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Tremendous potential in the field of anti-biofouling coatings to prevent stainless steel (SS)-based underwater pipelines, sea vessels and other marine structures have been recognized to protect from biofouling, which is often initiated by algae attachment over the surface. In this work, hydrophobicity in spray-pyrolysed tungsten oxide (TO) coating on SS-316 substrate has been reported for the first time, via post-processing treatment using octadecyltrimethoxysilane (ODTMS) to induce self-assembled monolayer (SAM). Initially, structural and vibrational characteristics of ODTMS and ODTMS-treated TO (OTO) coating on SS were analysed using X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopies. OTO-coating depicted a water contact angle (WCA) of 121°, revealing its hydrophobic nature, with further affirmation from X-ray photoelectron spectroscopy (XPS). Durability of the TO-coating was explored using the scratch hardness (Hs) test at different loading conditions (5, 10 and 15 N). Biofouling study was conducted by culturing blue-green algae (BGA, Phormidium sp.) in an in-house laboratory setup for 40 days, using seawater (collected from the Arabian Sea, Karnataka). The SS, TO- and OTO-coatings were immersed for 14 days in a controlled sea-water environment in the laboratory with the presence of BGA. A comparative study on the areal-algae attachment was keenly analysed over SS-, TO- and OTO-coatings. This work can be projected as a promising application providing multi-dimensional solutions in creating scratch-resistant and anti-biofouling coatings on SS in the shipbuilding industry. [ABSTRACT FROM AUTHOR]

Despite the development of numerous coating techniques and materials, today’s anti-biofouling applications require coatings that are facile and mechanically robust in nature. Studies on the hydrophobicity of rare-earth oxides have risen due to their unusual chemical properties; ytterbium oxide is one such oxide substance. In this study, spray combustion was used to create a hydrophobic coating of ytterbium oxide (Yb2O3) on a stainless steel (SS) substrate, which was then vacuum-treated. GI-XRD analysis confirmed the sesquioxide cubic crystalline structure of Yb2O3. FESEM images displayed an underneath wavy morphological coating with discrete particles on the surface. The thickness and roughness were ~12 and ~0.17 µm, respectively. When 5 and 10 N loads were applied, the coating showed better scratch hardness than uncoated SS. Water contact angle (WCA) <10° indicated superhydrophilicity in the fabricated coating. After vacuum treatment, it became hydrophobic, and the WCA was 128°; because of the increment in the relative area fraction of the C–H bond. The proportion of area covered by blue–green algae (Phormidium sp.) on vacuum-treated Yb2O3 coating was only 3% compared to uncoated SS samples, 80%. [ABSTRACT FROM AUTHOR]

Over the past three decades, bioresorbable ceramics such as beta-tricalcium phosphate (β-TCP)-based porous scaffolds have been extensively studied. β-TCP-based scaffolds or cements for bone tissue applications have proved to be an outstanding alternative to repair and regenerate bone tissue defects caused by trauma or injury. In this study, an investigation on submicron β-TCP powders derived from prawn shell (Fenneropenaeus indicus, a source of marine biowaste) via solid-state reaction approach was carried out, which has calcite (CaCO3) in its exoskeleton (nonedible). The prawn shell-derived β-TCP can be prepared conventionally with dicalcium phosphate (CaHPO4) at different temperatures 900, 1000, 1100, and 1200 °C. The EDX spectra detect the Ca:P ratio of 1.5 confirming the formation of pure β-TCP at 1100 °C, which is in complete agreement with theoretical ratio. X-ray diffraction pattern revealed the phase-pure crystalline rhombohedral crystal structure of β-TCP with an average crystallite size of ~ 25.8 nm, prepared at 1100 °C. The field emission scanning electron microscopy images showed a homogeneous distribution of β-TCP powders with an average grain size of 3.07 µm at 1100 °C. Furthermore, Raman spectroscopy and Fourier transform infrared spectroscopy confirm the characteristics peaks of β-TCP. Differential scanning calorimetry and thermogravimetric analysis are performed to study the thermal behavior of the initial precursors mixture to synthesize β-TCP. β-TCP scaffolds sintered at 1100 °C exhibited compressive strength of ~ 6.2 MPa, for which Ca/P ratio is 1.51. Biodegradation study conducted on β-TCP scaffolds sintered at 1100 °C has shown slow degradation rate up to 5 days. Therefore, the prawn shell-derived β-TCP has physical and morphological properties which projects it as a promising implantable biomaterial for synthetic bone graft substitutes. [ABSTRACT FROM AUTHOR]

