Role of Noncovalent Interactions in N,P-Functionalized Luminescent Carbon Dots for Ultrasensitive Detection of Moisture in D2O: Boosting Visible-NIR Light Sensitivity

Water-Responsive Fluorescence and Room-Temperature Phosphorescence Carbon Dots for Trace Water Detection in Ethylene Glycol and Multimodal Anticounterfeiting

Identifying trace water in ethylene glycol is essential for maintaining stringent quality control in chemical processes and ensuring product purity. However, the development of highly sensitive detection methods for aqueous impurities within this viscous solvent presents significant challenges, primarily arising from the strong intermolecular hydrogen bonding network within ethylene glycol, which not only masks the presence of water but also interferes with conventional analytical techniques. This work introduces a novel fluorescence-based detection method that combines simplicity, efficiency, and rapid response by leveraging water-responsive carbon dots (CDs). Specifically, we synthesized water-responsive carbon dots (WCDs) that exhibit enhanced fluorescence in anhydrous ethylene glycol. Notably, the introduction of water induces a concentration-dependent fluorescence enhancement at 394 nm, establishing a linear correlation within the 0-0.284% (v/v) water content range (detection limit: 0.017%, 3σ/S) with a remarkably low. By exploiting the hydrogen bonding between WCDs and cellulose paper matrices, the triplet excited states are effectively stabilized, thereby enabling green room-temperature phosphorescence (RTP) emission. This enables precise modulation of the WCDs' aggregation-dispersion states through controlled water/ethanol addition, a mechanism that drives stimulus-responsive transitions between fluorescence and RTP. These tunable optical properties not only validate the detection mechanism but also create new opportunities for developing dual-mode dynamic anticounterfeiting technologies.

Highly Facile Strategy for the Ultrasensitive Differentiation of D2O and H2O by Red-Emitting Carbon Dots

Distinguishing between D2O and H2O is crucial for the utilization of high-purity D2O in the nuclear industry, chemical analysis, biological pathway tracing, and other fields, as well as for ensuring the integrity of water quality and safeguarding human health, but challenging due to their highly analogous physical and chemical properties. On the basis of the fact that D2O exhibits superior hydrogen bond strength and deprotonation capacity for phenolic OH group compared to H2O, the red-emitting carbon dots (RCDs) with excellent optical properties, salt tolerance, photobleaching resistance, long-term storage stability, and biocompatibility were synthesized via a one-step strategy at room temperature. The RCDs demonstrated sensitivity for detecting D2O content in H2O and H2O content in D2O was found to be 0.060% and 0.15%, respectively. Collectively, this research expanded the potential applications of carbon nanomaterials and introduced a highly facile strategy for analyzing the isotopic purity of D2O.

N-Doped Carbon Layer Encapsulated NiPx for Photocatalytic Alcohol Oxidation Coupled Hydrogen Evolution on Ag-In-Zn-S Quantum Dots

The photocatalytic oxidation of alcohols to value-added chemicals with simultaneous hydrogen (H2) generation is a promising sustainable process that suffers from slow charge transfer and poor integration of both reactions. Here, an NH2-containing Ni metal-organic framework (MOF) is used as a precursor for creating N-doped C layer encapsulated nickel phosphide (NiPx@NC), which effectively enhances the charge transfer and reaction coupling when modified on narrow-band-gap Ag-In-Zn-S quantum dots (AIZS QDs). The resulting AIZS/NiPx@NC photocatalysts demonstrate high efficiency for benzyl alcohol (BA) oxidation coupled H2 evolution, achieving H2/benzaldehyde production rates of 9.66/5.67 mmol g-1 h-1, which are 3.30 and 47.25 times higher than those of pure AIZS QDs, respectively. Additionally, the selectivity of benzaldehyde is enhanced to 77.96%. AIZS/NiPx@NC also shows improved performance for other organics, including 4-methoxybenzyl alcohol and biomass-derived furfuryl alcohol. Photoelectrochemical and transient photovoltage spectroscopy tests confirm the increased effective surface charges and charge transfer efficiency, while electron paramagnetic resonance spectroscopy reveals a carbon-centered radical pathway for selective benzaldehyde formation. DFT calculations suggest that the N-doped carbon enhances the proton adsorption on Ni sites and BA adsorption on the NiPx@NC surface. This work highlights the potential of multifunction integration in developing carbon-based cocatalysts for photocatalytic alcohol oxidation coupled H2 evolution.

Recent advances in optical heavy water sensors

D2O and H2O, as two important solvents with very similar properties, play a pivotal role in nuclear industrial production, life and scientific research. Unfortunately, D2O and H2O are highly susceptible to contamination by each other, so effective qualitative and quantitative analyses of both are necessary. This review comprehensively discusses the progress in optical sensing for the detection of a trace amount of H2O in heavy water or vice versa, mainly including five types of analytical systems: inorganic nanocrystals, carbon-based nanomaterials, lanthanide complexes, organic polymers, and organic small molecules. The whole article is divided into several sub-sections based on multiple mechanisms underlying the design of heavy water optical sensors, i.e., the difference in binding energy, the difference in quenching efficacy of oscillator types and the difference in acid-base of H2O and D2O. The working mechanism, advantages and disadvantages, analytical performance and applications of the reported sensors in recent years were analyzed in detail, and the future development is envisioned for the optical sensors towards distinguishing D2O and H2O.

Aggregation-induced-emission red carbon dots for ratiometric sensing of norfloxacin and anti-counterfeiting

The detection of trace antibiotic residues holds significant importance because it's related to food safety and human health. In this study, we developed a new high-yield red-emitting carbon dots (R-CDs) with aggregation-induced emission properties for ratiometric sensing of norfloxacin. R-CDs were prepared in 30 min using an economical and efficient microwave-assisted method with tartaric acid and o-phenylenediamine as precursors, achieving a high yield of 34.4 %. R-CDs showed concentration-dependent fluorescence and aggregation-induced-emission properties. A ratiometric fluorescent probe for detecting the norfloxacin was developed. In the range of 0-40 μM, the intensity ratio of two emission peaks (I445 nm/I395 nm) towards norfloxacin show good linear relationship with its concentrations and a low detection limit was obtained (36.78 nM). In addition, complex patterns were developed for anti-counterfeiting based on different emission phenomenon at different concentrations. In summary, this study designed a novel ratiometric fluorescent probe for detection of norfloxacin, which greatly shortens the detection time and improves efficiency compared with high-performance liquid chromatography and other methods. The study will promote the application of carbon dots in anti-counterfeiting and other related fields, laying the foundation for the preparation of low-cost photosensitive anti-counterfeiting materials.

Identification of Chinese baijiu from the same brand based on a graphene quantum dots fluorescence sensing array

The identification of Chinese baijiu is crucial to regulating the international market and maintaining legitimate rights, as the popularity, influence and awareness of baijiu are growing. A graphene quantum dot (GQD) based fluorescence sensor array is designed in this paper. Upon using only GQDs as a single sensing element, combining three different solvents improves the sensing array's detection sensitivity while simplifying material preparation and experimental detection. Adding organic substances creates intermolecular forces between the GQDs and the solvent, causing the fluorescence intensity to change. The sensor array was able to distinguish 21 types of organic matter, different ratios of quaternary mixed organic materials and 17 types of baijiu of the same brand. It also showed excellent performance in the detection of species in blind samples, with the machine learning algorithm successfully distinguishing baijiu from five other distilled spirits. The experiment provides guidance for the practical application of GQDs and provides a simple but effective reference for sensor arrays to detect baijiu.