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1.
石墨烯量子点(GQDs)作为石墨烯家族的最新一员,除了继承石墨烯的优异性能,还因量子限制效应和边界效应而显现出一系列新的特性,引起了化学、物理、材料和生物等各领域科研工作者的广泛关注。GQDs的制备方法通常分自上而下和自下而上的方法。对其各种制备方法和应用分别进行了介绍,并结合各种应用对GQDs的要求给出了制备方法的建议。指出了GQDs研究中存在的问题及发展方向。  相似文献   

2.
作为纳米载体,石墨烯量子点已广泛应用于生物医药领域,然而对于异质结构的石墨烯量子点细胞膜内化路径研究不足。从空间异质性结构设计出发,构建了一系列不同氧化程度与空间异质分布的Janus石墨烯量子点。基于分子动力学模拟研究了不同结构的Janus石墨烯量子点跨膜输运行为,通过分析跨膜输运过程中的构型变化、分子间作用能量、溶剂可及面积等参数,发现Janus石墨烯量子点跨膜输运行为由亲水-亲油平衡、空间异质分布控制,且呈现外力牵引依赖性变化。本文在分子水平上系统研究了Janus石墨烯量子点与细胞膜相互作用规律,对其结构设计及生物医药应用提供理论指导。  相似文献   

3.
作为纳米载体,石墨烯量子点已广泛应用于生物医药领域,然而对于异质结构的石墨烯量子点细胞膜内化路径研究不足。从空间异质性结构设计出发,构建了一系列不同氧化程度与空间异质分布的Janus石墨烯量子点。基于分子动力学模拟研究了不同结构的Janus石墨烯量子点跨膜输运行为,通过分析跨膜输运过程中的构型变化、分子间作用能量、溶剂可及面积等参数,发现Janus石墨烯量子点跨膜输运行为由亲水-亲油平衡、空间异质分布控制,且呈现外力牵引依赖性变化。本文在分子水平上系统研究了Janus石墨烯量子点与细胞膜相互作用规律,对其结构设计及生物医药应用提供理论指导。  相似文献   

4.
A simple and effective chemical method was reported to enhance the fluorescence of graphene quantum dots (GQDs). Specifically, water-soluble GQDs, prepared by solvothermal synthesis from graphene oxide, are chemically reduced by hydrazine hydrate to produce reduced GQDs (rGQDs). The results show that the hydrazine hydrate reduction not only decreases the O/C atomic ratio of GQDs, also changes the bonding type of N atoms. Such surface/edge chemical bond change of GQDs results in that as-made rGQDs exhibit more than two times fluorescence intensity as strong as that of the pristine GQDs.  相似文献   

5.
Wang J  Xin X  Lin Z 《Nanoscale》2011,3(8):3040-3048
Semiconductor quantum dots exhibit great potential for applications in next generation high efficiency, low cost solar cells because of their unique optoelectronic properties. Cu(2)ZnSnS(4) (CZTS) nanocrystals and graphene quantum dots (GQDs) have recently received much attention as building blocks for use in solar energy conversion due to their outstanding properties and advantageous characteristics, including high optical absorptivity, tunable bandgap, and earth abundant chemical composition. In this Feature Article, recent advances in the synthesis and utilization of CZTS nanocrystals and colloidal GQDs for photovoltaics are highlighted, followed by an outlook on the future research efforts in these areas.  相似文献   

6.
We report a novel method to prepare graphene quantum dots (GQDs) from graphene hydrogels. Graphene hydrogels were prepared using a hydrothermal technique, and GQDs were released from the hydrogels on immersion of the hydrogels in low-polarity organic solvents. This method did not require additional treatments such as the centrifugation, filtration and dialysis typical of the general hydrothermal method. These GQDs were observed to fluoresce, with their strongest emission in the near-UV region, at ∼347 nm. Moreover, these GQDs, when in their pure state, formed a highly viscous liquid insoluble in water due to their lack of many oxygen-containing functional groups.  相似文献   

7.
We report on a new method for synthesising strongly blue and green photoluminescent graphene quantum dots (GQDs). Graphene was prepared by a new feasible method using an intensive cavitation field in a pressurised ultrasonic batch reactor. The prepared graphene was quantitatively converted to graphene oxide using our modified, safer Hummer’s method. Graphene oxide was characterised by microscopic (AFM and TEM) and spectral (infrared and Raman) methods, and the thermal stability of graphene oxide was determined using thermal analysis (DTA-TG). GQDs were prepared by a one-pot reaction, refluxing graphene oxide in different solvents (ethylene glycol, polyethylene glycol, dimethylformamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone) at atmospheric pressure. The synthesised GQDs were characterised by infrared, UV–Vis absorption and photoluminescence spectroscopy, X-ray photoelectron spectroscopy (XPS) and AFM microscopy.  相似文献   

