Feasibility Study of Synthesizing Graphene Quantum Dots From the Spent Resin in a Nuclear Power Plant

Seungbin Yoon,Woo Nyun Choi,Jaehoon Byun,Hee Reyoung Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1

The feasibility study of synthesizing graphene quantum dots from spent resin, which is used in nuclear power plants to purify the liquid radioactive waste, was conducted. Owing to radiation safety and regulatory issues, an uncontaminated ion-exchange resin, IRN150 H/OH, prior to its use in a nuclear power plant, was used as the material of experiment on synthesis of graphene quantum dots. Since the major radionuclides in spent resin are treated by thermal decomposition, prior to conducting the experiment, carbonization of ion-exchange resin was performed. The experiment on synthesis of graphene quantum dots was conducted according to the general hydrothermal/solvothermal synthesis method as follows. The carbonized ion-exchange resin was added to a solution, which is a mixture of sulfuric acid and nitric acid in ratio of 3:1, and graphene quantum dots were synthesized at 115°C for 48 hours. After synthesizing, procedure, such as purifying, filtering, evaporating were conducted to remove residual acid from the graphene quantum dots. After freeze-drying which is the last procedure, the graphene quantum dots were obtained. The obtained graphene quantum dots were characterized using atomic force microscopy (AFM), Fourier-transform infrared (FT-IR) spectroscopy and Raman spectroscopy. The AFM image demonstrates the topographic morphology of obtained graphene quantum dots, the heights of which range from 0.4 to 3 nm, corresponding to 1–4 graphene layers, and the step height is approximately 2–2.5 nm. Using FT-IR, the functional groups in obtained graphene quantum dots were detected. The stretching vibrations of hydroxyl group at 3,420 cm?1, carboxylic acid (C=O) at 1,751 cm?1, C-OH at 1,445 cm?1, and C-O at 1,054 cm?1. The identified functional groups of obtained graphene quantum dots matched the functional groups which are present if it is a graphene quantum dot. In Raman spectrum, the D and G peaks, which are the characteristics of graphene quantum dots, were detected at wavenumbers of 1,380 cm?1 and 1,580 cm?1, respectively. Thus, it was verified that the graphene quantum dots could be successfully synthesized from the ionexchange resin.

Graphene transparent conductive electrodes doped with graphene quantum dots-mixed silver nanowires for highly-flexible organic solar cells

Shin, Dong Hee,Seo, Sang Woo,Kim, Jong Min,Lee, Ha Seung,Choi, Suk-Ho Elsevier 2018 Journal of alloys and compounds Vol.744 No.-

<P><B>Abstract</B></P> <P>Recent active studies on flexible photovoltaic cells strongly call for matchable flexible transparent electrodes. Graphene (GR) is one of the promising candidates as transparent conductive electrodes (TCEs) for flexible photovoltaic cells, but high sheet resistance of GR limits the efficiency of the cells. Here, we first fabricate GR TCEs doped with graphene quantum dots (GQDs)-mixed silver nanowires (Ag NWs) on polyethylene terephthalate substrates for highly-flexible organic solar cells (OSCs). With increasing doping concentration of GQDs to 0.03 g/L, the sheet resistance of the Ag NWs/GR TCE decreases to ∼92 Ω/sq whilst its work function increases to ∼4.53 eV, resulting in 3.66% power-conversion efficiency (PCE). In addition, the GQDs enhance the bending flexibility of the Ag NWs/GR TCEs, thereby maintaining the initial PCE of the OSCs over 90% even after 1000 bending cycles at a curvature radius of 4 mm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> First use of graphene transparent conductive electrodes doped with graphene quantum dots-mixed silver nanowires. </LI> <LI> Graphene quantum dots make the doped graphene more suitable for anode electrodes of organic solar cells. </LI> <LI> Graphene quantum dots enhance the power-conversion efficiency of organic solar cells to 3.66%. </LI> <LI> Graphene quantum dots enhance the bending flexibility of organic solar cells. </LI> </UL> </P>

Low dimensional graphene nanomaterials; Synthesis of graphene quantum dots from graphene oxide

한태희 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0

Carbon-based quantum dots has been gathering great interests due to their optical, chemical stabilities, easy synthetic procedure. In this work, we present a facile strategy for preparing graphene-based quantum dots (GQDs) by extraction of the crystallites from the amorphous matrix of the GO sheets. The colors of GQDs were controlled by introducing various ratios of chemical functionalities. Our approach presented in this study provides straightforward strategy for achieving large-scale production and long-time optical stability of the GQDs, and the hybrid assembly of GQD and polymer.

