Graphite-like graphitic carbon nitride (g-C 3 N 4 ) has gained considerable interest in the past few years. However, merely a few studies have been undertaken regarding the application of g-C 3 N 4 for metal adsorption and visible-lightdriven reduction of aromatic nitro compounds. Here, we describe a versatile method for the preparation of g-C 3 N 4 nanocomposite decorated with magnetite nanoparticles (g-C 3 N 4 @Fe 3 O 4 NPs) that subsequently showed their efficiency in sequestration of Cr(VI)/Cr(III) and NaBH 4 -mediated conversion of 2-nitroaniline (2-NA) and 4-nitroaniline (4-NA) under visible-light exposure. The as-synthesized g-C 3 N 4 @Fe 3 O 4 NPs adsorbent revealed excellent water dispersibility, superior magnetic property, and porous structure. Numerous surface hydroxyls (−OH) and amino groups (−N, −NH, −NH 2 ) enabled g-C 3 N 4 @Fe 3 O 4 NPs to rapidly isolate Cr(VI) from aqueous solution through applying an outer magnetic field. The adsorbed Cr(VI) on the g-C 3 N 4 @Fe 3 O 4 NPs surface offered a maximum equilibrium adsorption capacity of 555 mg g −1 , and their absorption behavior followed the Langmuir isotherm and pseudo-second-order kinetics model. The morphology, surface properties, crystalline structure, and chemical compositions of g-C 3 N 4 @Fe 3 O 4 NPs were thoroughly investigated. In real-world applications, g-C 3 N 4 @Fe 3 O 4 NPs was implemented for the determination of total chromium in industrial soil sludge samples. Additionally, NaBH 4 -induced reduction of 2-NA to 2-aminoaniline and 4-NA to 4-aminoaniline catalyzed by g-C 3 N 4 @ Fe 3 O 4 NPs (catalyst loading as low as 20 mg) was achieved within 8 min.

Metal nanocluster-based nanomaterials for the simultaneous determination of temperature and pH variations in micro-environments are still a challenge. In this study, we develop a dual-emission fluorescent probe consisting of bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) and fluorescein-5-isothiocyanate (FITC) as temperature- and pH-responsive fluorescence signals. Under single wavelength excitation the FITC/BSA-AuNCs exhibited well-separated dual emission bands at 525 and 670 nm. When FITC was used as a reference fluorophore, FITC/BSA-AuNCs showed a good linear response over the temperature range 1-71 °C and offered temperature-independent spectral shifts, temperature accuracy, activation energy, and reusability. The possible mechanism for high temperature-induced fluorescence quenching of FITC/BSA-AuNCs could be attributed to a weakening of the Au-S bond, thereby lowering the charge transfer from BSA to AuNCs. Additionally, the pH- and temperature-responsive properties of FITC/BSA-AuNCs allow simultaneous temperature sensing from 21 to 41 °C (at intervals of 5 °C) and pH from 6.0 to 8.0 (at intervals of 0.5 pH unit), facilitating the construction of two-input AND logic gates. Three-input AND logic gates were also designed using temperature, pH, and trypsin as inputs. The practicality of using FITC/BSA-AuNCs to determine the temperature and pH changes in HeLa cells is also validated.

Poly(diallydimethylammonium chloride) (PDDA) has been demonstrated to be valuable in diverse fields, such as layer-by-layer assembly and material surface modification. Herein, we report a novel application of PDDA for exfoliating bulk tungsten disulfide (WS 2 ) into few-layer WS 2 nanosheets (FL-WS 2 -NSs) under ultrasonication treatment. Cationic PDDA molecules were capable of firmly binding to the WS 2 surface to expose quaternary ammonium moieties in water, thereby creating electrostatic repulsion between each FL-WS 2 -NS. The formation of FL-WS 2 -NSs was proven by absorption spectroscopy, high-resolution transmission electron microscopy, and atomic force microscopy. Additionally, PDDA molecules enable FL-WS 2 -NSs to be stable in 200 mM NaCl for more than six months without thermal-triggered nanosheet aggregation. Given that PDDA-stabilized FL-WS 2 -NSs (PDDA-FL-WS 2 -NSs) exhibit sulfur vacancy sites, thiolated boron−dipyrromethene (BODIPY) molecules were selfassembled onto the surface of PDDA-FL-WS 2 -NSs. As a result, the fluorescence of BODIPY was quenched by the mixing of static and dynamic quenching processes. The presence of glutathione (GSH) induced the liberation of BODIPY from BODIPYconjugated PDDA-FL-WS 2 -NSs, thereby restoring its fluorescence. This fluorescent probe allowed for the quantitative determination of GSH in erythrocytes and the fluorescence imaging of GSH-related reactions in HeLa cells. Additionally, PDDA-FL-WS 2 -NSs were implemented as a platform for complexing with citrate-capped nanoparticles of Au, Pd, and Pt. The hybrids of PDDA-FL-WS 2 -NSs and metal nanoparticles (NPs) were more efficient for catalyzing the NaBH 4 -mediated reduction of 4-nitrophenol than metal NPs. It is evident that PDDA-FL-WS 2 -NSs are readily conjugated to thiol-terminated organic dyes and other existing nanomaterials.

Protein-stabilized gold nanoclusters (AuNCs) are intensively used in nanoscale biological systems and biosensors. However, protein-stabilized AuNCs that exhibit an emission peak at the first near-infrared (NIR) window (700–900 nm) have rarely been explored. Herein, we present a rapid microwave synthetic approach for developing NIR-emissive AuNCs (named NIR750-AuNCs) through pH-mediated NaBH4 reduction of HAuCl4 in the presence of lysozyme as a template. The NIR750-AuNCs exhibited emission peaks at 750 nm with luminescence lifetimes of 1.0 μs and quantum yields (QY) of 4.9%. The incorporation of Ag­(I) into NIR750-AuNCs [named NIR750-AuNCs@Ag­(I)] efficiently enhanced their QY (13.7%) and luminescence lifetime (1.9 μs) due to the coordination of the Ag­(I) ions with electron-rich residues of the lysozyme shell that mediates the ligand-to-metal–metal charge transfer (LMMCT) process. Additionally, this coordination reaction enables NIR750-AuNCs@Ag­(I) to exhibit excellent resistance to photobleaching. The lysozyme shell allowed the conjugation of NIR750-AuNCs@Ag­(I) with FITC molecules. As a result, the as-made FITC/NIR750-AuNCs@Ag­(I) display two well-resolved emission peaks at 525 and 750 nm with almost equal intensities. These outstanding features allowed the use of FITC/NIR750-AuNCs@Ag­(I) for ratiometric sensing of 5–25 μM NaHS in environmental samples with an excellent reproducibility (relative standard deviation of intensity ratio (<2.5%), satisfactory selectivity, and acceptable recovery (94.4%–101.9%). The sensing mechanism of FITC/NIR750-AuNCs@Ag­(I) is attributable to HS–-triggered removal of Ag­(I) from the electron-rich residues of the lysozyme shell. Also, FITC/NIR750-AuNCs@Ag­(I) were implemented for ratiometric imaging of exogenous and endogenous H2S in live cells. This work demonstrates the synthesis of protein-stabilized AuNCs with an emission maximum of 750 nm, paving the road to designing NIR-emitting AuNCs.