ABSTRACT Harnessing the synergistic interactions between adjacent bimetallic atoms, dual‐atom catalysts (DACs) emerge as promising candidates for the CO 2 reduction reaction (CO 2 RR). However, precise regulation of neighboring effects at dual‐atom sites to optimize and enhance CO 2 RR performance remains highly challenging. This review focuses on Fe‐, Co‐, Ni‐, and Cu‐based DACs, systematically elucidating how proximity effects modulate reaction intermediates and product selectivity in both homonuclear and heteronuclear systems. The distinct electronic configurations of homonuclear and heteronuclear DACs lead to diversified CO 2 RR pathways and product distributions. When the two metal atoms are spatially separated, the weakened electronic coupling primarily lowers the energy barrier for C 1 intermediates, thereby improving the selectivity toward C 1 products. In contrast, a reduced metal–metal distance strengthens interatomic electronic interactions through the formation of N/O‐coordinated or direct metal–metal structures, facilitating C─C coupling and thus enhancing C 2 product formation. A mechanistic understanding of C─C coupling serves as a fundamental basis for directing CO 2 RR toward multi‐carbon products with higher energy density and practical relevance. Additionally, theoretical investigations provide valuable insights into structure–activity relationships, offering guidelines for the rational design of efficient DACs for CO 2 RR.

A novel bottom-up green approach is presented for synthesizing blue fluorescent sulfur quantum dots (SQDs) utilizing L-cysteine as the sulphur source and the unique structure of carboxymethyl cellulose macromolecule as the passivating agent. The method accomplishes synthesis within a shortened reaction time of only 4 h. The formation of SQDs involves three steps: heating of L-cysteine to produce H2S, which then reacts with H2O2 to form elemental sulphur, eventually assembling into SQDs. The prepared SQDs exhibit favorable water dispersibility and photostability, rendering them highly suitable for fluorescent sensors. Notably, fluorescence detection experiments reveal that fluorescence resonance energy transfer (FRET) between the SQDs and curcumin (Cur) results in diminished fluorescence of the SQDs (F435) and an increase in scattered light signal (S690). In addition, it shows promising ratiometric linearity of the Cur concentration in the range 0.10–12.00 µM with an impressive limit of detection of 19 nM. This work not only provides valuable insights into the green and convenient sustainable preparation of SQDs but also opens up avenues for their versatile applications.

Carbon quantum dots (CQDs) are considered very promising zero-dimensional nanomaterials in the fields of catalysis, optoelectronic materials, sensing and bioimaging. Nevertheless, its complex framework and variable photovoltaic effects pose challenges for its synthesis and design. Theoretical computations play an important role in materials science as a predictive tool, especially in understanding the structure and properties of materials. This review summarizes the progress made in modeling CQDs with GGA, LDA and SHE + U. According to the CQDs used in different domains, the structure–property relationships of the CQDs models are analysed in the areas of catalysis, optoelectronic materials, sensing and bio-imaging. Moreover, challenges and opportunities for theoretical computations in the application of CQDs are discussed.

Based on the fluorescence resonance energy transfer (FRET) principle, a yellow-green light fluorescent probe was designed and synthesized for the detection of neutral red using fluorescein monoaldehyde-3-acetylcoumarin as the fluorophore. The fluorescein moiety in the probe structure is readily interchangeable and heterogeneous in the form of an anion, and the neutral red is a quaternary ammonium salt structure with N. Therefore, the two are bound together in the form of ionic bonds through the mutual attraction of anions and cations. At the same time, FRET occurs, resulting in the absorption of the fluorescence emitted by the probe by the neutral red molecule, leading to a significant quenching of its fluorescence. The probe has a high selectivity for neutral red with a linear range of 0-30 & mu;M and a detection limit of 8. 68 & mu;M. Furthermore, the fluorescent probe has been successfully applied to the detection of neutral red content in real water samples with a recovery of 101 %-115 %. The probe has promising potential in the quantitative detection of neutral red.

The composition of composite photocatalysts with both broad spectral response and efficacious separation of photoinduced carriers were essential. The CDs were installed on the surface of the three-dimensional hollow microsphere nanophotocatalyst Bi2WO6 by the hydrothermal approach. Crystal structure, morphology and composition revealed the synthesis of the composite catalyst. The higher photocatalytic capability of 0.5% CDs/Cl–Bi2WO6 (0.0317 min−1) was observed in the degradation procedure, explained that the doping of Cl and the presence of CDs remarkably strengthened the visible light capture and depressed the rate of electron-hole pair complexation. Notably, scavenger-quenching assays results verified that activities of h+, •OH and •O2‾ were the primary actors in the degradation procedure. Ultimately, the degradation mechanism of a feasible TCH was submitted. This study presented a novel concept for the exploitation of composite nanophotocatalysts for the effective degradation of organic pollutants.

