Short‐Peptide‐Based Hydrogel: A Template for the In Situ Synthesis of Fluorescent Silver Nanoclusters by Using Sunlight

Abstract

N-terminally Fmoc-protected dipeptide, Fmoc-Val-Asp-OH, forms a transparent, stable hydrogel with a minimum gelation concentration of 0.2% w/v. The gelation property of the hydrogel was investigated by using methods such as transmission electron microscopy, field-emission scanning electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy. The silver-ion-encapsulating hydrogel can efficiently and spontaneously produce fluorescent silver nanoclusters under sunlight at physiological pH (7.46) by using a green chemistry approach. Interestingly, in the absence of any conventional reducing agent but in the presence of sunlight, silver ions were reduced by the carboxylate group of a gelator peptide that contains an aspartic acid residue. These clusters were investigated by using UV/Vis spectroscopy, photoluminescence spectroscopy, high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) studies. Mass spectrometric analysis shows the presence of a few atoms in nanoclusters containing only Ag(2). The reported fluorescent Ag nanoclusters show excellent optical properties, including a very narrow emission profile and large Stokes shift (>100 nm). The reported fluorescent Ag nanoclusters within hydrogel are very stable even after 6 months storage in the dark at 4 °C. The as-prepared hydrogel-nanocluster conjugate could have applications in antibacterial preparations, bioimaging and other purposes.

Self-assembly of guanosine and deoxy-guanosine into hydrogels: monovalent cation guided modulation of gelation, morphology and self-healing properties

“…8a). 83 Here, we believe that some Ag + ions (surface cations 23 not within the channel cavity between the two Gquartets) are photo-reduced in situ. TEM study showed the development of homogeneous small AgNPs having an average diameter of 7 nm within the gel network ( Fig.…”

Fluorescent Ag nanoclusters templated by carboxymethyl-β-cyclodextrin (CM-β-CD) and their in vitro antimicrobial activity

“…The reducibility of carboxylic groups under a photoreaction has also been put forward by other works [28]. In order to prove the role of carboxylic group, we replaced CM-β-CD by β-CD, which has no carboxylic groups.…”

Different surface properties of l-arginine functionalized silver nanoparticles and their influence on the conductive and adhesive properties of nanosilver films

“…Herein we have attempted to determine the mechanism involved in this reduction. According to the XPS results, silver ions were complexed with the carboxylic group of L-Arginine, and that can significantly decrease the energy barrier for silver-ion reduction [32]. Besides, the guanidine group of L-arginine can interact with ethylene glycol which accelerates the reduction of silver salts with ethylene glycol [33].…”