8.
Water-soluble and blue luminescent graphene fluoroxide quantum dots (GFOQDs) with tunable fluorine coverage and size were effectively synthesized from exfoliated fluorinated graphene (FG) by sacrificing certain fluorine to improved solubility and reaction activity. Morphology investigation indicates that the obtained GFOQDs possess narrow size distribution and the average size is 2.5–3.5 nm. Chemical composition analysis confirms that besides C–F covalent bonds, C–O bonds in the forms of hydroxyl and carbonyl co-exist on the structure of GFOQDs. Moreover, photoluminescence performance research considering the surface state and size has also been conducted, and as anticipated in carbon-based quantum dots the GFOQDs exhibit excitation wavelength-dependent properties. Additionally, rather different from other graphene quantum dots (GQDs) that are often susceptible to pH without additional surface passivation, the GFOQDs themselves are poised to resist pH effects and display stable luminescence in both acid and alkali conditions. These results indicate that our method not only opens up a new avenue to prepare GQDs decorated with fluorine and oxygen, but also can find practical applications in novel GQDs-based devices that require water solubility while keep chemical stability and resistance against pH.  相似文献   

9.
Graphene quantum dots (GQDs) have been developed as promising optical probes for bioimaging due to their excellent photoluminescent properties. Additionally, the fluorescence spectrum and quantum yield of GQDs are highly dependent on the surface functional groups on the carbon sheets. However, the distribution and cytotoxicity of GQDs functionalized with different chemical groups have not been specifically investigated. Herein, the cytotoxicity of three kinds of GQDs with different modified groups (NH2, COOH, and CO-N (CH3)2, respectively) in human A549 lung carcinoma cells and human neural glioma C6 cells was investigated using thiazoyl blue colorimetric (MTT) assay and trypan blue assay. The cellular apoptosis or necrosis was then evaluated by flow cytometry analysis. It was demonstrated that the three modified GQDs showed good biocompatibility even when the concentration reached 200 μg/mL. The Raman spectra of cells treated with GQDs with different functional groups also showed no distinct changes, affording molecular level evidence for the biocompatibility of the three kinds of GQDs. The cellular distribution of the three modified GQDs was observed using a fluorescence microscope. The data revealed that GQDs randomly dispersed in the cytoplasm but not diffused into nucleus. Therefore, GQDs with different functional groups have low cytotoxicity and excellent biocompatibility regardless of chemical modification, offering good prospects for bioimaging and other biomedical applications.  相似文献   

10.
Graphene and its derivatives exhibit many interesting photoluminescence (PL) properties because of their unique electronic structures. In spite of the absence of the bandgap, graphene shows PL due to hot electrons. Graphene oxide (GO) fluorescence is different from that of a single organic fluorophore, for which the spectral properties and emission lifetime are independent of wavelength. Single-layered GO sheets are made of a large number of covalently connected independent fluorophores of varying sizes. These fluorophores are aromatic π-conjugated sp2-hybridized subsystems of carbon atoms surrounded by sp3 regions. The PL of GO is pH dependent because of the presence of many oxygen-containing groups in GO sheets. Reduced graphene oxide (rGO) PL is somewhat different from GO because the number and size of sp2 fragments are increased in rGO due to the elimination of the functional groups containing oxygen via reduction. Nanosized graphene/GO possesses a strong quantum confinement effect and hence emits intense excitation wavelength-dependent PL. Moreover, graphene quantum dots show upconversion PL due to anti-Stokes transition. The diverse PL properties including the effect of reduction, pH, and solvent have been reported in many recent studies. Here, the versatile PL features of graphene derivatives are reviewed to elucidate the mechanism of PL.  相似文献   

11.
Wang ZF  Liu F 《Nanoscale》2011,3(10):4201-4205
Quantum cellular automata (QCA) is an innovative approach that incorporates quantum entities in classical computation processes. Binary information is encoded in different charge states of the QCA cells and transmitted by the inter-cell Coulomb interaction. Despite the promise of QCA, however, it remains a challenge to identify suitable building blocks for the construction of QCA. Graphene has recently attracted considerable attention owing to its remarkable electronic properties. The planar structure makes it feasible to pattern the whole device architecture in one sheet, compatible with the existing electronics technology. Here, we demonstrate theoretically a new QCA architecture built upon nanopatterned graphene quantum dots (GQDs). Using the tight-binding model, we determine the phenomenological cell parameters and cell-cell response functions of the GQD-QCA to characterize its performance. Furthermore, a GQD-QCA architecture is designed to demonstrate the functionalities of a fundamental majority gate. Our results show great potential in manufacturing high-density ultrafast QCA devices from a single nanopatterned graphene sheet.  相似文献   

