Chemically modulated graphene quantum dot for tuning the photoluminescence as novel sensory probe

A band gap tuning of environmental-friendly graphene quantum dot (GQD) becomes a keen interest for novel applications such as photoluminescence (PL) sensor. Here, for tuning the band gap of GQD, a hexafluorohydroxypropanyl benzene (HFHPB) group acted as a receptor of a chemical warfare agent was chemically attached on the GQD via the diazonium coupling reaction of HFHPB diazonium salt, providing new HFHPB-GQD material. With a help of the electron withdrawing HFHPB group, the energy band gap of the HFHPB-GQD was widened and its PL decay life time decreased. As designed, after addition of dimethyl methyl phosphonate (DMMP), the PL intensity of HFHPB-GQD sensor sharply increased up to approximately 200% through a hydrogen bond with DMMP. The fast response and short recovery time was proven by quartz crystal microbalance (QCM) analysis. This HFHPB-GQD sensor shows highly sensitive to DMMP in comparison with GQD sensor without HFHPB and graphene. In addition, the HFHPB-GQD sensor showed high selectivity only to the phosphonate functional group among many other analytes and also stable enough for real device applications. Thus, the tuning of the band gap of the photoluminescent GQDs may open up new promising strategies for the molecular detection of target substrates. © The Author(s) 20166511sciescopu

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Graphene quantum dots and their possible energy applications: A review

As new carbon-based materials, graphene quantum dots (GQDs) many advantages due to the additional unique properties that arise from their nanoscale small size. GQDs are expected to be suitable for various applications. For use of GQDs in various fields, mass production is critically required. To date, many methods for preparing GQDs with good properties and high yield have been introduced. The main synthesis strategies are known as bottom-up and top-down methods. Synthesis of GQDs from small organic molecules, known as the bottom-up approach, is appropriate for controlling the size of GQDs but requires multistep organic reactions and purification at each step. However, the top-down approach of breaking the carbon-carbon bonds of a large carbon source is easy and simple, and therefore suitable for mass production. Here, we briefly introduce the solution-process synthesis of GQDs using a top-down method and recent energy-related applications such as capacitors, lithium ion batteries, and solar cells. © 2016 Elsevier B.V.118201sciescopuskc

The effect of the dopant's reactivity for high-performance 2D MoS2 thin-film transistor

© 2020 Springer Nature Switzerland AG. Part of Springer Nature. There are many studies on the solution-processed thin-film transistor (TFT) using transition metal dichalcogenide (TMD) materials. However, it is hard to control the electrical property of chemically exfoliated TMD materials compared to the chemical vapor deposition TMD. An investigation into the electrical modulation behavior of exfoliated two-dimensional (2D) material is important to fabricate well-modulated electronic devices via solution processing. Here, we report the effects of reactivity of organic dopants on MoS(2)and investigate how the chemical doping behavior influences the electrical properties of MoS2. The band state of dopants, which is related to the electron-withdrawing and donating behavior of chemical dopant, provides a proportional shift in the threshold voltages (V-th) of their field-effect transistors (FETs). However, on/off current ratio (I-on/I-off) and mobility (mu) are strongly influenced by the defect density depending on the reactivity of doping reaction, rather than the band state of organic dopants. Through the in-depth study on the doping reaction, we fabricate a FET and a TFT, having high mobility and a relatively high on/off ratio (10(4)) using a solution process.11Nsciescopu

Phase-selective modulation of TiO 2 for visible light-driven C–H arylation: Tuning of absorption and adsorptivity

© 2019 Elsevier B.V. To understand and modify TiO 2 for organic photoreaction, two points are important: improving light absorption and retaining adsorption sites for organic reagents. Herein, we tuning the absorption and adsorption of TiO 2 by introducing the defects on each phase of TiO 2 , called phase-mixed structures of ordered anatase (OA) and disordered rutile (DR) (OA/DR P25) and disordered anatase (DA) and ordered rutile (OR) (DA/OR P25). Disordered structure of TiO 2 broadened the absorption wavelength range including visible light, but changed surface structure reduced the adsorptivity of organic reactant. Additionally, anatase and rutile phase of TiO 2 has different surface properties and energy band structure, so keeping the crystalline anatase surface for adsorption was important while introducing the TiO 2 . Thus, it is assumed that the phase combination of OA and DR can be the best photocatalytic structure of TiO 2 even without any supporting materials and/or co-catalysts. In fact, the arylation yield of OA/DR P25 is the highest (63.4%), compared to those of untreated P25 (40.0%) and DA/OR (20.1%), highlighting the potential of OA/DR P25 in various visible light-driven photocatalytic organic reaction

FeIn2S4 Nanocrystals: A Ternary Metal Chalcogenide Material for Ambipolar Field-Effect Transistors