Cu 2+ is one of the basic trace elements in organisms. As a catalytic cofactor in cells, it is involved in various enzyme reactions,hematopoietic function and some other life processes. In this paper, the HBT-RhB fluorescent probe was synthesized with benzothiazole（HBT） as the parent structure. The probe has high selectivity and sensitivity to Cu 2+ , excellent fluorescence characteristics and good temperature and pH stability,realizing a logical detection response strategy. The probe has a good linearity for Cu 2+ in the linear range of 0.04～160 nM, and the minimum detection limit is 2.6 nM. The good response of HBT-RhB to Cu 2+ was further proved by fluorescence spectrum and ultraviolet absorption spectrum. This new method of designing Cu 2+ responsive probes is provided for the detection of relevant analytes, aiming to play a more important role in environmental,biological imaging, and disease therapy.

The present quest for sulfur quantum dots (SQDs) has been to circumvent the inefficient and laborious process involved in previous synthesis strategies. Here, intensely blue-emitting SQDs with a quantum yield up to 14.22 % are prepared by an effective ethylenediamine-assisted acceleration strategy with sublimated sulfur to SQDs conversion on the order of 6 h. The forming of SQDs includes the cleavage of bulk sublimated sulfur powders into small particles of sulfur-nitrogen compounds in the presence of ethylenediamine, which are oxidized to SQDs. The critical finding of this work is that sublimated sulfur can be rapidly converted from zero-valent sulfur to polysulfide by simple heating in the effect of ethylenediamine that dramatically boosts preparation efficiency. Significantly, the combination of SQDs and MnO2 nanosheets achieve fluorescence/scattered light ratiometric sensing of ascorbic acid with a limit of detection of 11.31 nM. This work provides a facile and rapid method for the fabrication of SQDs that could even enable SQDs to be applied in more expansive fields than carbon QDs and silicon QDs in the future.

Metal–organic frameworks (MOFs) can be combined with nanomaterials and the combined composites have excellent optical properties. Carbon dots (CDs) with tiny particle size, non-toxic and rich surface functional groups are novel fluorescent materials. Carbon dots@metal–organic frameworks (CDs@MOFs) are synthesized by encapsulating CDs into MOFs. CDs@MOFs are promising composites for the preparation of a new generation of fluorescence sensors, which combine the hybrid properties of MOFs and the special optical properties of CDs. Urged as such, we are encouraged to categorize according to the sensing mechanisms. These include fluorescence resonance energy transfer (FRET), aggregation-caused quenching (ACQ), static quenching, dynamic quenching, photo-induced electron transfer (PET), inner filter effect (IFE) and so on. Based on the above mechanisms, CDs@MOFs can specifically interact with target analytes to generate fluorescence quenching. This review covers the research progress of CDs@MOFs in recent five years (with 103 refs), synthetic design of CDs@MOFs and introduces the sensing mechanism. The current challenges and future research directions are discussed briefly. The sensing mechanism and applications of CDs@MOFs

Solid-state fluorescent and phosphorescent carbon dots (CDs) have widespread applications, with difficulties in obtainment. In this study, solid-state carbon dots (SCDs) emitting green, yellow, and orange fluorescence were fabricated using urea and phthalic acid as precursors. The band gap size was systematically controlled by varying the ratio of raw material nitrogen. By changing the temperature during synthesis, the phosphorescent properties of SCDs were adjusted, and the longest lifetime possessed 156.8 ms of orange phosphorescence. CDs were attached to the crystals of phthalimide, allowing a certain spacing between the particles and suppressing the phenomenon of aggregation-induced quenching (ACQ), thus obtaining solid-state fluorescence. Detailed characterization and density flooding theory (DFT) calculations further indicate that the reduction of the conjugation domain leads to the redshift of the solid-state fluorescence. The phosphorescence appearance is attributed to the presence of crystals that inhibit the nonradiative relaxation channels, and N elements that promote spin-orbit coupling interactions. Based on their special luminescent properties, they have been successfully applied in the fabrication of (0.38,0.54), (0.44,0.54) and (0.51, 0.47) light-emitting diodes, as well as in the production of secure anti-counterfeit cryptographic inks and their successful application in digital encryption.

