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1.
Hollow and hierarchical nanostructures have received wide attention in new‐generation, high‐performance, lithium ion battery (LIB) applications. Both TiO2 and Fe2O3 are under current investigation because of their high structural stability (TiO2) and high capacity (Fe2O3), and their low cost. Here, we demonstrate a simple strategy for the fabrication of hierarchical hollow TiO2@Fe2O3 nanostructures for the application as LIB anodes. Using atomic layer deposition (ALD) and sacrificial template‐assisted hydrolysis, the resulting nanostructure combines a large surface area with a hollow interior and robust structure. As a result, such rationally designed LIB anodes exhibit a high reversible capacity (initial value 840 mAh g?1), improved cycle stability (530 mAh g?1 after 200 cycles at the current density of 200 mA g?1), as well as outstanding rate capability. This ALD‐assisted fabrication strategy can be extended to other hierarchical hollow metal oxide nanostructures for favorable applications in electrochemical and optoelectronic devices.  相似文献   

2.
Periodic arrays of plasmonic nanopillars have been shown to provide large, uniform surface-enhanced Raman scattering (SERS) enhancements. We show that these enhancements are the result of the combined impact of localized and propagating surface plasmon modes within the plasmonic architecture. Here, arrays of periodically arranged silicon nanopillars of varying sizes and interpillar gaps were fabricated to enable the exploration of the SERS response from two different structures; one featuring only localized surface plasmon (LSP) modes and the other featuring LSP and propagating (PSP) modes. It is shown that the LSP modes determine the optimal architecture, and thereby determine the optimum diameter for the structures at a given incident. However, the increase in the SERS enhancement factor for a system in which LSP and PSP cooperatively interact was measured to be over an order of magnitude higher and the peak in the diameter dependence was significantly broadened, thus, such structures not only provide larger enhancement factors but are also more forgiving of lithographic variations.  相似文献   

3.
Hollowed Ag nanostructures are, for the first time, electrodeposited on ITO glass without use of surfactant. The hollowed Ag nanostructure was investigated via a collaboration of scanning electron microscopy (SEM), XRD, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), XRD, and UV-vis. Results exhibited that the formation of the hollowed Ag nanostructure can be interpreted as the synergy effect of twin defect and low nucleation driving force. Surface-enhanced Raman scattering (SERS) spectra of rhodamine 6G and adenine molecules adsorbed on the surface of these Ag nanostructures were recorded. The smallest RSD of 1651 cm?1 Raman bands of rhodamine 6G was 14.7 %, indicating that the hollowed Ag nanostructures can be utilized for reproducible SERS application. Through comparison, it was found the good crystallinity was beneficial for SERS.  相似文献   

4.

It was shown experimentally that the action of continuous electric field on nanoporous silicate glasses with interconnecting pores, containing silver nanoparticles, leads to the spatial redistribution of nanoparticles. The concentration of nanoparticles near the negative electrode increases and results in silver nano- and microdendrite structure growth. The main mechanisms of the described effects are the field emission of silver ions from silver nanoparticles near negative electrode, migration of silver ions in the external electric field to the negative electrode, reduction of silver ions by free electrons, and new silver nanoparticle formation. The experiments have shown that at the ends of microdendrites, local field enhancement appears, which results in luminescence enhancement and in SERS.

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5.
This paper describes the fabrication of gold nanopillar and nanorod arrays and theoretical calculations of electromagnetic fields (EMFs) around ordered arrangements of these nanostructures. The EMFs of both single nanopillars and dimers of nanopillars—having nanoscale gaps between the two adjacent nanopillars forming the dimers—are simulated in this work by employing the finite-difference time-domain method. In the case of simulations for dimers of nanopillars, the nanoscale gaps between the nanopillars are varied between 5 and 20 nm, and calculations of the electromagnetic fields in the vicinity of the nanopillars and in the gaps between the nanopillars were carried out. Fabrication of gold nanopillars in a controlled manner for forming SERS substrates involves focused ion beam (FIB) milling. The nanostructures were fabricated on gold-coated silica, mica, and quartz planar substrates as well as on gold-coated tips of four mode and multimode silica optical fibers.  相似文献   

6.
We fabricated nanostructured Pt thin films with two different morphologies and studied their effects on the Raman spectrum of rhodamine 6G. The syntheses were achieved by templating mesoporous silica thin films which are characterized by 8-nm-sized pore channels and 3–4-nm-thick walls in two different orientations of the channels. Therefore, the resultant nanostructured Pt thin films are composed of Pt nanorods of 8 nm in diameter vertically standing in one morphology and horizontally lying in the other. The latter produced stronger Raman signals than the former. Simulations based the discrete-dipole approximation on model nanostructures showed that the horizontally lying nanorods produce stronger local electromagnetic field than the vertically standing ones, in agreement with the experimental observations.  相似文献   

