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Considering the high probability of recurrence or metastasis after thyroidectomy, it is meaningful to develop a rapid, sensitive and specific method for monitoring thyrophyma-related biomarkers. In this study, a homogeneous electrochemiluminescence immunoassay (HO-ECLIA) coupled with magnetic beads (MBs)-based enrichment tactic was established for the determination of thyrophyma-related thyroglobulin (Tg). Importantly, owing to the abundant surface groups and good biocompatibility of carbon quantum dots (CQDs), the incorporation of CQDs onto the Tg antigen surface was achieved, resulting in the formation of Tg-encapsulated CQDs (CQDs-Tg), which served not only as an ECL probe but as a biorecognition element. Under optimal experimental conditions, the proposed platform demonstrated a wide linear range from 0.01 to 100 ng·mL -1 with a detection limit of 6.9 pg·mL -1 (S/N = 3), and performed well in real serum sample analysis against interference. Collectively, the proposed platform exhibited the rapid response, satisfactory sensitivity and specificity toward Tg in complex serum milieu, and held a considerable potential for clinical prognosis monitoring of thyrophyma., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Since microRNAs (miRNAs) are predictors of tumorigenesis, accurate identification and quantification of miRNAs with highly similar sequences are expected to reflect tumor diagnosis and treatment. In this study, a highly selective and sensitive electrochemiluminescence (ECL) biosensor was constructed for miRNAs determination based on Y-shaped junction structure equipped with locked nucleic acids (LNA), graphene oxide-based nanocomposite to enrich luminophores, and conductive matrix. Specifically, two LNA-modified probes were designed for specific miRNA recognition, that is, a dual-amine functionalized hairpin capture probe and a signal probe. A Y-shaped DNA junction structure was generated on the electrode surface upon miRNA hybridizing across the two branches, so as to enhance the selectivity. Carbon quantum dots-polyethylene imine-graphene oxide (CQDs-PEI-GO) nanocomposites were developed to enrich luminophores CQDs, and thus enhancing the ECL intensity. For indirect signal amplification, an electrochemically activated poly(2-aminoterephthalic acid) (ATA) film decorated with gold nanoparticles was prepared on electrode as an effective matrix to accelerate the electron transfer. The fabricated ECL biosensor achieved sensitive determination of miRNA-222 with a limit-of-detection (LOD) as low as 1.95 fM (S/N = 3). Notably, Y-shaped junction structures equipped with LNA probes endowed ECL biosensor with salient single-base discrimination ability and anti-interference capacity. Overall, the proposed Y-shaped ECL biosensor has considerable promise for clinical biomarker determination., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Recently, sensitive and selective detection of exosomal microRNAs (miRNAs) has been garnering significant attention, because it is related to many complex diseases, including cancer. Herein, we report a ratiometric fluorescent bioprobe based on DNA-labeled carbon dots (DNA-CDs) and 5,7-dinitro-2-sulfo-acridone (DSA) coupling with the target-catalyzing signal amplification for the detection of exosomal miRNA-21. There was high fluorescence resonance energy transfer (FRET) efficiency between carbon dots (CDs) and DSA when the bioprobe was assembled. However, in the presence of the target, with disassembling of the fluorescent bioprobe, the fluorescence intensities of CDs and DSA were changed simultaneously. Because of the ratio of dual fluorescence intensities, this ratiometric fluorescent bioprobe was able to cancel out environmental fluctuations by calculating emission intensity ratio at two different wavelengths, being robust and stable enough for detection of exosomal miRNA-21. In addition, we displayed that a single miRNA-21 can catalyze the disassembly of multiple CDs with DSA theoretically, yielding significant change in the fluorescence ratio for the detection of miRNA-21. With this signal amplification strategy, the limit of detection was as low as 3.0 fM. Furthermore, because of the introduction of lock nucleic acid to mediate the strand displacement reaction, the selectivity of this strategy was improved remarkably, even against single base mismatch sequence. More importantly, our strategy could monitor the dynamic change of exosomal miRNA-21, which maybe becomes a potential tool to distinguish cancer exosomes and nontumorigenic exosomes. In a short, this ratiometric fluorescence bioprobe possessed high stability, sensitivity and selectivity coupling with ease of operation and cost efficiency, leading to great potential for wide application.

