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In this presented work, a series of designs and experiments have been constructed to study how a DNA structure affected the fluorescence of silver nanoclusters (AgNCs). A "bulb"-like DNA structure was firstly used as the synthesizing template, and bright green-emitting AgNCs were obtained with a quantum yield of 17.2%. The "DNA bulb" structure was assembled using three single-stranded oligonucleotides (ssDNAs), with a flexible ssDNA part serving as the "filament". The results seemed intriguing as luminous AgNCs could be obtained only when the complete spatial structure was formed. To further investigate the role of the "bulb" structure, thirteen cytosine-rich sequences were employed as the "filament", respectively. Interestingly, the fluorescence intensities of AgNCs were all enhanced after the "filament" ssDNA was integrated into the "bulb" structure. The enhancement was as much as 175.2-fold, and the minimum enhancement was 1.3-fold. Spectral analyses were then conducted to give an understanding of the role of cytosine. When the sequences in the "bulb shell" were changed, the "DNA bulb" structure still showed an enhancing effect. Finally, the green-emitting AgNCs were utilized toward the selective detection of Hg2+ to demonstrate potential applications.

[Display omitted] • A dual-ligand laccase mimic enzyme (Cu-BH) with excellent fluorescence properties is successfully constructed. • The substrate for laccase mimic enzymes is extended from traditional phenolic to amines inspired by natural laccase. • Cu-BH exhibits both favorable catalytic activity stability and fluorescence signal stability. • A multi-modal sensing strategy based on Cu-BH/OPD with boosted catalytic activity and fluorescence signal amplification is adopted for kanamycin analysis. • The visualization of kanamycin analysis is achieved by RGB reading from a smartphone. A copper-based dual-ligand biomimetic enzyme (Cu-BH) inspired by natural laccase was constructed, which had promising laccase-like activity and excellent fluorescence properties. More remarkably, Cu-BH can oxidize not only traditional phenolic substrates, but also catecholamines and amine substrates. As expected, OPD could be catalyzed by Cu-BH to produce the yellow fluorescent product DAP with absorbance and emission peaks at 426 nm and 566 nm, respectively. The generated DAP could quench the Cu-BH fluorescence at 440 nm by fluorescence internal filtration effect (IFE), thus constructing a ratiometric fluorescence signal(F 566 /F 440). Kanamycin further promoted the catalytic activity of Cu-BH by accelerating electron transfer, resulting in a gradual increase in absorbance at 426 nm and fluorescence signal amplification at 566 nm. Based on this, a sensitive dual-mode sensing strategy was established to analyze kanamycin with the LOD of 0.033 and 0.26 nM, which was successfully applied to the monitoring of kanamycin in tap water, milk and honey. The visualization analysis was also achieved by RGB reading from a smartphone. In conclusion, this novel biomimetic enzyme (Cu-BH) had provided a new application path in bioanalysis and environmental monitoring. [ABSTRACT FROM AUTHOR]

The elegant electroswitchable color/emission properties of electrochromic/electrofluorochromic dual-functional materials motivates the exploration of their new applications. In this work, a new poly (urea-urethane) was synthesized via nucleophilic copolymerization of electroactive oligoaniline derivative, solid-emissive tetraphenylethylene groups, and alkyl isocyanate. The resultant poly (urea-urethane) exhibited good electroactivity and desirable aggregation-induced emission properties. High-performance electrochromic/electrofluorochromic behavior had been disclosed with a high optical contrast ratio of ΔT = 50.4%, a moderate fluorescence on/off ratio of 10.5, and high coloration efficiency of 503 cm2/C at 768 nm. A reflective/emissive dual-mode display device had also been manufactured based on the resultant poly (urea-urethane) and charge-balancing V 2 O 5 , exhibiting a reversible color change and tunable fluorescence conversion upon the electric stimulus. Furthermore, this polymer showed an interesting color/fluorescence response to H 2 O 2 , due to the linkage mechanism between its redox states and optical properties. The spray-coated poly (urea-urethane) test strips were employed in visualized dual-determination of H 2 O 2 with gradual color change from gray to dark green, along with an obvious fluorescence change from light blue to dark, which displays easy operation and rapid detection. This work reports the synthesis of an electrochromic/electrofluorochromic poly (urea-urethane) bearing AIE-active groups and electroactive oligoaniline segments, which shows great potentials in reflective/emissive dual-mode display and colorimetric/fluorometric dual-determination of H 2 O 2. [Display omitted] • A new poly (urea-urethane) (PUU) bearing AIE and oligoaniline groups was synthesized. •PUU displays electrochromic/electrofluorochromic dual-functional performance. •A reflective/emissive dual-mode display device was fabricated based on PUU and V 2 O 5. •Spray-coated PUU test strips were employed in visualized dual-determination of H 2 O 2. [ABSTRACT FROM AUTHOR]