12.
The effective use of solar energy in sewage disposal has been extensively investigated. This work focuses on the photocatalytic property of graphene quantum dots (GQDs) and polymer-modified GQDs under visible light. A hydrothermal synthesis route to GQDs was developed by using citric acid as a carbon precursor. The GQDs were modified with polyethylenimine (PEI) and polyethylene glycol (PEG). The obtained GQDs, GQDs-PEIs, and GQDs-PEGs were characterized and their structural information was determined through Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), photoluminescence spectroscopy, and UV–Vis absorption spectroscopy. Results revealed that the GQDs were uniform in size (2–5 nm) and rich in oxygen-containing groups. The GQDs exhibited a strong blue and excitation-independent photoluminescent behavior under excitation wavelengths of 320–420 nm. The photocatalytic performance of these samples was demonstrated on the basis of methylene blue (MB) degradation. The photocatalytic rates of GQDs, GQDs-PEIs, and GQDs-PEGs decreased successively. The polymer-modified GQDs could qualitatively control the degradation rate of MB. Free radical species were generated to oxidize MB under light irradiation. Thus, photocatalytic organic matter degradation, sustained drug release, and tracking can be combined to implement proper sewage disposal.Prime noveltyThe main object of this work is to find out a novel property of graphene quantum dots (GQDs) as efficient nanomaterials for degradation of organic pollutant dyes under visible light irradiation. And, the GQDs exhibited a strong blue and excitation-independent photoluminescent behavior under excitation wavelengths of 320–420 nm. Moreover, the degradation rate could be qualitatively controlled by using different polymer-modified GQDs. Thus, photocatalytic organic matter degradation, sustained drug release, and tracking can be combined to implement proper sewage disposal. Also, the degradation mechanism is discussed.  相似文献   

13.
Graphene quantum dots (GQDs) have inspired growing research efforts. Although continuous progresses have been achieved in the syntheses of diverse GQDs, it is still a challenge in size-controllable and high-yield preparation of well dispersed GQDs via simple routes. Herein, we present a top-down synthesis of GQDs by using a SBA-15 template as a nanoreactor via a HNO3 vapor cutting strategy. With the recyclable ordered mesoporous SBA-15 template and a silica grid, a high-yield (48%) preparation as well as a facile separation of yellow-luminescent GQDs have been achieved. The obtained GQDs containing abundant oxygen-containing groups (ca. 30% for oxygen content) showed a narrow size distribution (2.5–5.2 nm), good water solubility, good photostability and high selectivity for Fe(III) sensing in tap water with satisfying recovery. Further experiments indicated that Cu(II), Co(II), Mn(II), Ni(II) could also quench the fluorescence of the as-prepared GQD after its surface states being adjusted, which might presage more possible applications of this material.  相似文献   

14.
An easy bottom–up method for the preparation of photoluminescent (PL) graphene quantum dots (GQDs) and graphene oxide (GO) has been developed by tuning the carbonization degree of citric acid and dispersing the carbonized products into alkaline solutions. The GQDs are nanosheets ~15 nm in width, and 0.5–2.0 nm in thickness. They show a relatively strong (9.0%) PL quantum yield and an excitation-independent PL emission activity. In contrast, the GO nanostructures consist of sheets that are hundreds of nanometers in width and ~1 nm in height. They exhibit a relatively weak (2.2%) PL quantum yield and an excitation-dependent PL emission activity.  相似文献   

15.
Recently, nano-based cancer therapeutics have been researched and developed, with some nanomaterials showing anticancer properties. When it comes to cancer treatment, graphene quantum dots (GQDs) contain the ability to generate 1O2, a reactive oxidative species (ROS), allowing for the synergistic imaging and photodynamic therapy (PDT) of cancer. However, due to their small particle size, GQDs struggle to remain in the target area for long periods of time in addition to being poor drug carriers. To address this limitation of GQDs, hollow mesoporous silica nanoparticles (hMSNs) have been extensively researched for drug delivery applications. This project investigates the utilization and combination of biomass-derived GQDs and Stöber silica hMSNs to make graphene quantum dots-hollow mesoporous silica nanoparticles (GQDs-hMSNs) for fluorescent imaging and dual treatment of cancer via drug delivery and photodynamic therapy (PDT). Although the addition of hMSNs made the newly synthesized nanoparticles slightly more toxic at higher concentrations, the GQDs-hMSNs displayed excellent drug delivery using fluorescein (FITC) as a mock drug, and PDT treatment by using the GQDs as a photosensitizer (PS). Additionally, the GQDs retained their fluorescence through the surface binding to hMSNs, allowing them to still be used for cell-labeling applications.  相似文献   

