Ag/ZnO microcavities with high sensitivity and self-cleaning properties for fast repetitive SERS detection.

A SERS substrate with high sensitivity and reusability was proposed. The chip consists of multiple ZnO microcavities loaded with silver particles. Based on structural characteristics, this coupling between cavity modes and localized surface plasmon modes can highly localize the electric field, where experimental results revealed a detection limit of 10-11 M for R6G. In addition, during carrier control in semiconductors with localized electromagnetic fields, our substrate also exhibits high self-cleaning efficiency and in situ detection stability. Even in a dry environment, it exhibits excellent light-mediated cleaning ability across multiple reuse test cycles. The convenient, rinse-free substrate, with its cost-effective and sustainable features, shows great promise for the study on detection and degradation of active materials.

Atomic layer deposition assisted fabrication of large-scale metal nanogaps for surface enhanced Raman scattering.

Metal nanogaps can confine electromagnetic field into extremely small volumes, exhibiting strong surface plasmon resonance effect. Therefore, metal nanogaps show great prospects in enhancing light-matter interaction. However, it is still challenging to fabricate large-scale (centimeter scale) nanogaps with precise control of gap size at nanoscale, limiting the practical applications of metal nanogaps. In this work, we proposed a facile and economic strategy to fabricate large-scale sub-10 nm Ag nanogaps by the combination of atomic layer deposition (ALD) and mechanical rolling. The plasmonic nanogaps can be formed in the compacted Ag film by the sacrificial Al2O3deposited via ALD. The size of nanogaps are determined by the twice thickness of Al2O3with nanometric control. Raman results show that SERS activity depends closely on the nanogap size, and 4 nm Ag nanogaps exhibit the best SERS activity. By combining with other porous metal substrates, various sub-10 nm metal nanogaps can be fabricated over large scale. Therefore, this strategy will have significant implications for the preparation of nanogaps and enhanced spectroscopy.

Growth Mechanism, Ambient Stability, and Charge Trapping Ability of Ti-Based Maleic Acid Hybrid Films by Molecular Layer Deposition.

Ti-based maleic acid (MA) hybrid films were successfully fabricated by molecular layer deposition (MLD) using organic precursor MA and inorganic precursor TiCl4. The effect of deposition temperature on the growth rate, composition, and bonding mode of hybrid thin films has been investigated systematically. With increasing temperature from 140 to 280 °C, the growth rate decreases from 1.42 to 0.16 Å per MLD cycle with basically unchanged composition ratio of C:O:Ti in the films. Fourier transform infrared spectra indicate that all hybrid films show preference for bidentate bonding mode. Further analyses of X-ray photoelectron spectroscopy and in situ quartz crystal microbalance elucidate that as-deposited MLD Ti-MA hybrid films consist of inorganic Ti-O-Ti units and organic-inorganic Ti-MA units. In addition, the density functional theory calculation was performed to investigate the possible reaction mechanism of the TiCl4-MA MLD process, which is well consistent with experimental results. More importantly, upon comparison with the TiCl4-fumaric acid MLD system, it is demonstrated that the cis- and trans-configurations of butenedioic acid influence the MLD growth, bonding mode, stability, and charging ability of MLD hybrid films. Ti-MA hybrid films exhibit better stability and charging ability than Ti-FA hybrid films, benefiting from the inorganic Ti-O-Ti units in the hybrid films.

The magnetic and adsorption properties of ZnO1-xSx nanoparticles.

Sulfur is easy to be incorporated into ZnO nanoparticles by the solution-combustion method. Herein, the magnetic and adsorption properties of a series of ZnO1-xSx (x = 0, 0.05, 0.1, 0.15, and 0.2) nanoparticles were systematically investigated. The X-ray diffraction patterns show that the as-prepared ZnO1-xSx nanoparticles have the hexagonal wurtzite structure of ZnO with a low sulfur content that gradually transforms into the zinc blende structure of ZnS when the x value is greater than 0.1. PL spectra show several bands due to different transitions, which have been explained by the recombination of free excitons or defect-induced transitions. The introduction of sulfur not only modifies the bandgap of ZnO, but also impacts the concentration of Zn vacancies. The as-prepared ZnO shows weak room-temperature ferromagnetism, and the incorporation of sulfur improves the ferromagnetism owing to the increased concentration of Zn vacancies, which may be stabilized by the doped sulfur ions. The adsorption capability of ZnO1-xSx nanoparticles has been significantly improved, and the process can be well described by the pseudo-first-order kinetic model and the Freundlich isotherm model. The mechanism has been confirmed to be due to the active sulfate groups existing in zinc oxysulfide nanoparticles.

