Nanoparticle-laden contact lens for controlled release of vancomycin with enhanced antibiotic efficacy.

Vancomycin is the last resort antibiotic for the treatment of severe bacterial keratitis. Its clinical application is limited due to its hydrophilicity and high molecular weight. To overcome this, this study aims to develop nanoparticles-laden contact lens for controlled ocular delivery of vancomycin. Polyvinyl alcohol (PVA) was used as encapsulant material. The nanoparticles had a negative surface charge and an average size of 147.6 nm. A satisfactory encapsulation efficiency (61.24%) was obtained. The release profile was observed to be slow and sustained, with a release rate of 1.29 µL mg-1 h-1 for 48 h. Five out of 6 test bacteria were suppressed by vancomycin nanoparticles-laden contact lens. Vancomycin is generally ineffective against Gram-negative bacteria and unable to pass through the outer membrane barrier. In this study, vancomycin inhibited Proteus mirabilis and Pseudomonas aeruginosa. Nano-encapsulation enables vancomycin to penetrate the Gram-negative cell wall and further destroy the bacterial cells. On Hohenstein challenge test, all test bacteria exhibited significant reduction in growth when exposed to vancomycin nanoparticles-laden contact lens. This study created an effective and long-lasting vancomycin delivery system via silicone hydrogel contact lenses, by using PVA as encapsulant. The antibiotic efficacy and vancomycin release should be further studied using ocular in vivo models.

Large-scale sonochemical fabrication of a Co3O4-CoFe2O4@MWCNT bifunctional electrocatalyst for enhanced OER/HER performances.

Herein, we have prepared a mixed-phase Co3O4-CoFe2O4@MWCNT nanocomposite through a cheap, large-scale, and facile ultrasonication route followed by annealing. The structural, morphological, and functional group analyses of the synthesized catalysts were performed by employing various characterization approaches such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The resultant samples were tested for bifunctional electrocatalytic activity through various electrochemical techniques: cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The prepared Co3O4-CoFe2O4@MWCNT nanocomposite achieved a very high current density of 100 mA cm-2 at a lower (290 mV and 342 mV) overpotential (vs. RHE) and a smaller (166 mV dec-1 and 138 mV dec-1) Tafel slope in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, compared to Co3O4-CoFe2O4. The excellent electrochemical activity of the as-prepared electrocatalyst was attributed to the uniform incorporation of Co3O4-CoFe2O4 over MWCNTs which provides high redox active sites, a greater surface area, better conductivity, and faster charge mobility. Furthermore, the enhanced electrochemical active surface, low charge-transfer resistance (Rct), and higher exchange current density (J0) of the Co3O4-CoFe2O4@MWCNT ternary composite are attributed to its superior behavior as a bifunctional electrocatalyst. Conclusively, this study demonstrates a novel and large-scale synthesis approach for bifunctional electrocatalysts with a high aspect ratio and abundance of active sites for high-potential energy applications.

Unveiling the non-polar [3+2] cycloaddition reactions of cyclic nitrones with strained alkylidene cyclopropanes within a molecular electron density theory study.

The role of cyclopropane substitution on the ethylene in zw-type [3+2] cycloaddition (32CA) reactions of cyclic nitrones has been studied within Molecular Electron Density Theory (MEDT) at the ωB97X-D/6-311G(d,p) computational level. Electron Localization Function (ELF) analysis of the ethylenes shows that the presence the cyclopropane only slightly increases the electron density in the C-C bonding region. Analysis of the Conceptual DFT reactivity indices indicates that the presence of the cyclopropane does not produce any remarkable change in the reactivity of these strained ethylenes. The marginal electrophilic character of ethylene makes the zw-type 32CA reactions of non-polar character. The presence of the cyclopropane in the ethylene decreases the activation enthalpy of the 32CA reactions by only 1.7 and 2.6 kcal mol-1, and also decreases the ortho regioselectivity. The loss of the strain present in the cyclopropane is responsible for the reduction of the activation enthalpy and the increase of the reaction enthalpy in these non-polar 32CA reactions. The presence of the cyclopropane does not cause any change, neither in the transition state structure (TS) geometries nor in their electronic structure. The very low global electron density transfer (GEDT) computed at the TSs confirms the non-polar character of these 32CA reactions. The ortho regioselectivity experimentally observed in these non-polar 32CA reactions is determined by the most favorable two-center interaction between the less electronegative C1 carbon of nitrone and the non-substituted methylene C5 carbon of the ethylenes.

