Preparation of silver-montmorillonite nanocomposites by reduction with formaldehyde and borohydride

Abstract

Montmorilonita rica em sódio (MMT) foi intercalada com cátions prata, os quais foram subsequentemente reduzidos com formaldeído ou boroidreto de sódio. Os nanocompostos prata-montmorilonita foram estudados por espectrometria UV-Vis, microscopia eletrônica de transmissão (TEM) e difratometria de raios-X (XRD). A influência de diferentes agentes redutores na dispersão e no tamanho das partículas de prata depositadas na superfície da montmorilonita foi investigada. A redução com boroidreto produziu partículas de prata dispersas uniformemente, com tamanhos limitados entre 3 e 13 nm. A redução com formaldeído gerou partículas dispersas irregularmente com uma distribuição de tamanho muito maior, variando entre 3 e 100 nm. Além disso, entre as partículas de prata preparadas por redução com formaldeído, algumas partículas de Ag 2 O foram obtidas como resultado de redução incompleta. Os compósitos de prata-montmorilonita preparados por redução com boroidreto e formaldeído contêm 2,4% e 5,3% em massa de Ag, respectivamente. Na-rich montmorillonite (MMT) was intercalated with silver cations, which were subsequently reduced with formaldehyde or sodium borohydride. The silver-montmorillonite nanocomposites were studied by UV-visible spectrometry, transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The influence of different reducing agents on the dispersity and size of silver particles deposited on montmorillonite surface was investigated. The reduction with borohydride gives rise to uniformly dispersed silver particles with a narrow particle size distribution from 3 nm to 13 nm. Formaldehyde reduction forms unevenly dispersed particles with a much wider size distribution, ranging from 3 to 100 nm. In addition, some Ag 2 O particles were found among silver particles prepared with formaldehyde, likely as a result of incomplete reduction. Silvermontmorillonite composites prepared by reduction with borohydride and formaldehyde contain 2.4 wt% and 5.3 wt% of Ag, respectively.

DEVELOPMENT OF ANTIBACTERIAL MtCu/PLA NANOCOMPOSITES BY CASTING METHOD FOR POTENTIAL USE IN FOOD PACKAGING

“…Later, MtCu 0 suspensions were centrifuged at 4000 rpm and washed several times with a 50:50 etanol/water solutions to remove residual reactants. Finally the product was dried at 40 °C for 3 days in oven and ground in a mortar to sizes less than 270 mesh (< 45 µm) 45 .…”

Synthesis of silver nanoparticles in montmorillonite and their antibacterial behavior

“…For the synthesis of Ag NPs in the solid substrate, AgNO 3 is often used as the primary source of Ag + . Among the numerous ways of Ag + reduction are: γ-ray, 16 UV, 17 or laser irradiations, 18 heating, 19 electrochemical reduction, 20 application of reducing chemicals, such as hydrazine, 21 sodium borohydride, 14 glycerol, 12,22 N,N-dimethylformamide, 23 glucose, 24 ethylene glycol, 25 formaldehyde, 26 and sodium in liquid ammonia. 27 The investigation of the antibacterial activity of Ag NPs has regained importance due to increasing bacterial resistance to antibiotics.…”

Green biosynthesis of silver nanoparticles using Curcuma longa tuber powder

“…There are several ways to reduce Ag + , eg, use of γ-rays, 4 ultraviolet (UV) irradiation, 5 heating and electrochemical reduction, 6 and application of reducing chemicals, such as hydrazine, 7 sodium borohydride, [8][9][10] polyethylene glycerol, 11 N,N-dimethylformamide, 12 glucose, 13 ethylene glycol, 14 formaldehyde, 15 and sodium in liquid ammonia. 16 However, there is still need for a more economic, commercially viable, and environmentally green synthesis route to synthesize Ag-NPs.…”