This report outlines a rapid and highly sensitive colorimetric sensing platform based on a novel water-soluble WO x quantum dots (QDs) as enzymatic mimics. The WO x QDs, synthesized by a green hydrothermal method, were proven to possess excellent intrinsic peroxidase-like activity. The peroxidase substrate, 2, 2'-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS) could be catalyzed oxidation by WO x QDs quickly in the present of H 2 O 2 to form a green color. Due to its excellent properties such as excellent water-solublity, good biocompatibility, easy preparation, and high stability, the proposed system showed typical Michaelis-Menten kinetics and high affinity for ABTS and H 2 O 2 , indicating WO x QDs can be used as satisfactory peroxidase mimics. Together with the fast detection process, WO x QDs-based colorimetric sensing system provided a facile, sensitive, and accurate method for the determination of H 2 O 2 and glucose. The real glucose samples in human serum samples were detected with satisfying results. The proposed sensing platform not only expands the applications of WO x and WO x QDs-based nanocomposites, but also provides an alternative technique for biological, biomedical and environmental sample assay., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Fluorescent quantum dots have great potential to act as labeling tools in biological research, especially cellular tracking and imaging. Tat peptide conjugated quantum dots were introduced into living human hematopoietic stem cells (HSCs). The internalized quantum dots were assessed by laser confocal microscope and flow cytometer. The quantum dots labeled HSCs were injected intravenously into the tail veins of NOD/SCID beta2M null mice. The tissue collections in the major organs were examined with fluorescence microscope to assess the distribution of transplanted stem cells. HSCs with internalized quantum dots offer a promising approach for stem cell transplantation, which will hold a significant impact on stem cell based therapy for several disorders, especially to cure leukemia in current China.

Fluorescent quantum dots have great potential to act as labels in biological research, especially cellular tracking in vivo. Here, small thiol molecules-capped CdSe/ZnS quantum dots attached to Tat peptide were used for label agents, and introduced into living stem cells. The stem cells labeled with quantum dots were intravenously injected into the tail veins of NOD/SCID beta2M null mice, and whose tissue sections of major organs of null mice were examined with fluorescence microscope to assess the distribution of transplanted stem cells. Stem cells with internalized quantum dots offer a promising approach in stem cell transplantation, which will hold a significant impact on stem cell based therapy for several disorders.

Fluorescent quantum dots have great potential in cellular labeling and tracking. Here, PEG encapsulated CdSe/ZnS quantum dots have been conjugated with Tat peptide, and introduced into living mesenchymal stem cells. The Tat peptide conjugated quantum dots in mesenchymal stem cells were assessed by fluorescent microscopy, laser confocal microscope and. flow cytometry. The result shows that Tat peptide conjugated quantum dots could enter mesenchymal stem cells efficiently. The Tat-quantum dots labeled stem cells were further injected into the tail veins of NOD/SCID beta2 M null mice, and the tissue distribution of these labeled cells in nude mice were examined with fluorescence microscope. The result shows that characteristic fluorescence of quantum dots was observed primarily in the liver, the lung and the spleen, with little or no quantum dots accumulation in the brain, the heart, or the kidney.

The thiol-capped CdTe nanocrystals were obtained by a clean chemical approach with hydrazine hydrate. In alkaline aqueous solution, hydrazine hydrate reduced commercial tellurium to be active reactant, and further reduced to negative bivalent telluride for the preparation of CdTe nanocrystals. The resulting CdTe nanocrystals were characterized by UV-Vis absorption spectra, photoluminescence spectra, X-ray diffraction, and high-resolution transmission electron microscopy. The synthesized CdTe nanocrystals were stable with relatively strong photoluminescence in neutral and close neutral range, and further combined with living Corynebacterium glutamicum without any post-preparative treatment. The conjugation samples were observed on laser confocal microscope, and the photoluminescence signals can only be detected at the positions of Corynebacterium glutamicum, which suggests that the CdTe nanocrystals have been combined with Corynebacterium glutamicum successfully.

