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Graphene quantum dot based charge-reversal nanomaterial for nucleus-targeted drug delivery and efficiency controllable photodynamic therapy
摘要： Graphene quantum dots (GQD), the new zero-dimensional carbon nanomaterial, has been demonstrated as a promising material for biomedical applications due to its good biocompatibility and low toxicity. However, the integration of multiple therapeutic approaches into a nano-sized platform based on the GQD has not been explored yet to our best knowledge. In this report, we regulate the generation of reactive oxygen species (ROS) when using the GQD as a photosensitizer by varying the doping amount of nitrogen atoms to achieve efficiency controllable photodynamic therapy (PDT). On the other hand, charge-reversal (3-Aminopropyl) triethoxysilane (APTES) was employed to conjugate on the surface of GQD for nucleus targeting drug delivery for the first time. The treatment outcome of produced ROS and nucleus-targeting drug delivery was investigated by fluorescence imaging. The results demonstrated that the N-GQD-DOX-APTES in dual roles as a drug carrier and photosensitizer could achieve nucleus-targeting delivery and strong ROS production simultaneously. This approach provides a promising strategy for the development of multifunctional therapy in one nano platform for biomedical applications.
关键词： nucleus-targeted drug delivery,Graphene quantum dots,nitrogen doped graphene quantum dots,charge-reversal,photodynamic therapy
更新于2025-11-21 11:24:58
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Highly sensitive and selective label-free detection of dopamine in human serum based on nitrogen-doped graphene quantum dots decorated on Au nanoparticles: Mechanistic insights through microscopic and spectroscopic studies
摘要： A rapid, facile and label-free sensing strategy is developed for the detection of dopamine (DA) in the real samples by exploiting nitrogen-doped graphene quantum dots (N-GQDs) decorated on Au nanoparticles (Au@N-GQD). The as-grown Au@N-GQD exhibits strong blue fluorescence at room temperature and the fluorescence intensity is drastically quenched in presence of DA in neutral medium. The mechanistic insight into the DA sensing by Au@N-GQDs is explored here by careful monitoring of the evolution of the interaction of Au NPs and N-GQDs with DA under different conditions through electron microscopic and spectroscopic studies. The highly sensitive and selective detection of DA over a wide range is attributed to the unique core-shell structure formation with Au@N-GQD hybrids. The quenching mechanism involves the ground state complex formation as well as electron transfer from N-GQDs. The presence of Au NPs in Au@N-GQD hybrids accelerates the quenching process (~14 fold higher than bare N-GQDs) by the formation of stable dopamine-o-quinone (DQ) in this present detection scheme. The fluorescence quenching follows the linear Stern-Volmer plot in the range 0-100 μM, establishing its efficacy as a fluorescence-based DA sensor with a limit of detection (LOD) 590 nM, which is ~27 fold lower than the lowest abnormal concentration of DA in serum (16 μM). This sensing scheme is also successively applied to trace DA in Brahmaputra river water sample with LOD 480 nM including its satisfactory recovery (95-112%). Our studies reveal a novel sensing pathway for DA through the core-shell structure formation and it is highly promising for the design of efficient biological and environmental sensor.
关键词： Dopamine,Fluorescence quenching,Nitrogen-doped graphene quantum dots,Colorimetric sensing,Core-shell structure,Gold nanoparticles
更新于2025-11-21 11:01:37
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Sulfur and Nitrogen Co-Doped Graphene Quantum Dots as a Fluorescent Quenching Probe for Highly Sensitive Detection toward Mercury Ions
摘要： Sulfur and nitrogen co-doped graphene quantum dots (SN-GQDs) were synthesized through an efficient infrared (IR)-assisted pyrolysis of glucose, urea, and ammonia sulfate at 260°C. These served as a highly selective probe for the sensing of Hg2+ ions in an aqueous solution. The IR technique can also prepare N-doped graphene quantum dots (N-GQDs), which have been compared with SN-GQDs for their fluorescence (FL) quenching sensitivities by Hg2+ ions. The FL intensities of both GQDs show decreasing functions of concentration of Hg2+ ions within the entire concentration ranges of 10 ppb?10 ppm. The sensitivity of SN-GQD is 4.23 times higher than that of N-GQD, based on the calculation of the Stern-Volmer equation. One inter-band gap structure of SN-GQDs for the detection of mercury ions is proposed. The S doping can coordinate with phenolic groups on the edge of SN-GQDs (i.e., the formation of (CxO)2Hg2+) and induce the cutting off or alleviation of photon injection paths, thereby leading to significant FL quenching. This work proves that SN-GQD offers sufficient sensitivity for probing the quality of drinking water to ensure that it contains less than 10 ppb of Hg2+ ions, as per the World Health Organization standard.
