Abstract
Two xerogels made of 4-pyridyl cholesterol (PC) and silver-nanocomposites (SNCs) thereof have been studied for their efficient reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of aqueous sodium borohydride. Since in-situ silver doping will be effective in ethanol and acetone solvents with a PC gelator, two silver-loaded PC xerogels were prepared and successive SNCs were achieved by using an environmentally benign trisodium citrate dehydrate reducing agent. The formed PC xerogels and their SNCs were comprehensively investigated using different physico-chemical techniques, such as field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), powdered X-ray diffraction (XRD) and UV-Visible spectroscopy (UV-Vis). The FE-SEM results confirm that the shape of xerogel-covered silver nanoparticles (SNPs) are roughly spherical, with an average size in the range of 30–80 nm. Thermal degradation studies were analyzed via the sensitive graphical Broido’s method using a TGA technique. Both SNC-PC (SNC-PC-X1 and SNC-PC-X2) xerogels showed remarkable catalytic performances, with recyclable conversion efficiency of around 82% after the fourth consecutive run. The apparent rate constant (kapp) of SNC-PC-X1 and SNC-PC-X2 were found to be 6.120 × 10-3 sec-1 and 3.758 × 10-3 sec-1, respectively, at an ambient temperature.
Highlights
A variety of metal-nanocomposites were prepared in recent years, and mostly utilized for advanced catalytic and sensor applications [1,2,3,4,5,6,7,8,9,10,11]
The entrapping of solvent molecules in three-dimensional self-assembled fibrillar arrangements confine the formation of strong non-covalent interactions between low molecular-mass organic gelators (LMOGs) units and solvents, resulting in network structures signified as gels [22]
We report the successful development of two pyridine-containing silver nanocomposite xerogels, where where silver nanoparticles (SNPs)
Summary
A variety of metal-nanocomposites were prepared in recent years, and mostly utilized for advanced catalytic and sensor applications [1,2,3,4,5,6,7,8,9,10,11]. Considerable research interest has been focused on low molecular-mass organic gelators (LMOGs) due to their numerous dynamic applications [17,18,19,20,21]. The entrapping of solvent molecules in three-dimensional self-assembled fibrillar arrangements confine the formation of strong non-covalent interactions between LMOG units and solvents, resulting in network structures signified as gels [22]. A gel consists of one or more gelators (gelling agents) and a fluid (organic solvent, water or supercritical liquid) which behaves as a soft visco-elastic matter due to the immobilization of solvent molecules in a three-dimensional (3D) network. Property (1) MGC is the lowest possible concentration of a gelator required to form a stable gel. If the MGC of a gelator is < 1 weight %, Materials 2020, 13, 1486; doi:10.3390/ma13071486 www.mdpi.com/journal/materials
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