S‐graphene quantum dots (GQDs), N‐GQDs, P‐GQDs, and Cl‐GQDs are prepared by a solution chemistry method and further incorporated with ZnxCd1−xSe by one‐step hydrothermal method. In the previous study, ZnxCd1−xSe reached the optimal photoelectric performances at the Zn/Cd ratio of 0.9:0.1, so the Zn0.9Cd0.1Se were combined with doped GQDs (D‐GQDs) to form Zn0.9Cd0.1Se/doped‐GQDs. The influence of GQDs doped with different elements on the photoelectric properties of Zn0.9Cd0.1Se composites is discussed. Compared with pristine Zn0.9Cd0.1Se, Zn0.9Cd0.1Se/Cl‐GQDs, and Zn0.9Cd0.1Se/P‐GQDs can improve the photocurrent response and current intensity, therein, Zn0.9Cd0.1Se/Cl‐GQDs reaches the lowest interfacial charge transfer resistance and the highest photocurrent response of 5.48 × 10−6 A cm−2. Mott–Schottky analysis shows that the fitting slope of Zn0.9Cd0.1Se/Cl‐GQDs composites is significantly lower than that of Zn0.9Cd0.1Se/GQDs with other doped elements. The results indicate that Zn0.9Cd0.1Se/Cl‐GQDs composites has the largest carrier density, which is beneficial to charge conduction. [ABSTRACT FROM AUTHOR]

In the work, CdS x Se 1-x /N-GQDs composites were fabricated via a simple one-step hydrothermal process and their tunable composition, structure and photoelectric properties were characterized by various techniques. The photoelectric properties of CdS x Se 1-x /N-GQDs could be adjusted by different Se/S ratios and tunable band-gaps. CdS x Se 1-x /N-GQDs composites reached the optimal photocurrent response and the lowest interfacial impedance at the Se/S ratio of 0.75:0.25. Mott-Schottky plots and LSV spectra showed that the n-type CdS 0.25 Se 0.75 /N-GQDs presented a higher carrier density under light illumination. The excellent properties of the composites could be attributed to the mechanism involved in the excitation and electron-transfer process. On one hand, the band-gap of CdS 0.25 Se 0.75 /N-GQDs was narrowed, and more electrons were excited by the lower band-gap energy to promote a superior electron separation and transportation. On the other hand, N-GQDs acted as charge carriers and conductive way providers for electron-transfer instead of electron-hole recombination in the composites. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) as a sensitive detection method had attracted tremendous attention. Graphene quantum dots (GQDs) were synthesized by a top–down approach, and the W18O49 samples were prepared by a solvothermal method with WCl6 as the tungsten source. The size of prepared GQDs presented a size of 10 nm and a topographic height of 1.5 nm, corresponding to 1–3 layers of graphene sheets. There were two different lattice fringes of 0.34 nm and 0.378 nm matched with the (002) and (010) lattice planes of GQDs and W18O49, respectively. After the modification of GQDs, the band gap energy of W18O49 was narrowed, and the separation and electron transport capability of W18O49 were improved due to the existence of GQDs. In this work, the detection sensitivity of SERS was effectively improved by chemical and electromagnetic field enhancement when W18O49/GQDs composites were used as SERS substrates. Therefore, it will be an effective way to improve the SERS performance of W18O49 by modifying GQDs. [ABSTRACT FROM AUTHOR]

