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Synthesis of reduced graphene oxide quantum dots from graphene oxide via hydrothermal process and theirs structural, luminescence and magnetic properties
(2023-01-01)
Buatong, Nattha
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Ruttanapun, Chesta
;
Sriwong, Chaval
Background: Reduced graphene oxide quantum dots (rGO-QDs) have attracted much interest because of its exceptional chemical and physical properties and novel applications in a new technology and devices such as, energy storage, electrochemical, photocatalysis, sensing, drug delivery, bioimaging and anticancer therapy. Methods: In this work, we reported a correlation study of the structural, morphological, luminescence and magnetic behavior of rGO-QDs as a function of hydrothermal reduction temperatures (such as 90 °C, 120 °C, 150 °C and 180 °C) of GO sheets precursor via hydrothermal process. GO precursor and the obtained rGO-QDs samples were confirmed and analyzed by several techniques such as, XRD, Raman, XPS, TEM, PL, UV–Visible, Fluorescence and EPR. Significant findings: Influence of hydrothermal cutting process with different temperatures (90 °C, 120 °C, 150 °C and 180 °C) on the evolution of structural, morphologies, luminescence and magnetic behavior for the changes of large GO sheets into ultra-small rGO-QDs is presented. XRD result confirmed the effect of increasing temperature on the hydrothermal cutting process which led to a decrease in D-spacing values of rGO-QDs products. While Raman results indicates the trend of I<inf>D</inf>/I<inf>G</inf> ratio decreases along with increasing hydrothermal reduction temperatures. XRS analysis revealed that the percentage of carbon content of GO precursor (∼64%) was shifted value to ∼83% for obtained rGO-QDs sample prepared at 180 °C. TEM images shown that a very thin plate-like shape with ultrasmall average diameter of rGO-QDs samples in rage of 22±2 nm to 8 ± 2 nm. The optical and PL results well-confirmed the characteristic quantum size effect of all rGO-QDs samples. Finally, the EPR signals indicate the crossover between paramagnetic and diamagnetic are depended on the reduction temperature. The rGO-QDs prepared at 180 °C do not give any EPR signal, signify the nonmagnetic nature. This indicate that the basal plane of rGO-QDs at 180 °C has nearly perfect sp<sup>2</sup> network of graphene.
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Investigation on influence of seeding layer on morphological properties of ZnO-based nanostructure prepared by hydrothermal process
(2018-01-01)
Chongsri, Krisana
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Boonyarattanakalin, Kanokthip
;
Pecharapa, Wisanu
In this present work, bare ZnO low-dimensional structures were synthesized by hydrothermal process with crystal growth assistance using seed layers. Different seeding layer species including ZnO and Ga-doped ZnO films prepared by sol-gel dip coating were introduced onto the substrate before the hydrothermal growth of ZnO-based nanostructures. Zn(NO<inf>3</inf>)<inf>2</inf> and GaN<inf>3</inf>O<inf>9</inf> were utilized as Zn and Ga source during hydrothermal process. The influence of seeding layer types on morphological and shapes of the hydrothermally grown nanostructures have been extensively scrutinized by Field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD) and optical spectroscopy. It was revealed that different morphologies and exceptional shapes in form of nanorods of ZnO-based nanostructures were obtained as different seeding layers were introduced. More detailed studies for clarification of seed layer effect on the growth of ZnO-based nanostructures are mentioned and discussed.
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Effect of UV-induce ozone treatment on physics and morphological properties of hydrothermally grown Ga-F-codoped ZnO nanostructure
(2018-01-01)
Mekla, Vatcharinkorn
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Boonyarattanakalin, Kanokthip
The effects of ultraviolet ozone treatment (UVO treatment) on the physical and morphological structure of Ga/F co-doped Zn Onanorods. The ZnO seeding layers were prepared by sol-gel dip coating method based on zinc acetate dehydrate (CH<inf>3</inf>COO)<inf>2</inf>Zn•<inf>2</inf>H<inf>2</inf>O and diethanolamine ((HOCH<inf>2</inf>CH<inf>2</inf>)<inf>2</inf>NH, DEA) into absolute ethanol (C<inf>2</inf>H<inf>5</inf>OH) with concentration of 0.5 M. The seeding solution was dip-coated onto the cleaned glass substrates. The G/F co-doped ZnO nanorods were synthesized by hydrothermal process. The G/F co-doped ZnO nanorods were grown on seed layer with varied ultraviolet ozone treatment at 2, 4, 6, 8, 10, 12, 14, 16 and18 min. The influence of ultraviolet ozone treatment on physical, optical and morphological of G/F co-doped ZnO nanorods have been extensively scrutinized by X-ray diffraction (XRD) and optical spectroscopy, UV-Visible Spectrophotometer (UV-vis) and Field emission scanning electron microscope (FE-SEM). The effects of ultraviolet ozone treatment on different density of Ga/F co-doped ZnO nanorods were obtained as different ultraviolet ozone treatment were introduced.
