Carbon dots (CDs)-based nanoparticles have been extensively explored for biological applications in sensing and bioimaging. However, the major translational barriers to CDs for imaging and sensing applications include synthetic strategies to obtain monodisperse CDs with tunable structural, electronic, and optical properties in order to achieve high-resolution deep-tissue imaging, intracellular detection, and sensing of metal ions with high sensitivity down to nanomolar levels. Herein, we report a novel strategy to synthesize and develop a multifunctional nitrogen-doped CDs probe of different sizes using a new combination of carbon and nitrogen sources. Our results show that the structural characteristics (i.e., the surface density of emissive traps and bandgaps levels) depend on the size of the CDs, which ultimately influences their optical properties. This work also demonstrates the development of a two-photon dual-emissive fluorescent multifunctional probes (3-FCDs) by conjugating fluorescein isothiocyanate on the surface of nitrogen-doped CDs. 3-FCDs show excellent near-infrared two-photon excitation ability, single-wavelength excitation, high photostability, biocompatibility, low cytotoxicity, and good cell permeability. Using two-photon fluorescence imaging, our multifunctional probe shows excellent deep-tissue high-resolution imaging capabilities with penetration depth up to 3000 and 280 μm in hydrogel scaffold and pigskin tissue, respectively. The designed probe exhibits ultrasensitivity and specificity toward Fe3+ ions with a remarkable detection limit of 2.21 nM using two-photon excitation. In addition, we also demonstrate the use of multifunctional CDs probe for ultrasensitive exogenous and real-time endogenous sensing of Fe3+ ions and imaging in live fibroblasts with rapid response times for intracellular ferric ion detection.

The unique and long-range ordered-vacancy structure in wafer-scale grown single-unit-cell-thick In2S3 facilitates excellent electronic performance.

Developing bifunctional electrocatalysts is the primary challenge to improve the reaction efficiency of zinc-air batteries. Lattice-strain engineering constructs high-efficiency oxygen redox catalysts by tuning the physicochemical properties of nanomaterials. However, the randomness and complexity of lattice mismatch make it difficult to effectively identify the structure-activity relationship between the strain and catalyst. Herein, a strategy of Ru triggered partial coordination environment mutation of ZnIn 2 S 4 (R 0.1 ZIS) to regulate the d-band center of catalytic sites is provided, which dramatically activates intrinsic activity and accelerates electron transfer. Density functional theory calculations and system characterizations reveal that local lattice strain causes anti-bonding orbital to occupy more electrons and narrower bandwidth, reduce the migration energy barrier of * OH deprotonation and optimize the adsorption/desorption process of oxygen-containing intermediates, thus demonstrating extraordinary catalytic performance in oxygen reduction reaction and oxygen evolution reaction. Expectedly, the R 0.1 ZIS-based cell delivers the open circuit potential of 1.587 V almost identical to the theoretical voltage, and an ultralow voltage gap of 0.71 V after undergoing 262 h operation. This work offers a promising avenue for building lattice-strain engineering to realize robust bifunctional electrocatalysts.