Graphene Quantum Dots Decorated Al-doped ZnS for Improved Photoelectric Performance

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.

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Inhibition of Photoconversion Activity in Self-Assembled ZnO-Graphene Quantum Dots Aggregated by 4-Aminophenol Used as a Linker

Molecules ◽

10.3390/molecules25122802 ◽

2020 ◽

Vol 25 (12) ◽

pp. 2802 ◽

Cited By ~ 2

Author(s):

Kyu Seung Lee ◽

Young Jae Park ◽

Jaeho Shim ◽

Guh-Hwan Lim ◽

Sang-Youp Yim ◽

...

Keyword(s):

Quantum Dots ◽

Graphene Quantum Dots ◽

Visible Region ◽

Photocurrent Density ◽

Solvothermal Process ◽

High Contribution ◽

Photoluminescence Lifetime ◽

Pec Cells ◽

Calculated Average ◽

Light Scattering Effect

The aggregation of zinc oxide nanoparticles leads to an increased absorbance in the ultraviolet-visible region by an induced light scattering effect. Herein, we demonstrate the inhibition of photoconversion activity in ZnO-graphene core-shell quantum dots (QD) (ZGQDs) agglomerated by 4-aminophenol (4-AP) used as a linker. The ZnO-graphene quantum dots (QD) aggregates (ZGAs) were synthesized using a facile solvothermal process. The ZGAs revealed an increased absorbance in the wavelengths between 350 and 750 nm as compared with the ZGQDs. Against expectation, the calculated average photoluminescence lifetime of ZGAs was 7.37 ns, which was 4.65 ns longer than that of ZGQDs and was mainly due to the high contribution of a slow (τ2, τ3) component by trapped carriers in the functional groups of graphene shells and 4-AP. The photoelectrochemical (PEC) cells and photodetectors (PDs) were fabricated to investigate the influence of ZGAs on the photoconversion activity. The photocurrent density of PEC cells with ZGAs was obtained as 0.04 mA/cm2 at 0.6 V, which was approximately 3.25 times lower than that of the ZGQDs. The rate constant value of the photodegradation value of rhodamine B was also decreased by around 1.4 times. Furthermore, the photoresponsivity of the PDs with ZGAs (1.54 μA·mW−1) was about 2.5 times as low as that of the PDs with ZGQDs (3.85 μA·mW−1). Consequently, it suggests that the device performances could be degraded by the inhibition phenomenon of the photoconversion activity in the ZGAs due to an increase of trap sites.

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Synthesis of Zn0·1Cd0·9S heterostructure with N-doped graphene quantum dots and graphene for enhancing photoelectric performance in UV–visible light

Ceramics International ◽

10.1016/j.ceramint.2020.03.127 ◽

2020 ◽

Vol 46 (10) ◽

pp. 15801-15811

Author(s):

Zicong Jiang ◽

Yun Lei ◽

Yuanyuan Lin ◽

Jiaxin Hu ◽

Zhong Ouyang

Keyword(s):

Quantum Dots ◽

Visible Light ◽

Graphene Quantum Dots ◽

Photoelectric Performance ◽

Doped Graphene ◽

Uv Visible

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Fabrication of Nitrogen-Doped Graphene Quantum Dots-Cu2O Catalysts for Enhanced Photocatalytic Hydrogen Evolution

NANO ◽

10.1142/s1793292018500996 ◽

2018 ◽

Vol 13 (08) ◽

pp. 1850099 ◽

Cited By ~ 4

Author(s):

Yilin Wu ◽

Ming Yan ◽

Jia Gao ◽

Peng Lv ◽

Xinlin Liu ◽

...

