Paper-based cultural relics often undergo acidification and deterioration during long-term preservation. Accurate detection of paper acidity is of great significance to assess aging status and extend the preservation lifetime of paper-based cultural relics. Rapid identification of the acidification degree and acid distribution across multiple regions of paper is essential. Inspired by fluorescent sensing technology, pH-sensitive cadmium telluride (CdTe) quantum dots (QDs) and rhodamine B (RB) fluorescent probes are synthesized and incorporated onto the nanofibers of a bacterial cellulose (BC) membrane to enable visual acidity detection of paper. Due to the complementary pH detection range of CdTe QDs and RB probes, the composite BC membrane exhibits a clear pH response across an acidic to neutral range (pH 3.0-7.5). Notably, the contrasting fluorescent colors of the two probes within the BC membrane allow for easy visualization of paper pH and acidity distribution with the naked eyes. A distinct color transition from red to green was observed on the fluorescent BC membrane when it is applied to a model paper with a gradient pH distribution. The feasibility of this method was verified by using the flat-headed pH electrode method. Additionally, common metal ions in most paper fillers, inks, pigments, as well as some sugars and amino acids showed minimal interference with the pH response of the composite BC membrane, highlighting its potential and broad applicability for visual acidity detection in paper-based cultural relics.

Kojic acid (KA) has gained significant attention due to its widespread use in the food and cosmetics industries. However, concerns about its potential carcinogenic effects have heightened the need for sensitive detection methods. This study introduces a fluorescence-based optical sensor for the quantification of KA in food samples, utilizing fluorescent carbon dots (CDs) synthesized from pomegranate peel via a hydrothermal method. The Stern-Volmer plot demonstrated a linear response for KA in the range of 120 to 1200 µM, with a Pearson correlation coefficient (r) of 0.9999 and. The sensor exhibited a detection limit of 30 ± 0.04 µM and a limit of quantification (LOQ) of 90 ± 0.14 µM. Application of the developed method to soy sauce and vinegar samples yielded accurate KA determinations, with recoveries of 103.11 ± 0.96% and 104.45 ± 2.15%, respectively. These findings highlight the potential of the proposed sensor for practical applications in food quality and safety assessment, offering valuable insights into the presence of KA in food products.

The capped CdS-ZnS quantum dots (QDs) were synthesized with various thiol capping agents of glycolic acid (TGA), mercaptosuccinic acid (MSA), and L-cysteine (LCY) and used as fluorescence probe for determination of Cu (II) ions. The method of two-level three-factor full-factorial experiment design was used to achieve the best optical fluorescence emission. Results revealed that Cu (II) ions can effectively quench the emission of QDs, and the fluorescence intensity is linearly decreased with increasing Cu (II) ion concentration. The limit of detection for CdS-ZnS@ QDs capped with TGA, MSA, and LCY was obtained at 1.15 × 10-7, 1.32 × 10-7, and 2.19 × 10-7 mol L-1, respectively, with linear dynamic range of 3.13 × 10-6 to 1.41 × 10-4 mol L-1. Luminescence quantum yields of CdS-ZnS@LCY, CdS-ZnS@MSA, and CdS-ZnS@TGA were obtained at 4.17, 1.92, and 2.47, respectively. Results indicated that no significant quenching occurred in the presence of the other metal ions. The binding constant (Kb) of capped CdS-ZnS@ QDs with Cu2+ and the other metal ions was also investigated and discussed. The Kb value for Cu2+ was obtained considerably more than that the other ions. This work presents a new and sensitive method for determination of Cu2+ ion.