7.
The main objective of the present study is to investigate the shell thickness-dependent Raman enhancement activity of silver-coated gold nanoparticles (Au@Ag NPs) when bound to a model analyte 2-mercaptobenzoic acid (2-MBA). With an optimized Ag:Au ratio, dimeric and trimeric Au@Ag nanostructures were prepared in the presence of 2-MBA and are characterized by spectroscopic and microscopic techniques. These dimeric junctions act as hot spots and the molecules trapped at these junctions showed higher Raman signal enhancements due to the presence of amplified electric field.  相似文献   

8.
Au nanorod (Au NR) is one of the most studied colloidal nanostructures for its tunable longitudinal surface plasmon resonance (SPRL) property in the near infrared region. And surface coating Au NRs into core-shell nanostructures is particularly important for further investigation and possible applications. In this paper, Au NRs colloids were synthesized using an improved seed method. Then as-prepared Au NRs were coated with SiO2 to form a core-shell nanostructure (Au@SiO2) with different shell thickness. And the influence of SiO2 shell on the SPRL of Au NRs was investigated based on the experimental results and FDTD simulations. Under the 808 nm laser irradiating, the stability of Au@SiO2 was studied. Compared with Au NRs, the Au@SiO2 is stable with increasing laser power (up to 8 W), whereas Au NRs undergo a shape deformation from rod to spherical nanoparticle when the laser power is 5 W. The high stability and tunable optical properties of core-shell structured Au@SiO2, along with advantages of SiO2, show that Au@SiO2 composites are promising in designing plasmonic photothermal properties or further applications in nanomedicine.  相似文献   

9.
We describe a simple, precise, and sensitive experimental protocol for direct measurement of N(inf2) fixation using the conversion of (sup15)N(inf2) to organic N. Our protocol greatly reduces the limit of detection for N(inf2) fixation by taking advantage of the high sensitivity of a modern, multiple-collector isotope ratio mass spectrometer. This instrument allowed measurement of N(inf2) fixation by natural assemblages of plankton in incubations lasting several hours in the presence of relatively low-level (ca. 10 atom%) tracer additions of (sup15)N(inf2) to the ambient pool of N(inf2). The sensitivity and precision of this tracer method are comparable to or better than those associated with the C(inf2)H(inf2) reduction assay. Data obtained in a series of experiments in the Gotland Basin of the Baltic Sea showed excellent agreement between (sup15)N(inf2) tracer and C(inf2)H(inf2) reduction measurements, with the largest discrepancies between the methods occurring at very low fixation rates. The ratio of C(inf2)H(inf2) reduced to N(inf2) fixed was 4.68 (plusmn) 0.11 (mean (plusmn) standard error, n = 39). In these experiments, the rate of C(inf2)H(inf2) reduction was relatively insensitive to assay volume. Our results, the first for planktonic diazotroph populations of the Baltic, confirm the validity of the C(inf2)H(inf2) reduction method as a quantitative measure of N(inf2) fixation in this system. Our (sup15)N(inf2) protocols are comparable to standard C(inf2)H(inf2) reduction procedures, which should promote use of direct (sup15)N(inf2) fixation measurements in other systems.  相似文献   

10.
Multilayer gold surface-enhanced Raman scattering (SERS) substrates, which consist of continuous gold films that are separated by self-assembled monolayers (SAMs) and cast over 430-nm diameter silica nanospheres on a glass slide, have been evaluated as a means of further enhancing the SERS signals produced from conventional metal film over nanostructure substrates. Evaluation of the effect of various SAMs, with different terminal functional groups, on the SERS enhancement factor were measured and compared to conventional single-layer gold film over nanostructure substrates, revealing relative enhancements as great as 22.4-fold in the case of 2-mercapto-ethanol spacer layers. In addition to evaluation of the effect of different terminal functionalities, the effect of spacer length was also investigated, revealing that the shorter chain length alcohols provided the greatest signals. Employing the optimal SERS multilayer geometry, SERS nanoimaging probes were fabricated and the SERS enhancement factor and variability in enhancement factor were measured over the SERS active imaging area, providing absolute enhancements similar to previous silver-based SERS nanoimaging probes (i.e., 1.2 × 108). