M.A. Hernández-Pérez

Bio: M.A. Hernández-Pérez is an academic researcher from Instituto Politécnico Nacional. The author has contributed to research in topics: Thin film & Raman spectroscopy. The author has an hindex of 10, co-authored 26 publications receiving 226 citations.

Comparative optical and structural studies of CdSe films grown by chemical bath deposition and pulsed laser deposition

Abstract: Cadmium selenide thin films were prepared by chemical bath deposition (CBD) and pulsed laser deposition (PLD) methods. For CBD films, cadmium chloride (CdCl 2 ) and cadmium acetate (Cd(CH 3 COO) 2 ) solutions were employed as Cd 2+ source while a freshly prepared sodium selenosulfite (Na 2 SeSO 3 ) solution provided the Se 2- ions. The pH of the bath was adjusted by adding ammonium hydroxide. The effects of the bath temperatures (30-90°C) and the Cd/Se ratio on film properties were investigated. On the other hand, PLD films were grown by the ablation of a sintered pure CdSe target using a Nd:YAG laser beam (355nm) with 1 J/cm 2 fluence. The deposition chamber was maintained under vacuum pressure (10 -6 mbar) and at room temperature. The CBD films are constituted by crystallites of metastable cubic phase (7nm) with some amorphous phase present, whereas the PLD films showed better crystalline quality and higher crystalline size. Optical absorption analysis shows that the band gap value of the CBD films is higher than that of the bulk material and decreases with the bath temperature. Annealing transforms the metastable cubic phase into the hexagonal phase and causes a "redshift" in the band gap of the CBD and PLD films due to the crystal size increase.

Plant-based green synthesis of metallic nanoparticles: scientific curiosity or a realistic alternative to chemical synthesis?

Abstract: Currently, thousands of tons of metallic nanoparticles (MNPs) are produced and utilized in nano-enabled devises, personal care, medicinal, food and agricultural products. It is generally accepted that the reaction compounds and the techniques used in industrial production of MNPs are not environmentally friendly. The green synthesis has been proposed as an alternative to reduce the use of hazardous compounds and harsh reaction conditions in the production of MNPs. In this endeavor, investigators have used organic compounds, microbes, plants and plant-derived materials as reducing agents. Research papers are published every year, and each one of them stresses the benefits of the green approach and the advantages over the traditional syntheses. However, after almost two decades since the explosion of the reports about the new approach, the commercial production of green-synthesized nanoparticles does not seem to find a way to scale up commercial production. This review includes descriptions of the traditional and green synthesis and applications of MNPs and highlights the factors limiting the use of plant-based synthesis as a real alternative to the traditional synthesis of MNPs.