absorption increased and band gap energy decreased gradually in the range of 2.40–3.62 eV upon doping was identified using UV-Vis spectroscopy. The elemental composition of Zn, Ni and O were confirmed with EDX spectra and FTIR spectra demonstrate the presence of chemical bonding and functional groups at the interface of ZnO. This report highlights the effect of nanocatalyst on the degradation rate of methylene blue through NaBH4, results revealed that doped nanocatalyst has better catalytic action than ZnO and will provide an insight for the synthesis of catalytic agents that could prevent environment pollution issue.

Preparation and scintillating study of ZnO: Hf ceramic to gamma rays

In this work pure and Hf-doped ZnO nanopowders were synthesized by cost-effective sol-gel technique to prepare ceramic pellets by isostatic pressing. Structural, optical and morphological properties of prepared samples were examined by XRD, FESEM, TEM, EDX, UV–vis, FTIR, Raman and PL measurements. Also the scintillation sensitivity of ceramics was studied by a 60Co radiation source. X-ray diffraction pattern analysis confirmed the hexagonal wurtzite structure of samples; Rietveld refinement for crystallite structure determined the lattice parameters of the nanopowders. FTIR and Raman results confirmed the presence of functional group and chemical bonding attributed to ZnO. FESEM image revealed that the size of HZO nanoparticles was obtained a bout 62 nm. For the first time prepared HZO ceramic showed suitable scintillation sensitivity to gamma ray and exhibited strong violet, blue and red emissions at room temperature. Fabricated ceramic showed good characteristics that can be applied for future photonic applications.

Down-conversion characteristics of Eu3+ doped M2Y2Si2O9 (M = Ba, Ca, Mg and Sr) nanomaterials for innovative solar panels

Down-conversion properties of Eu3+ doped M2Y2Si2O9 (M = Ba, Ca, Mg, Sr) phosphors have been investigated in detail. These phosphors were synthesized via the simple, fast and cost-effective sol-gel technique at a temperature of 950 °C. Color coordinates and emission color can be altered by the varying concentration of dopant ion in Ca2Y2Si2O9 phosphor. Optimum luminescence intensity was obtained when doping 0.03 mol of Eu3+ ion. Using the excitation wavelength of 395 nm, these silicates showed strong red color, pure and sharp spectral peaks in visible region due to 5D0→7F1-3 transitions of Eu3+ present in the lattice. Effect of reaction temperature on luminescence was also analyzed for these phosphors. The sharp peaks in the X-ray diffraction pattern indicated the high crystallinity of prepared phosphors. Ca2Y2Si2O9 has shown an orthorhombic crystal structure. The FTIR results confirmed the metal-oxygen vibrational modes available in the range of 400–1600 cm−1. Transmission electron microscopy images have revealed that the variation of alkaline earth metal provided a very different crystal structure. Excellent down conversion response of these phosphor materials can provide a great significance in the application of the coming solar devices.

NATURAL HIBISCUS DYE AND SYNTHETIC ORGANIC EOSIN Y DYE SENSITIZED SOLAR CELLS USING TITANIUM DIOXIDE NANOPARTICLES PHOTO ANODE: COMPARATIVE STUDY

Titanium dioxide (TiO[Formula: see text] nanoparticles have been synthesized by the cost effective Sol–Gel technique. Characteristics of TiO2 nanoparticles were investigated by X-ray diffraction and Fourier Transform Infrared spectroscopy. The Eosin Y dye and dye extracted from Hibiscus tea have been successfully used in fabrication of the dye sensitized solar cell. The photovoltaic performance of the dye sensitized solar cell indicates that the short circuit photo current, open circuit voltage and efficiency of the DSSC using Eosin Y dye is 10 times more compared to the DSSC using the Hibiscus dye.

Studies on transport properties of manganite based nano–micro particles–matrix composites

