Cesium−lead-halide perovskite quantum dots (PQDs) are a highly promising class of the next-generation optical material for bioimaging applications. Herein, we present a nanocomposite strategy for the design of water-soluble, highly luminescence CsPbBr 3 PQD nanocomposites without modifying the crystal symmetry and photoluminescence (PL) property. Water-soluble PQDs are reproducibly synthesized via encapsulating CsPbBr 3 PQDs with polystyrene-blockpoly(ethylene-ran-butylene)-block-polystyrene (PS−PEB-PS) and poly-(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol (PEG−PPG-PEG). In the reported design, the polystyrene triblock polymers strongly interact with the hydrophobic parts of PQDs, and the water-soluble PEG moiety acts as a protection layer to effectively prevent degradation of PQDs in water. The outer shell PEG layer also helps to develop biocompatible PQDs. Reported data indicate that encapsulating CsPbBr 3 PQDs with a polymer helps to improve the photoluminescence quantum yield (PLQY) from 83% to 88%, which may be due to a decrease in the surface defects after the effective polymer coating. Experimental data show that the PL intensity from CsPbBr 3 PQD nanocomposites remains unchanged even after 30 days of exposure in air. Similarly, reported data indicate that nanocomposites retain their luminescence properties in water for the first 8 days and then decrease slowly to 60% of its initial PL intensity after one month. On the other hand, the PL emission for the PQD without polymer encapsulation is completely quenched within a few hours. Exosomes are a highly promising avenue for accessing tumor type and stage and monitoring cancer treatment response. Reported data reveal that anti-CD63 antibody-attached PQD nanocomposites are capable of tracking triple-negative MDA-MB-231 breast tumor-derived exosomes via binding using anti-CD63 antibody and selective green luminescence imaging using PQD nanocomposites.

Two-photon absorption (2PA) and three-photon absorption (3PA) processes feature many technological applications for fluorescence microscopy, photodynamic therapy, optical data storage, and so on, Herein, we reveal that the giant 2PA and 3PA properties for all-inorganic CsPbX3 (X = Cl, Br, I, and mixed Cl/Br and Br/I) perovskite quantum dots (PQDs) can be enhanced several orders of magnitude, respectively, by simply changing the halide stoichiometry at the X site. Notably, reported data show excellent 2PA and 3PA properties for CsPbI3 (σ2 ∼ 2.1 × 106 GM and σ3 ∼ 1.1 × 10–73 cm8 s3/photon3), which is 2–4 orders of magnitude higher than those of conventional red-emitting QDs and 5–7 orders of magnitude higher than well documented organic molecules. Experimental results show multiphoton absorption (MPA) cross sections can be adjusted 2–3 orders of magnitude by band gap engineering in a predictable manner, via increasing the Pauling electronegativity of the halide. Two-photon luminescence imaging data show that PQDs can be used for very good multiphoton imaging applications. Importantly, reported results provide a new strategy for manipulating MPA properties by halide composition engineering which will be instrumental in the design of next-generation technological devices.

Near-infrared (NIR) light between 700 and 2500 nm, which is in the range of the first, second, and third biological windows, has the capability to penetrate biological tissues and blood, which provides a huge advantages of higher penetration depth. However, because of the lack of available biocompatible single photon probes in NIR window, there is an urgent need for new theranostic material, which could be used for two-photon bioimaging as well as for two-photon photodynamic therapy (PDT) in biological window. Driven by the need, the current manuscript reports gold nanoclusters (GNCs) attached graphene quantum dot (GQD) based twophoton excited theranostic nanoplatform with high two-photon absorption, very strong two-photon luminescence, as well as two-photon stability in NIR region. Experimental result shows strong two-photon luminescence and twophoton-induced PDT, which is based on fluorescence resonance energy transfer (FRET) mechanism, where graphene quantum dots with very high two-photon absorption act as two-photon donors and gold nanoclusters act as acceptors. Reported data indicate that 1 O 2 generation efficiency enhances tremendously due to the FRET process, which increases the two-photon excited PDT efficiency for multiple drug resistance bacteria (MDRB). Reported data indicate that the nanoplatform has the capability for bright two-photon bioimaging and two-photon photodynamic therapy for MRSA and carbapenem-resistant (CRE) Escherichia coli. Reported nanoplatform is a promising candidate to serve as a contrast agent for multiphoton imaging as well as for two-photon excited PDT agent to eliminate multidrug-resistant strains. KEYWORDS: gold nanoclusters attached graphene quantum dot based nanoprobes, two-photon-induced FRET, multiple drug resistance MRSA and Escherichia coli, two-photon luminescence image, two-photon photodynamic therapy for MDRB

In the last three decades, there has been a huge increase in the number of antibiotic-resistant bacterial strains, which is becoming a serious threat to public health. Since the discovery of new effective antibiotics has dramatically decreased in last ten years, there are huge initiatives to develop new antimicrobial approaches to fight drug-resistant bacterial infections. In the last decade, a new nanoparticle-based tool has emerged to combat deadly bacterial infections, which may overcome the barriers faced by antibiotic resistance. The current mini-review highlights recent reports on two-dimensional (2D) graphene oxide (GO), 2D transition metal dichalcogenides (TMD), 2D MXenes, and 2D heterostructure material-based approaches to tackle bacteria. Notably, we discuss the major design criteria which have been used to develop novel antimicrobial 2D and heterostructure materials to eliminate bacterial infections. Next, details on the various mechanisms underlying antibacterial activity for 2D and heterostructure materials such as physical/mechanical damage, lipid extraction, oxidative stress, and photothermal/photodynamic effects have been discussed. Finally, we highlight the promises, major challenges, and prospects of nanomaterial-based approaches to combat multidrug-resistant bacterial infections.

Drinking water supplies are now proven to contain pharmaceutical residues, which are becoming a huge global problem. Pharmaceutical residues in water are also responsible for developing drug-resistant superbugs, which has emerged as a significant threat to global health. To tackle the above challenges, the present manuscript reports the development of a chitosan-attached gold nanoparticle conjugated graphene oxide architecture-based multifunctional threedimensional (3D) porous membrane which has the capability for effective separation and label-free surface enhanced Raman spectroscopy (SERS) identification of pharmaceutical contaminants from environmental samples. In the reported design, due to the formation of 3D pores, a multifunctional membrane acted as channels for water passage. On the other hand, due to the presence of several adsorption mechanisms, the hybrid 3D graphene oxide (GO) surface can be used to remove contaminants from water. Due to the presence of a plasmonic nanoparticle-based "hot spot" on the 3D surface, the experimental data presented show that after separation, the 3D SERS substrate has label-free fingerprint identification capability for captured kanamycin antibiotics, the doxorubicin (DOX) chemotherapy drug, and methicillin-resistant Staphylococcus aureus (MRSA) super bugs. The reported data show that due to the presence of antimicrobial nontoxic biopolymer chitosan, the multifunctional 3D architecture can be used for efficient separation, label-free SERS identification, and eradication of MRSA superbugs. A detailed mechanism for label-free identification and killing of super bugs using a 3D membrane have been discussed.