The current work delivers room-temperature ammonia (NH3) gas-detectable pristine, Nb-doped TiO2 air- and vacuum-annealed films obtained through the solution-combustion process. Polycrystalline anatase crystal structured films without any dopant oxide phases were processed at 400°C on glass substrates. The crystallinity was higher in pristine films than in doped films; the morphological features were similar in all the films. The films were > 50% transparent, and the estimated optical energy band gap was greater in doped films than in pristine films. All the films detected NH3 gas (25 ppm to 100 ppm) at room temperature, and the gas response was highly dependent on the crystallinity and relative area fraction of adsorbed oxygen (% of OA). The vacuum-annealed pristine film exhibited a better gas response than the other films at all NH3 gas concentrations due to high crystallinity and % of OA (10.15%). The film demonstrated maximum gas response of ~16 towards 100 ppm of NH3 gas and displayed good selectivity. Even though the doping reduced the crystallite size from ~17 nm to ~9 nm, it also diminished the crystallinity of the films, which significantly impacted the deterioration of their gas response. [ABSTRACT FROM AUTHOR]

In this contribution, pure, polycrystalline wurtzite crystal structured, spin-coated pristine ZnO and Ti-doped (1, 2, and 3 wt%) ZnO transparent films were accomplished at 400 °C through a facile solution combustion synthesis method. Crystallinity, roughness, and porosity in the pristine film were relatively higher than in the doped films. The demonstrated films were transparent, with ~ 70 to 90% in the visible region. The room temperature detection of ammonia (NH3) gas (25–100 ppm) was recognized in all the films. The pristine film revealed a superior gas response at every concentration of NH3 gas in contrast to all the doped films; it is probably due to comparatively high crystallinity, porosity, more oxygen vacancy concentration (1.788), and high fraction of adsorbed oxygen (20.55%). The film exhibited the highest gas response of 34.7 at 100 ppm of NH3 gas and a limit of detection of ~ 10.7 ppm with superior selectivity towards NH3 gas. Although doping enhanced the transparency but diminished the NH3 gas response due to the combined effect of deterioration in the mentioned properties achieved in pristine film. [ABSTRACT FROM AUTHOR]

High entropy oxides (HEOs) have captivated significant concentration due to their unique properties. Manipulation of configurational entropy is the main key for extraordinary behaviours, leading to unprecedented material design and innovations. Substantial research has been conducted on HEO bulk systems, but films are still in the cradle stage. Inspired by the ground-breaking results of HEOs, a novel form of films named high entropy oxides films (HEOFs) are being fabricated. The focus in this review is on the fabrication process, structure and properties of HEOFs with attention to their strengths and liabilities. Iconic investigations from recent articles are highlighted. The first overview is provided on how HEOFs are fabricated and interesting phenomena such as the impact of processing parameters, the role of dopants on the film are discussed. This review also highlights the structural–microstructural appearance and physical properties, concluding with future possibilities and applications. [ABSTRACT FROM AUTHOR]