Interfacial catalysis in and initial reaction mechanism of Al2O3 films fabricated by atomic layer deposition using non-hydrolytic sol-gel chemistry.

Atomic layer deposition (ALD) is a powerful nanofabrication technique that can precisely control the composition, structure, and thickness of thin films at the atomic scale, and is widely used in the fields of electronic displays, microelectronics, catalysis, coatings, and energy storage and conversion. ALD of metal oxide thin films can be completed using metal alkoxides as the oxygen source, which is similar to the non-hydrolytic sol-gel (NHSG) technique. Density functional theory calculations show that metal alkoxides, such as Al(OiPr)3 and Al(OEt)3, can directly form M-O bonds through strong chemisorption on the surface. Meanwhile, alkyl groups can be eliminated through the formation of alkyl halides and alkenes, which can be catalyzed by interfacial interactions between alkyl groups and the surface. Such noncovalent catalysis resulting from interfacial interaction can be termed as interfacial catalysis. This can be characterized by the difference between the interfacial interaction energies of the transition state and the corresponding intermediate based on natural bond analysis. We expect that such interfacial catalysis can be used in precursor designs, improvement of ALD of oxides and as a new characterization method for other interfacial catalysis and noncovalent catalysis processes.

[ Epidemiological Analysis of Imported Malaria in Shijiazhuang City from 2010 ].

Epidemiological analysis was performed on the 103 reported malaria cases during 2010-2014 in Shijiazhuang City. All the cases were imported from abroad, comprising 18（17.5%） cases of vivax malaria, 43 （41.7%） falciparum malaria, 2（1.9%） ovale malaria, 18（17.5%） cases with mixed infections， and 22（21.4%） unclassified cases. No significant seasonal variation in disease onset was observed. The male-to-female ratio was 33.3 : 1 and the cases were concentrated within 20-50 years. Africa was the main source of imported cases (92.2%).

Atomic layer deposition of Co3O4 on carbon nanotubes/carbon cloth for high-capacitance and ultrastable supercapacitor electrode.

Co3O4 nanolayers have been successfully deposited on a flexible carbon nanotubes/carbon cloth (CC) substrate by atomic layer deposition. Much improved capacitance and ultra-long cycling life are achieved when the CNTs@Co3O4/CC is tested as a supercapacitor electrode. The improvement can be from the mechanically robust CC/CNTs substrate, the uniform coated high capacitance materials of Co3O4 nanoparticles, and the unique hierarchical structure. The flexible electrode of CNTs@Co3O4/CC with high areal capacitance and excellent cycling ability promises great potential for developing high-performance flexible supercapacitors.

Photocatalytic activity and photocorrosion of atomic layer deposited ZnO ultrathin films for the degradation of methylene blue.

ZnO ultrathin films with varied thicknesses of 7-70 nm were prepared at 200 °C on Si and fused quartz substrates by atomic layer deposition (ALD). The impact of film thickness and annealing temperature on the crystallinity, morphology, optical bandgap, and photocatalytic properties of ZnO in the degradation of methylene blue (MB) dye under UV light irradiation (λ = 365 nm) has been investigated deeply. The as-deposited 28 nm thick ZnO ultrathin film exhibits highest photocatalytic activity, ascribed to the smallest band gap of 3.21 eV and proper thickness. The photocorrosion effect of ALD ZnO ultrathin films during photocatalytic process is observed. The presence of MB significantly accelerates the dissolution of ZnO ultrathin films. The possible photoetching mechanism of ZnO in MB solution is proposed.

Change in hepatitis B virus large surface antigen variant prevalence 13 years after implementation of a universal vaccination program in China.

