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Developing hollow-structure quantum dot carriers to increase quantum luminous efficiency is a creative idea for designing a novel sensor. A ratiometric hollow CdTe@H-ZIF-8/CDs@MIPs sensor was developed for the sensitive and selective detection of dopamine (DA). CdTe QDs and CDs were used as the reference signal and recognition signal, respectively, and thus showed a visual effect. MIPs provided high selectivity toward DA. The TEM image demonstrated that the sensor was a hollow structure, which could have ample opportunity to excite quantum dots to emit light through multiple light scattering through holes. In the presence of DA, the fluorescence intensity of the optimum CdTe@H-ZIF-8/CDs@MIPs was remarkably quenched by DA, achieving a linear range of 0–600 nM and a limit of detection of 12.35 nM. The developed ratiometric fluorescence sensor showed an obvious and meaningful color change with a gradual increase in DA concentration under a UV lamp. Moreover, the optimum CdTe@H-ZIF-8/CDs@MIPs was remarkably sensitive and selective in detecting DA among various analogs and showed good anti-interference ability. The HPLC method also further confirmed that CdTe@H-ZIF-8/CDs@MIPs shows good practical application prospects. [ABSTRACT FROM AUTHOR]

The fluorescence detection of environmental pollution residues is hugely significant; thus, the improvements in sensitivity and selectivity are still a great task. In this work, a novel molecularly imprinted fluorescence sensor (CDs&ZIF-8@MIPs) with a core–shell structure was prepared for the highly sensitive and selective quantification of malachite green (MG). The high sensitivity was contributed from carbon dots (CDs) as the fluorescence materials and ZIF-8 nanoparticles served as the support materials to ameliorate the dispersibility of CDs. The high selectivity is mainly derived from fabricating thin molecular imprinting polymers in ZIF-8 surfaces. Under the optimum conditions, CDs&ZIF-8@MIPs displayed rapid reaction time (2.0 min), lower detection limit (2.93 nM) with the concentration linear range of 20–180 nM and high selectivity to MG among MG analogs. Importantly, the developed monitoring method was successfully applied to MG determination with the satisfactory recoveries in environmental water samples. This present work effectively improved the sensitivity and selectivity of fluorescence sensors for MG detection. [ABSTRACT FROM AUTHOR]

In this study, a conversion method and molecular imprinting technology were used to design molecularly imprinted polymers (MIP)-based ratiometric fluorescence test papers. The ZnO quantum dots (ZnO QDs) acted as the background quantum dots and ZIF-8 raw material. Carbon dots (CDs) were used as the identification signals. The imprinting layer achieved a selective function. Therefore, a ZnO@ZIF-8/CDs@MIPs sensor was designed for the detection of Bisphenol A (BPA). The sensor exhibited a fast response time for BPA detection. In addition, the sensor demonstrated that effective detection of BPA can still be achieved in complex environments. The detection limit of this sensor was 0.778 nM with a linear range of 0–60 nM. The corresponding test solutions exhibited clear changes from blue to yellow. The selectivity experiments results demonstrated that ZnO@ZIF-8/CDs@MIPs only exhibit excellent selective recognition effect for BPA. ZnO@ZIF-8/CDs@MIPs-2 was used for the detection of BPA in canned food and compared with the results of HPLC detection of BPA. The two spiked recovery ranges were 96.58–102.04% and 97.43–103.82%, respectively. In addition, the prepared ZnO@ZIF-8/CDs@MIPs-2 test paper visually recognized BPA under ultraviolet light. This study provides guidelines for the design and application of fluorescent test papers for quick detection in practical applications. A ZnO@ZIF-8/CDs@MIPs fluorescence sensor was constructed for selective and sensitive detecting bisphenol A (BPA) with naked-eye observation. [Display omitted] • ZnO@ZIF-8 core-shell nanodots were prepared by self-template method. • A novel ZnO@ZIF-8/CDs@MIPs-2 with visualization and selectivity was synthesized by precipitation polymerization. • Portable fluorescent test strips were designed for timely detection. • The actual sample detection results of the fluorescence sensor were consistent with HPLC method. [ABSTRACT FROM AUTHOR]