DNA-templated silver nanoclusters (DNA-AgNCs) is a kind of fluorescent nanoclusters in-situ synthesized on DNA, thereby giving the DNA probe an inherent function of label-free signal output. Herein, the DNA-AgNCs with a GCC-loop-structure which has a quantum field of 51.6% was firstly proposed. It was proved that the addition of the double-stranded structure on the GCC-loop drastically enhanced the fluorescence intensity of the AgNCs. Through the further studies of the relationship between DNA secondary structure and AgNCs, a kind of DNA-AgNCs-probe was designed based on the change of the secondary structure which was induced by the target strand. By this, the fluorescence signal of probe was in "turn on" mode. The probe system could be directly used for the detection of Norovirus RNA, which had a linearity of 20 nM to 1.8 μM with a detection limit of 18 nM. Moreover, this detection platform was also selective to differentiate mismatched RNA. It was expected to be a universal method for different RNA detection by changing the recognition sequence of the probe. • The biosensor succeeds in realizing the quantitative detection of the target RNA. • DNA-templated silver nanoclusters with a quantum yield of 51.60% was found. • It was found that DNA with stable secondary structure facilitates the formation of fluorescent silver nanoclusters. • The constructed probe has great potential in label-free detection of the nucleic acids. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sulfydryl-functionalized nitrogen-doped carbon dots (SH-NCDs) was synthesized and used to detect patulin selectively. • The addition reaction between patulin and the -SH on the SH-NCDs surface resulted in enhanced fluorescence. • The SH-NCDs fluorescent sensor has a high sensitivity for patulin detection with a LOD of 0.053 ng mL−1. In this study, sulfydryl-functionalized nitrogen-doped carbon dots (SH-NCDs) was synthesized by amide reaction of hydrothermally synthesized carbon dots with l -cysteine and used to detect patulin selectively. The SH-NCDs exhibited excitation wavelength-independent fluorescence in the range 300–360 nm. The modified sulfhydryl group (-SH) on the surface of NCDs served as a specific recognition site to capture patulin. The addition reaction between patulin and the -SH on the SH-NCDs surface resulted in enhanced fluorescence. SH-NCDs was used as a fluorescent probe for label-free detection of patulin, showing excellent sensitivity in the linear range of 0.1–400 ng mL−1, with detection limits as low as 0.053 ng mL−1. The fluorescent probe has specific selectivity for patulin. The recoveries of patulin in apple juice and grape juice were 88.9 %–99.2 % and 92.5 %–101.8 %, respectively. These results showed that the sensor designed in this experiment selectively detected the target patulin from complex food systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Natural N and S co-doped carbon dots (NSCDs) were fabricated by hydrothermal method. • The prepared NSCDs exhibited a blue emission with a quantum yield up to 18.57%. • An "off–on" fluorescence sensor for pentachlorophenol (PCP) assessment has been successfully established. Natural N and S co-doped carbon dots (NSCDs) were synthesized via hydrothermal synthesis using food-derived crawfish shells as green precursors. The relationship between quantum yield (QY) and protein content of six crawfish shells treated with different alkalis was investigated. The synthesized NSCDs displayed a large QY of 18.57 %, which was higher than most of the chitin-derived CDs. Due to the oxidation of hydroxyl radicals, adding H 2 O 2 and horseradish peroxidase (HRP) quenched the fluorescence of NSCDs, resulting in a detection limit (LOD) of 1.25 μM for H 2 O 2. The addition of pentachlorophenol (PCP) was supposed to consume part of the hydroxyl radicals and protect NSCDs from being oxidized. Accordingly, a facile and rapid "off–on" fluorescence sensor was developed to detect PCP with a LOD of 2.30 μM. Further, the method described was successfully used to detect PCP in three real samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new ionic liquid featuring electroactivity and fluorescence (EFIL-TTM) is proposed. • EFIL-TTM//BQ device exhibits reflective/emissive dual-modal display behavior. • Low driving voltage, fast switching speed, and good cycling durability are disclosed. • The device without electrolyte salt can show color/fluorescence change behavior. Integrated reflective and emissive dual-modal displays capable of versatile applicability in both bright and dark environments have promoted the development of electrochromic/electrofluorochromic bifunctional