Keyword(s):

Quantum Dots ◽

Hydrogen Evolution ◽

Water Splitting ◽

Graphene Quantum Dots ◽

Photocatalytic Property ◽

Photogenerated Electron ◽

Nitrogen Doped ◽

Nitrogen Doped Graphene ◽

Doped Graphene ◽

Pure Cu

Development of efficient visible light driven photocatalysts for water splitting has attracted great research interest. Herein, a novel H2-producing nitrogen-doped graphene quantum dots (NGQDs)-Cu2O was successfully constructed and synthesized. The as-prepared NGQDs-Cu2O photocatalysts were benefited for light harvesting and charge separation and showed highly efficient photocatalytic property for hydrogen production by water splitting. Results displayed that the amount of NGQDs exhibited significant influence for H2 production, and the optimum sample of 3%NGQDs-Cu2O performed the highest hydrogen-evolution rate of 22.6[Formula: see text][Formula: see text]mol h[Formula: see text] g[Formula: see text], which was about 2 times higher than that of the pure Cu2O (10.1[Formula: see text][Formula: see text]mol h[Formula: see text] g[Formula: see text]). By further study, the enhanced photocatalytic performance could be ascribed to the crucial role of NGQDs, which widely improve the separation of photogenerated electron-hole pair’s.

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Graphene Quantum Dots-Modified Ternary ZnCdS Semiconductor for Enhancing Photoelectric Properties

Journal of Nanomaterials ◽

10.1155/2019/6042026 ◽

2019 ◽

Vol 2019 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Zicong Jiang ◽

Yun Lei ◽

Mingzhen Zhang ◽

Zheng Zhang ◽

Zhong Ouyang

Keyword(s):

Quantum Dots ◽

Photoelectric Property ◽

Graphene Quantum Dots ◽

Photocurrent Density ◽

Solvothermal Route ◽

Photoelectric Properties ◽

Good Lattice

A series of graphene quantum dots-modified ZnCdS (ZnCdS/G) composites with different contents of graphene quantum dots (GQDs) were prepared by a solvothermal route and characterized via various measurements. GQDs have a type graphene height of 2 nm and exhibit an excitation-dependent PL behavior. GQDs-modified ZnCdS composites present good lattice fingers that can be assigned to the (110) plane of GQDs and (112) plane of ZnCdS. The effect of different GQDs contents on the photoelectric property of ZnCdS was investigated. The results show that the photocurrent density of ZnCdS/G first increases and achieves a maximum of 11.4 μA/cm2 with the addition of 0.06 wt% and then decreases as the GQDs content changes from 0.06 wt% to 0.12 wt%. Photocurrent counts as a function of time present a decrease of 10% and remains stable after 1600 s.

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Application of doping graphene quantum dots and gold nanoparticles on dye-sensitized solar cells

Modern Physics Letters B ◽

10.1142/s0217984921410177 ◽

2021 ◽

Author(s):

Kao-Wei Min ◽

Ming-Ta Yu ◽

Chi-Ting Ho ◽

Pin-Ru Chen ◽

Jenn-Kai Tsai ◽

...

Keyword(s):

Quantum Dots ◽

Titanium Dioxide ◽

Graphene Quantum Dots ◽

Dye Sensitized Solar Cells ◽

Single Layer ◽

Single Layer Graphene ◽

Dye Sensitized ◽

Layer Graphene ◽

Photogenerated Electrons ◽

Sensitized Solar Cells

The doctor blade coating method is used to prepare dye-sensitized solar cells (DSSCs) and dope the original titanium dioxide (TiO2, P25) photoanode (PA) with single-layer graphene (G), graphene quantum dots (GQDs), and gold (Au) nanoparticles in this research. The results show that doping PAs with G, GQDS, and Au effectively increases the short-circuit current density [Formula: see text], conversion efficiency [Formula: see text], and decreases the internal structure impedance [Formula: see text] of DSSCs. [Formula: see text] increases from 13.62 to 17.02, 15.22, 16.05 mA/cm2, while [Formula: see text] (%) increases from 6.36 to 7.50, 7.08, 7.04% when doping G, GQDs, and Au, respectively. The analysis of Electrochemical Impedance Spectroscopy (EIS) reveals that the doping decreases [Formula: see text] from 11.28 to 8.36, 8.78, 8.54 [Formula: see text], respectively. Then, the titanium dioxide (TiO2)-doped G-GQDs, G-Au, and QDs-Au on DSSCs influence [Formula: see text] that increases to 5.45, 15.37, and 15.31 mA/cm2, respectively. In this case, the values of [Formula: see text] are found to be 7.21%, 7.35%, and 7.00%, while those of [Formula: see text] are 8.44, 8.63, and 9.18 [Formula: see text]. The values of [Formula: see text] and [Formula: see text] are highest but that of [Formula: see text] are lowest when doping with G, which proves that the photoanode of the DSSC effectively activates the photogenerated electrons in the film by doping single-layer graphene and TiO2 captures its electrons through graphene. The decreasing electron–hole recombination rate allows the photogenerated electrons to be quickly transferred to the external circuit. As a result, the efficiency of DSSCs is improved.