In the present study, a heterostructure based on Zn 0·1 Cd 0·9 S, N-doped graphene quantum dots (N-GQDs), and graphene was successfully prepared by a simple method. Various analyses are conducted to determine the structure, morphology, and materials performance of the synthesized composite. The results exhibit that the Zn 0·1 Cd 0·9 S/N-GQDs/graphene heterostructure presents excellent photoelectric performance with a high photocurrent of 4.43 × 10−5 A/cm2 and 3.43 × 10−5 A/cm2 under light irradiation of 365 nm and 405 nm, respectively. It demonstrates a two-fold photocurrent enhancement in comparison to blank Zn 0·1 Cd 0.9 S. This remarkable improvement is ascribed to a mechanism in which the N-GQDs act as photosensitizers, enhancing the absorption ability. Concurrently, graphene serves as a carrier mobility substrate, facilitating the separation of the photogenerated electron–hole pairs. The synergetic effect between Zn 0·1 Cd 0·9 S, the N-GQDs, and graphene enhances the photoelectric performance. The Zn 0·1 Cd 0·9 S/N-GQDs/graphene heterostructure provides a new route for the enhancement of the photoelectric performance of a semiconductor under UV–visible light. [ABSTRACT FROM AUTHOR]

Cadmium selenide and S, N co-doped graphene quantum dots (CdSe/S, N-GQDs) nanocomposites were synthesized via a solvothermal method. The results show that S, N-GQDs have a grain size of around 5 nm and an average height of 0.5 nm, which contains only 1–2 layers of graphene sheets. The CdSe/S, N-GQDs composites exhibit distinct lattice fringes with a layer spacing of 0.24 and 0.35 nm, corresponding to (1120) and (111) crystal planes of S, N-GQDs and the cubic CdSe, respectively. The photoelectric properties of CdSe/S, N-GQDs were evaluated under ultraviolet light (365 nm) irradiation. Compared with CdSe and CdSe/GQDs, CdSe/S, N-GQDs composites have the largest photocurrent density of 4.286 × 10–5 A cm−2, which is about 10.5 times and 7.5 times as high as that of CdSe and CdSe/GQDs, respectively. The increase in photocurrent density of CdSe/S, N-GQDs can be attributed to the incorporation of S and N to promote separation of photogenerated carriers. Moreover, S, N-GQDs are nano-fragments of graphene, which can provide a larger specific surface area and greatly increase the contact surface with CdSe. In addition, the photoelectric properties of CdSe/S, N-GQDs composites can be adjusted by varying the doping ratio. When the doping ratio is 1:1, CdSe/S, N-GQDs have the best photoelectric performance. [ABSTRACT FROM AUTHOR]

A facile and green method has been demonstrated to synthesize ultrasmall tungsten oxide quantum dots (WOx QDs). The water-soluble WOx QDs present high luminescence stability, strong peroxidase-like activity, and excellent electrochemiluminescence properties. This work provides an eco-friendly strategy to prepare multifunctional WOx QDs, and opens the door for bioapplications of the WOx QDs. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene quantum dots modified SnO 2 composites (SnO 2 /N-GQDs) were prepared by a solvothermal method, where N-GQDs were synthesized through a hydrothermal process with citric acid and urea as sources. The lattice stripes of 0.33 nm, 0.26 nm and 0.24 nm were ascribed to (110) and (101) crystal planes of SnO 2 and (1120) crystal plane of N-GQDs, respectively. The photoelectric properties of SnO 2 /N-GQDs composites with different N-GQDs contents were characterized using I-t, LSV, EIS, and Mott-Schottky. Among them, SnO 2 /N-GQDs-2 composites reached the smallest electrochemical impedance and achieved the optimal transient photocurrent value of 1.880 × 10−4 A/cm2. Compared with pure SnO 2 , SnO 2 /N-GQDs-2 presented a 5-fold increase in the photocurrent density. LSV showed that the incorporation of N-GQDs could enhance the photocurrent intensity of SnO 2. The Mott-Schottky slope of SnO 2 /N-GQDs-2 in light was smaller than that of SnO 2 and SnO 2 /N-GQDs-2 in dark, indicating that more carriers were generated under UV illumination and transferred with the doping of N-GQDs. [ABSTRACT FROM AUTHOR]

