Yu-Sheng He

Bio: Yu-Sheng He is an academic researcher from Jiangsu University. The author has contributed to research in topics: Nanoclusters & Electrochemiluminescence. The author has an hindex of 4, co-authored 7 publications receiving 165 citations.

Highly sensitive and selective dual-emission ratiometric fluorescence detection of dopamine based on carbon dots-gold nanoclusters hybrid

Abstract: In this work, a novel fluorescence resonance energy transfer (FRET)-based ratiometric fluorescent probe, carbon dots-gold nanoclusters hybrid (CDots-AuNCs), was fabricated for selective, sensitive and reliable sensing of dopamine (DA). This FRET probe is comprised of a two-fluorophore, where carbon dots (CDots) serve as the energy donor and gold nanoclusters (AuNCs) as the acceptor, with dual emission peaks at 420 nm and 610 nm under a single excitation wavelength of 380 nm. The addition of DA to this probe solution resulted in the fluorescence at 610 nm quenching, while the blue fluorescence at 420 nm recovering. By monitoring the change of ratiometric fluorescent intensity at 420 and 610 nm, the DA could be detected with the range from 5 to 180 nM and a limit of detection around 2.9 nM. Finally, the developed sensing method was successfully applied to DA determination in serum samples with satisfactory recoveries in the range of 95%–105%.

Facile preparation of amino-carbon dots/gold nanoclusters FRET ratiometric fluorescent probe for sensing of Pb2+/Cu2+

Abstract: Ratiometric fluorescent probes could eliminate the influence from experimental factors and improve the detection accuracy. In this work, under mild conditions, through the electrostatic attraction between positively charged amino-carbon dots (N-CDots) and negatively charged gold nanoclusters (AuNCs), a novel Forster resonance energy transfer (FRET) ratiometric fluorescent probe was fabricated for reliable, selective, and sensitive sensing of Pb2+ and Cu2+. The as-prepared probe shows dual emission peaks at 440 nm and 565 nm with efficient FRET under a single excitation wavelength of 380 nm. The red fluorescence of AuNCs is enhanced by Pb2+ and quenched by Cu2+, while the blue fluorescence of N-CDots stay stable, resulting in fluorescent ratiometric changes. With this strategy, the probe was successfully applied to detect Pb2+ or Cu2+ in real water samples with satisfactory recoveries at three spiking levels ranging from 94 to 104%. Moreover, it could realize the visual semi-quantitative determination of these two heavy metal ions by naked eyes. The good results imply that the developed N-CDots/AuNCs probe is conducive to Pb2+ or Cu2+ determination and possesses the great application potential for water-quality monitoring.

A fluorometric aptasensor for bisphenol a based on the inner filter effect of gold nanoparticles on the fluorescence of nitrogen-doped carbon dots

Abstract: An aptamer-based fluorometric assay is described for the determination of bisphenol A (BPA). The aptamer against BPA is first attached to the surface of the red AuNPs, and this prevents the AuNPs from salt-induced formation of a blue-colored aggregate. Hence, the blue fluorescence of added nitrogen-doped carbon dots (NCDots) is quenched via an inner filter effect (IFE) caused by the red AuNPs. After addition of BPA, the BPA/aptamer complex is formed, and the AuNPs are no longer stabilized agains aggregation. This weakens the IFE and results in the recovery of the fluorescence of the NCDots which is measured best at excitation/emission wavelengths of 300/420 nm. The recovered fluorescence increases linearly in the 10 to 250 nM and 250 to 900 nM BPA concentration ranges, and the detection limit is 3.3 nM. The method was successfully applied to the determination of BPA in spiked environmental tap water samples.

Aptamer based electrochemiluminescent determination of bisphenol A by using carboxylated graphitic carbon nitride

Abstract: An electrochemiluminescence (ECL) based assay is described for the determination of the endocrine disruptor bisphenol A (BPA). The method is based on the use of carboxylated graphitic carbon nitride (C-g-C3N4) carrying an immobilized aptamer against BPA. In the presence of BPA, the ECL signal decreases due to ECL energy transfer from excited-state C-g-C3N4 to the BPA oxidation product. Under the optimal conditions, ECL intensity increases linearly in the 0.1 pM to 1 nM BPA concentration range. The detection limit is as low as 30 fM. The assay has excellent sensitivity, outstanding stability and high selectivity. It was applied to the determination of BPA in spiked water samples.

The fluorescence mechanism of carbon dots, and methods for tuning their emission color: a review

Abstract: Carbon dots (CDs) display tunable photoluminescence and excitation-wavelength dependent emission. The color of fluorescence is affected by electronic bandgap transitions of conjugated π-domains, surface defect states, local fluorophores and element doping. In this review (with 145 refs.), the studies performed in the past 5 years on the relationship between the fluorescence mechanism and modes for modulating the emission color of CDs are summarized. The applications of such CDs in sensors and assays are then outlined. A concluding section then gives an outlook and describes current challenges in the design of CDs with different emission colors. Graphical abstract Schematic representation of the relationship between the color-emitting (blue, green, yellow, red and multicolor) modulation of carbon dots and fluorescence mechanism including bandgap transitions of conjugated π-domains and surface defect states.