materials, whose color and fluorescence properties can be electrochemically modulated on demand. However, conventional electrochromic/electrofluorochromic devices suffer from slow response speed and low long-term durability. Herein, an electroactive fluorescent ionic liquid (EFIL-TTM) was facilely synthesized based on electroactive triphenylamine, fluorescent tetraphenyl ethylene, and ionic conductive imidazole groups, exhibiting desired electrochemically-induced color and fluorescence change synchronously. A quasi-solid-state electrochromic/electrofluorochromic device based on EFIL-TTM exhibited desirable simultaneous reflective and emissive display behavior of low driving voltage (0.7 V), fast response speed (color: 0.8/1.1 s; fluorescence: 1.7/2.3 s), and outstanding cycling durability (color retention of 97 % and fluorescence retention of 94 % after 10,000 cycles). It was intriguing that an EFIL-TTM//BQ device without electrolyte salt could still exhibit acceptable reflective/emissive dual-modal display behavior. Considering its facile synthetic strategy, scalable assembled approach, and superior performance, this EFIL-TTM-based electrochemical device may provide another avenue for the synergetic improvement of reflective/emissive dual-modal display performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ligand's conformational changes during the synthesis of SP-AuNCs were investigated. • The fluorescence intensity was dominated by the Au nucleus in early phases. • An ordered-disordered-ordered structure transition happened to the ligand. • The growth of Au core and LMCT caused the structural changes of protein ligand. In this paper, the potential relationship between fluorescence and changes in the ligand conformation observed during the synthesis of soy protein-templated fluorescent gold nanoclusters (SP-AuNCs) was studied using a series of spectroscopic techniques. The results show that the determinants of the fluorescence effect in SP-AuNCs changed with the reaction time during the synthesis process. In the early stage of the reaction (within 60 min), the fluorescence intensity was dominated by the Au nucleus, followed by the combination of the Au nucleus and protein ligand. The structure of the protein ligand also underwent a transition from ordered to disordered to ordered. At the same time, its role in the reaction also changed from providing the reducing power to protecting the Au nucleus and contributing to the transition of the fluorescence effect in the AuNCs via ligand-to-metal charge transfer (LMCT). Using two-dimensional (2D) photon spectra correlation analysis, the formation and growth of the Au nuclei and the LMCT effect observed during the synthesis of the SP-AuNCs were found to be the major causes for the changes in the conformation of the protein ligand. Our results are an important discovery and can be used to explain the mechanism of protein ligands in the synthesis of gold nanoclusters. [ABSTRACT FROM AUTHOR]

This review specifically focused on the natural protein-templated fluorescent gold nanoclusters (AuNCs). The syntheses and applications of different natural protein-templated AuNCs were summarized and classified by two groups: animal protein and plant protein. Some merits, challenges and prospects in this research area were dialectically discussed to arouse the interest of researchers in food science. • This review focused specifically on the naturual protein-templated fluorescent gold nanoclusters. • The main contents were organized based on the natural protein classification: animal and plant proteins. • Fundamental of synthesis was comprehensively and carefully discussed. • Recent reported protein-templated gold nanoclusters were collected in one table with application details. • Drawbacks and prospects were discussed in the last part of this review. For the past decades, the synthesis of metal nanoclusters has been a great interest for research, for their unique physicochemical properties and great contributions to the catalytic, electrical and biomedical applications. Protein-templated gold nanoclusters (AuNCs) is a kind of fluorescent nanomaterials with good solubility, excellent stability, biocompatibility, decent quantum yields and active groups (–COOH, –NH 2) for facilitating modifications. Natural proteins are easily available, commercially affordable, diverse and multitudinous in animals, plants and foods, which provide a template pool for the exploration of AuNCs. This is one of the few reviews of specifically focusing on the natural protein-templated fluorescent AuNCs. The syntheses, properties and applications of different AuNCs were enumerated. Prospects were given on utilizing structure-modified proteins, bioactive enzymes, antibodies which should endow the AuNCs more favourable fluorescence performances and functional characteristics. The applications of AuNCs in analytical, biomedical and food sciences would be further heightened. [ABSTRACT FROM AUTHOR]