In this communication, low resistive bulk La0.7Ca0.3MnO3 (LCMO) was prepared by solid state reaction (SSR) route whereas high resistive nanoparticles of LaMnO3 (LMO) was prepared by cost effective sol–gel technique. Composites of LMO and LCMO were prepared by mixing them in different weight ratios, i.e. LMO = 10%, 20% and 30% in LCMO manganite matrix. In the present study, LMO have been used as nanoparticle fillers in the LCMO matrix lattice to study the transport properties of the composites. X–ray diffraction (XRD) measurement reveals the single phasic nature of the composites without any detectable impurity within the measurement range studied. XRD pattern of higher LMO content based composite possesses slightly different structural phases of LMO and LCMO. Resistivity measurement reveals that all the composites exhibit metal to insulator electronic phase transition at respective TP, wherein values of resistivity and TP get modified due to the cooling or heating cycles performed, measurement current used and LMO nanoparticle filler content in the composites. These variations have been discussed in the context of scattering centres created due to the presence of LMO fillers and complex phase separation scenario of the composites. A clear phase separation in higher filler content based composite has been displayed in its resistivity behaviour. To understand the charge transport mechanisms responsible for metallic and insulating (or semiconducting) regions in resistivity behaviours of the composites, most suitable zener double exchange polynomial law and Mott type variable range hopping mechanism were fitted theoretically to the obtained experimental results. Fittings show that spin fluctuations in the composites are highly dependent on the cycles performed, current applied and LMO nanoparticle filler content in the composites. Applied negative and positive current and voltage dependent resistance of the composites reveal the negative electroresistance. Both, resistance of the composites as well as electroresistance are highly affected by the cycles performed, current applied and LMO nanoparticle filler content in the composites understudy. Temperature dependent electroresistance was studied for better insight into an active role of phase separation near electronic phase transition temperatures for all manganite based composites.

Size effects on electrical properties of chemically grown zinc oxide nanoparticles

In the present article, we study ZnO nanoparticles grown by cost effective sol–gel technique for various electrical properties. Structural studies performed by x-ray diffraction (XRD) revealed hexagonal unit cell phase with no observed impurities. Transmission electron microscopy (TEM) and particle size analyzer showed increased average particle size due to agglomeration effect with higher sintering. Dielectric constant (ε′) decreases with increase in frequency because of the disability of dipoles to follow higher electric field. With higher sintering, dielectric constant reduced owing to the important role of increased formation of oxygen vacancy defects. Universal dielectric response (UDR) was verified by straight line fitting of log (fε′) versus log (f) plots. All samples exhibit UDR behavior and with higher sintering more contribution from crystal cores. Impedance studies suggest an important role of boundary density while Cole–Cole (Z″ versus Z′) plots have been studied for the relaxation behavior of the samples. Average normalized change (ANC) in impedance has been studied for all the samples wherein boundaries play an important role. Frequency dependent electrical conductivity has been understood on the basis of Jonscher’s universal power law. Jonscher’s law fits suggest that conduction of charge carrier is possible in the context of correlated barrier hopping (CBH) mechanism for lower temperature sintered sample while for higher temperature sintered ZnO samples, Maxwell–Wagner (M–W) relaxation process has been determined.

Magnetoelectric Properties of Nanostructured YMnO3 Prepared by Sol–Gel Technique

Nanostructured yttrium manganese oxide (YMnO3) has been synthesized using cost effective Sol-Gel technique in order to understand effect of magnetic field on the electrical properties and its magnetoelectric coupling. XRD measurement has been carried out using powder diffractometer. To confirm the particle morphology, TEM measurement was carried out. Frequency dependent dielectric properties and impedance spectroscopy have been carried out in the range of 20Hz to 2MHz frequency at room temperature (RT). Universal dielectric relaxation (UDR) has been fitted to understand effect of magnetic field on electrical properties in detail.

Enhanced photocatalytic degradation of dyes under sunlight using biocompatible TiO2 nanoparticles

As TiO2 is one of the most popular photocatalysts, we have studied here the photocatalytic degradation of the most common dyestuffs like rhodamine B (RhB), congo red (CR) and methylene blue (MB), which mainly come from the textile and photographic industries using nanoparticles of TiO2. Nanoparticles of TiO2 synthesized through a simple and cost effective sol-gel technique crystallizes in the anatase phase, showing a band gap less than that of bulk value. Particles consisting of coherently scattered domains of size 33 nm are found to be agglomerated and polycrystalline in nature. While the degradation rates of MB, CR and RhB after irradiating with a renewable source of energy, i.e. sunlight, show 100% degradation, TiO2 irradiated with UV light of 4.8 eV shows a much slower degradation rate. To use the waste water after photocatalysis, we examine further the biocompatibile nature of the TiO2 nanoparticles by platelet interaction activity, hemolysis effect and MTT assay. It is worth mentioning here that TiO2 nanoparticles are found to be highly hemocompatible, show no platelet aggregation, and the level of intracellular ROS in human platelets does not show significant change in ROS level. We conclude that TiO2 nanoparticles constitute an excellent photocatalyst and biocompatible material, and that after photocatalytic degradation of dye effluents obtained from textile industries, purified water can be used in agriculture and domestic sectors.

