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Anomalous Stokes shift of colloidal quantum dots and their influence on solar cell performance
摘要： We report an anomalous Stokes shift effect observed in colloidal solutions containing down-shifting Carbon quantum dots (CQDs) of different sizes that is expected to have a positive in?uence on the power conversion ef?ciency of photovoltaic structures. Speci?cally, with an excitation wavelength of 390 nm, individual colloidal solutions of CQDs whose diameter was determined by the applied current during synthesis, exhibited photoluminescent (PL) emission wavelength peaks centered at 420 nm. However, the colloidal solution comprising the mixture of all the previously synthesized CQDs of different diameters was observed to have an anomalous PL Stokes shift centered at 515 nm. Furthermore, the afore-mentioned anomalous SSE was also observed in CdTe QDs when added to the CQD mixed-solution (CMS). Thus, whereas a mixture of CdTe QDs of different sizes, exhibited a down-shifted photoluminescence centered at 555 nm, the peak was observed to have an anomalous Stokes shift centered at 580 nm when combined with the CMS. Quantum dot characterization included crystal structure analysis as well as photon absorption and photoluminescence wavelengths. Subsequently, the synthesized QDs were dispersed in a polymeric layer of PMMA and incorporated on functional and previously characterized solar cells, to quantify their in?uence in the electrical performance of the photovoltaic devices. The observations indicate an improvement in the PCE of 4.6% when incorporating Carbon QDs, 2.9% with CdTe QDs and 4.8% when employing both C and CdTe QDs.
关键词： solar cell performance,photoluminescence,Carbon quantum dots,Anomalous Stokes shift,colloidal quantum dots,CdTe quantum dots,power conversion efficiency
更新于2025-09-11 14:15:04
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A Facile One Step Hydrothermal Synthesis of Carbon Quantum Dots For Label -Free Fluorescence Sensing Approach to Detect Picric Acid in Aqueous Solution
摘要： In this work, a facile one step approach has been applied for the synthesis of nitrogen and sulphur co-doped water soluble carbon quantum dots (NS-CQDs) through hydrothermal treatment of L-Lysine and thiourea. The obtained NS-CQDs have a high quantum yield (QY) of 53.19 % and emit strong blue fluorescence under UV light excitation of wavelength 365 nm. The morphology of NS-CQDs is spherical in shape and their sizes are distributed in the range 5-8 nm with average diameter 6.86 nm. Moreover the NS-CQDs show excitation dependent emission behavior due to quantum confinement effect. Additionally, NS-CQDs serve as a fluorescent probe for the selective and sensitive detection of picric acid (PA) in aqueous solution. A good linear response to PA in the concentration range 1-10 μM with a detection limit 0.24 μM has been obtained. The high selectivity of PA by NS-CQDs is suggested to be arises from fluorescence resonance energy transfer (FRET) mechanism. Finally these NS-CQDs fluorescent probes have been examined in real water sample by measuring the concentration of PA in tap water.
关键词： Fluorescence,quantum yield,Picric acid,Carbon quantum dots
更新于2025-09-11 14:15:04
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High Amplification of the Antiviral Activity of Curcumin through Transformation into Carbon Quantum Dots
摘要： It is demonstrated that carbon quantum dots derived from curcumin (Cur-CQDs) through one-step dry heating are effective antiviral agents against enterovirus 71 (EV71). The surface properties of Cur-CQDs, as well as their antiviral activity, are highly dependent on the heating temperature during synthesis. The one-step heating of curcumin at 180 °C preserves many of the moieties of polymeric curcumin on the surfaces of the as-synthesized Cur-CQDs, resulting in superior antiviral characteristics. It is proposed that curcumin undergoes a series of structural changes through dehydration, polymerization, and carbonization to form core–shell CQDs whose surfaces remain a pyrolytic curcumin-like polymer, boosting the antiviral activity. The results reveal that curcumin possesses insignificant inhibitory activity against EV71 infection in RD cells [half-maximal effective concentration (EC50) >200 μg mL?1] but exhibits high cytotoxicity toward RD cells (half-maximal cytotoxic concentration (CC50) <13 μg mL?1). The EC50 (0.2 μg mL?1) and CC50 (452.2 μg mL?1) of Cur-CQDs are >1000-fold lower and >34-fold higher, respectively, than those of curcumin, demonstrating their far superior antiviral capabilities and high biocompatibility. In vivo, intraperitoneal administration of Cur-CQDs significantly decreases mortality and provides protection against virus-induced hind-limb paralysis in new-born mice challenged with a lethal dose of EV71.