A nationwide hepatitis B virus (HBV) vaccination program was implemented in China starting in 1992. To study the change in HBV variant prevalence with massive immunization, large HBV surface protein (LHBs) genes from HBV surface antigen (HBsAg)-positive sera were amplified and sequenced. The prevalences of LHBs mutants were compared between the 1992 and 2005 surveys in child and adult groups. The prevalence of "α" determinant mutants in the children increased from 6.5% in 1992 to 14.8% in 2005, where the G145R mutant occurred most frequently. In contrast, mutation frequencies showed little difference between 1992 (9.4%) and 2005 (9.9%) in adults. Moreover, compared to the 1992 survey, the child group surface (S) protein mutation frequency specifically increased (P = 0.005) in the 2005 survey, but the pre-S region mutation frequency did not show a significant difference (P > 0.05). However, the mutation frequency in the adult group increased in both the pre-S and S regions. Furthermore, the frequencies of the disease-related pre-S2 deletion and start codon mutations were significantly higher in the adult groups than in the child groups in both the 1992 and 2005 surveys (P < 0.01). Massive immunization enhances the HBV S protein mutation; the prevalence of LHBs mutants, particularly disease-related mutants, tends to increase with patient age.

TiO2 nanorod arrays@PDA/Ag with biomimetic polydopamine as binary mediators for duplex SERS detection of illegal food dyes.

Based on TiO2 nanorod arrays@PDA/Ag (TNRs@PDA/Ag), a better surface-enhanced Raman scattering (SERS) sensor with effective enrichment and enhancement was investigated for duplex SERS detection of illicit food dyes. Biomimetic PDA functions as binary mediators by utilizing the structural characteristics of polydopamine (PDA), which include the conjugated structure and abundant hydrophilic groups. One PDA functioned as an electron transfer mediator to enhance the efficiency of electron transfer, and the other as an enrichment mediator to effectively enrich rhodamine B (RhB) and crystal violet (CV) through hydrogen bonding, π-π stacking, and electrostatic interactions. Individual and duplex detection of illicit food dyes (RhB and CV) was performed using TNRs@PDA/Ag to estimate SERS applications. Their linear equations and limits of detection of 1 nM for RhB and 5 nM for CV were derived. Individual and duplex food colour detection was successfully accomplished even in genuine chili meal with good results. The bifunctional TNRs@PDA/Ag-based highly sensitive and duplex SERS dye detection will have enormous potential for food safety monitoring.

Atomic layer deposition assisted non-destructive strategy for cleaning Ag dendrites based SERS substrates.

Ag dendrites have recently been widely reported due to their excellent surface-enhanced Raman scattering (SERS) properties. However, prepared pristine Ag dendrites are usually contaminated by organic impurities, which has a huge negative impact on their Raman detection and greatly limits their practical applications. In this paper, we reported a facile strategy to obtain clean Ag dendrites by high temperature decomposition of organic impurities. With the assistance of ultra-thin coating via atomic layer deposition (ALD), the nanostructure of Ag dendrites can be retained at high temperature. SERS activity can be recovered after etching ALD coating. Chemical composition tests indicate that the organic impurities can be effectively removed. As a result, the clean Ag dendrites can obtain more clearly discernible Raman peaks and lower limits of detection than the pristine Ag dendrites. Furthermore, it was demonstrated that this strategy is also applicable to clean other substrates, such as gold nanoparticles. Therefore, high temperature annealing with the help of ALD sacrifice coating is a promising and non-destructive strategy to clean the SERS substrates.

Structure-evolution-designed amorphous oxides for dielectric energy storage.

Recently, rapidly increased demands of integration and miniaturization continuously challenge energy densities of dielectric capacitors. New materials with high recoverable energy storage densities become highly desirable. Here, by structure evolution between fluorite HfO2 and perovskite hafnate, we create an amorphous hafnium-based oxide that exhibits the energy density of ~155 J/cm3 with an efficiency of 87%, which is state-of-the-art in emergingly capacitive energy-storage materials. The amorphous structure is owing to oxygen instability in between the two energetically-favorable crystalline forms, in which not only the long-range periodicities of fluorite and perovskite are collapsed but also more than one symmetry, i.e., the monoclinic and orthorhombic, coexist in short range, giving rise to a strong structure disordering. As a result, the carrier avalanche is impeded and an ultrahigh breakdown strength up to 12 MV/cm is achieved, which, accompanying with a large permittivity, remarkably enhances the energy storage density. Our study provides a new and widely applicable platform for designing high-performance dielectric energy storage with the strategy exploring the boundary among different categories of materials.

Growth behavior of Ir metal formed by atomic layer deposition in the nanopores of anodic aluminum oxide.