Graphene quantum dots (GQDs) as excellent conductive materials could effectively enhance the electron transmission efficiency of W 18 O 49 nanofibers after their combination. In order to investigate the effect of different crystal phase WO 3 on the optoelectric properties of GQDs/W 18 O 49 composites, the orthogonal phase WO 3 (o-WO 3), hexagonal phase WO 3 (h-WO 3) and tetragonal phase WO 3 (t-WO 3) had been used to produce GQDs/W 18 O 49 /WO 3 homojunction with GQDs/W 18 O 49. After comparing them, it was found that the photocurrent intensity of GQDs/W 18 O 49 /t-WO 3 was 2.35 times, 1.68 times and 1.08 times as high as that of GQDs/W 18 O 49 , GQDs/W 18 O 49 /o-WO 3 and GQDs/W 18 O 49 /h-WO 3 at 1.2 V versus Hg/Hg 2 Cl 2 , respectively. And the t-WO 3 could effectively decrease the band gap, reduce the interfacial resistance, prolong the electron lifetime, accelerate the electron conduction and increase the photocurrent magnitude of the homojunction. The photoelectric performance of the composites could be adjusted by regulating the ratios of GQDs/W 18 O 49 and t-WO 3 , the ratio 2:1 of GQDs/W 18 O 49 /t-WO 3 composites presented a higher photocurrent density and lower interfacial resistance than other proportions. The physical mechanism of such enhanced photoconduction in this homostructure have been discussed. • GQDs promote the separation of photoelectron and reduce the interfacial transfer resistance of GQDs/W 18 O 49. • Comparison of GQDs/W 18 O 49 /t-WO 3, GQDs/W 18 O 49 / o-WO 3 and GQDs/W 18 O 49 / h-WO 3 homostructures. • GQDs/W 18 O 49 /t-WO 3 reduced the band gap and promoted the interfacial accumulation and transfer. • GQDs/W 18 O 49 /t-WO 3 at ratio of 2:1 processed the smallest electron-transfer resistance and highest photocurrent density. [ABSTRACT FROM AUTHOR]

Abstract: The fluorescent quantum dot–polymer composites were fabricated by incorporating thioglycolic acid capped CdTe quantum dots into polyacrylamide via cross-linking agents. The CdTe–polyacrylamide composites were characterized by fluorescence spectrophotometer and fluorescence microscope. The result shows that the quantum dot–polymer composites show strong photoluminescence in aqueous solution. The photoluminescence spectrum of quantum dot–polymer composites exhibits a slight blue shift compared to that of initial CdTe quantum dots. The slight shift might be attributed to the covalently bonding between the carboxyl groups of thiolglycolic acid capped on CdTe quantum dots and the amide groups of the polyacrylamide chains. [Copyright &y& Elsevier]

Graphene quantum dots (GQDs) were synthesized via the Hummers' method and the hydrothermal cutting process. The lateral size of GQDs was 50 nm, and the thickness was 6 nm. The cubic phase ZnSe nanoparticles were obtained by the hydrothermal method, and the diffraction peaks could be ascribed to the (111), (220), (311), (400), (331) and (422) crystal planes of ZnSe. By controlling the addition amount of GQDs with 0.04%, 0.06%, 0.08%, and 0.1%, ZnSe-GQDs composites were prepared by a simple one-step hydrothermal method. When testing composite materials, we could clearly obtain two lattice stripes belonging to GQDs and ZnSe in HRTEM, respectively. ZnSe-GQDs composites could also be found the characteristic peaks representing GQDs and ZnSe at 284 nm and 446 nm on the UV–Vis absorption spectra, respectively. The effect of different GQDs contents on the photoelectric property of ZnSe-GQDs film was investigated. The optimal photocurrent density of ZnSe-0.08 wt% GQDs was three times larger than that of pure ZnSe. The semicircle radius of electrochemical impedance spectrum was reduced with the addition of GQDs gradually, which proved that the appropriate amount of GQDs could reduce the charge transfer resistance of ZnSe in this composite. [ABSTRACT FROM AUTHOR]