关键词： Fluorescence quenching,Nitrogen doping,Infrared-assisted heating,Graphene quantum dots,Sulfur doping,Mercury detection
更新于2025-11-19 16:56:42
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Nitrogen-doped graphene quantum dots: Optical properties modification and photovoltaic applications
摘要： In this work, we utilize a bottom-up approach to synthesize nitrogen self-doped graphene quantum dots (NGQDs) from a single glucosamine precursor via an eco-friendly microwave-assisted hydrothermal method. Structural and optical properties of as-produced NGQDs are further modified using controlled ozone treatment. Ozone-treated NGQDs (Oz-NGQDs) are reduced in size to 5.5 nm with clear changes in the lattice structure and ID/IG Raman ratios due to the introduction/alteration of oxygen-containing functional groups detected by Fourier-transform infrared (FTIR) spectrometer and further verified by energy dispersive X-ray spectroscopy (EDX) showing increased atomic/weight percentage of oxygen atoms. Along with structural modifications, GQDs experience decrease in ultraviolet–visible (UV–vis) absorption coupled with progressive enhancement of visible (up to 16 min treatment) and near-infrared (NIR) (up to 45 min treatment) fluorescence. This allows fine-tuning optical properties of NGQDs for solar cell applications yielding controlled emission increase, while controlled emission quenching was achieved by either blue laser or thermal treatment. Optimized Oz-NGQDs were further used to form a photoactive layer of solar cells with a maximum efficiency of 2.64% providing a 6-fold enhancement over untreated NGQD devices and a 3-fold increase in fill factor/current density. This study suggests simple routes to alter and optimize optical properties of scalably produced NGQDs to boost the photovoltaic performance of solar cells.
关键词： photovoltaics,optical properties,ozone treatment,nitrogen-doped graphene quantum dots,solar cells
更新于2025-11-19 16:56:42
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Microwave-assisted synthesis of graphene quantum dots and nitrogen-doped graphene quantum dots: Raman characterization and their optical properties
摘要： In this report we will present completely new results on the improvement of the graphene quantum dots (GQDs) and nitrogen-doped graphene quantum dots (N-GQD) production method, using the microwave with different power levels and durations, from citric acid and urea. This is a new and unprecedented method of fabrication. The use of microwave has allowed ultra-fast fabrication of GQDs and nitrogen doped GQDs. These GQDs had their characteristics identi?ed by Raman scattering spectra for the characteristic C–C graphene vibration mode (G-peak) and defects of GQDs (D-peak). The absorption spectra of GQDs samples were fabricated under different conditions, with the expectation of different sizes, to be compared and analyzed. These absorption spectra were also compared with those of the N-GQD produced under the same conditions. The absorption mechanism of GQDs and N-GQD will be presented in detail. Measurements of the photoluminescence (PL) spectra in GQDs and N-GQD have also been recorded and analyzed. The ?uorescence mechanism will be presented, explained, and compared with other international publications of other authors. Some of the TEM and HR-TEM images of these two samples were also presented to con?rm the shape, size and in-plane spacing lattice of the GQD structure.
关键词： graphene quantum dots (GQDs),PL spectra,nitrogen-doped graphene quantum dots (N-GQD),microwave,Raman spectra,absorption spectra
更新于2025-11-19 16:56:42
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Determination of Thiourea by On–Off Fluorescence Using Nitrogen-Doped Graphene Quantum Dots
摘要： A thiourea-detecting fluorescence sensor with Hg2t as a switch was developed using nitrogen-doped graphene quantum dots (N-GQDs). The surface of N-GQDs had many organic functional groups on which Hg2t was effectively bound and turned off the fluorescence of the N-GQDs. The fluorescence of N-GQDs was turned on by the thiol functional group of thiourea that bound strongly with Hg2t and formed Hg2t/thiourea complexes. After constructing the sensor, the experimental conditions and parameters, such as the pH and Hg2t concentration, were investigated and optimized. Under the optimum conditions, the constructed fluorescence sensor showed high sensitivity to thiourea at concentrations from 0.5 to 14 mM with a low detection limit of 41.7 nM. The sensor also exhibited high specificity, excellent stability, and good reproducibility so that the determination of thiourea in various samples had acceptable values with good recoveries from 99% to 106%. The relative standard deviation was less than 4.1% (n ? 3).
关键词： thiourea,Fluorescence,nitrogen-doped graphene quantum dots (N-GQDs),Hg2t,sensor
更新于2025-11-14 17:04:02
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Directed Nanoscale Self-assembly of Natural Photosystems on Nitrogen-doped Carbon Nanotubes for Solar Energy Harvesting
摘要： Natural photosystems (PSs) have received much attention as a biological solar energy harvester because of their high quantum efficiency for energy transfer. However, the PSs hybridized with solid electrodes exhibit low light-harvesting efficiencies because of poor interface properties and random orientations of PSs, all of which interfere with efficient charge extraction and transfer. Herein, we report the linker-free, oriented self-assembly of natural PSs with nitrogen-doped carbon nanotubes (NCNTs) via electrostatic interaction. Protonated nitrogen-doped sites on the NCNTs facilitate spontaneous immobilization of the negatively charged stroma side of PSs, which provides a favorable orientation for electron transfer without electrically insulating polymer linkers. The resulting PS/NCNT hybrids exhibit a photocurrent density of 1.25 ± 0.08 μA cm-2, which is much higher than that of PS/CNT hybrids stabilized with polyethylenimine (0.60 ± 0.01 μA cm-2) and sodium dodecyl sulfate (0.14 ± 0.01 μA cm-2), respectively. This work emphasizes the importance of the linker-free assembly of PSs into well-oriented hybrid structures to construct an efficient light-harvesting electrode.
