Anhui Jianzhu University

Carbon dots (CDs) have been widely employed to fabricate various fluorescent chemosensors owing to their favorable photo-physicochemical properties and versatile surface modification feasibility. However, reports on CDs as a dual recognition platform for sensitive and selective detection of different analytes are very limited. In this study, highly negatively charged green emitting nitrogen-doped CDs were synthesized by a hydrothermal approach using 1,3,6-trinitropyrene and ascorbic acid as precursors, which subsequently self-assembled with positively charged methylviologen (MV²⁺) and polyethyleneimine (PEI) to form CDs-MV²⁺ and CDs-PEI nanocomposites, respectively, by electrostatic interaction and hydrogen bond. Based on the facts of forming tetrahedral anionic glucoboronate esters between organic boronic acids and diol-containing compounds, and a Meisenheimer complex between amino groups and 2,4,6-trinitrotoluene (TNT), CDs-MV²⁺ for glucose detection and CDs-PEI for TNT detection were surveyed. The CDs-based nanocomposites exhibited highly sensitive and selective responses to analytes by turning off or on the green emission of the CDs, showing a very good linearity in the ranges of 0.05-200 mM glucose with 0.036 mM of LOD for CDs-MV²⁺, and of 5-160 nM TNT with 3.2 nM of LOD for CDs-PEI. No matrix interferences were found. The proposed method is conducive to develop a dual/multiple targets sensing platform for detecting related or unrelated analytes.

Electrically Modulated Surface-enhanced Raman spectroscopy (E-SERS) technology can effectively increase Raman signal intensity. Compared with conventional E-SERS, self-powered E-SERS sensors provide an electric field through energy conversion, which reduces the dependence on external power sources and thus facilitates the development of portable real sample detection. Herein, high-performance piezoelectric lead zirconate titanate (PZT) with dopamine-functionalized reduced graphene oxide (rGO@PDA) was embedded into a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) matrix, which was innovatively used for E-SERS technology. In particular, by applying external pressure to the PVDF-TrFE/PZT-rGO@PDA/Ag self-powered sensors, the surface localized electromagnetic field can be efficiently enhanced, which combines with the localized surface plasmon resonance (LSPR) effect of the Ag nanoparticles (NPs) to achieve highly tunable signal enhancement. As a proof-of-concept, voltage and current signals were generated by pressing the substrate, and Raman signal enhancement was also realized for molecules such as Rhodamine 6G (R6G) and Methyl Orange (MO). The self-powered sensor exhibits ultra-high sensitivity and excellent reproducibility for a wide range of probe molecules, especially thiram, with a low limit of detection (LOD) of 10^-12 M, determining a low variation of 8.5 %. Additionally, the substrate successfully detected 10^-7 M malachite green (MG) fungicide residue on fish skin and 10^-7 M sulfamonomethoxine (SMM) antibiotic residue in chicken breast by pressing, proving its great potential for application in food contaminant monitoring.

Development of NIR type I photosensitizers (PSs) that can specifically target subcellular organelles remains a significant challenge in photodynamic therapy (PDT). In this work, two D-π-A PSs named TPE-IN and TPA-IN were constructed via the strategy of changing donors. In detail, replacing donor group tetraphenylethylene (TPE-IN) with triphenylamine (TPA-IN) could extend the emission wavelength of PSs into the NIR-I region. Meanwhile, the singlet-triplet energy gap (ΔE_ST = 0.53 eV) of PSs was also narrowed, which efficiently promoted the production of superoxide anion radical (O₂^-) and hydroxyl radical (OH), especially for TPA-IN. Further mechanistic studies demonstrated that the generation of OH mainly relied on the cascaded electron-transfer process mediated by the Haber-Weiss reaction (O₂^- → H₂O₂ → OH). More importantly, TPA-IN could specifically accumulate in mitochondria through electrostatic interactions (Pr = 0.81), which could decrease mitochondrial membrane potential, inducing cell late apoptosis (95.8 %) upon light exposure. This study established innovative theoretical and technological groundwork for designing high-efficiency, precision-targeted optical theranostic agents aimed at eliminating cancer cells.