The conformal coating or surface modification in high aspect ratio nanostructures is a tough challenge using traditional physical/chemical vapor deposition, especially for metal deposition. In this work, the growth behavior of iridium (Ir) metal formed by atomic layer deposition (ALD) in anodic aluminum oxide (AAO) templates was explored deeply. It is found that the surface hydrophilicity is crucial for the nucleation of ALD Ir. An in situ ALD Al2O3 layer with an ultra-hydrophilic surface can greatly promote the nucleation of ALD Ir in AAO nanopores. The effect of the Ir precursor pulse time, diameter, and length of AAO nanopores on the infiltration depth of ALD Ir was investigated systematically. The results show that the infiltration depth of ALD Ir in AAO nanopores is in proportion to the pore diameter and the square root of the Ir precursor pulse time, which follows a diffusion-limited model. Furthermore, the Ir precursor pulse time to obtain conformal Ir coating throughout all the AAO channels is in proportion to the square of the aspect ratio of AAO templates. In addition, the conformal Ir deposition in AAO nanopores is also related to the Ir precursor purge time and the O2 partial pressure. Insufficient Ir purge time could cause a CVD-like reaction, leading to the reduction of the infiltration depth in AAO. Higher O2 partial pressure can facilitate Ir nucleation with more Ir precursor consumption at the entrance of nanopores, decreasing the infiltration depth in AAO nanopores, so appropriate O2 partial pressure should be chosen for ALD Ir in high aspect ratio materials. Above all, our research is valuable for surface modification or coating of metal by ALD in high aspect ratio nanostructures for 3D microelectronics, nano-fabrication, catalysis and energy fields.

The complete chloroplast genome of Cycas bifida, an extremely small population protected species.

Cycas bifida (Dyer) K.D.Hill (2004) is an extremely small population-protected species of China. In this study, we reported the first chloroplast genome sequence of C. bifida. The chloroplast genome of C. bifida included two single-copy regions (large single-copy (LSC) and small single-copy (SSC)) and a pair of inverted repeats (IRs) regions comprising 88,946 bp, 23,107 bp, and 25,053 bp, respectively. The complete chloroplast genome of C. bifida contains 131 genes, including 86 protein-coding genes, 37 transfer RNA genes, and 8 ribosomal RNA genes. The overall GC content of the C. bifida chloroplast genome is 39.41%, and the LSC, SSC, and IR regions occupy 38.70%, 36.52%, and 42.02%, respectively. A phylogenetic analysis was performed based on complete chloroplast genomes from 15 species and found that C. bifida was closely related to Cycas szechuanensis W.C.Cheng & L.K.Fu.

Reorganization of the topological surface mode of topological insulating α-Sn.

α-Sn is a topologically nontrivial semimetal in its natural structure. Upon compressively strained in plane, it transforms into a topological insulator. But, up to now, a clear and systematic understanding of the topological surface mode of topological insulating α-Sn is still lacking. In the present work, first-principle simulations are employed to investigate the electronic structure evolution of Ge1-xSnxalloys aiming at understanding the band reordering, topological phase transition and topological surface mode of α-Sn in detail. Progressing from Ge to Sn with increasing Sn content in Ge1-xSnx, the conduction band inverts with the first valence band (VB) and then with the second VB sequentially, rather than inverting with the latter directly. Correspondingly, a topologically nontrivial surface mode arises in the first inverted band gap. Meanwhile, a fragile Dirac cone appears in the second inverted band gap as a result of the reorganization of the topological surface mode caused by the first VB. The reorganization of the topological surface mode in α-Sn is very similar to the HgTe case. The findings of the present work are helpful for understanding and utilizing of the topological surface mode of α-Sn.

Titanicone-derived TiO2 quantum dot@carbon encapsulated ZnO nanorod anodes for stable lithium storage.

To address the issues of large volume expansion and low electrical conductivity of ZnO anode nanomaterials during lithium ion battery operation, herein we engineered a rod-like ZnO anode with robust and conductive TiO2 quantum dot (QD)@carbon coating derived from molecular layer deposited titanicone, in which the TiO2 QDs are well confined inside the carbon layer. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) confirm the formation of TiO2 QDs and carbonization of fumaric acid in hybrid films after annealing in H2 atmosphere at 700 °C. Benefiting from a unique protective layer design, the prepared TiO2 QD@carbon@ZnO nanorod (NR) anodes display outstanding cycling performance with a discharge capacity of 1154 mA h g-1 after 100 cycles and 70% capacity retention, along with a high rate capacity of 470 mA h g-1 for 500 cycles at 2 A g-1. Moreover, our work demonstrates an innovative and promising approach toward a robust and conductive metal oxide QD@carbon nanocomposite layer for electrode materials in the future.

