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Graphene quantum dots and carbon nano dots for the FRET based detection of heavy metal ions
摘要： We demonstrate the development of a FRET based novel optical sensing system for the efficient detection of heavy metal pollutants. The studied sensing system is comprised of graphene quantum dots (GQDs) as donor and carbon nano dots (C-Dots) as an acceptor component. When these fluorescent nano-dots are within the FRET distance, fluorescence of the donor GQDs is quenched by the non-radiative energy transfer to acceptor C-Dots. Fluorescence lifetime is measured by time resolved photo-luminescence spectroscopic study to validate the FRET efficacy of the mix dot based sensor system. Upon gradual addition of heavy metals like arsenic (As5+) and mercury (Hg2+) into this sensor system, a significant amount of reduction in the investigated FRET signal is experienced. The detailed mechanisms of the molecular interactions between GQDs and C-Dots are thoroughly studied by UV–Visible absorption, infrared, steady state and time resolved spectroscopy.
关键词： FRET,Carbon nano dot,Metal ions,Sensor,Graphene quantum dot
更新于2025-11-19 16:46:39
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Charge transport in graphene-based mesoscopic realizations of Sachdev-Ye-Kitaev models
摘要： We consider a recent proposal for a physical realization of the Sachdev-Ye-Kitaev (SYK) model in the zeroth-Landau-level sector of an irregularly shaped graphene flake. We study in detail charge transport signatures of the unique non-Fermi-liquid state of such a quantum dot coupled to noninteracting leads. The properties of this setup depend essentially on the ratio p between the number of transverse modes in the lead M and the number of the fermion degrees of freedom N on the SYK dot. This ratio can be tuned via the magnetic field applied to the dot. Our proposed setup gives access to the nontrivial conformal-invariant regime associated with the SYK model as well as a more conventional Fermi-liquid regime via tuning the field. The dimensionless linear-response conductance acquires distinct p dependencies for the two phases, respectively, in the low-temperature limit, with a universal jump at the transition. We find that corrections scale linearly and quadratically in either temperature or frequency on the two sides of the transition. In the weak-tunneling regime, we find differential conductance proportional to the inverse square root of the applied voltage bias U for bias energy eU larger than temperature scale kB T. This dependence is replaced by a conventional Ohmic behavior with constant conductance proportional to 1/sqrt(T) for bias energy eU smaller than temperature scale kB T. We also describe the out-of-equilibrium current-bias characteristics and discuss various crossovers between the limiting behaviors mentioned above.
关键词： Sachdev-Ye-Kitaev model,tunneling conductance,graphene,quantum dot,charge transport,non-Fermi-liquid,conformal invariance
更新于2025-09-23 15:23:52
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Electrochemiluminescence revealing that HNO3-oxidized single-walled carbon nanotubes are essentially tubular graphene quantum dot-nanoassemblies
摘要： Graphene quantum dots (GQDs) as recently emerging 0-D graphitic nanomaterials, have attracted much attention due to their unique optical, electrical and catalytic properties. However, some properties of GQDs, such as very small size, low density, and excellent water-solubility, make it difficult to be separated and immobilized. This may limit the recycle and purification of GQDs, and thus their applications in catalysis and sensing. In this work, we prepared tubular GQD-nanoassemblies (t-GQD-NAs) by etching single-walled carbon nanotubes (SWCNTs) with concentrated HNO3. The synthesized t-GQD-NAs were characterized by TEM, SEM, XPS, Raman spectroscopy and electrochemiluminescence (ECL) in details. t-GQD-NAs were much shorter and slimmer in morphology, bore more oxygen-containing groups, and had a higher surface defect density compared with SWCNTs. t-GQD-NAs not only maintained good UV absorption property of SWCNTs but also showed strong infrared ECL emission and broad ECL spectrum, verifying that t-GQD-NAs were assembled from GQDs of various sizes and some graphene nanoribbons. This is for the first time that 0-D GQDs were reported to be assembled into 1-D tubular carbon structures. The t-GQD-NAs with abundant surface states and good ECL activity could be easily separated, purified, and immobilized, suggesting their promising applications in ECL sensing and catalysis.
