Photo-formed Metal Nanoparticle Arrays in Monolithic Silica-Biopolymer Aerogels

Abstract

Transparent monolithic aerogels based on silica, the bioderived polymer chitosan, and coordinated ions have been employed to serve as a three-dimensional scaffold decorated with Au, Pt and Pd ions. The coordination states of metal ions and the initial gel in one or several of the ions are established in the thickness of the monolith that is produced by supercritical CO 2 extraction to form the aerogels. Also in this work, it has been found that the Au(III) aerogels can be imaged photolytically in the two planar dimensions. The spatially controlled photolysis produces nanoparticles, (Au) n in the range of from 5 to 85 nm, for example, that constitute two dimensionally imaged arrays whose volumetric concentration also varies in the third dimension. These images microarrays of nanoparticles provide a basis for localization and detection of thiols, disulfides, amino acids and protein molecules. The formation of these arrays, including the dependence of their properties on light intensity, frequency and exposure, and distribution of target molecules and ions in the initial aerogel is presented.

Facile One-Pot Synthesis of Mechanically Robust Biopolymer–Silica Nanocomposite Aerogel by Cogelation of Silicic Acid with Chitosan in Aqueous Media

“…Evidence for the incorporation of the chitosan into the composite structure could be found in the FT-IR spectra of the composite materials (Figure ): A typical composite reveals the amide II vibrational signatures arising from the acetylated residual groups on the chitosan and which are absent in the pure silica spectra. There are peaks at 1546 and 1595 cm –1 corresponding to protonated and free amine groups on the backbone of chitosan, and in the fingerprint region, the peak in the range of 1100–1150 cm –1 can be assigned as C–N, which belongs to the stretching vibrations of the amine groups present in the chitosan.…”

“…In terms of chemical functionality, it is a polysaccharide as well as a polyamine. Previous studies have shown the versatile nature of chitosan and the good chemical compatibility with sol–gel based silica materials. ,− The abundant amino and hydroxyl functional groups on the backbone of chitosan promote the widespread application of the material as effective biosorbents for the removal of dyes, , heavy metals, , and inorganic ions . The presence of polar functional groups (amine and hydroxyl) on the polymer backbone introduce strong dipole moments which favor the interaction with polar molecules (solvent, silica but also other chitosan units) through hydrogen bonding or dipole–dipole interactions.…”

Chapter 7. Hybrid Green Aerogels: Processing and Morphology

“…Finally, such functional groups can also act as reducing sites that react with nanoparticle precursors to nucleate nanoparticles. 10,34,[47][48][49][50][51][52][53][54][55][56][57] The resulting hybrid bio-based aerogel may 24,31,33,34,[43][44][45][48][49][50] or may not 46 exhibit a synergistic effect. In some cases, cellulose aerogel was calcined 58 to recover the nanoparticles, as cellulose can easily be burned.…”

Additive Manufacturing of Nanocellulose Aerogels with Structure‐Oriented Thermal, Mechanical, and Biological Properties

“…After Sc-CO 2 drying, the composites were exposed to UV irradiation (95% at 254 nm) for 10 h to form the Ag nanoparticles in situ. [38] Rehydration of the Aerogels: To check the structure change and cell viability of the aerogels after rehydration, the Sc-CO 2 dried aerogels were placed into a 2 wt.% CaCl 2 solution for 12 h and cyclic compression was placed on the rehydrated aerogels. The gels were exchanged with ethanol (95/5 wt.% ethanol/IPA, Alcosuisse AG), and the alcogels were supercritically dried using a continuous drying apparatus; the dried gels were examined for pore structures using N 2 sorption.…”

“…After Sc‐CO 2 drying, the composites were exposed to UV irradiation (95% at 254 nm) for 10 h to form the Ag nanoparticles in situ. [ 38 ]…”