Graphene impregnated electrospun nanofiber sensing materials: a comprehensive overview on bridging laboratory set-up to industry

Al-Dhahebi Adel Mohammed,Gopinath Subash Chandra Bose,Saheed Mohamed Shuaib Mohamed 나노기술연구협의회 2020 Nano Convergence Vol.7 No.27

Owing to the unique structural characteristics as well as outstanding physio–chemical and electrical properties, gra‑ phene enables significant enhancement with the performance of electrospun nanofibers, leading to the generation of promising applications in electrospun-mediated sensor technologies. Electrospinning is a simple, cost-effective, and versatile technique relying on electrostatic repulsion between the surface charges to continuously synthesize various scalable assemblies from a wide array of raw materials with diameters down to few nanometers. Recently, electrospun nanocomposites have emerged as promising substrates with a great potential for constructing nanoscale biosensors due to their exceptional functional characteristics such as complex pore structures, high surface area, high catalytic and electron transfer, controllable surface conformation and modification, superior electric conductivity and unique mat structure. This review comprehends graphene-based nanomaterials (GNMs) (graphene, graphene oxide (GO), reduced GO and graphene quantum dots) impregnated electrospun polymer composites for the electro-device developments, which bridges the laboratory set-up to the industry. Different techniques in the base polymers (preprocessing methods) and surface modification methods (post-processing methods) to impregnate GNMs within elec‑ trospun polymer nanofibers are critically discussed. The performance and the usage as the electrochemical biosen‑ sors for the detection of wide range analytes are further elaborated. This overview catches a great interest and inspires various new opportunities across a wide range of disciplines and designs of miniaturized point-of-care devices.

Fully Transparent Quantum Dot Light-Emitting Diode Integrated with Graphene Anode and Cathode

Seo, Jung-Tak,Han, Junebeom,Lim, Taekyung,Lee, Ki-Heon,Hwang, Jungseek,Yang, Heesun,Ju, Sanghyun American Chemical Society 2014 ACS NANO Vol.8 No.12

<P>A fully transparent quantum dot light-emitting diode (QD-LED) was fabricated by incorporating two types (anode and cathode) of graphene-based electrodes, which were controlled in their work functions and sheet resistances. Either gold nanoparticles or silver nanowires were inserted between layers of graphene to control the work function, whereas the sheet resistance was determined by the number of graphene layers. The inserted gold nanoparticles or silver nanowires in graphene films caused a charge transfer and changed the work function to 4.9 and 4.3 eV, respectively, from the original work function (4.5 eV) of pristine graphene. Moreover the sheet resistance values for the anode and cathode electrodes were improved from ∼63 000 to ∼110 Ω/sq and from ∼100 000 to ∼741 Ω/sq as the number of graphene layers increased from 1 to 12 and from 1 to 8, respectively. The main peak wavelength, luminance, current efficiency, and optical transmittance of the fully transparent QD-LED integrated with graphene anode and cathode were 535 nm, ∼358 cd/m<SUP>2</SUP>, ∼0.45 cd/A, and 70–80%, respectively. The findings of the study are expected to lay a foundation for the production of high-efficiency, fully transparent, and flexible displays using graphene-based electrodes.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-12/nn505316q/production/images/medium/nn-2014-05316q_0006.gif'></P>

LiFePO₄ quantum-dots composite synthesized by a general microreactor strategy for ultra-high-rate lithium ion batteries

Wang, Bo,Xie, Ying,Liu, Tong,Luo, Hao,Wang, Bin,Wang, Chunhui,Wang, Lei,Wang, Dianlong,Dou, Shixue,Zhou, Yu Elsevier 2017 Nano energy Vol.42 No.-