With advances in nanotechnology and the development of emerging therapeutic modalities, a surge in research on the use of nanomedicines for biomedical applications has occurred over the past three decades. Carbon dots (CDs) are new members of carbon-based nanomaterials that can be used in cancer treatment to reduce side effects of drugs and improve treatment efficiency, offering new medical opportunities for further research. Urged as such, we are encouraged to classify CDs-based cancer treatments, including photodynamic therapy (PDT), photothermal therapy (PTT), sonodynamic therapy (SDT), chemodynamic therapy (CDT), chemotherapy (CT), and synergistic therapy. The advantages of these approaches are summarized, as well as ways to improve certain shortcomings. Meanwhile, this review highlights the feasible practice of CDs in cancer treatment, which is further developed and widely used in the biomedical field.

Fluorescence-tunable sulfur quantum dots (SQDs) were obtained by an assembly-fission process and assisted etching with H2O2. The morphological and structural characterization indicated that the obtained SQDs possess excellent dispersion, high water solubility and abundant surface functional groups, which is beneficial to its further application. In the Gaussian software, the electron cloud density distribution around the entire molecular structure is simulated and the density generalization calculations confirms that the main reason for the red shift of emission is the synergistic effect of SQDs size and surface states. Moreover, blue fluorescent SQDs (B-SQDs) showed high sensitivity and specific selectivity toward berberine hydrochloride with detection limits as low as 0.24 nM, and have been successfully used for water sample and actual drug detection. It is noteworthy that the solid-state luminescence properties of SQDs are mainly attributed to the adsorption of chain PEG on the surface of SQDs. By mixing SQDs with epoxy resin, dual-color fluorescent films were prepared and used as the fluorescence conversion layer to manufacture high-performance light-emitting diodes. The CIE (Commission Internationale d ' Eclairage) coordinates of WLED is (0.27,0.29), CCT (Correlated color temperature) is 5793 K and CRI (Color rendering index) is 85.2. Moreover, the prepared SQDs are highly fluorescent and enable latent fingerprint imaging for identity recognition. This work has advanced the development of SQDs for analytical sensing, optical devices, and fingerprint imaging.

Sunset yellow (FCF), a commonly used food additive, can brighten foods, but the improper amount of addition can also cause various diseases. Herein, the fluorescence sensor CDs‐PTD for detecting FCF is synthesized by functionalizing carbon dots (CDs) with 3,4,9,10‐pertetracarboxylic dianhydride (PTD). The prepared CDs‐PTD shows excitation‐independent fluorescence behavior with maximum fluorescence emission at 553 nm under 490 nm excitation and high quantum yields (21.4%). With the presence of FCF, the fluorescence of the sensor is quenched due to fluorescence resonance energy transfer (FRET). The CDs‐PTD exhibits excellent selectivity and sensitivity toward FCF in the range of 0–180 × 10 −6 m with a low detection limit of 106.8 × 10 −9 m . In addition, the sensor is applied to the detection of FCF in beverage samples with recoveries ranging from 97% to 106%. And a portable CDs‐PTD/agarose gel reagent strip is prepared for the assessment of FCF content within 15 min. The CDs‐PTD can be an ideal sensor for detecting FCF in food, and provides a new idea for the detection of food additives.

Supramolecular host molecules are used as tools in the design of multifunctional nanoparticles for sensors, catalysts, biometric elements, etc. Combining with carbon dots (CDs) has excellent host-guest recognition properties and fluorescence characteristics, which can precisely capture and identify target analytes. Consequently, supramolecular host molecules-based CDs can significantly improve the detection performance of ions and molecules with different structures or intrinsic chemical properties. This currently responds to a wide range of analytes including metal cations, anions, organic compounds and other biomolecules, yielding fascinating achievements in the field of chemistry. Therefore, the present review summarizes outstanding supramolecular host molecules-based CDs reported in the past ten years. The focus is on elucidating the mechanisms, methodologies, advantages and disadvantages of modifying or preparing CDs with supramolecular host molecules. Current challenges encountered and outlooks are also be discussed.

Solid-state carbon dots (SCDs) have been widely investigated by scholars owing to their stability, environmental friendliness, and their good optical properties. The current studies on carbon dots (CDs) are mainly focused on the solutions of CDs, while the researches on SCDs are relatively few in comparison. Nowadays, the fabrication and design of high-performance SCDs have attracted much interest. However, due to resonance energy transfer and π-π interactions, CDs undergo aggregation-induced quenching (ACQ) phenomena. This poses an obstacle to the acquisition of SCDs and affects their luminescence performance. Publications of the past 5 years are reviewed on how to suppress the ACQ phenomenon and improve the fluorescence and phosphorescence emission of CDs (Ref. 87) and about the mechanism of achieving the luminescence of SCDs. Then, the applications of SCDs in the fields of luminescent devices, anti-counterfeiting, and detection are outlined. The concluding section analyzes the current challenges faced by SCDs and provides an outlook. Mechanism of photoluminescence from solid state carbon dots.