In this paper, a novel fluorescent nanoswitch based on carbon dots (CDs) was developed for the sensitive and selective determination of Hg and I. The CDs were obtained by simple hydrothermal process and had a strong fluorescence emission at 440nm. The fluorescence of the CDs can be selectively quenched by Hg ion, and then the I was added into the system, which can interact with Hg and recover fluorescence of the CDs. Under optimal conditions, the quenching fluorescence intensity on addition of Hg has obtained a satisfactory linear relationship covering the linear range of 0-50M with the linear relationship (), and the limit of detection is 0.047M. The additions of I could lead to the fluorescence intensity of the solution of CDs and Hg (50M) recover rapidly, which is linearly related () to the concentration of I in the range from 0 to 70M, the detection limit for I was calculated to be 0.084M. Moreover, the developed method to detect Hg and I was evaluated in real examples, and the fluorescence switching can sensitively and selectively detect Hg and I over some potentially interfering ions, the recoveries were up to 97.8-107.0% and 96.7-106.6%, respectively. A water-soluble fluorescent nanoswitch of carbon dots (CDs) has been designed for detecting Hg and I, which was fabricated by hydrothermal process. Hg ions can be recognized by the amino groups of the CDs to form charge-transfer state and result in quenching fluorescence of the CDs. After adding I ions to the system of CDs/ Hg, the Hg ions were extracted from the CDs due to the stronger binding between Hg and I, leading to the released CDs having restrained the photo-induced electron transfer and recovered the fluorescence. [ABSTRACT FROM AUTHOR]

Developing a green, non-toxic and easy to synthesize of fluorescence probe for fast and visual detecting trace water in various organic solvents was an important task. Here, a novel dual-emission fluorescence probe (b/r-CDs) was designed based on the red CDs (r-CDs) and blue CDs (b-CDs) to detect the trace water and enhance the visualization for naked-eye observation in different organic solvents. Among, the red fluorescence carbon dots (CDs) was found to have the capability to monitor trace amounts of water, which synthesized with green tea by facile ultrasonic method. Further, Such a dual-emission probe could fast monitor trace water in various organic solvents with high stability and fast response. Importantly, a synergistic mechanism of the dynamic process (b-CDs) and static quenching (r-CDs) was proved for the study of water detection. Moreover, the test paper was made for detecting trace water in different organic solvents, achieving convenient and effective detection. Image 1 • A red fluorescence CDs obtained from green tea and showed the potential for monitoring trace water in organic solvents. • The dual-emission fluorescence probe was designed with blue and red fluorescence CDs for detecting trace water.. • The synergistic mechanism of the dynamic process and static quenching for enhancing visualization effect. • The test strips made for quick and easy visual inspection of trace water. [ABSTRACT FROM AUTHOR]

• CsPbBr 3 QDs were successfully adhered to BN nanosheets by an easy heterogeneous nucleation method. • The improving stability of CsPbBr 3 @BN sensor was realized by the protection of BN nanosheets for CsPbBr 3 QDs. • The fluorescence of CsPbBr 3 @BN sensor could be sensitively quenched by tetracycline through electron transfer process. The abuse of tetracycline (TC) antibiotics would seriously affect human health and hence the detection had become essential. Here, we had constructed a hydrophobicity of fluorescence sensor based on the excellent photoluminescence emission of CsPbBr 3 QDs and the hydrophobic ability of Boron Nitride (BN). This design effectively solved the instability of CsPbBr 3 QDs and realized the sensitive detection of TC. Under optimum conditions, the linear range of TC was 0–0.44 mg L−1 with the 6.5 μg L−1. Furthermore, the sensor was successfully used for the recognition of TC in honey and milk samples. This work also provided an ideal for designing CsPbBr 3 QDs-based on fluorescence sensor. [ABSTRACT FROM AUTHOR]

• Specific sensors with tailor-made selective recognition sites to OTC were developed. • Ratiometric fluorescence sensors were successfully employed to detect OTC in milk. • The detection limit of the prepared fluorescence sensors was low to 3.5 nM. Ratiometric fluorescence imprinting sensors (GQDs/CdTe@MIPs) were successfully constructed by precipitation polymerization method for the recognition and detection of oxytetracycline (OTC) in milk samples. GQDs/CdTe@MIPs were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), fourier transform infrared (FT-IR), thermal gravity analysis (TGA), UV–visible spectroscopy (UV–vis) and X-ray photoelectron spectroscopy (XPS) techniques. A satisfying linear relationship under 0–80 μM OTC concentration (R2 = 0.99699) was exhibited. High sensitivity was showed with the limit of detection of 3.5 nM and high recovery ranged from 99.93% to 100.20%. In addition, the selectivity of GQDs/CdTe@MIPs to OTC was well comparing with other antibiotics. With the injection of different concentrations of OTC, the fluorescent color change of GQDs/CdTe@MIPs under the 365 nm UV lamp further verified that GQDs/CdTe@MIPs were used successfully for the visual detection to OTC in milk samples. [ABSTRACT FROM AUTHOR]