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Efficient Synthesis of Î±-Oximinoketones using Carboxyl and Nitrite Functionalized Graphene Quantum Dots: Dual role of Nanostructure as a Catalyst and Reagent

JOURNAL OF ADVANCES IN CHEMISTRY ◽

10.24297/jac.v12i6.6098 ◽

2017 ◽

Vol 12 (6) ◽

pp. 4089-4096

Author(s):

Ashkan Shomali ◽

Hassan Valizadeh

Keyword(s):

Quantum Dots ◽

Graphene Quantum Dots ◽

Reaction Times ◽

Mineral Acid ◽

Homogeneous Catalyst ◽

Spectroscopic Techniques ◽

Functionalized Graphene ◽

Efficient Synthesis ◽

Ft Ir ◽

High Yields

Carboxyl and nitrite functionalized graphene quantum dots (CNGQDs) was used for the efficient synthesis of Î±-oximinoketones under free mineral acid conditions at room temperature. CNGQDs was prepared via o-nitrozation of carboxyl and hydroxyl graphene quantum dots (CHGQDs) and used as a nitrosonium source and also as an efficient acidic catalyst for the synthesis of Î±-oximinoketones. The structure of the catalyst was characterized by FT-IR, XRD, TGA and photoluminescence techniques. The structures of the synthesized products were confirmed by FT-IR, 1H-NMR and 13C-NMR spectroscopic techniques. Stability and recyclability of the prepared homogeneous catalyst was studied in details. Reaction times and yields of the products were compared with previous reported methods resulting high yields and also shorter reaction times.

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Detection of Escherichia coli O157:H7 with Antibody Conjugated Amino-Functionalized Graphene Quantum Dots as Immunofluorescence Probes

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.807.151 ◽

2019 ◽

Vol 807 ◽

pp. 151-158

Author(s):

Xiao Zhan Yang ◽

Wen Lin Feng ◽

Gao Chen ◽

Hong Feng Guo ◽

Dao Yuan Wang

Keyword(s):

Escherichia Coli ◽

Quantum Dots ◽

Pathogen Detection ◽

Low Cost ◽

Graphene Quantum Dots ◽

Spectroscopic Properties ◽

Spectroscopic Techniques ◽

Functionalized Graphene ◽

Raman Spectroscopic ◽

E Coli

Escherichia coli O157: H7 (E. coli O157: H7) is a foodborne pathogenic bacterium which can cause fever, diarrhoea and vomiting in humans. Thus, a rapid, simple, and specific bioprobe for pathogen detection in contaminated foods has been attracted more and more attention. In this work, the strong fluorescent amino-functionalized graphene quantum dots (af-GQDs) were prepared by hydrothermal method. The microtopographic height, surface morphology and spectroscopic properties of af-GQDs are characterized by the high resolution transmission electron microscope (HRTEM), atomic force microscope (AFM), UV-vis, fluorescence, Raman spectroscopic techniques. All the results showed that the af-GQDs can be effectively applied in the preparation of biocompatible immunofluorescence probe and in the detection of E. coli O157: H7. The minimum detection limit is 100 cfu/mL. It is a simple, rapid, sensitive, low-cost and easy to be popularized method, which provides a feasible way to monitor E. coli O157: H7 in food safety.

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