Carbon dots (CDs) attract interests from researchers in the field of membranes owing to their ultra-small size, non-toxic, highly hydrophilic, abundant surface functional groups, stable photoluminescence, fast proton conductivity and excellent light capture capability. The integration of membranes with CDs (CDs@membranes) can enhance the overall performance of membranes significantly and CDs@membranes relies on three approaches: doping, grafting and layer-by-layer (LbL) self-assembly. This paper reviews the research progress of CDs@membranes in the past five years, introduces the mechanism of CDs to improve membrane performance and the methods for preparing CDs@membranes, categorizes them into water treatment, sensing, electrochemistry, light processing and other fields for review, and finally discusses the current challenges and outlook the future direction.

Since carbon dots (CDs) were reported in 2004, they have been widely used in various fields due to their outstanding optical properties. However, most CDs are self-quenched due to the direct pi-pi interaction in the solid-state aggregation. This shortcoming limits the wide application of CDs, because numerous optoelectronic devices and sensors usually require photoluminescent materials in the solid state. Therefore, designing and preparing carbon dots with multicolor solid emission is necessary. Here, solid-state fluorescence (SSF) CDs were prepared via a one-step solvothermal method, using MA and APTES as raw materials. Through adjusting the ratio of raw materials, solid-state emitting CDs with green, yellow, and orange colors are obtained. The fluorescence spectrum ranges from 490-625 nm, and the QYs are 34.06%, 38.07%, and 20.37%, respectively. For prepared CDs, the main reason for the solid-state emission is that the Si-O, Si-C, and Si-N bonds generated during the formation process can prevent the pi-pi interaction between the graphitized cores. The red shift mechanism of solid and liquid fluorescence is attributed to the decrease in particle size and the increase in the degree of particle aggregation within the unit range. In addition, based on these excellent photoluminescence properties, we have prepared colored light-emitting diodes-the CIEs are (0.22, 0.41), (0.38, 0.47), and (0.50, 0.43) (Commission Internationale de l'Elcairage coordinate)-and solid-state emitting CDs/epoxy films with high transparency and stability.

MXene quantum dots (MQDs) derived from MXene with photoluminescent properties have attracted considerable attention. Herein, nitrogen-doped MQDs (N-MQDs) were constructed by a solvothermal method using Ti3C2 MXene as precursors and o-phenylenediamine (oPD) as the nitrogen source. The morphology, element composition and optical properties of N-MQDs were investigated by transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and spectroscopy etc. The obtained N-MQDs are dispersed quasi-spherical nanoparticles, mainly composed of carbon, oxygen and nitrogen, with yellow fluorescence at 580 nm and quantum yield of 5.42 %. In further, N-MQDs can detect Alizarin Red (ARS) based on inner filter effect (IFE) with linear range and detection limit of 0-80 mu M and 1.21 mu M, respectively. N-MQDs can detect ARS in real water samples, and were expected to have further applications in the fields of environmental monitoring and biosensing.

Carbon dots (CDs) are emerging photoluminescent materials with excellent optical properties. However, the lack of active sites in primitive CDs has limited their development applications. Herein, functionalized carbon dots (Z‐CDs) are successfully prepared by surface modification of CDs with mono (6‐amino‐6‐deoxy) cyclodextrin (β‐CD). The introduction of β‐CD increases the spatial potential resistance between CDs, which effectively reduces the self‐quenching effect. Moreover, the conjugated domains of Z‐CDs are expanded, which improves the optical properties with a quantum yield of 48.74%. Z‐CDs are able to be used in the sequential detection of morin and Al 3+ , and the fluorescence mechanisms are confirmed to be internal filtration effect and fluorescence resonance energy transfer, respectively. The limits of detection are 0.817 and 0.231 × 10 −6 m . This study not only provides an idea to solve the problem of self‐quenching of CDs but also enriches the detection means of flavonoids and ions, which is expected to be applied to biosensing and environmental monitoring.

With their unique optical and electronic properties, carbon dots (CDs) are showing great momentum in many fields such as biosensing, imaging, drug delivery, and photocatalysis. Due to their efficient light harvesting, extraordinary upconversion photoluminescence, and excellent photoinduced electron transfer capabilities, the combination of CDs with photocatalytic materials will promote light absorption resulting in increased generation of electron‐hole pairs and faster photogenerated electron transfer, effectively suppressing the rate of electron‐hole pair complexation and thus improving photocatalytic activity. In this paper, the mechanism of CDs photocatalysis and various photocatalytic materials such as TiO2, Bi‐based, CdS, and g‐C3N4 complexed with CDs are reviewed. It is hoped that research into CDs in the field of photocatalysis will be advanced and that CDs will be used more widely in environmental and energy applications.