A simple and highly sensitive spectrophotometric determination of Cr(VI) in food samples by using 3,4-dihydroxybenzaldehydeisonicotinoylhydrazone (3,4-DHBINH)

A simple, rapid, sensitive and inexpensive method has been developed for the determination of trace amounts of chromium(VI) using 3,4-dihydroxybenzaldehydeisonicotinoylhydrazone (3,4-DHBINH). The metal ion gives a yellow coloured complex with 3,4-DHBINH in acetate buffer of pH 5.5 with 1:1 (metal:ligand) composition. The complex shows a maximum absorption at 400 nm. Beer’s law is obeyed in the range 0.5–7.7 ppm of Cr(VI). The molar absorptivity, Sandell’s sensitivity and detection limit were found to be 1.35 × 10⁴ L mol⁻¹ cm⁻¹, 0.0075 μg cm⁻² and 0.0045 μg mL⁻¹, respectively. The correlation co-efficient and regression co-efficient of the Cr(VI)–3,4-DHBINH complex were 0.99 and 0.12, respectively. Major cations and anions did not show any interference. The developed method has been successfully applied for the analysis of Cr(VI) in food samples (leafy vegetables), comparing the results simultaneously with those obtained using an Atomic Absorption Spectrophotometer, whereby the validity of the method has been tested.     

Palladium-catalysed vapour phase aerobic acetoxylation of toluene to benzyl acetate

Supported Pd–Sb acetoxylation catalysts with different Pd and Sb amounts as well as varying supports were prepared by impregnation technique. The contents of Pd and Sb are varied over a wide range, for instance Pd is varied from 0.5 to 20 wt% by keeping Sb content at 8 wt%. In a similar way, Sb content is varied from 4 to 20 wt% by keeping Pd loading constant at 10 wt%. Four different supports such as TiO₂, γ-Al₂O₃, SiO₂ and ZrO₂ are applied at constant Pd (10 wt%) and Sb (8 wt%) contents. Catalytic performance of these solids is evaluated for the gas phase acetoxylation of toluene to benzyl acetate (BA) at T = 210 °C and p = 2 bar. XPS revealed a considerable loss of both Pd and Sb in the near-surface region in the used catalysts. TEM showed that Pd particles exhibit spherical morphology and their size increased dramatically in the spent catalysts compared to their corresponding fresh ones. Monometallic catalysts showed very poor acetoxylation performance but high total oxidation, which results in an increase of the yield of CO_x up to ca. 50%. However, combination of both Pd and Sb was found to suppress total oxidation and thereby enhance the acetoxylation performance with high BA selectivity of ≥85%. Catalytic activity was observed to increase continuously with increase in Pd loading. The catalyst with the highest Pd loading (20 wt% Pd) displayed the best performance (toluene conversion = > 90%, BA yield = > 75%). The activity is however decreasing with time-on-stream due to coke deposits. Nevertheless, the deactivated samples can be regenerated in air to restore their maximum activity. Nature of support, content of co-components showed strong influence on the catalytic performance.     

Enhanced wound healing activity of Ag–ZnO composite NPs in Wistar Albino rats

In the present study, silver (Ag) and Ag–zinc oxide (ZnO) composite nanoparticles (NPs) were synthesised and studied their wound‐healing efficacy on rat model. Ultraviolet–visible spectroscopy of AgNPs displayed an intense surface plasmon (SP) resonance absorption at 450 nm. After the addition of aqueous Zn acetate solution, SP resonance band has shown at 413.2 nm indicating a distinct blue shift of about 37 nm. X‐ray diffraction analysis Ag–ZnO composite NPs displayed existence of two mixed sets of diffraction peaks, i.e. both Ag and ZnO, whereas AgNPs exhibited face‐centred cubic structures of metallic Ag. Scanning electron microscope (EM) and transmission EM analyses of Ag–ZnO composite NPs revealed the morphology to be monodispersed hexagonal and quasi‐hexagonal NPs with distribution of particle size of 20–40 nm. Furthermore, the authors investigated the wound‐healing properties of Ag–ZnO composite NPs in an animal model and found that rapid healing within 10 days when compared with pure AgNPs and standard drug dermazin.Inspec keywords: wounds, tissue engineering, biomedical materials, nanocomposites, nanofabrication, nanomedicine, silver, zinc compounds, II‐VI semiconductors, wide band gap semiconductors, ultraviolet spectra, visible spectra, nanoparticles, particle size, surface plasmon resonance, spectral line shift, X‐ray diffraction, scanning electron microscopy, transmission electron microscopyOther keywords: enhanced wound healing activity, Ag‐ZnO composite nanoparticles, Wistar Albino rats, wound‐healing efficacy, ultraviolet‐visible spectroscopy, intense surface plasmon resonance absorption, aqueous Zn acetate solution, SP resonance band, blue shift, X‐ray diffraction analysis, diffraction peaks, face‐centred cubic structures, scanning electron microscope, SEM, transmission electron microscope, TEM, monodispersed hexagonal nanoparticles, quasihexagonal nanoparticles, particle size, animal model, time 10 d, size 20 nm to 40 nm, Ag‐ZnO