A highly water-soluble and fluorescent N,S-doped carbon dots/europium (N,S-CDs/Eu) was successfully synthesized via a secondary hydrothermal method. This involved surface modification of N,S-CDs derived from sunflower stem pith (SSP) with europium ions (Eu3+) doping. When excited within the range of 400-470 nm, N,S-CDs/Eu exhibited a stable and broad optimal emission wavelength ranging from 505 to 540 nm. Notably, the photoluminescence quantum yield (PLQY) of N,S-CDs/Eu is 31.4%, significantly higher than the 19.5% observed for N,S-CDs. Additionally, by dissolving N,S-CDs/Eu into polyvinyl alcohol (PVA), a uniform fluorescent anti-counterfeiting ink can be prepared. The N,S-CDs/Eu/TiO2 composite demonstrates excellent photocatalytic degradation ability towards the organic dye methylene blue (MB). N,S-CDs/Eu has potential in the field of fluorescent inks and photocatalysis due to its simple and efficient preparation and excellent properties.

The microenvironment of wound healing is susceptible to bacterial infection, chronic inflammation, oxidative stress, and inadequate angiogenesis, requiring the development of innovative wound dressings with antibacterial, anti-inflammatory, antioxidant, and angiogenic capabilities. This research crafted a new multifunctional bacterial cellulose composite membrane infused with copper-doped carbon dots (BC/Cu(II)-RCDs). Findings validated the successful loading of copper-doped carbon dots onto the BC membrane via hydrogen bonding interactions. Compared to the pure BC membrane, the BC/Cu(II)-RCDs composite membrane exhibited significantly enhanced hydrophilicity, tensile properties, and thermal stability. Diverse in vitro assays demonstrated excellent biocompatibility and antibacterial activity of BC/Cu(II)-RCDs composite membranes, alongside their ability to expedite the inflammatory phase and stimulate angiogenesis. In vivo trials corroborated the membrane\'s ability to foster epithelial regeneration, collagen deposition, and tissue regrowth in full-thickness skin wounds in rats while also curbing inflammation in infected full-thickness skin wounds. More importantly, the treatment of the BC/Cu(II)-RCDs composite membrane may result in the activation of VEGF and MAPK signaling proteins, which are key players in cell migration, angiogenesis, and skin tissue development. In essence, the developed BC/Cu(II)-RCDs composite membrane shows promise for treating infected wounds and serves as a viable alternative material for medicinal bandages.

BACKGROUND: Curcumin has been used in traditional medicine because of its pharmacological activity, including antioxidant, antibacterial, anticancer, and anticarcinogenic properties. Therefore, sensitive and selective monitoring of curcumin is highly demand for practical application.
RESULTS: In this study, we describe the construction of a fluorescence method for curcumin assay based on nitrogen-doped MoS2 quantum dots (N-MoS2 QDs). The N-MoS2 QDs are constructed by a solvothermal method using sodium molybdate and Cys as precursors. With the addition of curcumin, the bright blue fluorescence of N-MoS2 QDs is quenched by the inner filter effect (IFE). The QDs emitted bright blue fluorescence and could be quenched by the addition of curcumin via IFE. The dynamic range is the range of 0.1-10 μM for curcumin detection, with a detection limit of 59 nM. N-MoS2 QDs were applied for curcumin assay in real samples with good recovery. In addition, the N-MoS2 QDs exhibited relative low cytotoxicity and could be applied for fluorescence-based imaging in biological samples.
CONCLUSIONS: Our study indicates that the sensor possesses good selectivity to monitor curcumin in water samples, human urine samples, ginger powder samples, mustard samples, and curry samples with satisfactory recoveries. The N-MoS2 QDs possess less cytotoxicity with excellent biocompatibility and were applied for in vitro cell imaging.