CdO-supported ZrO2heterojunctions: facile synthesis and rapid visible-light oxidation of atrazine herbicide with superb recyclability.

The advancement in ceramic oxide-based photocatalysis has got much attention recently for environmental issues. Atrazine (AZ) is one of the major used herbicides in agricultural and related industries. This work familiarizes a polymeric-assisted sol-gel preparation of high surface area zirconium oxide (ZrO2) supported with cadmium oxide nanoparticles at minor content (0.5-2.0 wt%). Exploration of the synthesized heterostructures revealed the enhancement of visible-light absorbance and reduction of bandgap energy to 2.76 eV keeping the same crystalline form and high surface area of 170 m2g‒1. The prepared photocatalysts were used to degrade AZ in water at a concentration of 231.8µM (50 ppm). The 1.5%-introduced CdO to ZrO2revealed the best-performed photocatalyst for complete oxidation of AZ within 40 at an optimized dose of 1.6 g l-1. This novel ceramic photocatalyst showed a chemical and structural ability to keep 98.5% of its initial efficiency after five regenerated cycles. The construction of p-n heterojunction between the p-type ZrO2and the n-type CdO contributed to the comprehensive photocatalytic competence toward the efficient charge separation and photooxidation process.

Adsorption of Magenta Dye on PbO Doped MgZnO: Interpretation of Statistical Physics Parameters Using Double-Layer Models.

This article reports the synthesis of PbO doped MgZnO (PbO@MgZnO) by a co-precipitation method, followed by an ultrasonication process. PbO@MgZnO demonstrates a significant adsorption capability toward Magenta Dye (MD). The greatest adsorption capability was optimized by varying parameters such as pH, MD concentration, and adsorbent dose. The kinetics study illustrates that the adsorption of MD on PbO@MgZnO follows the pseudo-second-order. The isotherm study revealed that Langmuir is best fitted for the adsorption, but with little difference in the R2 value of Langmuir and Freundlich, the adsorption process cloud be single or multi-layer. The maximum adsorption capacity was found to be 333.33 mg/g. The negative ΔG refers to the spontaneity of MD adsorption on PbO@MgZnO. The steric parameters from statistical physics models also favor the multi-layer adsorption mechanism. As a function of solution temperature, the parameter n pattern has values of n = 0.395, 0.290, and 0.280 for 298, 308, and 318 K, respectively (i.e., all values were below 1). Therefore, horizontal molecule positioning and multiple locking mechanisms were implicated during interactions between MD and PbO@MgZnO active sites.

Mesopores silica nanotubes-based sensors for the highly selective and rapid detection of Fe2+ ions in wastewater, boiler system units and biological samples.

Mesopores silica nanotubes (MSNTs)-based chemical sensors for the rapid detection and of highly selective Fe2+ ions have been prepared. The novel nanosensors were prepared via immobilization of 1,10-phenanthroline-5-amine (PA) and bathophenanthroline (BP) onto the MSNTs. The resultant PA and BP sensors display high sensitivity for detection the Fe2+ ions in tap water, river water, sea water, two units in simple cycle power station, and biological samples. More interestingly, upon meeting ultra-trace amount of Fe2+ ions, a red complex appears at once. Color changes can be seen from the naked eye and tracked with a smartphone or spectrophotometric techniques. The response time that is necessary to achieve a stable signal was less than 15 s. The Univariate (Univar) calibration technique had been utilized for the determination of figures of merits. The detection limit obtained from the digital image analysis was 19 ppb (7.04 × 10-7 M) for Fe2+ ions, while the obtained from the spectrophotometric method was 6.7 ppb (2.48 × 10-7 M). Therefore, the two sensors had been successfully used in the determination of Fe2+ in several real samples with high sensitivity and selectivity. In addition, they can be used as a simple, rapid, and portable method to detect and quantify the pre rust in any cooler system.

Intense Visible-Light Absorption in SrRuO3/C3N4 Heterostructures for the Highly Efficient Reduction of Hg(II).

