다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

We present a new type of dual-band terahertz metamaterial absorber formed by a patterned metallic strip and a dielectric layer on top of a metallic ground plane. It is found that besides a strong absorption in the fundamental resonance, a prominent high-order resonance with near-unity absorption is also unveiled. The origin of the induced dual-band absorption was elucidated. Importantly, the quality factor (Q) and the figure of merit (FOM) of the high-order resonance are 8.4 and 22.7 times larger than that of the fundamental resonance, respectively, which makes the proposed absorber to have significant potential in biological monitoring and sensing. Moreover, we demonstrate a dual-band and insensitive for two orthogonal polarizations terahertz absorber based on a metallic cross and a metallic ground plane separated by a dielectric layer. The Q and FOM of the high-order resonance are still larger than that of the fundamental resonance. The proposed absorbers appear to be very promising for solar cells, detection, and imaging applications.

A novel dual-band terahertz metamaterial absorber for a sensor application

The reduced graphene oxide (RGO)-based composites have attracted intensive attention in research due to its superior performance as photocatalysts, but still lacking is the theoretical understanding on the interactions between constituents, as well as the connection between such interaction and the enhanced photoactivity. Herein, the interaction between the g-C3N4 and RGO sheets is systematically explored by using state-of-the-art hybrid density functional theory. We demonstrate that the O atom plays a crucial role in the RGO-based composites. Compared to the isolated g-C3N4 monolayer, the band gap of composites obviously decreases, and at higher O concentration, the levels in the vicinity of Fermi level are much more dispersive, indicating the smaller effective mass of the carrier. These changes are nonlinear on the O concentration. Interestingly, appropriate O concentration alters the direct-gap composite to indirect-gap one. Most importantly, at a higher O concentration, a type-II, staggered band align...

Insights into Enhanced Visible-Light Photocatalytic Hydrogen Evolution of g-C3N4 and Highly Reduced Graphene Oxide Composite: The Role of Oxygen

A novel Ag3PO4/CeO2 composite was fabricated by in situ wrapping CeO2 nanoparticles with Ag3PO4 through a facile precipitation method. The photocatalytic properties of Ag3PO4/CeO2 were evaluated by the photocatalytic degradation of MB and phenol under visible light and UV light irradiation. The photocatalytic activity of the composite is much higher than that of pure Ag3PO4 or CeO2. The rate constant of MB degradation over Ag3PO4/CeO2 is more than 2 times and 20 times than those of pure Ag3PO4 and CeO2 under visible light irradiation, respectively. The Ag3PO4/CeO2 composite photocatalyst also shows higher photocatalytic activity for the colorless phenol degradation compared to pure Ag3PO4. Moreover, the Ag3PO4/CeO2 sample has almost no loss of photocatalytic activity after five recycles under the irradiation of visible light and UV light, indicating that the composite has good photocatalytic stability. The excellent photocatalytic activity of the Ag3PO4/CeO2 composite is closely related to the fast transfer and efficient separation of electron–hole pairs at the interfaces of the two semiconductors derived from the matching band positions between CeO2 and Ag3PO4. This newly constructed Ag3PO4/CeO2 composite, with promising and fascinating visible light-driven photocatalytic activity as well as good stability, could find potential applications in environmental purification and solar energy conversion.

Novel Ag3PO4/CeO2 composite with high efficiency and stability for photocatalytic applications

Visible-light absorption and photocatalytic activity of Cr-doped TiO2 nanocrystal films

Broadband absorbers have attracted considerable attention due to their great prospect for practical applications. The mechanism is usually a superposition of several sets of structures with different geometrical dimensions. Herein, we numerically investigate an unconventional to existing metamaterial-based broadband terahertz absorber based on the multilayer same-sized square plate structure. Greater than 99% absorption across a frequency range of 300 GHz with the central frequency ~ 1.96 THz can be obtained. The FWHM of this device can be up to 42% (with respect to the central frequency), which is 2.6 times greater than that of the single layer structure. Such a property is retained well at a very wide range of incident angles. The mechanism of the broadband absorber is attributed to longitudinal coupling between layers. The results of the designed metamaterial absorber appear to be very promising for solar cell, detection, and imaging applications.

Wei-Qing Huang

Papers

A novel dual-band terahertz metamaterial absorber for a sensor application

Insights into Enhanced Visible-Light Photocatalytic Hydrogen Evolution of g-C3N4 and Highly Reduced Graphene Oxide Composite: The Role of Oxygen

Novel Ag3PO4/CeO2 composite with high efficiency and stability for photocatalytic applications

Visible-light absorption and photocatalytic activity of Cr-doped TiO2 nanocrystal films

Theoretical Investigation of Broadband and Wide-Angle Terahertz Metamaterial Absorber