Pyrene‐based fluorescent supramolecular hydrogel: scaffold for nanoparticle synthesis

Abstract

The present work illustrates the design and development of pyrene-based fluorescent supramolecular hydrogel consisting of L-phenylalanine residue as the linker and ethyleneoxy unit with free primary amine at C-terminal. The gelator efficiently immobilized aqueous media, and the critical gelation concentration (CGC) was found at 2.8 mM of the compound. Interestingly, the presence of pyrene moiety in the structure made the hydrogel intrinsically fluorescent.The self-aggregation properties of the thermo-reversible hydrogel were investigated using different microscopic and spectroscopic techniques such as highresolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy, and X-ray diffraction (XRD) spectroscopy. A balanced participation of noncovalent interactions like hydrogen bonding, π-π stacking, and van der Waals interaction was identified as the driving force for gelation. Rheological experiments were performed to confirm the viscoelastic nature of the prepared hydrogel. Furthermore, primary amine (─NH 2 ) group of hydrogelator was utilized for the in situ synthesis of silver nanoparticles (AgNPs) within the soft material under sunlight in the absence of any external reducing and stabilizing agent.

Gel scaffolds and emerging applications in biomedicine

“…12c). 41 The ambidextrous gelator ( 29) was an efficiently gelatinized organic solvent as well as aqueous media at suitable pH. The crucial role of the HLB in self-assembled gelation was studied by the sensible alteration of the amino acid residue present in the gelator.…”

“…(b) Self-assembly of perylene bisimides hydrogels (40). (c) Structure of perylene bisimide organogels (41). (d) Self-assembly of multi-stranded perylene dye (42).…”

Tuning Rheological Behaviors of Supramolecular Aqueous Gels via Charge Transfer Interactions

“…These bands could be identified as the N−H stretching, the CO stretching of carboxyl, the amide I band (1660 and 1640 cm −1 ), and the amide II band, respectively. 33,65 The black line in Figure 3d is the spectrum of the PyFF powder, and its corresponding bands shifted to 3294, 1633, and 1541 cm −1 in comparison to the band of the aerogels. Therefore, the blueshifts (3285 to 3294, 1538 to 1541 cm −1 ) and the redshift (1640 to 1633 cm −1 ) of characteristic peaks could be identified as a difference in the strength of the hydrogen bonding interactions in the two states.…”

Luminescent Behavior of Gels and Sols Comprised of Molecular Gelators

“…Kar et al, reported the in situ synthesis of 25–40 nm silver nanoparticles by irradiating with sunlight a hydrogel containing AgNO 3 without an extrinsic reducing agent. The gelator, PyPheAla, was comprised of pyrenyl and L-phenylalanine substituents ( Figure 29 ) [ 34 ]. A 5.6 × 10 −4 mM solution of PyPheAla in water upon excitation at 340 nm emitted strongly at 376, 395 and 417 nm, indicative of emission from a pyrenyl monomer.…”

“…In this way, they can be thermo-reversible, thixotropic, acid-base sensors, etc., in ways that affect their luminescent properties. As a result, these gels have been studied widely for applications in diverse fields, such as excitation energy transfer and light harvesting [ 23 , 24 , 25 , 26 ], dye-sensitized solar cells [ 27 ], sensing of metal ions and explosives [ 28 , 29 , 30 , 31 ], acid and base sensing [ 32 , 33 ], and as templates for nanoparticle synthesis [ 34 , 35 , 36 ].…”