<P><B>Abstract</B></P> <P>Due to the relatively slow, diffusion-controlled faradaic reaction mechanisms of conventional LiFePO<SUB>4</SUB> (LFP) materials, which is hard to deliver satisfied capacity for high rate applications. In this work, ultrafine LFP quantum dots (LFP-QDs) co-modified by two types of carbonaceous materials - amorphous carbon and graphitized conductive carbon (graphene) have been successfully synthesized through a novel microreactor strategy. Because of the very limited area constructed by the dual-carbon microreactor for the growth of LFP crystal, it's demension was furthest suppressed to a very small level (~ 6.5nm). Such a designed nano-composite possesses a large specific surface area for charge adsorption and abundant active sites for faradaic reactions, as well as ideal kinetic features for both electron and ion transport, and thus exhibits ultra-fast, surface-reaction-controlled lithium storage behavior, mimicking the pseudocapacitive mechanisms for supercapacitor materials, in terms of extraordinary rate capability (78mAhg<SUP>−1</SUP> at 200C) and remarkable cycling stability (~ 99% over 1000 cycles at 20C). On the other side, due to the quasi-2D structure of the synthesized LFP-QDs composite, which can be used as the basic unit to further fabricate free-standing film, aerogel and fiber electrode without the addition of binder and conductive agent for different practical applications. In addition, to deeper understand its electrochemical behavior, a combined experimental and density functional theoretical (DFT) calculation study is also introduced.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A general microreactor strategy has been developed for structure-optimized Li-contained electrode materials. </LI> <LI> Ultrafine LiFePO<SUB>4</SUB> quantum dots are first reported through the designed microreactor strategy. </LI> <LI> The synthesized G/LFP-QDs@C exhibits ultra-fast, surface-reaction-controlled Li storage behavior. </LI> <LI> A combined experimental and DFT calculation study is introduced to reveal the energy storage mechanism of G/LFP-QDs@C. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Ultrafine LiFePO<SUB>4</SUB> quantum dots (~ 6.5nm) co-modified by two types of carbonaceous materials - amorphous carbon and graphitized conductive carbon (graphene) have been successfully synthesized through a novel microreactor strategy, which exhibit ultra-fast, surface-reaction-controlled energy storage behavior, mimicking the pseudocapacitive mechanisms for supercapacitor materials, in terms of excellent rate capability and outstanding cycling stability.</P> <P>[DISPLAY OMISSION]</P>

Highly-flexible and -stable deep-ultraviolet photodiodes made of graphene quantum dots sandwiched between graphene layers

Jang, Chan Wook,Shin, Dong Hee,Choi, Suk-Ho Elsevier 2019 Dyes and pigments Vol.163 No.-

<P><B>Abstract</B></P> <P>We first report highly-flexible and -stable deep-ultraviolet (DUV) photodiodes (PDs) by employing graphene (GR) quantum dots (GQDs) sandwiched between top/bottom GR layers on polyethylene terephthalates (PETs). Here, 3-aminopropyl triethoxysilane is inserted between the bottom GR and the PET substrate to enhance the bending stabilities without degradation or delamination by the chemical bonding. GQDs of ∼5 nm diameter are proved to be well formed on the bottom GR by various structural and optical analysis tools including high-resolution transmission electron microscopy, Raman scattering, and photoluminescence. The DUV PDs exhibit 10 photo-/dark-current ratio, 0.1 AW<SUP>-1</SUP> responsivity (R), and 1.1 × 10<SUP>13</SUP> cm Hz<SUP>1/2</SUP>/W detectivity at a wavelength of 254 nm. In addition, the R is reduced by only 13% even after 1000-times repeated bending tests at a bending curvature of 4 mm, and is almost consistent during the operations for 1000 h under ambient conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> First report of flexible deep UV photodiodes by employing graphene quantum dots. </LI> <LI> 0.1 AW<SUP>-1</SUP> responsivity and 1.1 × 10<SUP>13</SUP> cm Hz<SUP>1/2</SUP>/W detectivity is achieved. </LI> <LI> Stability maintaining ∼87% of initial responsivity after 1000 bending cycles. </LI> </UL> </P>

Live cell biosensing platforms using graphene-based hybrid nanomaterials

Kim, Tae-Hyung,Lee, Donghyun,Choi, Jeong-Woo Elsevier 2017 Biosensors & bioelectronics Vol.94 No.-