Transparent Al+3 doped MgO thin films for functional applications

The present work reports the utilization of a relatively simple, cost effective sol-gel technique based route to synthesize highly transparent, spin coated 4.1 at% Al+3 doped MgO thin films on quartz substrates. The films were characterized by XRD, XPS, Raman spectroscopy, and SIMS techniques. The microstructures were characterized by FESEM and TEM while the nanomechanical properties were assessed by the nanoindentation technique. Finally the optical transmittance was measured by UV–vis technique. The x-ray diffraction (XRD) study suggests the crystal facet (2 0 0) of MgO lattice to be distorted after incorporation of Al+3 into MgO lattice. From FESEM the doped films were found to have a dense microstructure with a crystallite size of about 20 nm as revealed by the TEM studies. Nanoindentation measurements indicated drastic increase of elastic modulus for the Al+3 doped MgO thin films by ~73% compared to that of the pristine MgO thin films along with retaining the nanohardness at ~8 GPa. The transmittance of Al+3 doped MgO thin films in the visible range was significantly higher (~99%) than that of pristine MgO (~90%) thin films. The films also had a relatively higher refractive index of about 1.45 as evaluated from the optical properties. The enhanced transmittance as well as the improved elastic modulus of Al+3 doped MgO thin films suggest its promising candidature in magnetic memory devices and as buffer layers of solar cells.

Effect of sapphire substrate orientations on the microstructural, optical and NO2 gas sensing properties of Zn(1−x)CdxO thin films synthesized by sol gel spin-coating method

A simple and cost-effective sol–gel technique was employed to elaborate ZnO and Zn(1−x)CdxO thin films deposit by spin coating onto the c- and r-plane sapphire substrates. The deposited films were characterized for their structural, morphological and optical properties using high resolution X ray diffraction (HRXRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) as function of Cd incorporation and employed substrate. Higher Cd incorporation (4.5%) is obtained for ZnCdO layer deposited on r-plane sapphire, which is confirmed by the greatest energy shift (110 meV) to lower energy measured by low temperature photoluminescence. X-ray diffraction study revealed that all films are polycrystalline with a hexagonal wurtzite structure. A preferred orientation along [001] and [110] direction is obtained respectively for layer deposited on c- and r-plane sapphire. However, the (002) and (110) XRD layers peak were shifted towards the lower 2θ values after Cd incorporation showing a slight variation of cell parameters. SEM and AFM image show no very significant variation in the morphology of the layers depending on the substrate orientation and Cd content incorporated. A mixture of large and small hexagonal grains are obtained which are more pronounced for ZnCdO deposited on r-plane sapphire and their agglomeration leaves more empty space in films.The gas sensing performances were tested in NO2 containing air for different operating temperatures as function of Cd incorporation and sapphire substrate orientation. The experimental result exhibited that ZnCdO sensors deposited on r-plane sapphire shows a more better gas response with fast response and recovery time at moderate operating temperatures as Cd contend increase.

Enhanced Photocatalytic Performance of Chromium Doped Zinc Oxide Nanoparticles

Pure and chromium doped ZnO nanoparticles were successfully synthesized by eco-friendly and cost effective sol–gel technique. Structural, morphological and optical properties of pure and Cr doped ZnO nanoparticles were analyzed by X-ray diffraction, transmission electron microscope, and UV–vis spectroscopic techniques, respectively. The crystallite size of pure ZnO nanoparticles were observed to decrease from 29 to 24 nm as dopant concentration was increased to 3 %. Band gap of pure ZnO nanoparticles were also observed to decrease from 3.5 to 3.37 eV with increase in dopant concentration. The photo-catalytic degradation of methyl blue dye under UV irradiation was examined for synthesized samples. The chromium doped zinc oxide nanoparticles were found to give enhanced photo degradation efficiency (75.5 %) than the pure zinc oxide nanoparticles (51.2 %).

A new type of counter electrode for dye sensitized solar cells based on solution processed SnO2 and activated carbon

A new type of nano-composite material is investigated for use as the counter electrode of a dye sensitized solar cell. The proposed material consists of SnO2 and activated carbon, which can be deposited using a cost-effective sol–gel technique. The effects of the activated carbon concentration on the structural and optoelectronic properties were investigated using scanning electron microscopy, X-ray diffraction, UV–vis spectroscopy and four probe measurements. It was found that the addition of activated carbon reduces resistivity and optical transmittance, and suppresses fluorine doped tin oxide (FTO) growth. The nanocomposite material was integrated into a dye sensitized solar cell and evaluated using cyclic voltammetry and J–V characteristics under solar light illumination, and demonstrated power conversion efficiency ~2.35%.