It is beneficial to develop the cost-effective, ultra-sensitive ZnO-based sensor for the rapid detection and quantification of the ammonia and formaldehyde breath markers under ambient conditions. Here, one-step solution route was adopted to formulate the aqueous combustible molecular precursor-based clogging free screen-printing ink consisting of zinc nitrate as an oxidizer, glycine as fuel, and eco-friendly binder sodium carboxymethylcellulose. The formulated precursor was deposited on the glass substrates via a screen-printing technique followed by annealing at different temperatures for an hour. Screen printed ZnO sensors processed at 500 °C with high crystallinity, less lattice distortion, low optical bandgap, and high concentration of donor defects showed remarkably high NH3 gas response ~ 336 and a moderate HCHO response ~ 16.4 towards the 5 ppm and 10 ppm of the respective gases. In addition it's LOD values is drawn as 0.6 ppm and 2.9 ppm for NH3 and HCHO gases, respectively, and exhibits superior selectivity towards ammonia. Faster diffusion of oxygen vacancies (Vo) in the smaller crystallites resulted expeditious sensor kinetics in the screen-printed sensor processed at 400 °C. Response and recovery time were recorded to be 50 s and 50 s to the 5 ppm of NH3, respectively. The crystallinity-dominant domain overcomes the adverse effect of larger grains on the gas response of screen-printed ZnO sensor processed at 500 °C. Robust, scalable, and cost-effective screen-printed ZnO conductometric sensors demonstrated here has a potential application in clinical diagnosis, and also in monitoring the NH3 and HCHO gases at low ppm-level. [ABSTRACT FROM AUTHOR]

In the present work, gas sensing properties of the screen printed ceria and ruthenate-sensitized BaSnO3 (BSO) with La doping heterostructure sensors towards the detection of ammonia and formaldehyde gases at room temperature were studied. Adhered, porous screen printed films with different morphologies were obtained by depositing the LaxBa1−xSnO3−δ (x = 0 and 0.05) powder particles prepared by the polymerized complex method. Ceria and ruthenate sensitization for screen printed LaxBa1−xSnO3−δ (x = 0.05) film was processed through dip-coating in the 0.03 M aqueous solution of CeCl3 and RuCl3, respectively. La-doped BaSnO3 (LBSO) sensor with smaller crystallites, needle-like morphology and high concentration of oxygen vacancies exhibited superior gas response of 65 and 29 towards 50 ppm of ammonia and formaldehyde gases, respectively. Superabundant sensitization of ceria and ruthenate reduced the oxygen vacancy and structural open porosity in the LBSO sensor; therefore, the ammonia gas response was decreased from 65 to 14 and 3, respectively, whereas the formaldehyde gas response was reduced to less than 1/6th times the LBSO sensor. Limit of detection of LBSO sensors was estimated to be ~ 1 and ~ 2 ppm against ammonia and formaldehyde, respectively. The presence of fluorite structured phase ceria with high oxygen atoms storage capacity facilitates the rapid oxidization of analyte gases and caused the expeditious response (75 s) and recovery (60 s) in CeOx-sensitized LBSO sensor. This study might give a new insight into the development of doped and sensitized BSO-based gas sensors operating at ambient conditions. [ABSTRACT FROM AUTHOR]

In this work, high fracture toughness graphene–alumina composite was developed through a novel chemical method using boehmite and graphene, which is followed by extrusion and consolidation. The mixed precursors were consolidated by sintering at 1550 °C in a nitrogen atmosphere. The plate-like structures of boehmite form α-alumina; meanwhile, graphene particles at the grain boundaries hinder the growth of alumina grains. The graphene reinforcement was bonded to α-alumina matrix by van der Waals forces. The XRD pattern reveals the presence of graphene with a plane (002) along with α-alumina. Properties such as fracture toughness (5.6 ± 0.01 MPa m0.5), Vickers hardness (1872 ± 25 kgf/mm2) and true density (3.8 g/cm3) were achieved in 0.5 wt.% graphene–alumina composite when compared to α-alumina with fracture toughness (5.3 ± 0.1 MPa m0.5), Vickers hardness (1984 ± 28 kgf/mm2) and true density (3.91 g/cm3). The bridging and deviation of cracks in 0.5 wt.% graphene–alumina composite are attributed to the anchoring and dissipation of energy during crack growth, which enhances the fracture toughness, whereas α-alumina exhibits failure caused by linear crack propagation. Meanwhile, the slight decrease in Vickers hardness and true density of 0.5 wt.% graphene–alumina composite is due to the tribological and low-density properties of graphene. The obtained properties of composite could be suitable in high-temperature, wear-resistant applications such as crucibles, bearings, etc. [ABSTRACT FROM AUTHOR]