Strontium ruthenium oxide (SrRuO3) is recognized as a metallic itinerant ferromagnet and utilized as a conducting electrode in heterostructure oxides with unforeseen optical characteristics, including remarkably low-reflection and high-absorption visible-light spectrum compared to classical metals. By coupling mesoporous SrRuO3 nanoparticles (NPs) with porous g-C3N4 nanosheets for the first time, we evidence remarkably promoted visible light absorption and superior photocatalytic performances for Hg(II) reduction under illumination with visible light. The photocatalytic performance of g-C3N4 increased upon boosting the SrRuO3 percentage to 1.5%, and this (1.5% SrRuO3/g-C3N4 heterostructure) is considered the optimum condition to obtain a high photocatalytic efficiency of about 100% within 50 min. It was promoted 3.68 and 5.75 times compared to SrRuO3 and g-C3N4, respectively. Also, a Hg(II) reduction rate of 1.5% SrRuO3/g-C3N4 was enhanced3.84- and 6.28-fold than those of pure SrRuO3 NPs and g-C3N4, respectively. Such a high photocatalytic performance over SrRuO3/g-C3N4 photocatalysts was explained by the characteristics of SrRuO3 NPs incorporated on porous g-C3N4 layers, which demonstrate strong absorption of visible light with a narrow band gap, a large photocurrent density of ∼9.07 mA/cm2, well-dispersed and small particle sizes, and cause facile diffusion of HCOOH and Hg(II) ions and electrons. The present work provides a dramatic novel approach to the challenge of constructing visible-light photosensitive photocatalysts for wastewater remediation.

CoAl2O4-g-C3N4 Nanocomposite Photocatalysts for Powerful Visible-Light-Driven Hydrogen Production.

There is no doubt that the rate of hydrogen production via the water splitting reaction is profoundly affected to a remarkable degree based on the isolation of photogenerated electrons from holes. The precipitation of any cocatalysts on the substrate surfaces (including semiconductor materials) provides significant hindrance to such reincorporation. In this regard, a graphite-like structure in the form of mesoporous g-C3N4 formed in the presence of a template of mesoporous silica has been synthesized via the known combustion method. Hence, the resulting g-C3N4 nanosheets were decorated with varying amounts of mesoporous CoAl2O4 nanoparticles (1.0-4.0%). The efficiencies of the photocatalytic H2 production by CoAl2O4-doped g-C3N4 nanocomposites were studied and compared with those of pure CoAl2O4 and g-C3N4. Visible light irradiation was carried out in the presence of glycerol as a scavenger. The results showed that the noticeable photocatalytic enhancement rate was due to the presence of CoAl2O4 nanoparticles distributed on the g-C3N4 surface. The 3.0% CoAl2O4-g-C3N4 nanocomposite had the optimum concentration. This photocatalyst showed extremely high photocatalytic activities that were up to 22 and 45 times greater than those of CoAl2O4 and g-C3N4, respectively. This photocatalyst also showed 5 times higher photocatalytic stability than that of CoAl2O4 or g-C3N4. The presence of CoAl2O4 nanoparticles as a cocatalyst increased both the efficiency and productivity of the CoAl2O4-g-C3N4 photocatalyst. This outcome was attributed to the mesostructures being efficient charge separation carriers with narrow band gaps and high surface areas, which were due to the presence of CoAl2O4.

Crystal modification of calcium sulfate dihydrate in the presence of some surface-active agents.

The effect of surface-active agents (surfactants), as additives, on the crystallization of gypsum was studied under conditions of the simulated dihydrate process of phosphoric acid production. Calcium hydrogen phosphate and sulfuric acid were mixed with dilute phosphoric acid at 80 degrees C, and the turbidity of the reaction mixture was measured at different time periods to determine the induction time of gypsum crystal formation. Two types of surfactants, namely, cetyltrimethylammonium bromide (CTAB) as a cationic surfactant and sodium dodecyl sulfate (SDS) as an anionic surfactant were added to investigate their effects on the crystallization of gypsum. Addition of CTAB decreased the induction time and increased the growth efficiency, while addition of SDS increased the induction time and decreased the growth efficiency compared with the baseline (without additives). The surface energy increased with CTAB and decreased with SDS compared with the baseline. The percentage of fine crystals decreased in the presence of CTAB and increased in the presence of SDS compared with the baseline. Gypsum morphology changed from needle-like in the absence of additives to tabular in the presence of CTAB.