The depth of surface trap states in semiconductor quantum dots (QDs) is influenced by the degree of covalency, which in turn affects the charge recombination process in hybrid donor–acceptor systems. By taking relatively ionic cadmium selenide (CdSe) QDs with shallow trap states and covalent indium phosphide (InP) QDs having deep trap states as examples, the charge-transfer dynamics are explored using viologen derivative as an electron acceptor. Light-induced electron transfer in a 1:1 stoichiometric complex of both the donor–acceptor systems occurs in a picosecond time scale. The presence of deep hole trap states in InP QDs retards the charge recombination to a submillisecond time scale, which is 7 orders of magnitude lower than that in CdSe QDs in homogeneous solutions. The immobile quenchers in the quenching sphere of InP further stabilize the electron-transfer products to seconds through charge hopping, which extends the potential of these systems for charge-transfer and transport applications in photovoltaics.

Biomolecular condensation via liquid–liquid phase separation of intrinsically disordered proteins/regions (IDPs/IDRs) along with other biomolecules is proposed to control critical cellular functions, whereas aberrant phase transitions are associated with a range of neurodegenerative diseases. Here, we show that a disease-associated stop codon mutation of the prion protein (PrP) at tyrosine 145 (Y145Stop), resulting in a truncated, highly disordered, N-terminal IDR, spontaneously phase-separates into dynamic liquid-like droplets. Phase separation of this highly positively charged N-terminal segment is promoted by the electrostatic screening and a multitude of weak, transient, multivalent, intermolecular interactions. Single-droplet Raman measurements, in conjunction with an array of bioinformatic, spectroscopic, microscopic, and mutagenesis studies, revealed a highly mobile internal organization within the liquid-like condensates. The phase behavior of Y145Stop is modulated by RNA. Lower RNA:protein ratios promote condensation at a low micromolar protein concentration under physiological conditions. At higher concentrations of RNA, phase separation is abolished. Upon aging, these highly dynamic liquid-like droplets gradually transform into ordered, β-rich, amyloid-like aggregates. These aggregates formed via phase transitions display an autocatalytic self-templating characteristic involving the recruitment and binding-induced conformational conversion of monomeric Y145Stop into amyloid fibrils. In contrast to this intrinsically disordered truncated variant, the wild-type full-length PrP exhibits a much lower propensity for both condensation and maturation into amyloids, hinting at a possible protective role of the C-terminal domain. Such an interplay of molecular factors in modulating the protein phase behavior might have much broader implications in cell physiology and disease.

The moisture‐induced structural decomposition of lead halide perovskites is the major challenge in solar cells and light‐emitting diodes based on perovskites as the active material. The presence of moisture results in the structural conversion of cubic 3D CsPbBr3 nanocrystals to 2D CsPb2Br5 nanosheets before its decomposition to PbBr2. The capping agent used, oleyl amine, plays a crucial role in this structural transformation. The presence of moisture converts the capping agent, oleyl amine, to its salt, which transforms the 3D CsPbBr3 perovskite nanocrystals to 2D CsPb2Br5 nanosheets. Further, these CsPb2Br5 nanosheets decompose to trigonal PbBr2, in the presence of higher amounts of water. Also, the amount of capping agent, oleyl amine, plays an important role in the rate of moisture‐induced structural transformations. The rate of decomposition increases with the amount of oleyl amine used as a result of the reaction of water with the excess ligands. By revealing the exact mechanism of the structural alterations in the presence of water, new design strategies can be used to prevent the decomposition of perovskites.

Biomolecular condensation via liquid-liquid phase separation of proteins and nucleic acids is associated with a range of critical cellular functions and neurodegenerative diseases. Here, we demonstrate that complex coacervation of the prion protein and α-synuclein within narrow stoichiometry results in the formation of highly dynamic, reversible, thermo-responsive liquid droplets via domain-specific electrostatic interactions between the positively-charged intrinsically disordered N-terminal segment of prion and the acidic C-terminal tail of α-synuclein. The addition of RNA to these coacervates yields multiphasic, vesicle-like, hollow condensates. Picosecond time-resolved measurements revealed the presence of transient electrostatic nanoclusters that are stable on the nanosecond timescale and can undergo breaking-and-making of interactions on slower timescales giving rise to a liquid-like behavior in the mesoscopic regime. The liquid-to-solid transition drives a rapid conversion of complex coacervates into heterotypic amyloids. Our results suggest that synergistic prion-α-synuclein interactions within condensates provide mechanistic underpinnings of their physiological role and overlapping neuropathological features.