We report a comparative study on enhancing and inhibiting the sensing performance of Sr-doped ZnO (Sr0.01 Zn0.99O) and RuO2-activated Sr-doped ZnO heterostructured sensors towards the low concentration (≤ 50 ppm) of ammonia gas at ambient. Sub-microns sized with high specific surface area, high reactive, oxygen-deficient Sr-doped ZnO particles were synthesized at low temperature (196 °C) through facile glycine–nitrate solution combustion synthesis (SCS) method. Porous, adhered screen-printed film of Sr-doped ZnO with optical bandgap (3.22 eV) was dip-coated using 0.02 M RuCl3 aqueous solution to obtain RuO2 activation. Smaller crystallite size and lesser lattice distortion obtained with Sr-doping in ZnO enhance the gas response (S = 71) towards the 50 ppm of ammonia gas at room temperature. RuO2-activated Sr-doped ZnO sensor associated with lesser oxygen vacancies and a lower concentration of chemisorbed oxygen species due to passivation layer and no-spill-over activity of RuO2, which inhibits the gas response from 71 to 3. Sr-doped ZnO-based sensor shows high selectivity towards ammonia against 50 ppm of volatile organic compound (VOCs) vapor. Expeditious sensor kinetics (response time and recovery time) in the Sr-doped ZnO sensor was observed, in which smaller crystallite size offers a shorter distance for the diffusion of oxygen vacancies (Vo). Ultra-high-sensitive and selective sensors with ease and economical fabrication offer feasibility in industries and domestic applications where detection of the less concentration ammonia vapor is crucial. [ABSTRACT FROM AUTHOR]

Exposure to ultraviolet (UV) radiation has been known to cause skin cancer, erythema, and sunburn. Continuous efforts have been made to make sunscreens more efficient and non-toxic. Inorganic sunscreens like TiO2 and ZnO are continued to be used for a few decades, and they are efficient in giving protection against harmful UV radiation, but they are photochemically active as well. They generate free radicals upon irradiation, which leads to reactive oxygen species (ROS) generation which is harmful to the human skin. Hydroxyapatite (HA) is a biocompatible material as it has a composition the same as the mineral content of the human bone; therefore, it is suitable for the dermatological application. Though HA itself does not provide protection against UV, studies on doped HA with various ions showed excellent performance. Pure HA absorbs only between 200 and 340 nm, with an intense band below 247 nm. HA doped with bivalent Zn2+, Fe2+, and trivalent Fe3+ and Cr3+, showed absorbance in the entire UV region. TiO2 provides absorbance in the entire UV range, while ZnO does so only in UVA. Compared to HA (refractive index, n = 1.6), TiO2 (n = 2.6) and ZnO (n = 1.9) have higher refractive index, which gives unwanted whitening effect. Additional properties can be brought in HA composites by adding material while retaining their individual properties. As HA is not photocatalytic, it does not lead to a generation of free radicals. This paper throws light on several aspects of HA-based sunscreen filters as an emerging future cosmetic material, and brief analysis and conclusions. [ABSTRACT FROM AUTHOR]

In this study, a facile spray pyrolysed hydrophobic robust tungsten oxide (WO3) films were deposited at an annealing temperature of 400°C on inexpensive glass substrates, using clear and homogeneous precursor solution containing tungsten hexachloride and 2-methoxyethanol. The 10 and 15 times sprayed films were polycrystalline with the monoclinic crystal structure, uniform with the submicron-sized grain morphology (size ~320–420 nm), with an average surface roughness ranging from 12 to 17 nm and transparent above 60% in the visible region with a thickness of 380 and 550 nm, respectively. Elemental existence of tungsten and oxygen was recognized on the surface of the films possessing the highest lattice oxygen percentage of 91.1. Increment in the scratch hardness of the films with the number of sprays compared to uncoated glass was identified. The films were hydrophilic in nature (water contact angle <8°), converted to hydrophobic (>120°) by treating chemically with octadecyltrichlorosilane to form a self-assembled monolayer on the top and the hydrophobicity remained same (~120°) even after a year. These films with unique and combined properties of scratch hardness and hydrophobicity can serve in the potential application as antifouling coatings. [ABSTRACT FROM AUTHOR]