In this study, Zn x Cd 1-x S/N-GQDs composites with different Zn/Cd ratios were synthesized via a facile solvothermal process. A series of techniques were introduced to investigate the effect of Zn/Cd ratios and N-GQDs on the performances of Zn x Cd 1-x S/N-GQDs. The results show that the crystal structure and photoelectric performance of the composites can be tuned via adjusting the Zn/Cd ratios. Zn x Cd 1-x S/N-GQDs composites transform from a hexagonal structure to a cubic structure with the increase of Zn content, and the diffraction peaks are located between hexagonal phase CdS and cubic phase ZnS. Meanwhile, the photocurrent responses and electrochemical impedance present good tunability via adjusting the Zn/Cd ratios. Zn 0.9 Cd 0.1 S/N-GQDs composites with the higher photocurrent value of 3.79 μA cm−2 and lower interfacial impedance are superior to Zn x Cd 1-x S/N-GQDs composites with other Zn/Cd ratios. Moreover, the introduction of N-GQDs obviously enhances the photoelectric properties of the semiconductor. • We successfully synthesized Zn x Cd 1-x S/N-GQDs composites by facile solvothermal process. • Zn x Cd 1-x S/N-GQDs composites exhibit alloyed Zn x Cd 1-x S structure instead of the independent ZnS and CdS. • The photoelectric properties of Zn x Cd 1-x S/N-GQDs present a good tunability via adjusting the Zn/Cd ratios. • The introduction of N-GQDs enhanced the photoelectric properties of Zn 0.9 Cd 0.1 S with the higher photocurrent intensity. [ABSTRACT FROM AUTHOR]

Graphene quantum dots (GQDs) were synthesized by a hydrothermal cutting method, and SnO 2 /GQDs composites were prepared by a one-step solvothermal method with SnCl 4 ·5H 2 O as a tin source. GQDs presented a size of 10 nm and a topographic height of 1 nm, indicating that GQDs are roughly 2–3 graphene layers. The interplanar spacing of 0.24 nm and 0.34 nm corresponded to the crystal plane of GQDs (1120) and (002), respectively. Owing to the electrostatic interaction, the incorporation of positive SnO 2 with negative GQDs results in the zeta potential decreased from 7.08 mV to −2.22 mV. The photoelectric properties of SnO 2 /GQDs composites were investigated. When the ratio of GQDs reached 0.30 wt%, the photocurrent value of SnO 2 /GQDs composites achieved a maximum of 3.008 × 10−4A/cm2 and the corresponding interface contact impedance reached a minimum. [ABSTRACT FROM AUTHOR]

Sulfur, nitrogen co-doped graphene quantum dots (S, N-GQDs) with high crystallinity were obtained by a top-down strategy. The as-prepared S, N-GQDs were investigated and the results indicate that S, N-GQDs exhibit a transverse dimension about 20 nm and a topographic height of 1–2 layers graphene. The incorporation of S, N can effectively reduce the layers of GQDs and strip the graphene sheets. Moreover, the S, N-GQDs reveal an absorption band located at 405 nm and exhibit an adjustable fluorescence characteristic in the excitation-visible range. Meanwhile, the S, N-GQDs shows a high specific capacitance of 362.60 F g−1 at a fixed scan rate of 5 mV s −1. This high performance is ascribed to the additional high pseudocapacitance provided by the doped S, N and the doping state acting as a trap state to enhance the charge storage capacity. The high specific capacitance advantages of S, N-GQDs illustrate their potential prospects in the capacitors. [ABSTRACT FROM AUTHOR]

Graphene quantum dots (GQDs) decorated Al-doped ZnS composites were prepared using the solvothermal process, and the hydrothermal method was used to prepare GQDs. Various spectroscopic techniques were used to characterize the products, and the results show that Al-ZnS attached GQD composites present lattice fringes that can be assigned to ZnS and GQDs, respectively. The absorption peaks of Al-ZnS/GQDs are red-shifted because of the doping of aluminum and the incorporation of GQDs. The luminescence intensity of Al-ZnS/GQDs shows a downward trend with the addition of GQDs. As the GQD content changes from 0.6 wt % to 1.8 wt %, the photocurrent density achieves a maximum at the addition of 1.2 wt %. The photocurrent of Al-ZnS/GQDs composites are about 700% and 200% of pure ZnS and Al-ZnS, respectively. The results indicate that Al doping can reduce the energy bandgap of ZnS and produce more photogenerated electrons. The photogenerated electrons from Al-ZnS can be extracted and transferred to GQDs, which act as conducting materials to decrease the recombination rate and improve the photogenerated electron-transfer. [ABSTRACT FROM AUTHOR]