关键词： Light-harvesting,Electrostatic interaction,Photosystems,Nitrogen-doped carbon nanotubes,Self-assembly
更新于2025-11-14 15:29:11
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Wafer-scale Fabrication of Nitrogen-doped Reduced Graphene Oxide with Enhanced Quaternary-N for High-Performance Photodetection
摘要： We demonstrated a simple and scalable fabrication route of nitrogen-doped reduced graphene oxide (N-rGO) photodetector on 8-inch wafer-scale. The N-rGO was prepared through in-situ plasma-treatment in an acetylene-ammonia atmosphere to achieve n-type semiconductor with substantial formation of quaternary-N substituted into the graphene lattice. The morphology, structural, chemical composition and electrical properties of the N-rGO was carefully characterized and being used for the device fabrication. The N-rGO devices were fabricated in a simple metal-semiconductor-metal (MSM) structure with unconventional metal-on-bottom configuration to promote high-performance photodetection. The N-rGO devices exhibited enhanced photoresponsivity as high as 0.68 A W?1 at 1.0 V, which is about two orders of magnitude higher compared to a pristine graphene and wide-band photo-induced response from visible to near-infrared (NIR) region with increasing sensitivity in the order of 785 nm, 632.8 nm and 473 nm excitation wavelengths. We also further demonstrated a symmetric characteristic of photo-induced response to any position of local laser excitation with respect to the electrodes. The excellent features of wafer-scale N-rGO devices suggest a promising route to merge the current silicon technology and two-dimensional materials for future optoelectronic devices.
关键词： photodetector,plasma treatment,quaternary-N,wafer-scale fabrication,Nitrogen-doped reduced graphene oxide
更新于2025-09-23 15:23:52
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Harnessing designer biotemplates for biomineralization of TiO2 with tunable photocatalytic activity
摘要： Biomineralization is a promising material synthesis strategy for environmentally benign production of nanostructured metal oxides. An important question is whether biomineralization can be used in the biomimetic synthesis of TiO2 with tunable photocatalytic properties that are conducive to diverse solar energy conversion applications. Here, we report the biomineralization of energy-state-modified TiO2 nanoparticles, where the critical properties closely related to their photocatalytic activity can be manipulated by tailoring the nature of the designer biotemplates. For this purpose, STB1 heptapeptide was employed as a nucleation center to induce TiO2 biomineralization. Three distinctive types of biomolecules (peptide, protein, and phage) were deliberately designed to contain the STB1 nucleation core at different local densities and intermolecular distances. The degree of substitutional nitrogen-doping and the morphology are all subject to the context-dependent differential availability of STB1 in the biomineralization milieu. Phage-induced biomineralization results in TiO2 with modified energy state and wire-like network morphology, which account for significantly enhanced charge dissociation/transport performance and high photocatalytic activity. This is the first study to report that a specific peptide with biomineralizing activity exerts differential impacts on the properties of resulting biomineralization products in a context-dependent manner, and will provide a powerful new strategy for tailoring of material properties via biomineralization.
关键词： Biomineralization,Titanium dioxide,Photocatalyst,in situ substitutional nitrogen-doping,Designer biotemplate
更新于2025-09-23 15:23:52
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A deep learning based feature extraction method on hyperspectral images for nondestructive prediction of TVB-N content in Pacific white shrimp (Litopenaeus vannamei)
摘要： Hyperspectral imaging (HSI) technique with spectral range of 900e1700 nm was implemented to predict total volatile basic nitrogen (TVB-N) content in Pacific white shrimp. Successive projections algorithm (SPA) and deep-learning-based stacked auto-encoders (SAEs) algorithm were comparatively used for spectral feature extraction. Least-squares support vector machine (LS-SVM), partial least squares regression (PLSR) and multiple linear regression (MLR) were used for prediction. The results demonstrated that the SAEs-based prediction models (SAEs-LS-SVM, SAEs-MLR and SAEs-PLSR) performed better than either full wavelengths-based or SPA-based prediction models. The SAEs-LS-SVM was considered to be the best model with RP2 value of 0.921, RMSEP value of 6.22 mg N [100 g]?1, RPD value of 3.58 and computational time of 3.9 ms for predicting TVB-N in prediction set. The results of this study indicated that SAEs has a high potential in the multivariate analysis of hyperspectral images for shrimp quality inspections.
关键词： Stacked auto-encoders,Pacific white shrimp,Total volatile basic nitrogen,Nondestructive prediction,Hyperspectral imaging
更新于2025-09-23 15:23:52