Co-Pt bimetallic nanoparticles with tunable magnetic and electrocatalytic properties prepared by atomic layer deposition.

Co-Pt bimetallic nanoparticles with adjustable composition and particle size were prepared by the combination of atomic layer deposition and H2 post-deposition annealing. The structure, magnetic and electrocatalytic properties of Co-Pt bimetallic nanoparticles can be facilely tuned by controlling the composition.

Enhanced visible light photocatalytic activity of Fe2O3 modified TiO2 prepared by atomic layer deposition.

In this work, commercial anatase TiO2 powders were modified using ultrathin Fe2O3 layer by atomic layer deposition (ALD). The ultrathin Fe2O3 coating having small bandgap of 2.20 eV can increase the visible light absorption of TiO2 supports, at the meantime, Fe2O3/TiO2 heterojunction can effectively improve the lifetime of photogenerated electron-hole pairs. Results of ALD Fe2O3 modified TiO2 catalyst, therefore, showed great visible light driven catalytic degradation of methyl orange compared to pristine TiO2. A 400 cycles of ALD Fe2O3 (~ 2.6 nm) coated TiO2 powders exhibit the highest degradation efficiency of 97.4% in 90 min, much higher than pristine TiO2 powders of only 12.5%. Moreover, an ultrathin ALD Al2O3 (~ 2 nm) was able to improve the stability of Fe2O3-TiO2 catalyst. These results demonstrate that ALD surface modification with ultrathin coating is an extremely powerful route for the applications in constructing efficient and stable photocatalysts.

Atomic layer deposition of ZnO/TiO2 nanolaminates as ultra-long life anode material for lithium-ion batteries.

In this work, we designed ZnO/TiO2 nanolaminates by atomic layer deposition (ALD) as anode material for lithium ion batteries. ZnO/TiO2 nanolaminates were fabricated on copper foil by depositing unit of 26 cycles ZnO/26 cycles TiO2 repeatedly using ALD. ZnO/TiO2 nanolaminates are much more stable than pristine ZnO films during electrochemical cycling process. Therefore, ZnO/TiO2 nanolaminates exhibit excellent lithium storage performance with an improved cycling performance and superior rate capability compared to pristine ZnO films. Moreover, coulombic efficiency (CE) of ZnO/TiO2 nanolaminates is above 99%, which is much higher than the value of pristine ZnO films. Excellent ultralong-life performance is gained for ZnO/TiO2 nanolaminates, retaining a reversible capacity of ~667 mAh g-1 within cut-off voltage of 0.05-2.5 V after 1200 cycles of charge-discharge at 500 mA g-1. Constructing nanolaminates structures via ALD might open up new opportunities for improving the performance of anode materials with large volume expansion in lithium ion batteries.

Flexible Metal-Insulator Transitions Based on van der Waals Oxide Heterostructures.

Recently, flexible and wearable electronics are highly desirable because of their great potential in the next-generation information devices. In this work, we demonstrate the realization of the metal-insulator transition (MIT) effect in flexible rare-earth nickelate heterostructures. The NdNiO3 thin films are grown on lattice-mismatched mica substrates along the pseudocubic (111) direction via the van der Waals heteroepitaxy, in which the MIT behaviors are induced and modulated by carefully controlling the lattice strain and the ionic valence state with SrTiO3 and LaAlO3 buffering layers. Enhanced MIT properties with sharp transition and significant resistivity change between the metallic and the insulating states are achieved in the NdNiO3/LaAlO3/SrTiO3/mica heterostructures with appropriate in-plane tensile strain and suppressed concentration of Ni2+ ions. In addition, the proposed NdNiO3-based heterostructures exhibit excellent flexibility with reliable MIT characteristics not only in statically concave/convex bending but also in dynamically bending cycling up to 1000 times. The present work provides a platform to design and fabricate new flexible devices integrated with the MIT effect.