Principles, mechanisms, and application of carbon quantum dots in sensors: a review

Abstract: Carbon quantum dots (CQDs) as an emerging class of quantum dots (QDs) with advantages such as good photoluminescence (PL) properties, easy synthesis routes, economical synthesis, cheap starting materials, water-solubility, low levels of toxicity, chemical stability, and easy functionalization have received great attention during recent years. CQDs have been used in versatile sensor applications. CQD sensors could be ultimately sensitive, and the limit of detection (LOD) for these sensors can reach the nanomolar, picomolar or even femtomolar ranges. CQD-based sensors and biosensors work with different mechanisms including fluorescence quenching, static quenching, dynamic quenching, energy transfer, inner filter effect (IFE), photo-induced electron transfer (PET), and fluorescence resonance energy transfer (FRET). CQD-based sensors and biosensors have been applied for the detection of different species such as metal ions, acids, proteins, biothiols, polypeptides, DNA and miRNA, water pollutants, hematin, drugs, vitamins, and other chemicals. It seems that CQD-based sensors and biosensors are promising candidates for high performance and yet accurate sensors in different areas. In this review, CQDs are introduced, and the synthesis methods and optical properties of CQDs are discussed. Different types of CQD-based sensors and biosensors and their working mechanisms are clarified.

Emerging Chemical Functionalization of g-C3N4: Covalent/Noncovalent Modifications and Applications.

Abstract: Atomically 2D thin-layered structures, such as graphene nanosheets, graphitic carbon nitride nanosheets (g-C3N4), hexagonal boron nitride, and transition metal dichalcogenides are emerging as fascinating materials for a good array of domains owing to their rare physicochemical characteristics. In particular, graphitic carbon nitride has turned into a hot subject in the scientific community due to numerous qualities such as simple preparation, electrochemical properties, high adsorption capacity, good photochemical properties, thermal stability, and acid-alkali chemical resistance, etc. Basically, g-C3N4 is considered as a polymeric material consisting of N and C atoms forming a tri-s-triazine network connected by planar amino groups. In comparison with most C-based materials, g-C3N4 possesses electron-rich characteristics, basic moieties, and hydrogen-bonding groups owing to the presence of hydrogen and nitrogen atoms; therefore, it is taken into account as an interesting nominee to further complement carbon in applications of functional materials. Nevertheless, g-C3N4 has some intrinsic limitations and drawbacks mainly related to a relatively poor specific surface area, rapid charge recombination, a limited light absorption range, and a poor dispersibility in both aqueous and organic mediums. To overcome these shortcomings, numerous chemical modification approaches have been conducted with the aim of expanding the range of application of g-C3N4 and enhancing its properties. In the current review, the comprehensive survey is conducted on g-C3N4 chemical functionalization strategies including covalent and noncovalent approaches. Covalent approaches consist of establishing covalent linkage between the g-C3N4 structure and the chemical modifier such as oxidation/carboxylation, amidation, polymer grafting, etc., whereas the noncovalent approaches mainly consist of physical bonding and intermolecular interaction such as van der Waals interactions, electrostatic interactions, π-π interactions, and so on. Furthermore, the preparation, characterization, and diverse applications of functionalized g-C3N4 in various domains are described and recapped. We believe that this work will inspire scientists and readers to conduct research with the aim of exploring other functionalization strategies for this material in numerous applications.

Inner filter effect in fluorescence spectroscopy: As a problem and as a solution

Abstract: This article discusses three aspects of inner filter effect (IFE) in fluorescence spectroscopy. (i) First, IFE as undesirable in fluorescence measurements: IFE results in non-linear fluorescence response of the analyte under study and it has been verified that IFE cannot be eliminated; it can either be minimized or corrected for intensity loss. Over the years, researchers have proposed many intensity correction methods to avoid IFE related issues. Often analysts using fluorescence spectroscopy, knowingly or unknowingly, ignore IFE or use an inappropriate intensity correction method. Herein, we have highlighted the basis and significances of various correction models that are proposed since 1970s to till date. (ii) Second, IFE mediated concentration dependent red shift (CDRS) as an analytical tool: the conventional fluorescence measurements and IFE correction strategies cannot be applied in analysis of optically dense multi-fluorophoric samples like oils, petrochemicals, biological samples and food samples etc. The strategy for exclusive inclusion of IFE and IFE induced CDRS as characteristics of the system for development of fluorescence based assay, towards maximizing fluorescence sensitivity of optically dense multi-fluorophoric systems, have been discussed. (iii) Third, IFE based sensing: when the sample contains chromophores, which absorb either at the excitation or at the emission wavelength range of the fluorophore, then the chromophores act as a filter. Thus tuning either the absorber or fluorophore concentration will lead to development of fluorescence based assay for a selective analyte. Principles and protocols are described to identify whether a sensing event is due to IFE or any other fluorescence mechanism. Additionally, a brief description is given on advanced findings and progresses made in sensing of for various classes of analytes in the recent past, using IFE concept. The second and third aspect combined together serve as a tool towards enhancing sensitivity of fluorescence measurement.