Research Progress of Single-Photon Emitters Based on Two-Dimensional Materials.

From quantum communications to quantum computing, single-photon emitters (SPEs) are essential components of numerous quantum technologies. Two-dimensional (2D) materials have especially been found to be highly attractive for the research into nanoscale light-matter interactions. In particular, localized photonic states at their surfaces have attracted great attention due to their enormous potential applications in quantum optics. Recently, SPEs have been achieved in various 2D materials, while the challenges still remain. This paper reviews the recent research progress on these SPEs based on various 2D materials, such as transition metal dichalcogenides (TMDs), hexagonal boron nitride (hBN), and twisted-angle 2D materials. Additionally, we summarized the strategies to create, position, enhance, and tune the emission wavelength of these emitters by introducing external fields into these 2D system. For example, pronounced enhancement of the SPEs' properties can be achieved by coupling with external fields, such as the plasmonic field, and by locating in optical microcavities. Finally, this paper also discusses current challenges and offers perspectives that could further stimulate scientific research in this field. These emitters, due to their unique physical properties and integration potential, are highly appealing for applications in quantum information and communication, as well as other physical and technological fields.

Enhance Carrier Diffusion of Monolayer MoSe2 by Interface Engineering.

Two-dimensional materials hold great potentials for beyond-CMOS (complementary metal-oxide-semiconductor) electronical and optoelectrical applications, and the development of field effect transistors (FET) with excellent performance using such materials is of particular interest. How to improve the performance of devices thus becomes an urgent issue. The performance of FETs depends greatly on the intrinsic electrical properties of the channel materials, meanwhile the device interface quality, such as extrinsic scattering of charged impurities, charge traps, and substrate surface roughness have a great influence on the performance. In this paper, the impact of the interface quality on the carrier diffusion behaviors of monolayer (ML) MoSe2 has been investigated by using an in situ ultrafast laser technique to avoid the surface contamination during device fabrication process. Two types of self-assembled monolayers (SAMs) are introduced to modify the gate dielectric surface through an interface engineering approach to obtain chemical-stable interfaces. The results showed that the transport properties of ML MoSe2 were enhanced after interface engineering, for example, the carrier mobility of ML MoSe2 was improved from ∼59.4 to ∼166.5 cm2 V-1 s-1 after the SAM modification. Meanwhile, the photocarrier dynamics of ML MoSe2 before and after interfacial engineering were also carefully studied. Our studies provide a feasible method for improving the carrier diffusion behaviors of such materials, and making them suited for application in future integrated circuit.

M-Ni-Co MOF (M=Zn, Fe, Mn) for high-performance supercapacitors by adjusting its morphology.

Metal-organic frameworks (MOF) have been wildly synthesised and studied as electrode materials for supercapacitors, and bimetallic MOF of Ni and Co has been broadly studied to enhance both specific capacitance and stability of supercapacitors. Herein, a best performance (about 320 F/g) of Ni-Co bimetallic MOF was found in a uniform preparation condition by adjusting the ratio of Ni to Co. Then tiny third metal ion was introduced, and we found that the morphology of material has a significant change on the original basis. Furthermore, certain ions (Zn, Fe, Mn) introduced make a huge improvement in capacitance based on Ni-Co MOF of 320 F/g. The result shows that Zn-Ni-Co MOF, Fe-Ni-Co MOF and Mn-Ni-Co MOF perform specific capacitance of 1135 F/g, 870 F/g and 760F/g at 1 A/g, respectively. Meanwhile, the asymmetric supercapacitor (ASC) was constructed by Zn-Ni-Co MOF as positive electrode and active carbon (AC) as negative electrode. The Zn-Ni-Co MOF//AC ASC possesses a energy density of 58 Wh/kg at a power density of 775 W/kg. This research provides a new methods to regulate the morphology of MOF and a novel viewpoint for assembling high-performance, low-price, and eco-friendly green energy storage devices.

Ultra-Small YPO4 -YAG:Ce Composite Nanophosphors with a Photoluminescence Quantum Yield Exceeding 50.

Synthesis of high quality colloidal Cerium(III) doped yttrium aluminum garnet (Y3 Al5 O12 :Ce3+ , "YAG:Ce") nanoparticles (NPs) meeting simultaneously both ultra-small size and high photoluminescence (PL) performance is challenging, as generally a particle size/PL trade-off has been observed for this type of nanomaterials. The glycothermal route is capable to yield ultra-fine crystalline colloidal YAG:Ce nanoparticles with a particle size as small as 10 nm but with quantum yield (QY) no more than 20%. In this paper, the first ultra-small YPO4 -YAG:Ce nanocomposite phosphor particles having an exceptional QY-to-size performance with an QY up to 53% while maintaining the particle size ≈10 nm is reported. The NPs are produced via a phosphoric acid- and extra yttrium acetate-assisted glycothermal synthesis route. Localization of phosphate and extra yttrium entities with respect to cerium centers in the YAG host has been determined by fine structural analysis techniques such as X-ray diffration (XRD), solid state nuclear magnetic resonance (NMR), and high resolution scanning transmission electron microscopy (HR-STEM), and shows distinct YPO4 and YAG phases. Finally, a correlation between the additive-induced physico-chemical environment change around cerium centers and the increasing PL performance has been suggested based on electron paramagnetic resonance (EPR), X-ray photoelectron spectrometry (XPS) data, and crystallographic simulation studies.

Antibacterial and Biofilm-Preventive Photocatalytic Activity and Mechanisms on P/F-Modified TiO2 Coatings.

Photocatalytic antibacterial and biofilm-preventive activity in liquid of heavy-metal-free coatings based on a phosphorus (P)- and fluorine (F)-modified TiO2 photocatalyst has been investigated. They reveal significantly higher immediate and longer-term (biofilm-preventive) inactivation capacity than a reference coating made of the commercial photocatalyst TiO2 P25 on three bacterial species differing in cell wall type and ability to resist oxidative stress (Escherichia coli, Staphylococcus epidermidis, Pseudomonas fluorescens) (up to more than 99% reduction of colonization on P/F-modified TiO2 coating compared to about 50% on P25 TiO2 coating for 10 min UV-A illumination). This results from the P- and F-induced improvement of photocatalyst properties and from the smoother surface topography, which shortens reactive oxygen species (ROS) diffusion to the outer membrane of the targeted adhered bacteria. Decrease in ROS-related impairment of cell wall, respiratory, and enzymatic activities confirms the loss of ROS throughout the bacterial cell degradation. Staphylococcus epidermidis and Pseudomonas fluorescens are less sensitive than Escherichia coli, with a probable relation to the bacterial oxygen stress defense mechanism. The coating antibacterial efficacy was highly affected by phosphate ions and the richness in dissolved oxygen of the reaction medium.