ZnS-graphene quantum dot (GQDs) composites were synthesized by a simple solvothermal method, in which GQDs were prepared by a hydrothermal cutting process. The products were characterized by transmission electron microscopy, atomic force microscopy, X-ray diffraction and ultraviolet-visible absorption spectroscopy. The results show that GQDs were obtained by size tailoring of 1–4 graphene layers and combined with cubic ZnS nanoparticles to form ZnS-GQDs composites. The photocurrent and electrochemical behavior of the products were evaluated by transient photocurrent responses and electrochemical impedance spectra. The photocurrent density of ZnS-GQDs achieves the value of 2.32 × 10−5 A/cm2, which is 2.4-times as high as that of ZnS-graphene. GQDs serve as an electrical conducting material, which decreases the conductive path and accelerates the electron transfer. The charge-transfer resistance of ZnS-GQDs is much lower than that of ZnS-graphene and pure ZnS due to the effective electron separation and transfer ability upon the incorporation of GQDs. [ABSTRACT FROM AUTHOR]

• CdSSe composites were prepared by a one-step hydrothermal method. • CdSSe/GQDs composites contained C–O–C and C C functional groups. • CdSSe/GQDs composites demonstrated a superior photoelectric performance. • GQDs contents have a great effect on the photocurrent density and charge transfer resistance of CdSSe/GQDs composites. CdSSe/graphene quantum dots (CdSSe/GQDs) composites were prepared by a hydrothermal method in the way of electrostatic interaction. The structure, morphology and material performance were investigated by various physical and chemical analyses. According to the results of X-ray photoelectron spectroscopy, the GQDs were compounded into composites. Moreover, the composites contained C–O–C and C C functional groups from Fourier transform infrared test results. The obtained CdSSe/GQDs composites demonstrated a superior photoelectric performance in comparison to the pure CdSSe semiconductor. The GQDs contents had a great effect on the photocurrent density and charge transfer resistance of the CdSSe/GQDs composites. As the amount of GQDs increased to 0.15 wt%, the photocurrent response reached 1.31 × 10−5 A/cm2, which was three times higher than that of CdSSe. [ABSTRACT FROM AUTHOR]

• A facile strategy was demonstrated to synthesis high stability and strong peroxidase-like activity MoOx QDs. • The MoOx QDs displayed peroxidase-like activity with high sensitivity and good specificity in the colorimetric assay. • The MoOx QDs was used to quantitative detection of H 2 O 2 released from PC12 cells on the μPADs. Diagnostic assays made of microfluidic paper-based analytical devices have become the focus of considerable attention in developing countries because of simplicity, low cost, user friendliness, and no requirement for complex equipment, which is suitable to point-of-care testing. Considering the intrinsic shortcomings of nature enzyme, synthesis of artificial peroxidase mimics possessing improved catalytic activities relative to native enzymes is of considerable interest for the development of highly sensitive and stable sensor. In this paper, water-soluble molybdenum oxide quantum dots (MoOx QDs) were developed as highly effective biomimetic catalysts which were prepared by a facile ultrasonic-assisted hydrothermal method. The resulted MoOx QDs displayed peroxidase-like activity with high sensitivity and specificity, and were constructed for efficient colorimetric quantitative detection of H 2 O 2 based on microfluidic paper-based device. As low as 0.175 μmol/L H 2 O 2 could be determined at a linear range from 1 to 20 μmol/L. Moreover, this biosensing device was successfully applied for visual detection of H 2 O 2 released from PC12 cells with the advantages of low cost, rapid response and portability, indicating that the designed sensor of H 2 O 2 has great potential in biotechnology and clinical diagnosis. [ABSTRACT FROM AUTHOR]