<P><B>Abstract</B></P> <P>A novel strategy to precisely detect or monitor various biomaterials in living cells poses paramount importance in understanding cellular processes. Graphene, a newly emerged two-dimensional carbon material, has been widely utilized for biosensors owing to its multifarious characteristics including mechanical, electrical, and optical properties (e.g. stability, conductivity, fluorescence quenching and photoluminescence). In addition, graphene derivatives and their innate characteristics, such as biocompatibility low cytotoxicity and water solubility have facilitated the use of graphene-based materials for live cell biosensing, wherein graphene is utilized as a core material by itself or in combination with other functional nanomaterials to load target-specific probes, fluorescent dyes, and other signaling molecules. Such graphene-based hybrid nanomaterials have been employed to detect various cellular entities in living cells, including ions, biomolecules, genetic molecules, proteins, enzymes, and even whole cells. The following review will discuss a number of previous studies in which graphene-based hybrid constructs were used for live cell biosensing, and their potential applications in cancer research and stem cell therapy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Live-cell biosensing is highly important to understand major cellular activities. </LI> <LI> Graphene hybrid nanomaterials for live-cell biosensing were summarized. </LI> <LI> Graphene-modified substrates for live-cell biosensing were highlighted. </LI> </UL> </P>

Room temperature pH-dependent ammonia gas sensors using graphene quantum dots

Chen, Wei,Li, Fushan,Ooi, Poh Choon,Ye, Yun,Kim, Tae Whan,Guo, Tailiang Elsevier 2016 Sensors and actuators. B, Chemical Vol.222 No.-

<P><B>Abstract</B></P> <P>We report a simple solution-process route to realize ammonia (NH<SUB>3</SUB>) gas sensor based on graphene quantum dots (GQDs). Transmission electron microscopy analysis confirmed that the 8–10nm GQDs were formed from multi-walled carbon nanotubes by using ultrasonication treatment. The as-fabricated gas sensor showed promising selectivity response when expose to NH<SUB>3</SUB> ambient at room temperature. It is indicated that by adjusting the pH value of the aqueous GQDs in acidic and neutral, two types of gas sensors with contrary current responses could be obtained, which might be resulted from quantum confinement, edge effects and presence of functional groups on GQDs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report an NH<SUB>3</SUB> gas sensor at room temperature based on graphene quantum dots. </LI> <LI> GQDs were formed from multi-walled carbon nanotubes by ultrasonication treatment. </LI> <LI> Adjusting the pH value of the GQDs can lead to gas sensors with different behavior. </LI> <LI> Sensing mechanism might be resulted from the unique properties of GQDs. </LI> </UL> </P>

Self-powered Ag-nanowires-doped graphene/Si quantum dots/Si heterojunction photodetectors

Shin, Dong Hee,Jang, Chan Wook,Kim, Jong Min,Choi, Suk-Ho Elsevier 2018 Journal of alloys and compounds Vol.758 No.-

<P><B>Abstract</B></P> <P>We report Ag-nanowires (Ag NWs)-doped graphene/p-type SiO<SUB>2</SUB>-embedded Si quantum dots (<I>p</I>-SQDs:SiO<SUB>2</SUB>)/n-Si heterojunction photodetectors (PDs). It is found that the p-n junctions show excellent PD characteristics including photocurrent/dark current (on/off) ratio of 10<SUP>5</SUP> at 0 V bias, meaning “self-powered”. The PDs optimized at an Ag NWs concentration of 0.1 wt % exhibit 0.32–0.65 AW<SUP>-1</SUP> responsivity (R), ∼85% external quantum efficiency (EQE), and ∼4.5 × 10<SUP>12</SUP> cm Hz<SUP>1/2</SUP>/W detectivity in the visible range of 500–900 nm. The linear dynamic range and response time of the PDs at 532 nm are ∼83 dB and ∼2 μs, respectively. The loss of the R is only 15% of its initial value while the PDs are kept for 700 h in air. In particular, the EQE of the self-powered PD is comparable to that of commercially-available Si PD and better than those of previously-reported graphene/Si PDs. These results suggest that the doped graphene/p-SQDs:SiO<SUB>2</SUB>/n-Si heterojunctions are promising for their applications in self-powered optoelectronic devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> First demonstration of self-power photodetector (PD) operation in graphene/Si quantum dots/Si heterojunctions. </LI> <LI> The PD parameters are comparable to those of commercial Si PDs and even better than those of graphene/Si PDs. </LI> <LI> The loss of the responsivity is only 15% of its initial value for 700 h in air. </LI> </UL> </P>