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The development of immobilization method of a chemoprobe on solid support without sacrificing its good original performance in homogeneous solution is a tricky problem. Herein, we make use of the transparent agarose hydrogel with semi-wet property which provided appropriate microenvironment to immobilize the chemoprobe and maintained its original performance to develop an excellent smartphone-enabled colorimetric platform. As a proof of concept, the sensing platform was fabricated with agarose hydrogel that captured diethylaminoethyldextran chloride (DEAE-dextran) and dithiothreitol modified copper nanoclusters (Cu NCs) as a fluorescence probe. Benefiting from the aggregation-induced emission (AIE) effect and confinement effect of hydrogel, the fluorescence quantum yield (QY) of Cu NCs hydrogel is three times higher than that of Cu NCs. Moreover, sensitively detection of Cr(VI) can be realized in the concentration range of 0.07–38.00 μM based on the amplified fluorescence probe. The outstanding analysis performance for Cr(VI) is also achieved when Cu NCs hydrogel was directly immobilized on paper as a smartphone-enabled colorimetric platform, indicating that our strategy can promote the further development of the application of hydrogel materials. [Display omitted] • An AIE-active copper nanoclusters (Cu NCs) functionalized hydrogel was prepared. • The amplified fluorescent detection of Cr(VI) by Cu NCs hydrogel was achieved. • Cu NCs hydrogel as a smartphone-enabled colorimetric platform showed an outstanding performance of detecting Cr(VI). • Smartphone-enabled colorimetric platform can realize instrument-free, portable and on-site detection of Cr(VI). [ABSTRACT FROM AUTHOR]

Carbon dots without heteroatoms-doping and surface modifications were designed to be a novel chemosensing strategy on the quantitative detection of uric acid (UA) with the aid of uricase-induced enzymatic reaction and Fenton reaction. In this work, ascorbic acid (AA)-derived carbon dots (A-CDs) were prepared in the mixture of ethanol and water via one-step hydrothermal synthesis at a relatively low temperature (120 °C) for 10 h. The resultant A-CDs were proved to be excitation-independent. When excited at the wavelength of 420 nm, the nanodots displayed green fluorescence (535 nm) which was then linearly quenched as UA concentration increased in the range of 0–56 μM, according to which the detection limit was calculated to be 0.49 μM. With regards to the excellent sensitivity and selectivity to UA, real sample assay was performed on the A-CDs detection system, which provided relatively reliable recoveries of UA contained in human serum/urine. Besides, in view of the high quantum yield, the A-CDs were applied to live-cell imaging assay and were considered to become an alternative tracer tool in biomedical imaging. [Display omitted] • Carbon dots are prepared at a relatively low temperature without heteroatoms doping and surface modification. • The sensing system based on the carbon dots has a low detection limit to uric acid. • The system not only allows for quantifying uric acid and H 2 O 2 , but also possesses the imaging ability to living cells. [ABSTRACT FROM AUTHOR]

• Carbon dots were made from nitrogen-rich adenine via simple hydrothermal strategy. • The sensing mechanism of carbon dots was based on aggregation-induced enhanced emission (AIEE). • Carbon dots can efficiently detect and quantify ClO− in real water samples. A novel fluorescent chemosensing strategy on the detection and determination of hypochlorite (ClO−) based on fluorescence enhancement was reported. In this work, nitrogen-doped carbon dots (N-CDs) were prepared via one-step hydrothermal conversion of nitrogen-rich adenine and ethylenediamine. The N-CDs solution showed excitation-dependent characteristic and displayed green fluorescence (535 nm) when excited by blue light (480 nm). The fluorescence intensity was linearly enhanced with the concentration of ClO− increasing in the range of 0.01–1 mM, and the limit of detection was calculated to be 0.82 μM. Other than the common oxidation of the N-CDs surface by ClO−, spectra change stemmed mainly from aggregation-induced enhanced emission (AIEE), including π-π staking and J-aggregation, which together induced red-shift absorption band and effective fluorescence enhancement. Based on the good sensitivity to ClO−, the N-CDs probe also underwent real sample assay and gave relatively reliable recoveries of ClO− contained in various water samples. In addition, the N-CDs showed excellent anti-interference in the selectivity test and exhibited good stability in complex solution environment with different pH values or ion strengths. In view of the results, the N-CDs sensing probe has impressive sensitivity and selectivity on ClO− determination and possesses good potential on bioimaging applications. [ABSTRACT FROM AUTHOR]