Changlun Tong

Rapid and on-site detection of formaldehyde (FA) is very important for public health. A ratiometric fluorescence and colorimetric dual-mode probe was fabricated for on-site and visual detection of FA based on Cu-MOFs-Eu³⁺-GMP/OPD composite catalysis. The Cu-MOFs-Eu³⁺-GMP was prepared by modifying copper-metal organic frameworks (Cu-MOFs) with europium/nucleotide coordination polymer nanoparticles (Eu³⁺-GMP), which could significantly enhance the water stability and fluorescence quantum yield of Cu-MOFs. The Cu-MOFs-Eu³⁺-GMP can directly catalyze OPD to yield a fluorescent and color product of 2, 3-diaminophenazine (DAP) via intrinsic oxidase-like activity, while the blue fluorescence of Cu-MOFs-Eu³⁺-GMP can be quenched by DAP via the inner filter effect (IFE). FA can specifically react with OPD to generate the Schiff base products, which restricts the yield of DAP and causes the recovery of the blue fluorescence and results in the solution fading from yellow to colorless. The dual-mode sensing platform has high sensitivity and excellent selectivity and can also be applied for ratiometric monitoring of FA in living cells. Furthermore, a point-of-care testing (POCT) strategy including a portable smartphone and hydrogel sensor was developed for on-site and visual measurement of FA in the vapor phase. A portable luminescent logic detector for the gradual determination of FA in the vapor phase was also fabricated. This work provides a new strategy for improving selectivity in catalytic systems and a useful approach for on-site and real-time qualitative identification and semiquantitative detection of FA in indoor air.

Chronic hyperglycemia in diabetes induces oxidative stress through excessive production of reactive oxygen/nitrogen species (ROS/RNS), leading to elevated 3-nitro-l-tyrosine (3-NT) concentration and depletion of endogenous antioxidants. This study presents a dual-mode sensing platform for simultaneous quantification of 3-NT and total antioxidant capacity (TAC) based on nitrogen- and boron-codoped carbon dots confined within AlPO-5 zeolite (N,B-CDs@AlPO-5). The composite exhibits robust room-temperature phosphorescence (RTP) with a quantum yield of 31.29% and a lifetime of 1.56 and 6 s aqueous afterglow. Leveraging these properties, time-resolved phosphorescence detection of 3-NT (10-1000 μM) with a detection limit of 2.19 μM is achieved due to the synergistic inner filter effect and static quenching. Concurrently, the composite's excited triplet state-induced generation of superoxide radicals (O₂^.-) and Mn²⁺ → Mn³⁺ redox cycling collaboratively mediate 3,3',5,5'-tetramethylbenzidine (TMB) oxidation to form blue ox-TMB, enabling colorimetric analysis of antioxidants and achieving ascorbic acid determination (5-50 μM) with a detection limit of 1.47 μM. Crucially, the RTP platform demonstrates clinical utility through reliable simultaneous detection of 3-NT and TAC in urine samples. This dual-mode sensing strategy establishes a novel paradigm for diabetes screening through rapid and noninvasive urinalysis through multidimensional biomarker verification.

A sensitized dual-response ratiometric fluorescent sensor integrated smartphone platform for accurate discrimination and detection of tetracycline (TC) homologues was fabricated based on N-CDs-Eu³⁺ complex. In the sensing system, N-CDs act as a sensitizer of Eu³⁺ and significantly enhance the fluorescence of TC-Eu³⁺ complex approximate 40-fold owing to the synergistic effect of antenna effect (AE) and fluorescence resonance energy transfer (FRET). A paper sensor integrated with a smartphone platform is further fabricated for on-site measurement of TC. The proposed sensing platform exhibits an obvious color change from blue to red with limit of detection (LOD) of 1.5 and 63.2 nM for spectrofluorimetry and paper sensor, respectively. In addition, to eliminate the interference from TC homologues, a simple and effective sensor array was constructed by regulating the pH of the system. The different fluorescence responses to four tetracycline homologues used widely (TC, OTC, CTC, and DOX) were examined and dealt with principal component analysis, and accurate differentiation of TC homologues was therefore achieved. This work provides an integrated method for identification and synchronous quantitative detection of TCs, and a potential application for visual and on-site detection of TCs in environmental monitoring and food safety. Graphical Abstract

A dual-emission ratiometric fluorescence probe for the simultaneous detection of tetracycline (TC) and Fe³⁺ in aqueous solution was fabricated based on a boron-doped carbon quantum dot (B-CQD)/CdTe–Eu³⁺ composite.