Printable temperature-responsive hybrid hydrogels with photoluminescent carbon nanodots

Fluorescent patterning of paper through laser engraving

While thermal treatment of paper can lead to the formation of aromatic structures via hydrothermal treatment (low temperature) or pyrolysis (high temperature), neither of these approaches allow patterning the substrates. Somewhere in between these two extremes, a handful of research groups have used CO2 lasers to pattern paper and induce carbonization. However, none of the previously reported papers have focused on the possibility to form fluorescent derivatives via laser-thermal engraving. Exploring this possibility, this article describes the possibility of using a CO2 laser engraver to selectively treat paper, resulting in the formation of fluorescent compounds, similar to those present on the surface of carbon dots. To determine the most relevant variables controlling this process, 3 MM chromatography paper was treated using a standard 30 W CO2 laser engraver. Under selected experimental conditions, a blue fluorescent pattern was observed when the substrate was irradiated with UV light (365 nm). The effect of various experimental conditions (engraving speed, engraving power, and number of engraving steps) was investigated to maximize the fluorescence intensity. Through a comprehensive characterization effort, it was determined that 5-(hydroxymethyl)furfural and a handful of related compounds were formed (varying in amount) under all selected experimental conditions. To illustrate the potential advantages of this strategy, that could complement those applications traditionally developed from carbon dots (sensors, currency marking, etc.), a redox-based optical sensor for sodium hypochlorite was developed.

Luminescent supramolecular hydrogels from a tripeptide and nitrogen-doped carbon nanodots

The combination of different components such as carbon nanostructures and organic gelators into composite nanostructured hydrogels is attracting wide interest for a variety of applications, including sensing and biomaterials. In particular, both supramolecular hydrogels that are formed from unprotected D,L-tripeptides bearing the Phe-Phe motif and nitrogen-doped carbon nanodots (NCNDs) are promising materials for biological use. In this work, they were combined to obtain luminescent, supramolecular hydrogels at physiological conditions. The self-assembly of a tripeptide upon application of a pH trigger was studied in the presence of NCNDs to evaluate effects at the supramolecular level. Luminescent hydrogels were obtained whereby NCND addition allowed the rheological properties to be fine-tuned and led to an overall more homogeneous system composed of thinner fibrils with narrower diameter distribution.

Semi-Interpenetrating Polymer Networks with Predefined Architecture for Metal Ion Fluorescence Monitoring

The development of new synthetic approaches for the preparation of efficient 3D luminescent chemosensors for transition metal ions receives considerable attention nowadays, owing to the key role of the latter as elements in biological systems and their harmful environmental effects when present in aquatic media. In this work, we describe an easy and versatile synthetic methodology that leads to the generation of nonconjugated 3D luminescent semi-interpenetrating amphiphilic networks (semi-IPN) with structure-defined characteristics. More precisely, the synthesis involves the encapsulation of well-defined poly(9-anthrylmethyl methacrylate) (pAnMMA) (hydrophobic, luminescent) linear polymer chains within a covalent poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) hydrophilic polymer network, derived via the 1,2-bis-(2-iodoethoxy)ethane (BIEE)-induced crosslinking process of well-defined pDMAEMA linear chains. Characterization of their fluorescence properties demonstrated that these materials act as strong blue emitters when exposed to UV irradiation. This, combined with the presence of the metal-binding tertiary amino functionalities of the pDMAEMA segments, allowed for their applicability as sorbents and fluorescence chemosensors for transition metal ions (Fe3+, Cu2+) in solution via a chelation-enhanced fluorescence-quenching effect promoted within the semi-IPN network architecture. Ethylenediaminetetraacetic acid (EDTA)-induced metal ion desorption and thus material recyclability has been also demonstrated.

Stimuli-responsive chitosan/poly (N-isopropylacrylamide) semi-interpenetrating polymer networks: effect of pH and temperature on their rheological and swelling properties

The aim of this work was to synthesize semi-interpenetrating polymer networks (semi-IPNs) by free radical polymerization of N-isopropylacrylamide [poly (NIPAAm)], in the presence of chitosan (CHI), and to study the effect of pH and temperature changes on their rheological and swelling properties. The semi-IPNs are thermally stable up to about 400 °C and the presence of CHI increases the thermal degradation rate compared to bare poly (NIPAAm). The prepared systems presents a well-defined porosity and proved to be non-toxic, in vitro, on human embryonic skin fibroblast, thus offering appropriate support for cell proliferation. The semi-IPNs present, at physiological pH, swelling degrees well below those of the pure poly (NIPAAm). Differently, at acidic pH, the CHI macromolecules are protonated and become much more permeable to the diffusion of water giving a swelling degree that approaches that of bare poly (NIPAAm). The viscoelastic moduli of the semi-IPNs increase as a function of pH while the LCST remain unchanged. Moreover, the semi-IPNs viscoelastic moduli increase with the increase of CHI content and, in particular, the difference between the elastic modulus before and after the sol/gel transition is higher for the semi-IPN than for bare poly (NIPAAm) just at about physiological conditions.

Self-Healing and Moldable Metallogels as the Recyclable Materials for Selective Dye Adsorption and Separation

Four multiresponsive and self-sustaining metallogels were synthesized by the reaction of the disodium salt of the ligand carboxymethyl-(3,5-di-tert-butyl-2-hydroxy-benzyl)amino acetic acid with Cd(II) and Zn(II) halides, which were found to show excellent selectivity for dye adsorption and separation, and one of the gels shows a rare self-healing property.

Composites of Polymer Hydrogels and Nanoparticulate Systems for Biomedical and Pharmaceutical Applications

Due to their unique structures and properties, three-dimensional hydrogels and nanostructured particles have been widely studied and shown a very high potential for medical, therapeutic and diagnostic applications. However, hydrogels and nanoparticulate systems have respective disadvantages that limit their widespread applications. Recently, the incorporation of nanostructured fillers into hydrogels has been developed as an innovative means for the creation of novel materials with diverse functionality in order to meet new challenges. In this review, the fundamentals of hydrogels and nanoparticles (NPs) were briefly discussed, and then we comprehensively summarized recent advances in the design, synthesis, functionalization and application of nanocomposite hydrogels with enhanced mechanical, biological and physicochemical properties. Moreover, the current challenges and future opportunities for the use of these promising materials in the biomedical sector, especially the nanocomposite hydrogels produced from hydrogels and polymeric NPs, are discussed.

Facile synthesis of biocompatible N, S-doped carbon dots for cell imaging and ion detecting

A facile, simple, effective and green method has been developed to synthesize nitrogen and sulfur co-doped carbon dots (N, S-CDs) from heparin sodium.

Study on the room temperature synthesis of highly photoluminescent and temperature-sensitive CDs/PNIPAM hybrid hydrogels and their properties

Highly photoluminescent and temperature-sensitive CDs/PNIPAM hybrid hydrogel was synthesized at room temperature by atom transfer radical polymerization (ATRP).

pH-responsive inorganic–organic hybrid supramolecular hydrogels with jellyfish-like switchable chromic luminescence

A novel hybrid hydrogel, based on electrostatic co-assembly of polyoxometaltate and the ABA triblock copolymers shows both sol–gel transition and luminescence variation in response to pH change.

Redox- and pH-responsive polymer gels with reversible sol–gel transitions and self-healing properties

Redox- and pH-responsive polymer gel with self-healing property was prepared by crosslinking of benzhydrazide-containing polytriazole with a disulfide-containing dialdehyde.