An ambipolar channel layer material is required to realize the potential benefits of ambipolar complementary metal-oxide-semiconductor field-effect transistors, namely their compact and efficient nature, reduced reverse power dissipation, and possible applicability to highly integrated circuits. Here, a ternary metal chalcogenide nanocrystal material, FeIn2S4, is introduced as a solution-processable ambipolar channel material for field-effect transistors (FETs). The highest occupied molecular orbital and the lowest unoccupied molecular orbital of the FeIn2S4 nanocrystals are determined to be -5.2 and -3.75 eV, respectively, based upon cyclic voltammetry, X-ray photoelectron spectroscopy, and diffraction reflectance spectroscopy analyses. An ambipolar FeIn2S4 FET is successfully fabricated with Au electrodes (E-F = -5.1 eV), showing both electron mobility (14.96 cm(2) V-1 s(-1)) and hole mobility (9.15 cm(2) V-1 s(-1)) in a single channel layer, with an on/off current ratio of 10(5). This suggests that FeIn2S4 nanocrystals may be a promising alternative semiconducting material for next-generation integrated circuit developmen

Facile C–H arylation using catalytically active terminal sulfurs of 2 dimensional molybdenum disulfide

The first methodology of C–H arylation of heteroarene via 2D transition metal dichalcogenides that have catalytically active edge functional groups was described. The terminal sulfur groups could effectively catalyze a formation of an azo-linked intermediate with aryl diazonium salts, leading to produce heteroarenes with good yields. This novel methodology using bulk 2D transition metal dichalcogenides that have catalytically active edge functional groups can apply for various reactions to achieve C–C bond formation in the fields of heterogeneous catalysis that is easily separable, highly reusable, and inexpensive method. © 2018 Elsevier L

One-Step Synthesis of Transition Metal Dichalcogenide Quantum Dots Using Only Alcohol Solvents for Indoor-Light Photocatalytic Antibacterial Activity

In this study, we report a one-step direct synthesis of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) quantum dots (QDs) through a solvothermal reaction using only alcohol solvents and efficient Escherichia coli (E. coli) decompositions as photocatalytic antibacterial agents under visible light irradiation. The solvothermal reaction gives the scission of molybdenum-sulfur (Mo-S) and tungsten-sulfur (W-S) bonding during the synthesis of MoS2 and WS2 QDs. Using only alcohol solvent does not require a residue purification process necessary for metal intercalation. As the number of the CH3 groups of alcohol solvents among ethyl, isopropyl, and tert(t)-butyl alcohols increases, the dispersibility of MoS2/WS2 increases. The CH3 groups of alcohols minimize the surface energy, leading to the effective exfoliation and disintegration of the bulk under heat and pressure. The bulky t-butyl alcohol with the highest number of methyl groups shows the highest exfoliation and yield. MoS2 QDs with a lateral size of about 2.5 nm and WS2 QDs of about 10 nm are prepared, exhibiting a strong blue luminescence under 365 nm ultraviolet (UV) light irradiation. Their heights are 0.68-3 and 0.72-5 nm, corresponding to a few layers of MoS2 and WS2, respectively. They offer a highly efficient performance in sterilizing E. coli as the visible-light-driven photocatalyst. © 2023 American Chemical Society11Nscopu

Phase-Selective Disordered Anatase/Ordered Rutile Interface System for Visible-Light-Driven, Metal-Free CO2 Reduction

Visible-light-driven photocatalytic CO2 reduction using TiO2 that can absorb light of all wavelengths has been sought for over half a century. Herein, we report a phase-selective disordered anatase/ordered rutile interface system for visible-light-driven, metal-free CO2 reduction using a narrow band structure, whose conduction band position matches well with the reduction potential of CO2 to CH4 and CO. A mixed disordered anatase/ordered rutile (Ad/Ro) TiO2 was prepared from anatase and rutile phase-mixed P25 TiO2 at room temperature and under an ambient atmosphere in sodium alkyl amine solutions. The Ad/Ro TiO2 showed a narrow band structure due to multi-internal energy band gaps of Ti3+ defect sites in the disordered anatase phase, leading to high visible light absorption and simultaneously providing fast charge separation through the crystalline rutile phase, which was faster than that of pristine P25 TiO2. The band gap of Ad/Ro TiO2 is 2.62 eV with a conduction band of -0.27 eV, which matches well with the reduction potential of -0.24 VNHE of CO2/CH4, leading to effective electron transfer to CO2. As a result, the Ad/Ro TiO2 provided the highest CH4 production (3.983 μmol/(g h)), which is higher than that of even metal (W, Ru, Ag, and Pt)-doped P25, for CO2 reduction under visible light11sciescopu