Debapratim Das

An AIE probe is reported that can sense heparin and protamine with high selectivity and sensitivity.

Liquid metals (LMs) are promising materials for flexible electronics because of their high electrical conductivity, fluidity, and biocompatibility. However, their practical use requires stable particle dispersions, which are challenging to maintain because of aggregation and oxidation. Here, we report the biocompatible short peptide Fmoc‐KC as an effective stabiliser for eutectic gallium–indium (EGaIn). Fmoc‐KC enabled homogeneous LM dispersion that remained stable for over three months under ambient conditions. Experimental and computational studies revealed that the exceptional stability originates from synergistic Ga–S coordination between cysteine thiols and the LM surface, together with cation–π interactions involving the Fmoc group. The stable peptide–LM dispersion was incorporated into a PVA matrix to produce a conductive, adhesive, and stretchable hydrogel with good biocompatibility, degradability, and strain flexibility up to 250%. The hydrogel exhibited reliable piezoresistive sensing, with a gauge factor of 3.74 over a strain range of 160%–250%. It enabled monitoring of human motion and subtle muscle activity, as well as Morse code generation and handwriting recognition, demonstrating the potential of peptide‐stabilised LM dispersions for wearable electronics, smart sensing, and secure information technologies.

Harnessing chemical reaction networks to regulate hydrogel actuators offers a promising route toward bioinspired smart materials with autonomous and programmable behaviours. Herein, we report a multi-stimuli-responsive bilayer hydrogel actuator that responds to both pH and metal ions. The bilayer actuator comprises two polyacrylamide-based layers, one functionalised with 1-vinylimidazole (VIm) and the other with methacrylic acid (MAA). The orthogonal ionizable groups impart distinct swelling responses across different pH regimes, enabling programmable bidirectional motion, while VIm's metal-ion coordination provides an additional stimulus-responsive mode. To emulate adaptive processes found in nature, the actuator was coupled with a newly developed autonomous NaOH–Sultone pH-clock. Addition of NaOH rapidly raises the pH to ~12, while the slower hydrolysis of Sultone generates sulfonic acid and gradually returns the system to the acidic region (~2.5), thereby creating a broad temporal pH window. Under these dynamically evolving chemical conditions, the bilayer displayed self-regulated bidirectional motion without any external intervention, converting transient chemical signals into programmed mechanical deformation. The pH-clock enables autonomous bidirectional actuation, driving the actuator from 0° to 140°, back through 0°, and subsequently to -135°. To further enhance its biomimetic character, a pH-responsive aggregation-induced emission luminogen (AIEgen) was incorporated into the VIm-containing layer. The resulting material exhibited autonomous, time-dependent fluorescence modulation synchronised with the evolving pH environment, thereby coupling macroscopic motion with transient luminescence. By integrating a new pH-clock with a multi-responsive hydrogel architecture, the system achieved simultaneous regulation of mechanical actuation and optical output, producing adaptive, life-like behaviour and providing a versatile platform for next-generation autonomous soft materials.

The expansion of global trade and digital information exchange has increased the risks of counterfeiting and data breaches, while conventional security measures remain limited by weak robustness and encryption. Introducing additional protection based on time and medium could improve security, but developing such materials is highly challenging. In this context, the intrinsic time‐gated afterglow of underwater room‐temperature phosphorescent (RTP) materials provides a promising solution.Conventional RTP films fail underwater due to hydrogen bonding with water and quenching by dissolved oxygen. Here, we report a simple and effective strategy to fabricate underwater RTP poly(vinyl alcohol) (PVA) films with enhanced afterglow. Crosslinking via immersion in concentrated boric acid (BA) forms B–O linkages with PVA hydroxyl groups, preventing water‐induced quenching. All five phosphors tested exhibited efficient underwater phosphorescence, with lifetimes up to 2350 ms, afterglows up to 23 s, and full‐spectrum emission. The BA‐crosslinked films also showed long‐term stability under ambient conditions and in diverse aqueous and organic media. By integrating time‐dependent phosphorescence with underwater stability, we demonstrate advanced information‐encryption prototypes that use time as an additional dimension (4D). This facile, synthesis‐free approach yields water‐stable RTP films suitable for underwater encryption and camouflage applications.