Biomolecular condensation via liquid–liquid phase separation (LLPS) of intrinsically disordered proteins/regions (IDPs/IDRs), with and without nucleic acids, has drawn widespread interest due to the rapidly unfolding role of phase‐separated condensates in a diverse range of cellular functions and human diseases. Biomolecular condensates form via transient and multivalent intermolecular forces that sequester proteins and nucleic acids into liquid‐like membrane‐less compartments. However, aberrant phase transitions into gel‐like or solid‐like aggregates might play an important role in neurodegenerative and other diseases. Tau, a microtubule‐associated neuronal IDP, is involved in microtubule stabilization, regulates axonal outgrowth and transport in neurons. A growing body of evidence indicates that tau can accomplish some of its cellular activities via LLPS. However, liquid‐to‐solid transition resulting in the abnormal aggregation of tau is associated with neurodegenerative diseases. The physical chemistry of tau is crucial for governing its propensity for biomolecular condensation which is governed by various intermolecular and intramolecular interactions leading to simple one‐component and complex multi‐component condensates. In this review, we aim at capturing the current scientific state in unveiling the intriguing molecular mechanism of phase separation of tau. We particularly focus on the amalgamation of existing and emerging biophysical tools that offer unique spatiotemporal resolutions on a wide range of length‐ and time‐scales. We also discuss the link between quantitative biophysical measurements and novel biological insights into biomolecular condensation of tau. We believe that this account will provide a broad and multidisciplinary view of phase separation of tau and its association with physiology and disease.

Developing a simple and cost‐effective substrate for the detection of the halide ions present in water is extremely important due to their adverse effects at higher concentrations. A good substrate should behave differently in the presence of different halide ions. Herein, a CsPbBr3‐coated paper substrate is used for the detection of fluoride, chloride, and iodide ions. As a result of the fast anion exchange reactions, in the presence of each halide ion, the CsPbBr3‐coated paper shows different emission behaviors. The presence of chloride and iodide ions results in blueshifted and redshifted absorption and emission, respectively. In the presence of fluoride ions, anion exchange followed by decomposition of the perovskite nanocrystal is observed. The anion exchange reactions of CsPbBr3 perovskites are faster than the moisture‐induced decomposition, which enables the detection of micromolar concentrations of fluoride, chloride, and iodide ions in water.

Tuning the emission of cesium lead halide perovskites by the post‐synthetic halogen exchange reactions is one of the easiest methods to obtain the opto‐electronic materials having emission in the entire visible region. Role of aggregation and the surface chemistry on the room temperature bi‐phasic anion exchange reactions of CsPbBr3 nanocrystal is investigated. Aggregation of the nanocrystals resulted in the decrease of surface bromide ions and CsPbBr3 became inactive towards the bi‐phasic anion exchange reactions. On the modification of the surface by enriching with bromide ions, aggregated CsPbBr3 nanocrystals became active towards anion exchange reaction. Surface halide ions have a significant role in the anion exchange reactions and the reaction starts at the surface and diffuses to the inner parts of the crystal as a result of its soft crystal nature. Understanding the role of surface chemistry on the anion exchange reactions, the potential of aggregated CsPbBr3 nanocrystals can be used for the opto‐electronic applications.

The chemical and physical properties of molecules and materials are known to be modified significantly under vibrational strong coupling (VSC). In order to gain insight into the effects of VSC on − interactions involved in molecular self-assembly, themselves sensitive to vacuum electromagnetic field fluctuations, the aggregation of two structural isomers (linear and V-shaped) of phenyleneethynylene under cooperative coupling was investigated. By coupling the aromatic C=C stretching band, the assembly of one of the molecules results in the formation of spheres as opposed to flakes under normal conditions. As a consequence, the electronic absorption and emission spectra of the self-assembled structures are also modified significantly. The VSC induced changes depend not only on the type of vibration that is coupled but also on the symmetry of the phenyleneethynylene isomer. These results confirm that VSC can be used to drive molecular assemblies to new structural minima and thereby provide a new tool for supramolecular chemistry.