In this study, we demonstrate that the initial morphology of nanoparticles can be transformed into small fragmented nanoparticles, which were densely contacted to each other, during electrochemical CO 2 reduction reaction (CO 2 RR). Cu-based nanoparticles were directly grown on a carbon support by using cysteamine immobilization agent, and the synthesized nanoparticle catalyst showed increasing activity during initial CO 2 RR, doubling Faradaic efficiency of C 2 H 4 production from 27% to 57.3%. The increased C 2 H 4 production activity was related to the morphological transformation over reaction time. Twenty nm cubic Cu 2 O crystalline particles gradually experienced in situ electrochemical fragmentation into 2−4 nm small particles under the negative potential, and the fragmentation was found to be initiated from the surface of the nanocrystal. Compared to Cu@CuO nanoparticle/C or bulk Cu foil, the fragmented Cu-based NP/C catalyst achieved enhanced C 2+ production selectivity, accounting 87% of the total CO 2 RR products, and suppressed H 2 production. In-situ X-ray absorption near edge structure studies showed metallic Cu 0 state was observed under CO 2 RR, but the fragmented nanoparticles were more readily reoxidized at open circuit potential inside of the electrolyte, allowing labile Cu states. The unique morphology, small nanoparticles stacked upon on another, is proposed to promote C−C coupling reaction selectivity from CO 2 RR by suppressing HER.

Monolayer transition metal dichalcogenides are materials with an atomic structure complementary to graphene but diverse properties, including direct energy bandgaps, which makes them intriguing candidates for optoelectronic devices. Various approaches have been demonstrated for the growth of molybdenum disulphide (MoS 2 ) on insulating substrates, but to date, growth of isolated crystalline flakes has been demonstrated at random locations only. Here we use patterned seeds of molybdenum source material to grow flakes of MoS 2 at predetermined locations with micrometre-scale resolution. MoS 2 flakes are predominantly monolayers with high material quality, as confirmed by atomic force microscopy, transmission electron microscopy and Raman and photoluminescence spectroscopy. As the monolayer flakes are isolated at predetermined locations, transistor fabrication requires only a single lithographic step. Device measurements exhibit carrier mobility and on/off ratio that exceed 10 cm 2 V À 1 s À 1 and 10 6 , respectively. The technique provides a path for in-depth physical analysis of monolayer MoS 2 and fabrication of MoS 2 -based integrated circuits.

This review article provides the recent progress in the electrochemical CO2 reduction reaction by understanding and tuning catalyst–electrolyte interfaces.

Although two-dimensional monolayer transition-metal dichalcogenides reveal numerous unique features that are inaccessible in bulk materials, their intrinsic properties are often obscured by environmental effects. Among them, work function, which is the energy required to extract an electron from a material to vacuum, is one critical parameter in electronic/optoelectronic devices. Here, we report a large work function modulation in MoS2 via ambient gases. The work function was measured by an in situ Kelvin probe technique and further confirmed by ultraviolet photoemission spectroscopy and theoretical calculations. A measured work function of 4.04 eV in vacuum was converted to 4.47 eV with O2 exposure, which is comparable with a large variation in graphene. The homojunction diode by partially passivating a transistor reveals an ideal junction with an ideality factor of almost one and perfect electrical reversibility. The estimated depletion width obtained from photocurrent mapping was ∼200 nm, which is much narrower than bulk semiconductors.

We report small hysteresis integrated circuits by introducing monolayer graphene for the electrodes and a single-walled carbon nanotube network for the channel. Small hysteresis of the device originates from a defect-free graphene surface, where hysteresis was modulated by oxidation. This uniquely combined nanocarbon material device with transparent and flexible properties shows remarkable device performance; subthreshold voltage of 220 mV decade(-1), operation voltage of less than 5 V, on/off ratio of approximately 10(4), mobility of 81 cm(2) V(-1) s(-1), transparency of 83.8% including substrate, no significant transconductance changes in 1000 times of bending test, and only 36% resistance decrease at a tensile strain of 50%. Furthermore, because of the nearly Ohmic contact nature between the graphene and carbon nanotubes, this device demonstrated a contact resistance 100 times lower and a mobility 20 times higher, when compared to an Au electrode.