关键词： Graphene quantum dots,Single-walled carbon nanotubes,Electrochemiluminescence,Tubular graphene quantum dot-nanoassemblies
更新于2025-09-23 15:21:01
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ZnO Nanosheets Modified with Graphene Quantum Dots and SnO2 Quantum Nanoparticles for Room-Temperature H2S Sensing
摘要： Overcoming the low selectivity issue of semiconductor oxide (SMO)-based gas sensors at room temperature and realizing the accurate detection of trace disease biomarkers are highly desirable for widespread deployments of sensors in exhaled breath. Here, a self-assembly strategy is proposed to create a graphene quantum dot (GQD) functionalized porous and hierarchical SnO2 quantum nanoparticles (SnO2QNP)/ZnO nanostructure. SnO2QNP/ZnO nanosheets self-assembled directly on the digital integrated electrodes with a post-synthetic humidity treatment (psHT), the construction of GQD and SnO2QNP loaded ZnO nanosheet heterostructure is highly controllable and reproducible. The strong synergistic effect and p-n heterojunction between the p-type GQD and n-type SnO2 and ZnO effectively enlarged the resistance variation due to the change in oxygen adsorption. In comparison with pristine ZnO and SnO2/ZnO sensors, the GQD modified hierarchical SnO2QNP/ZnO nanostructure exhibited a remarkably high response (S=15.9 for 0.1 ppm H2S) and rapid response/recovery time (14/13s), and good selectivity towards H2S against other interfering gases. In particular, we applied principal component analysis (PCA) to analyze the sensing performance of GQD-SnO2QNP/ZnO sensor and found that the combined effects of GQD/SnO2QNP/ZnO heterointerfaces contributed to the improvement of selectivity of sensors. The results demonstrate that the GQD modified SMO with the hierarchical structure has a high potential in the non-invasive exhaled diagnosis.
关键词： graphene quantum dot,principal component analysis,exhaled diagnosis,gas sensor,zinc oxide nanosheet,tin dioxide quantum nanoparticle
更新于2025-09-23 15:21:01
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Graphene quantum dot-gold hybrid nanoparticles integrated aptasensor for ultra-sensitive detection of vitamin D3 towards point-of-care application
摘要： Vitamin D is a sunshine vitamin required by the body for various physiological activities. Deficiency of vitamin D (≤ 29 ng mL-1) can cause dental diseases, sarcopenia, osteoporosis, depression, type 2 diabetes, cancer, etc. Additionally, elevated levels of vitamin D (>150 ng mL-1) can result in numerous infirmities such as anorexia, irregular heartbeat, hypercalcemia, fatigue, etc. Hence, periodic detection can help maintain an appropriate level (≥ 30 ng mL-1) of vitamin D in blood serum. Conventional techniques used for the detection of vitamin D are expensive, time consuming, require skilled work force and a specialised laboratory. Herein, we report a portable electrochemical aptasensor for the detection of vitamin D3 using graphene quantum dot-gold (GQD-Au) hybrid nanoparticles. The developed aptasensor has a linear range of 1 nM – 500 nM, limit of detection (LOD) of 0.70 nM (0.28 ng mL-1), limit of quantification (LOQ) of 2.09 nM (0.84 ng mL-1), sensitivity of 0.90 Ω nM-1 mm-2 and a response time <1 minute. The sensor shows high specificity towards vitamin D3, a good stability, shelf life of over 35 days and nearly 98% recovery with serum samples. The developed sensor has been integrated with controlled electronics, thus establishing a portable prototype.