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Effect of F incorporation on physical and optical properties of hydrothermally grown ZnO nanorods
(2018-01-01)
Sinornate, Wuttichai
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Chongsri, Krisana
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Boonyarattanakalin, Kanokthip
;
Pecharapa, Wisanu
F-doped ZnO nanorods were synthesized via hydrothermal process with variation of Fluorine doping contents (0-10%) starting from zinc oxide thin film as a seeding layer for nanorod growth. The zinc oxide seeding thin film was prepared by sol-gel spin coating at 2000 rpm on glass substrate using zinc acetate precursor with annealing at 500°C in air for 2 h. Ammonium fluoride (NH<inf>4</inf>F) was used as F doping precursor. The properties of F-doped ZnO nanorods were characterized by field emission electron microscope (FESEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and UV-Visible spectrophotometer. Corresponding results indicated that growth of ZnO:F nanorods with good crystallinity and grown in (002) plane in undoped ZnO and F-doped ZnO 5%. The average size diameter of undoped and F-doped ZnO nanorods at 3%, 5% and 10% are 56, 96, 70 and 103 nm, respectively. From cross section images the average length of undoped and F-doped ZnO nanorods at 3%, 5% and 10% are 400, 375, 199 and 478 nm, respectively. The transmittance spectra shows moderate transparency (<80%) of the ZnO nanorod film in visible region with corresponding band gap range of 3.25-3.28 eV.
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Effect of hexamethylenetetramine and temperature on morphological and structural properties of hydrothermally grown ZnSn(OH)6 structure
(2017-01-01)
Bangbai, Chatpong
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Kamsong, Jatuporn
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Nakhanivej, Puritat
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Mekprasart, Wanichaya
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Pecharapa, Wisanu
In this work, the effort has been conducted on the one-step hydrothermal synthesis of Zinc hydroxidestannate ZnSn(OH)<inf>6</inf>. Zinc chloride (ZnCl<inf>2</inf>) and tin(IV) chloride pentrahydrate (SnCl<inf>4</inf>•5H<inf>2</inf>O) were utilized as starting precursors of Zn and Sn and hexamethylenetetramine (HMT) was acted as pH buffer and OH<sup>-</sup> donator in the process. Effect of HMT during hydrothermal process on morphological and physical properties of the compound was investigated. The properties of hydrothermally grown ZnSn(OH)<inf>6</inf> were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It is revealed that HMT plays a key role on the formation of well-defined structure of ZnSn(OH)<inf>6</inf> in form of polyhedron structures with different size depending on hydrothermal temperature. Meanwhile the irregular shape of the as-synthesized product was obtained as the growth was conducted without the assistance of HMT. Further details of results and deep discussion on its role during the growth also represented.
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Growth and characterization of Ga/F co-doped ZnO nanorods/nanodisks via hydrothermal process
(2016-12-01)
Chongsri, Krisana
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Sinornate, Wuttichai
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Boonyarattanakalin, Kanokthip
;
Pecharapa, Wisanu
Ga/F co-doped ZnO nanorods/nanodisks (GFZO) were synthesized using a hydrothermal process by varying the Ga doping levels (1-5 wt.%) and F doping levels (1-5 wt.%). Zinc nitrate, gallium nitrate hydrate and ammonium fluoride were chosen as starting precursors for Zn, Ga and F sources, respectively. The nanorod growth was initiated by zinc oxide seeding film fabricated by spin coating on glass substrate using zinc acetate precursor and annealed at 500°C for 2 h. Effect of different dopant concentrations on morphologies, structural, and optical properties of the samples were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectroscopy (PL), respectively. The results of Ga/F codoped ZnO (GFZO) were compared to the single doped specimens including Ga:ZnO (GZO) and F:ZnO (FZO) samples, and bare ZnO sample. The results suggest that content of either Ga or F dopant has high influence on relevant properties of as-synthesized nanorods/nanodisks.
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Hydrothermal synthesis and characterization of ZnO:F nanorod structure
(2016-01-01)
Sinornate, Wuttichai
;
Chongsri, Krisana
;
Pecharapa, Wisanu
F-doped ZnO nanorod structures were synthesized via hydrothermal process with variation of doping content starting from zinc nitrate solution and zinc oxide thin film used as seeding layer. The zinc oxide seeding film was fabricated by spin coating on glass substrate using zinc acetate precursor and annealed at 500 °C for 2 h. Relevant properties of ZnO:F nanorod structures were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and UV-VIS spectrophotometer. Corresponding results indicated that ZnO:F nanorod array, grown in (002) plane, has the characteristics of good crystallinity. In addition, this study showed that ZnO:F nanorod with exceptional structure can be obtained by hydrothermal process, operated at proper treatment time, temperature and F-doping content.

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