In this contribution, screen printing of aqueous based particle-free silver ink is addressed using combustion chemistry, where inks embody a redox mixture of silver nitrate and citric acid in the presence of a binder, sodium-carboxymethylcellulose. The exothermic reaction at ~ 176 °C results in the formation of pure silver. Screen-printing process is optimized for three different silver loadings (14%, 18% and 22%) in ink. In depth rheological study of the inks reveals thixotropic nature and the ink with 18% of silver possessing a viscosity of 328 Pa.s has a recovery rate of 84% at 110 s with a shear rate of 1 s−1. The deposited silver films (~ 3 µm thick) on both rigid-glass and flexible-polyamide substrates have shown an electrical conductivity of 4.2 × 106 S m−1 and 2.6 × 106 S m−1 respectively. Film adhesion on glass substrates categorized under 3B as per ASTM D-3359. Present screen-printed silver films find their application as a gate electrode in thin film transistors (TFTs). The TFTs comprising of indium zinc tin oxide–semiconductor and sodium β -alumina dielectric with screen-printed silver as a gate electrode exhibited the saturation mobility, on:off ratio and threshold voltage of 0.88 cm2 V−1 s−1, 102 and ~ 0.3 V respectively. [ABSTRACT FROM AUTHOR]

We present high performance, low voltage (≤ 3 V) operation of thin film transistors (TFTs) with indium zinc tin oxide (IZTO: In4Sn4ZnO15)-semiconductor. The film of IZTO was fabricated via low-temperature (200 °C) solution combustion processing without incorporating an external fuel. As 2-methoxyethanol is a widely used organic solvent due to its high dissolution capability, serve the purpose of both the solvent and the fuel. On quantification from the balanced redox reaction, 0.3% of 2-methoxyethanol assisted for the action of fuel and helped in the formation of metal oxide, and the rest (99.7%) served the purpose of being dissolution medium. The balanced redox chemistry yielded a significant fraction of (56.5%) metal oxide at 200 °C confirmed via high-resolution oxygen 1s spectrum. Further, the chemically derived thin film of sodium β-alumina with a dielectric constant of ~ 21, while annealing at 350 °C incorporated in the TFT for the realization of low voltage operation. The performance assessment is systematically carried out both silicon dioxide (SiO2) and sodium β-alumina and found that the TFTs with SiO2 and IZTO exhibited a saturation mobility (µsat), Ion/Ioff ratio and the threshold voltage (Vth) of 0.50 ± 0.02 cm2 V−1 s−1, 1.25 × 104 and 6.6 ± 0.79 V respectively. While changing the dielectric to sodium β-alumina presented a µsat, Ion/Ioff ratio and Vth of 4.21 ± 0.18 cm2 V−1 s−1, 1.4 × 102 and 0.47 ± 0.08 V respectively. [ABSTRACT FROM AUTHOR]

In the present contribution, in situ formation of low-temperature high conductive composite films composed of pure silver and oxides of copper (CuxOy where, x = y = 1 for CuO and x = 2, y = 1 for Cu2O), are presented through spray combustion with a balanced stoichiometric redox reaction. High electrical conductivity (~ 7.8 × 105 S/cm) was retained in the composite film at an annealing temperature of 170 °C with matrix silver phase being 50% by volume. Whereas electrical conductivity of spray combustion processed pure silver is found to be ~ 2 × 106 S/cm. In situ formation of the composite film directly from the silver and cupric nitrate aqueous precursor solution through spray combustion proves it to be compositionally tunable with minimal usage of noble metal. Presence of Ag and CuxOy is confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. The ratio of Cu1+/Cu2+ in the composite is found to be 0.54 and 0.43 at an annealing temperature of 170 °C and 400 °C respectively. The transformation of Cu2O to CuO is highly a thermally activated phenomenon; as the vacancy driven electrical conductivity is more in Cu2O than CuO, stabilization of Cu2O at a lower temperature is desired. The composite electrode can have potential applications in optoelectronics, printed electronics and catalysis. [ABSTRACT FROM AUTHOR]