关键词： electrochemical,graphene quantum dot-gold hybrid,aptasensor,Vitamin D3,nanoparticles
更新于2025-09-23 15:21:01
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Graphene quantum dots doped ZnO superstructure (ZnO superstructure/GQDs) for weak UV intensity photodetector application
摘要： Usually, the photoresponse performances of zinc oxide based ultraviolet (UV) photodetector can be enhanced by improving the nanostructure of zinc oxide. Here, we demonstrate a kind of weak ultraviolet intensity photodetector which bases on ZnO superstructure doped with graphene quantum dots (ZnO superstructure/GQDs). The ZnO superstructure includes a ZnO nanoflower on the top of ZnO nanorod. The nanoflower has large specific surface area that is favor to the absorption of weak UV light, and the nanorod provides a good route for carriers transport. Also, the GQDs can assist the absorption of UV and the transport of carriers. The photo-response performance of the ZnO superstructure/GQDs we measured is obtained at a working bias of 3 V and an irradiate condition of 50 μW/cm2, under the excitation wavelength 365 nm. The results show that ZnO superstructure/GQDs has a low dark current (40 nA) and a good photocurrent (2.1 μA) in a low irradiation and power supply condition, and we calculate the current ratio of on/off is about 52.5 times. Further, we discuss in-depth the synthesis mechanism of ZnO superstructure and the transport mechanism of photo-generated carriers in this paper. At the same time, we develop a UV signal acquisition and voltage conversion system, which proves the practical application reference of ZnO superstructure/GQDs for weak UV intensity photodetector.
关键词： Weak ultraviolet detector,Practical application,Graphene quantum dot doping,ZnO superstructure
更新于2025-09-23 15:19:57
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Graphene Quantum Dot Reinforced Electrospun Carbon Nanofiber Fabrics with High Surface Area for Ultra-High Rate Supercapacitors
摘要： High surface area, good conductivity, and high mechanical strength are important for carbon nanofiber fabrics (CNFs) as high-performance supercapacitor electrodes. However, it remains a big challenge because of the trade-off between the strong and continuous conductive network and well-developed porous structure. Herein, we report a simple strategy to integrate these properties into the electrospun CNFs by adding graphene quantum dots (GQDs). The uniformly embedded GQDs play a crucial bi-functional role in constructing entire reinforcing phase and conductive network. Compared with the pure CNF, the GQD-reinforced activated CNF exhibits a greatly enlarged surface area from 140 to 2032 m2 g-1 as well as significantly improved conductivity and strength of 5.5 and 2.5 times, respectively. The mechanism of robust reinforcing effect is deeply investigated. As freestanding supercapacitor electrode, the fabric performs high capacitance of 335 F g-1 at 1 A g-1 and extremely high capacitance retentions of 77% at 100 A g-1 and 45% at 500 A g-1. Importantly, the symmetric device can be charged to 80% capacitance within only 2.2 s, showing great potential for high-power startup supplies.
关键词： graphene quantum dot,carbon nanofiber,ultra-high rate,high surface area,supercapacitor
更新于2025-09-23 15:19:57
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A novel aspect of functionalized graphene quantum dots in cytotoxicity studies
摘要： Graphene quantum dots (GQDs) represent a new generation of graphene-based nanomaterials with enormous potential for use and development of a variety of biomedical applications. However, up to now little studies have investigated the impact of GQDs on human health in case of exposure. GQDs were synthesized from citric acid as carbon precursor by hydrothermal treatment at 160 °C for 4 h. The synthesized GQDs showed strong blue emission under UV-Irradiation with fluorescence quantum yield of 9.8%. The obtained GQDs were further functionalized by nitric acid vapor method. Nitrogen carbonized, activated and adsorption/desorption isotherms were used to analyze the surface area and porous structures of GQDs. The results revealed that compared to GQDs, the specific surface area of functionalized graphene quantum dots (fGQDs) has been increased from 0.0667 to 2.5747 m2/g and pore structures have been enhanced significantly. The potential cytotoxic effect of GQDs, fGQDs and GO suspensions was evaluated on HFF cell line using MTT assays and flow cytometry method after 24 h incubation. We have for the first time demonstrated that by carbonization, activation and functionalization of GQDs they still showed cytocompatible properties. We observed excellent biocompatibility of GQDs and fGQDs at low concentrations. Moreover, the results suggested that modification of GQDs yields product suspensions with high surface area, enhanced pore volume and loading capacities. Thus, fGQDs represent an attractive candidate for further use in drug delivery systems and bio-imaging application.