16.
This work presents a novel method to prepare graphene quantum dots (GQDs) directly from graphite. A composite film of GQDs and ZnO was first prepared using the composite target of graphite and ZnO via magnetron sputtering, followed with hydrochloric acid treatment and dialysis. Morphology and optical properties of the GQDs were investigated using a number of techniques. The as-prepared GQDs are 4–12 nm in size and 1–2 nm in thickness. They also exhibited typical excitation-dependent properties as expected in carbon-based quantum dots. To demonstrate the potential applications of GQDs in electronic devices, pure ZnO and GQD–ZnO thin-film transistors (TFTs) using ZrOx dielectric were fabricated and examined. The ZnO TFT incorporating the GQDs exhibited enhanced performance: an on/off current ratio of 1.7 × 107, a field-effect mobility of 17.7 cm2/Vs, a subthreshold swing voltage of 90 mV/decade. This paper provides an efficient, reproducible and eco-friendly approach for the preparation of monodisperse GQDs directly from graphite. Our results suggest that GQDs fabricated using magnetron sputtering method may envision promising applications in electronic devices.  相似文献   

17.
Graphene quantum dots (GQDs) reinforced poly(vinyl alcohol) (PVA)/polypyrrole (WPPy) nanocomposite films with various GQDs loadings were synthesized using the versatile solvent casting method. The structural and morphological properties of PVA/WPPy/GQDs nanocomposite films were investigated by employing Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The thermogravimetric analysis revealed enhanced thermal stability of synthesized nanocomposites while enhanced dielectric properties were also observed. The maximum dielectric constant value for PVA/WPPy/GQDs nanocomposite films was observed to be ε = 6,311.85 (50 Hz, 150°C). The electromagnetic interference (EMI) shielding effectiveness (SE) of nanocomposite films was determined in the X-band (8–12 GHz) and Ku-band (12–18 GHz) frequency region. The EMI SE was found to be increased from 0.8 dB for the pure PVA film to 9.8 dB for the PVA/WPPy/GQDs nanocomposite film containing 10 wt% GQDs loading. The enhanced EMI shielding efficiency of nanocomposite films has resulted from the homogenous dispersion of GQDs in PVA/WPPy blend nanocomposites. Thus, the prepared nanocomposites are envisioned to utilize as a lightweight, flexible, and low-cost material for EMI shielding applications.  相似文献   

18.
Graphitic quantum dots (GQDs) are synthesized from natural graphite powder. This process involves a few steps such as oxidation, reduction and filtration to obtain the precursor to prepare GQDs. Finally, a combination of UV irradiation and sonication is used to produce GQDs. These quantum dots are further investigated by various characterization techniques. They exhibit blue luminescence and ferromagnetic behavior. The ferromagnetic nature of the GQDs is discussed and explained. Based on the experimental data obtained and theoretical models available in literature, a possible mechanism for the formation of GQDs is proposed. Their properties, including the production yield can be tuned by simply changing the synthesis parameters.  相似文献   

19.
We report on a novel, simple and easy method to produce graphene layers using chemically synthesized ZnO–graphene quasi core–shell quantum dots. Initially, graphite powder was partially oxidized by acid treatment of graphite powder, which was then mixed with zinc acetate dihydrate in a dimethyl formamide solution. During this process, graphene sheets were detached from the graphite oxide layers through a layer-by-layer chemical peel-off and then partially covered from ZnO quantum dots which formed in the dimethyl formamide solution. Therefore, the ZnO–graphene quantum dots were dissolved in hydrochloric acid solution and then pure graphene layers were extracted from solution. The structural, optical, and electrical properties of obtained graphene layers were analyzed by using X-ray diffraction, transmission electron microscope, Raman spectroscopy, X-ray photoemission spectroscopy instrument.  相似文献   

20.
The unique hybrid capsules of graphene quantum dots (GQDs) with platinum (Pt)–copper (Cu) nanoparticles have been prepared by a dually spontaneous reduction and assembly process of oxidized graphene quantum dots (ox-GQDs) and Pt precursor by galvanic displacement reaction on Cu microspheres. Cu@PtCu core–shell microspheres were first prepared by reaction of Cu with platinum (IV), which subsequently induced the reduction and assembly of ox-GQDs on them at room temperature. After removal of the Cu cores, the resultant capsules of PtCu@GQDs were collected. Based on the unique hybrid structure, PtCu@GQDs capsules showed remarkably enhanced catalytic activity for oxygen reduction reaction (ORR) with a 2 times higher mass activity and a 40 mV more positive onset potential than that of commercial Pt black, indicating the promise of the newly-prepared PtCu@GQDs capsules as catalysts for fuel cell applications.  相似文献   

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