关键词： carbon quantum dots,curcumin,enterovirus 71,antiviral agents,viral infection
更新于2025-09-11 14:15:04
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Improving the power conversion efficiency of perovskite solar cells by adding carbon quantum dots
摘要： High-quality perovskite films are the key factor in manufacturing high-performance devices. In this work, we for the first time use carbon quantum dots (CQDs) as additive in the methylammonium iodide solution for high-quality CH3NH3PbI3 films. Appropriate concentration of CQDs (0.04 mg ml-1) can passivate the crystal defects, improve the crystallinity, increase the grain size and reduce the grain boundary of MAPbI3 film. Various characterization results show that CQDs additive can reduce trap-state density, decrease carrier recombination and improve photoelectric performance. Compared with the pristine device, the average power conversion efficiency (PCE) of CQD-modified MAPbI3 device was increased from 15.8 ± 0.37% to 18.81 ± 0.45%, and the maximum PCE of champion device was increased from 16.21 to 19.17%. In this study, we propose a simple method for the preparation of stable and efficient inverted planar structure perovskite solar cells using CQD additives in a two-step spin-coated deposition method.
关键词： perovskite solar cells,additive engineering,photoelectric performance,power conversion efficiency,carbon quantum dots
更新于2025-09-11 14:15:04
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Determination of Dopamine by a Label-Free Fluorescent Aptasensor Based on AuNPs and Carbon Quantum Dots
摘要： In order to reduce the complex modification process and obtain a fast and label-free aptasensor, a label-free fluorescent aptasensor based on gold nanoparticles (AuNPs) and carbon quantum dots (CQDs) was constructed for rapid determination of dopamine (DA). In the absence of DA, CQDs were adsorbed on the surface of AuNPs through the electrostatic force between CQDs and aptamer, which led to the fluorescence quenching of CQDs. When DA were added, they combined with the corresponding aptamers with higher affinity and selectivity, resulting in CQDs far from the surface of AuNPs and thus the fluorescence intensity of CQDs was recovered. Under the optimal condition, the fluorescence intensity of the released CQDs was linearly proportional to the concentration of DA in a range of 5×10-8~2.5×10-4mol/L with a detection limit of 1×10-8mol/L. Moreover, the aptasensor exhibited a satisfactory detection result of DA in human serum samples. This study provided a more effective method to detect a broad range of targets by using appropriate aptamers, holding great potential in the field of food safety and biomedical diagnostics.
关键词： Label-free,Gold nanoparticles,Fluorescent aptasensor,Carbon quantum dots
更新于2025-09-11 14:15:04
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Chitosan-carbon quantum dots as a new platform for highly sensitive insulin impedimetric aptasensor
摘要： Considering the importance of measuring insulin in the prevention and diagnosis of diabetes-related illnesses, here we introduced an ultrasensitive electrochemical aptamer-based sensor for detection of insulin in human blood serum. In this research, carbon quantum dots (CQDs) were synthesized using simple, fast and cheap methods from candle soot. By dispersion of the CQDs in chitosan (Chi) matrix, homogenous CQD-Chit nano-composite was obtained. The experimental results demonstrate the good advantages of proposed CQD-Chit nano-composite, such as homogeneity, high stability and multiple amino groups for covalent immobilization of aptamer and fabrication of highly selective insulin aptasensor. CQD-Chit nano-composite was characterized by the transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDAX), Fourier transform infrared (FTIR) spectroscopy and electrochemical techniques. Under the optimized conditions with electrochemical impedance spectroscopy technique, a linear response ranges from 0.5 nM to 10 nM with the sensitivity of 80.07 ?/nM and the very low detection limit of 106.8 pM was obtained for insulin detection. The fabricated aptasensor is validated in comparison with standard methods for detection of insulin in human blood serum. Also, the analytical performances of the fabricated aptasensor can be a superiority compared to the current insulin electrochemical biosensors.
关键词： Modifies electrode,Biosensor,Impedimetric aptasensor,Carbon quantum dots,Insulin detection
更新于2025-09-11 14:15:04
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Green synthesized plasmonic nanostructure decorated TiO2 nanofibers for photoelectrochemical hydrogen production
摘要： We herein present the Au and Ag NPs synthesized via chemical reduction with green synthesized carbon nanolights (CNL) as a visible light photosensitizer for TiO2 nanofibers (TNFs) towards photoelectrochemical water splitting. The synthesized photoanodes (PA1: TNFs, PA2: Ag@CNLs/TNFs and PA3: Au@CNLs/TNFs) were probed ex-situ for morphological, structural, optical and electronic properties before being used for the PEC experiments. We first show the efficient photocatalytic activity of these photoanodes for the degradation of methylene blue under visible light irradiation. Followed by the photoelectrochemical (PEC) water splitting investigation, which reveals the substantially improved photocurrent density to 13 mA/cm2 and 18 mA/cm2, for PA2 and PA3, respectively under simulated AM 1.5 solar illumination at 1.36 V vs RHE, ~15 fold enhancement compared to that obtained for a PA1. This improvement we attributed to the synergic consequence, improved absorption and effective charge carrier separation & transport due to surface plasmonic effect, which is well evident in the decrease of measured charge transfer resistance (Rct), for PA2 (15.1 Ω) and PA3 (6.71 Ω), as compared to PA1 (139 Ω).