Despite the availability of large-area graphene synthesized by chemical vapor deposition (CVD), the control of a uniform monolayer graphene remained challenging. Here, we report a method of acquiring monolayer graphene by laser irradiation. The accumulation of heat on graphene by absorbing light, followed by oxidative burning of upper graphene layers, which strongly relies on the wavelength of light and optical parameters of the substrate, was in situ measured by the G-band shift in Raman spectroscopy. The substrate plays a crucial role as a heat sink for the bottom monolayer graphene, resulting in no burning or etching. Oscillatory thinning behavior dependent on the substrate oxide thickness was evaluated by adopting a simple Fresnel's equation. This paves the way for future research in utilizing monolayer graphene for high-speed electronic devices.

Flavonoids and carotenoids of pigmented rice ( Oryza sativa L.), including five black cultivars and two red cultivars, from Korea were characterized to determine the diversity among the phytochemicals and to analyze the relationships among their contents. Black cultivars were higher in flavonoids and carotenoids than the red and white cultivars. The profiles of eight phytochemicals identified from the rice grains were subjected to principal component analysis (PCA) to evaluate the differences among cultivars. PCA could fully distinguish between these cultivars. The Heugjinjubyeo (BR-1) and Heugseolbyeo (BR-2) cultivars were separated from the others based on flavonoid and carotenoid concentrations. Flavonoid contents had a positive correlation with carotenoid contents among all rice grains. The BR-1 and BR-2 cultivars appear to be good candidates for future breeding programs because they have simultaneously high flavonoid and carotenoid contents.

The next-generation electronic systems are expected to be light and portable for applications in wearable computers, fl exible displays, fl exible integrated circuit (IC)cards, fl exible potable solar cells, and artifi cial bodies. Flexibility and transparency are the key ingredients for these next generation electronic systems. Several studies have been executed to realize transparency and fl exibility using carbon nanotubes, [1][2][3][4][5][6][7][8] inorganics, [9][10][11] and organics [12][13][14][15][16] in transistors and memory devices. Most studies have focused on the transistor, in which fl exibility, stretchability, and transparency have been realized to some degree. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] In particular, nanocarbon materials such as carbon nanotubes (CNTs) and graphene have been regarded as strong candidates, because of their excellent electrical (mobility of 200 000 cm 2 V − 1 s − 1 ), mechanical (fracture strain of 30%), and optical properties (transparency of 97.5%). In practice, medium-scale integrated circuits using single-walled CNT (SWCNT) networks have been fabricated on fl exible substrates. [ 4 ] Furthermore, ultra transparent, stretchable, and fl exible transistors based on graphene electrodes and SWCNT network channels were realized with a 3.6% transmittance reduction and a resistance change of 36% at 50% tensile strain. [ 8 ] These results demonstrated the possibility of applying nano-carbon materials to fl exible electronic devices.On the other hand, there are relatively few reports relating to fl exible and transparent memory devices using organic channels and metal electrodes. [12][13][14][15][16] In these reports, fl exibility was achieved in the memory device by using a pentacene channel layer; however, the use of opaque and rigid metal electrodes degraded the transparency and fl exibility of these memory devices. Furthermore, mobility (0.25 cm 2 V − 1 s − 1 ) [ 16 ] was poor in these organic memory devices compared to that of carbon materials (∼80 cm 2 V − 1 s − 1 ). [ 4 ] Another drawback in achieving high transparency in the device is the use of opaque metal trap layers (transmittance decrease of 25%). [ 24 ] In this work, we fabricated ultra transparent (transmittance decrease of 3.6%) and fl exible memory devices by introducing nanocarbon materials, graphene electrodes, and SWCNT networks as an active channel. Oxygen atoms were bonded to the surface of graphene as C-O-C, C = O, and C-OH using ozone treatment, and these bonds acted as charge trap sites. [ 17 , 18 ] The memory device using this method showed no reduction in the transmittance after oxygen decoration, in good contrast with Au and Al [ 24 ] nanoparticle trap layers that provided a 11.4% and 25% decrease in transmittance, respectively. Moreover, our nonvolatile memory device showed a high mobility of ∼44 cm 2 V − 1 s − 1 , a fast operation speed of 100 ns, and good mechanical properties in bending tests because of the use of all-nanocarbon materials.Scheme 1 shows a schematic illustration of th...