representatives of this category. [21] Early attempts to render inorganic quantum dots with chiroptical activity involve the use of chiral stabilizers. Experimental studies showed that stabilizer-modified quantum dots, such as CdS and CdTe, enabled circular dichroism, however, they were circularly polarized luminescenceinactive. [22,23] Theoretical calculations suggested that the chiral stabilizers caused distortion of the surface layer, however, the core of quantum dots remained achiral, which may explain the circularly polarized luminescence inactivity. [24] It was later hypothesized that enclosing quantum dots in a chiral environment may render quantum dots with circularly polarized luminescence activity, indeed, such a hypothesis found experimental evidences in a chiral nanostructure of apoferritin encapsulating CdS. [25] This lead to new chiral inorganic nanomaterials based on quantum dots and some novel approaches for circularly polarized luminescence generation. Representative work include CdSe quantum dots grafted with chiral cysteine, [26] CdTe nanowires embedded in stretchable twisted fibers [4] and chiral nanostructures of chalcogenide quantum dots. [27] However, these inorganic nanostructures are inadequate for applications due to their tedious synthesis procedures and low CPL strength with dissymmetry factors in the range of 10 −3 -10 −4 . It is clear that circularly polarized luminescent quantum dot nanomaterials with high strength, precise handedness, tunable wavelengths, and suitable for scale-up are highly desirable.Carbon dots are remarkable inorganic phosphors with distinct features such as tunable photoluminescence, high emission intensity, photostability, biocompatibility, and easy availability, which are superior to many inorganic quantum dots. [28][29][30][31] They are promising for bioimaging, sensing, light emitting diodes, energy storage, photocatalysis, and optoelectronic applications. [32][33][34][35][36][37][38] It can be anticipated that conferring circularly polarized luminescence on carbon dots will avail novel circularly polarized luminescent nanomaterials for biomedicine and nanoscience. Such materials, to the best of our knowledge, are not reported to date.Cellulose nanocrystals are renewable, biocompatible, and low-cost nanomaterials. They have intrinsic ability to selfassemble forming a left-handed chiral nematic organization that can be preserved upon drying. [39][40][41] Taking advantage of this property, a realm of cellulose nanocrystal-based helical Circularly polarized luminescent carbon dot nanomaterials of self-organized helical superstructures based on cellulose nanocrystals enable strong, right-handed, and multicolor tunable circularly polarized luminescence with extraordinary dissymmetry factors up to −0.74. The effects of emission intensity and carbon dots loading on the strength of the righthanded circularly polarized luminescence are experimentally observed and theoretically explained. Potentials of the carbon dots-cellulose nanomaterials for circularly polarized ...

Carbon dots (CDs) are carbon-based fluorescent nanoparticles that can exhibit excitation-dependent photoluminescence (PL) "tunable" throughout the entire visible range, interesting for optoelectronic and imaging applications. The mechanism underlying this tunable emission remains largely debated, most prominently being ascribed to dot-to-dot variations that ultimately lead to excitation-dependent ensemble properties. Here, single-dot spectroscopy is used to elucidate the origin of the excitation-dependent PL of CDs. It is demonstrated that already single CDs exhibit excitation-dependent PL spectra, similar to those of the CD ensemble. The single dots, produced by a facile one-step synthesis from chloroform and diethylamine, exhibit emission spectra with several characteristic peaks differing in emission peak position and spectral width and shape, indicating the presence of distinct emission sites on the CDs. Based on previous work, these emission sites are related to the sp subregions in the carbon core, as well as the functional groups on the surface. These results confirm that it is possible to integrate and engineer different types of electronic transitions at the nanoscale on a single CD, making these CDs even more versatile than organic dyes or inorganic quantum dots and opening up new routes toward light-emission engineering.

Aggregation induced emission (AIE) has attracted considerable interest for the development of fluorescence probes. However, controlling the bioconjugation and cellular labeling of AIE dots is a challenging problem. Here, this study reports a general approach for preparing small and bioconjugated AIE dots for specific labeling of cellular targets. The strategy is based on the synthesis of oxetane-substituted AIEgens to generate compact and ultrastable AIE dots via photo-crosslinking. A small amount of polymer enriched with oxetane groups is cocondensed with most of the AIEgens to functionalize the nanodot surface for subsequent streptavidin bioconjugation. Due to their small sizes, good stability, and surface functionalization, the cell-surface markers and subcellular structures are specifically labeled by the AIE dot bioconjugates. Remarkably, stimulated emission depletion imaging with AIE dots is achieved for the first time, and the spatial resolution is significantly enhanced to ≈95 nm. This study provides a general approach for small functional molecules for preparing small sized and ultrastable nanodots.

Advances in the development of fluorescent carbon dots (CDs) for detecting nitro-explosives have attracted great interest. However, developing long-wavelength luminescence CDs for highly selective determination of 2,4,6-trinitrophenol (TNP) and getting insight into the detection mechanism remain further to be investigated. Here, excitation-independent yellow-green emission CDs with good photostability and low biotoxicity were introduced for detecting TNP selectively. Then, two types of electron transfer (ET) processes including hydrogen-bond interaction-assisted ET and proton transfer-assisted ET are suggested to be responsible for their photophysical behavior. Finally, the visual detection of TNP has been successfully developed by a CD-based indicator paper. The facile, highly sensitive, and selective detection for TNP in both of a solution and a solid phase makes CDs potentially useful in environmental sensor applications.

Homogeneous 2D lamellar assemblies of Au thiolate coordination polymer (ATCP) were obtained by two-ligand co-assembly. The orbital levels and the bandgap of the 2D Au -S network in the centre of the lamellae can be continuously tuned by means of the capping ligands on both sides, to give a new type of inorganic-organic composite semiconductor, the band structure of which can be easily tuned by low-temperature solution-phase co-assembly. Furthermore, the chemical reactivity of these ATCP co-assemblies also proved to be strongly dependent on the organic substituents, with well-tuneable transformation rates to gold nanoparticles. Apparently, this is the first work to demonstrate how organic substituents can continuously tune the electron band structure and chemical reactivity of inorganic atomic layers of semiconductor through co-assembly.

Two pseudopolymorphs are achieved in two solvents and exhibit high structure preservation but have distinct optical properties, morphology and thermal stability.

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Enriching the synthetic routes of functionalized carbon dots (C dots) and expanding their application are necessary for promoting research into carbon-based nanomaterials. In this study, we develop a one-step and efficient method to prepare excitation-dependent multicolor emissive carbon dots (M-C dots) with quaternary ammonium functional groups via a solvothermal reaction of chloroform, diethylamine, and ammonium carbonate. Through detailed structural characterizations and further reactions of surface functional groups (such as reduction, oxidation, and hydrolysis) on M-C dots, the excitation-dependent tunable photoluminescence behaviors are proposed to come from the multiple emission domains on the surface. The prepared M-C dots possess antibacterial activity against Gram-positive bacteria and Gram-negative bacteria. And the antibacterial effects of M-C dots were investigated by destroying the bacterial cell walls/membranes via strongly electrostatic interactions between positively charged M-C dots and negatively charged bacteria. This study provides a novel strategy to prepare functionalized C dots and reveals the nature of intrinsic multicolor emission of C dots.