Gracilaria salicornia as potential substratum for green synthesis of Cerium Oxide Nanoparticles coupled hydrogel: An effective antimicrobial thin film.

Sodium alginate based (SA) hydrogel supplemented Cerium Oxide nanoparticles (CeO2NPs) was produced to fabricate an antimicrobial thin film using an aqueous extract of G. salicornia (Gs). The Gs-CeO2NPs were characterized via SEM, FT-IR, EDX, XRD and DLS, the particle size was 200 nm, agreed with XRD. Gs-SA powder was extracted and incorporated with CeO2NPs. The Gs-SA and its composite thin film (Gs-CeO2NPs-SATF) were characterized including viscosity, FT-IR, TGA, and SEM. The adhesion of Gs-SA coating around Gs-CeO2NPs confirmed via FTIR. The antimicrobial properties of Gs-CeO2NPs and CeO2NPs-SATF were proved in MICs for E. coli and Candida albicans at 62.5 and 250.0 µg/mL. The biofilm inhibition efficiency of CeO2NPs-SATF was 74.67 ± 0.98% and 65.45 ± 0.40% for E. coli and Candida albicans. The CeO2NPs-SATF was polydisperse in nature and film structure gets fluctuated with NPs concentration. Increased NPs into SATF enhances pore size of gel and corroborated with viscous behaviour. The cytotoxicity of Gs-CeO2NP-SA in Artemia salina at higher concentration 100 µg/mL provides less lethal effect into the adult. The antioxidant activity of Gs-CeO2NP-SA in DPPH assay was noticed at 0.6 mg ml-1 with radical scavenging activity at 65.85 ± 0.81%. Thus the Gs-CeO2NP-SATF would be suitable in antimicrobial applications.

Synthesis of Acid Free Benzaldehyde by Highly Selective Oxidation of Benzyl Alcohol Over Recyclable Supported Palladium Catalyst.

AIM AND OBJECTIVES: This research work deals with the highly selective oxidation of benzyl alcohol to benzaldehyde by palladium doped graphene oxide catalyst, which was synthesized by a modified Hummer's method. The effect of reaction parameters like temperature, time and catalyst loading were studied. It was found that fine-tuning of reaction temperature and presence of a small amount of benzyl alcohol in a product prevented the undesirable formation of benzoic acid crystals, which form on auto-oxidation of benzaldehyde. Benzoic acid or substituted benzoic acid formation was hindered by the presence of < 2% benzyl alcohol at a reaction temperature of 50˚C, which was further supported by palladium doped graphene oxide catalyst. MATERIALS AND METHODS: Modified Hummer's method was used for the synthesis of graphene oxide and palladium doped graphene oxide was synthesized by in-situ method in which graphene oxide dispersed in 20mL of distilled water was ultrasonicated for 2h. Palladium solution was added and it was further ultrasonicated for 30min for homogeneous deposition of palladium on a graphene oxide support. To this, 2 mL of sodium borohydride solution was added and stirred at room temperature for 4h. The resulting solution was centrifuged, and the residue was dried at 60°C for 12 h. RESULTS: The morphological characteristics and the functional groups of supported catalysts were characterized by X-ray diffraction, Field emission scanning spectroscopy, and Fourier transform infrared spectroscopy. The produced benzaldehyde was characterized by gas chromatography. CONCLUSION: PdGO catalyst was prepared using sodium borohydride as a reducing agent by modified Hummer's method and utilized for the oxidation of benzyl alcohol to benzaldehyde. A maximum conversion of 89% and selectivity of 99% were obtained and the catalyst could be reused up to five times without any compromise on conversion and selectivity.