Advancement in the development of new materials with theranostic and phototherapeutic potential along with receptiveness to external stimuli has been persistently inspiring oncology research. Herein, titanium carbide-based MXene quantum dots (FHMQDs) have been synthesized and modified to take advantage of stimuli-responsive behavior and target specificity for breast cancer cells. With a size of around 3 nm, the developed FHMQDs demonstrate high fluorescent emission at around 460 nm. With ∼90 % encapsulation efficiency of doxorubicin (DOX), the developed system also offers rapid DOX release behavior when encountering an acidic pH (5.4). Further, the in vitro assessment of the developed FHMQDs on MDA-MB 231 breast cancer cells presents excellent target specificity to cancer cells which was reflected by its high cytotoxicity against cancer cells. Additionally, the outstanding photodynamic efficiency of FHMQDs due to excessive Reactive Oxygen Species (ROS) generating ability along with apoptosis promoting capability of FHMQDs in cancer cells demonstrates a synergistic approach in cancer theranostics. Encouragingly, the fabricated FHMQDs also exhibited fluorescent labelling and bioimaging capacity which makes it an incredible platform that ensures theranostic excellence in breast cancer research.

Okadaic acid (OA), a predominant toxic entity in Diarrhetic Shellfish Poisoning (DSP), carries substantial significance for both marine ecosystems and human well-being. The nascent organic photoelectrochemical transistor (OPECT) biosensor has emerged as a promising biometric methodology, poised to offer a fresh realm for the detection of marine biotoxins. In this work, a biosensor utilizing signal amplification based on Cd0.5Zn0.5S/ZnIn2S4 quantum dots (CZS/ZIS QDs) in OPECT was proposed for OA detection, where ZIS QDs were labeled on aptamer and a substantial quantity of QDs were generated via cyclic shearing facilitated through target-induced Exo I enzyme. Owing to the sensitizing influence of ZIS QDs on CZS, the photoelectric conversion efficiency was augmented, culminating in a notable anodic photocurrent upon exposure to light, thereby inducing a transformation in the channel state of the polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) and consequently producing a remarkable modification in the channel current. The detection limit of the biosensor as low as 12.5 pM and a superior stability and specificity was confirmed, which also showed commendable outcomes in actual samples testing. Consequently, this study not only introduces a novel pathway for swift OA detection, but unveils a novel perspective for future expedited and convenient on-site detection of marine biotoxins.

This study presents an efficient chemiluminescence (CL) probe based on perovskite nanocrystals (NCs) for detection of L-cysteine (L-Cys). It consists of nickel-doped CsPbBr3 NCs embedded in the mesoporous SiO2 matrix as CL reagent and cerium (IV) as an oxidant in aqueous environment. The probe was designed for the highly selective determination of L-Cys based on its remarkable enhancing effect on the CL intensity. The colloidal nanocomposite of nickel-doped CsPbBr3 NCs@SiO2 with photoluminescence quantum yield of 58% was fabricated by ligand-assisted re-precipitation method and characterized by using UV-Vis absorption, FT-IR, X-ray diffraction, and transmission electron microscopy. The sensor was utilized to determine L-Cys in the linear concentration range of 20-300 nM with a detection limit of 12.8 nM. Direct chemical oxidation of Ni-doped CsPbBr3 NCs@SiO2 by Ce(IV) was the single cause of the formation of the excited-state NCs and subsequent production of CL. The developed probe provides outstanding selectivity towards L-Cys over structurally related compounds. Accurate determination of L-Cys in human serum samples was achieved without interference, and the results were confirmed by HPLC method.

Easy, economical, and swift detecting tools are very demanded for assaying various chemical species. The introduction of label-free paper-based read-out devices has significantly reached the demand of analytical science for target analytes assays. Herein, a facile, and disposable inexpensive paper-based sensing tool was fabricated for sensing As3+ ion using graphene quantum dots (GQDs) as a fluorescent reader. The CA-GQDs were synthesized using citric acid (CA) as a precursor via the pyrolysis method, further physisorbed on the cellulose substrate for sensing of As3+ via aggregation-based fluorescence \"turn-off\" mechanism. The linear range for quantitating As3+ ion is in the range of 0.05-50 μM with a detection limit of 10 nM. The practical application of the CA-GQDs-based analytical platform was verified by assaying As3+ ion in water samples. The CA-GQDs-embedded paper strip can be easily extended for assaying of As3+ ion, which meets the demand for monitoring of As3+ ion in real samples.