A new gel-based highly sensitive moisture-responsive actuator is reported that show unidirectional actuation upon uniform exposure to moisture. The actuator showed hydrogen-bonding induced shrinkage-driven actuation.

Transient lights in biological systems inspire transient lights in abiotic chemical systems for modern and advanced applications.

Creating artificial systems that emulate the dynamic behavior of living assemblies remains a central goal in supramolecular chemistry. Here, a charge transfer-driven pH clock-regulated hydrogelation process is presented, arising from the interaction between a pyrene-lysine cysteine tripeptide (PyKC) and a phenylalanine-substituted naphthalene diimide (NDIF). Spectroscopic and structural analyses confirmed the formation of a 1:1 donor-acceptor complex organized through π-π stacking and β-sheet arrangements. The resulting hydrogel forms rapidly under alkaline conditions and exhibits reversible transitions triggered by variations in temperature and pH. Coupling the system with a Tris buffer-glucono-δ-lactone pH clock produces transient hydrogelation with lifetimes precisely tunable by the activator-deactivator ratio. The hydrogel repeatedly assembles and disassembles in synchrony with pH oscillations, maintaining its structural integrity.

Short peptide-based supramolecular systems, constructed from conserved building blocks and well-defined chemical reactions, play a pivotal role in the development of futuristic smart-materials.

False knowledge is more misleading than no information, and the rising threats from counterfeitors demand advanced strategies of secure, multilayered encryption. The fluorescence‐based routine systems have become recurrent, often requiring complicated synthesis and UV light for decoding. We have countered the common notion that novel applications need newer molecules by employing conventional molecules in unconventional ways. Motivated by nature, we implemented stimuli‐responsive organic dyes to develop color‐coded encryption—simple, harmless, and UV‐free alternatives that preserve crucial security features. pH‐ or redox‐responsive dyes were purposely selected so that time‐dependent color changes can be displayed under chemically triggered nonequilibrium conditions. This feature was exploited in designing time‐gated, multidimensional, diverse color codes. An alternative decryption method was demonstrated via smart windows—stimuli‐sensitive barriers that regulated access across parallel time scales managed by independent triggers. Our strategy affords dual time‐locked color codes with hierarchical security operated through orthogonal stimuli, achieving complex encryption with simple, synthesis‐free decoding. A highly accurate indigenous decoding strategy is successfully demonstrated.

The efficient and sustainable remediation of contaminated water calls for catalytic systems that must clean broadly, endure widely, and last repeatedly. In this regard, we report the development of sulfonate-functionalized core-shell hydrogel beads embedded with in situ synthesized gold nanoparticles (AuNPs) that exhibit intrinsic oxidase-like activity without requiring external light or chemical oxidants. The sulfonate ligands modulate the surface electronic environment of the AuNPs, facilitating singlet oxygen generation via a nonplasmonic, radiationless mechanism. These AuNPs, confined to the bead surface, provide rapid substrate access, eliminating diffusion barriers and enabling efficient catalytic oxidation of a broad spectrum of contaminants. The AuNP@Beads demonstrate excellent activity toward phenolic pollutants, azo dyes, and biologically relevant catecholamines such as dopamine and epinephrine. They also exhibit potent antibacterial efficacy against both Gram-negative and Gram-positive pathogens through ROS generation. The catalytic beads are reusable, structurally stable under ionic stress, and show negligible nanoparticle leaching. Furthermore, the treated wastewater supports healthy plant growth, underscoring its environmental compatibility. This study introduces a robust, multifunctional catalytic platform for water purification that combines oxidase-like catalysis, antibacterial action, and biosensing potential. The light-independent operation and broad-spectrum efficacy make it highly promising for real-world environmental remediation applications.