关键词： TiO2 nanofibers,Green synthesis,Hydrogen,Photo-electrochemical,Carbon quantum dots,Plasmonic nanostructures
更新于2025-09-11 14:15:04
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Aqueous Carbon Quantum Dot-Embedded PC60-PC <sub/>61</sub> BM Nanospheres for Ecological Fluorescent Printing: Contrasting Fluorescence Resonance Energy-Transfer Signals between Watermelon-like and Random Morphologies
摘要： To go beyond the PC60 surfactant structure, the double-layer micelle morphology in water motivates exploration of altered protocols to produce new morphologies. Furthermore, the low photoluminescence quantum yield of aqueous fullerene-based particles encourages high fluorescence to create a light-emitting display. With this in mind, we established new hybrid n-type nanospheres with carbon quantum dot (CQD)-embedded PC60-PC61BM particles, processed using two different protocols. The homogenizer-assisted PC60-CQD-PC61BM resulted in a watermelon-shaped spherical particle, whereas a circular morphology with randomly embedded CQDs was observed in the microwave-treated hybrids. More surprisingly, the watermelon-shaped colloid induced efficient fluorescence resonance energy transfer (FRET) between the CQD and C60 molecules of PC61BM, and the FRET-mediated emission signature diminished gradually as the stripe patterns collapsed. This phenomenon allowed different fluorescent colors in the colloidal printing film. We thereby provided the new carrier dynamics of the particle photonic activities of the developed aqueous PC60-based colloids with the possibility of ecological utilization.
关键词： water-processable organic semiconductor colloids,fullerene-based nanoparticles,fluorescence resonance energy transfer,ecological fluorescent printing,carbon quantum dots
更新于2025-09-11 14:15:04
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An Unexpected Transformation of Organic Solvents into 2D Fluorescent Quantum Dots During Ultrasonication Assisted Liquid Phase Exfoliation
摘要： Ultrasonication within organic solvents is widely used to exfoliate layered materials and produce two-dimensional (2D) nanostructures. Several 2D materials synthesized by such liquid phase exfoliation (LPE) approaches are reported to exhibit photoluminescence. In these approaches, it is presumed that while the 2D nanostructures are derived from the layered parent material undergoing delamination, the organic solvent serves as a dispersing medium. However, in this study, we show that the organic solvent also contributes towards formation of 2D nanostructures that are optically active. We show that that bare organic solvent, when exposed to ultrasonication, transforms into 2D photoluminescent carbon quantum dots (CQDs) that display blue, cyan, green, and yellow emissions depending upon the excitation wavelength. Although this finding is intuitive, it has remained unacknowledged in the design of experiments which require ultrasonication of layered materials in organic solvents. Our results suggest that optical properties of dispersions obtained by LPE embody a contribution not only from the 2D nanostructures derived from the layered material but also from the 2D CQDs that are formed as a natural result of the liquid medium being exposed to ultrasonication. We anticipate that this new physical insight would form an important addition to the guidelines for exfoliation and help in rightly inferring the optical properties of the 2D material dispersions produced by these methods.
关键词： 2D nanostructures,Carbon quantum dots,Organic solvents,Liquid phase exfoliation,Ultrasonication,Photoluminescence
更新于2025-09-11 14:15:04
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Effect of carbon quantum dots on the optical and electrical properties of polyvinylidene fluoride polymer for optoelectronic applications
摘要： In this work, the effect of carbon quantum dots (CQDs) on the optical and electrical properties of polyvinylidene fluoride (PVDF) has been investigated. Different weight percent (0, 1, 3, 5 and 10 wt%) ratios of CQDs/PVDF nanocomposite films were prepared using solution casting technique. The morphological properties of CQDs were examined using a transmission electron microscope (TEM). The optical properties of the prepared plain PVDF and CQDs/PVDF nanocomposite films were measured using UV–Visible spectrophotometer in the wavelength range 190–1200 nm. The direct energy band gap (Eg dir.) of the prepared films decreases from 5.28 to 2.96 eV as the wt% ratio of CQDs/PVDF increases from 0 to 10.0%. The DC electrical conductivity (σDC) of the prepared nanocomposite films are measured in the temperature range from 298 to 398 K. The electrical conductivity of the nanocomposite films has been enhanced six times in magnitude as compared with that of the plain PVDF film, as the wt% ratio of CQDs/PVDF increases up to 10 wt%. The enhancement in the optical and electrical properties of PVDF makes it as a novel candidate in various optoelectronic applications.
关键词： Optical properties,Electrical properties,Polyvinylidene fluoride,Nanocomposite films,Carbon quantum dots
更新于2025-09-11 14:15:04