关键词： Graphene quantum dot,Biocompatibility,Cytotoxicity,Flow cytometry,Functionalized graphene quantum dot
更新于2025-09-19 17:13:59
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Photoexcitation triggering via semiconductor Graphene Quantum Dots by photochemical doping with Curcumin versus perio-pathogens mixed biofilms
摘要： Background: Recently, antimicrobial photodynamic therapy (aPDT) as an alternative treatment modality has been used adjunctively in the treatment of periodontitis and peri-implantitis. Photosensitizing agents in the form of nanoparticles have been designed for improving the e?ciency of aPTD. Graphene quantum dots are a special type of nanocrystals that can promote aPDT when coupled with curcumin (Cur). The main objective of the present study was to investigate the e?ects of photoexcited GQD-Cur on the metabolic activity of perio-pathogen mixed bio?lms. Materials and methods: GQD-Cur was synthesized and characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible spectrometry (UV–Vis), and X-ray di?raction (XRD). The cell cytotoxicity e?ect of GQD-Cur was evaluated on primary human gingival ?broblast (HuGu) cells. Perio-pathogen mixed bio?lms including Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia photosensitized with GQD doped with Cur were irradiated with a blue LED at a wavelength of 435 ± 20 nm for 1 min, and then bacterial viability measurements were performed. The antimicrobial susceptibility pro?le, bio?lm formation ability, amount of reactive oxygen species (ROS) released, and variations of gene expressions involved in bio?lm formation were assessed. Results: The SEM, DLS, FTIR, UV–Vis spectrometry, and XRD pattern con?rmed that GQD-Cur was synthesized successfully. According to the results, GQD-Cur exhibited no cytotoxicity against HuGu cells. Photoexcited GQD-Cur resulted in a signi?cant reduction in cell viability (93%) and bio?lm formation capacity (76%) of peri-pathogens compared to the control group (P < 0.05). According to the results, a signi?cant concentration-dependent increase in the ROS generation was observed in perio-pathogens mixed cells treated with di?erent doses of GQD-Cur-aPDT. Moreover, rcpA, ?mA, and inpA gene expression pro?les were downregulated by 8.1-, 9.6-, and 11.8-folds, respectively. Conclusions: Based on the results, photoexcited GQD-Cur have a high potency of perio-pathogens suppression in planktonic and bio?lm forms and downregulation of the bio?lm genes expression pattern was exploited as a nanoscale-based platform for periodontitis.
关键词： Curcumin,Antimicrobial photodynamic therapy,Graphene Quantum Dot,Peri-implantitis,Periodontitis
更新于2025-09-19 17:13:59
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CO2-Triggered Reversible Phase Transfer of Graphene Quantum Dots for Visible Light-Promoted Amines Oxidation
摘要： Emerging as novel photoluminescent nanomaterials, carbon dots have attracted increasing attentions in photocatalytic application such as hydrogen evolution, carbon dioxide reduction, pollutants degradation and organic synthesis. However, it is always a cumbersome process to seperate the carbon dots from the reaction system, which may limit their application in photocatalysis. Here, we report a graphene quantum dot with CO2-switchable reversible phase transfer performance via a facile surface functionlization approach. The mechanism of this hydrophilicity and hydrophobicity alteration involves protonation-deprotonation transformation and reversibly formation of hydrophilic bicarbonates salts when bubbling and removal of CO2. Afterwards, the obtained graphene quantum dot is utilized as a visible light photocatalyst for oxidative coupling of amines. Our photocatalyst demonstrates an excellent catalytic efficiency with both high reaction conversion and selectivity being achieved. Furthermore, graphen quantum dot could be recycled via a simple CO2 bubbling method.
关键词： graphene quantum dot,reversible phase transfer,visible light photocatalysis,CO2-switchable,amines oxidation
更新于2025-09-19 17:13:59