Using the principles in defining and extending the Shapiro-Wilk W-statistic for exponentiality of a single distribution we develop procedures for testing a composite hypothesis of exponentiality of two distributions in the location-scale family having different location parameters and the same scale parameter. First, we propose a test statistic whose null distribution is the same as the Shapiro-Wilk W-exponential statistic corresponding to an appropriate sample size. The second test statistic (origin and scale invariant) turns out to be a normalized ratio of the square of the generalized least squares estimate (also the MVUE) of the common scale parameter to a pooled sum of squares about the sample means and has a null distribution that depends only on the sample sizes. We provide the empirical percentage points of the null distribution of the statistic. The two statistics are then modified when one or both samples are censored. In each case, we consider numerical examples to illustrate the applications of the proposed tests. Empirical power results for various types of probability distributions under the alternative hypothesis are given. We also carry out an extensive power study to address one important question whether our tests reject if the populations were exponential but with different scale parameters. [ABSTRACT FROM AUTHOR]

Fabrication of organic thin film transistor (OTFT) on flexible substrates is a challenge, because of its low softening temperature, high roughness and flexible nature. Although several organic dielectrics have been used as gate insulator, it is difficult to choose one in absence of a comparative study covering processing of dielectric layer on polyethylene terephthalate (PET), characterization of dielectric property, pentacene film morphology and OTFT characterization. Here, we present the processing and performance of three organic dielectrics, poly(4-vinylphenol) (PVPh), polyvinyl alcohol (PVA) and poly(methyl methacrylate) (PMMA), as a gate layer in pentacene-based organic thin film transistor on PET substrate. We have used thermogravimetric analysis of organic dielectric solution to determine annealing temperature for spin-coated films of these dielectrics. Comparison of the leakage currents for the three dielectrics shows PVA exhibiting lowest leakage (in the voltage range of −30 to +30 V). This is partly because solvent is completely eliminated in the case of PVA as observed by differential thermogravimetric analysis (DTGA). We propose that DTGA can be a useful tool to optimize processing of dielectric layers. From organic thin film transistor point of view, crystal structure, morphology and surface roughness of pentacene film on all the dielectric layers were studied using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). We observe pyramidal pentacene on PVPh whereas commonly observed dendritic pentacene on PMMA and PVA surface. Pentacene morphology development is discussed in terms of surface roughness, surface energy and molecular nature of the dielectric layer. [ABSTRACT FROM AUTHOR]

Abstract: Response-adaptive designs are used in phase III clinical trials to allocate a larger number of patients to the better treatment. Optimal response-adaptive designs have become popular in recent days for this purpose, where the design is derived from some optimal viewpoints, mostly by optimizing some objective function subject to some constraint(s). However, most of the optimal designs are derived with two treatments and only a few works are available for several treatments. The present paper provides a generalized framework to derive multi-treatment optimal response-adaptive designs. A detailed performance study is provided for three treatment trials minimising failures. The applicability is also judged by redesigning some real clinical trials. [Copyright &y& Elsevier]

In this work, the effect of annealing temperature on the conductivity of solution-combustion-synthesized calcium vanadium oxide (CVO) films was studied. Conductivity was tailored by the appearance of the phases like CaVO3, CaV2O5 and Ca2V2O7 as a function of annealing temperature; CaVO3 and CaV2O5 are responsible for high conductivity, whereas V5+ presence in Ca2V2O7 contributes towards dielectric nature. Evolution of phases of CVO was identified through X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A detailed conductivity measurement as a function of annealing temperature helps us to identify the decreasing trend of conductivity with increasing temperature up to 400∘C; beyond this it behaves like an insulator. There was a stable conductivity while aging the films in ambient for a few days. This study revealed safe application temperature domain of CVO, and a clear correlation of electrical conductivity with the in-depth structural-compositional-morphological study. [ABSTRACT FROM AUTHOR]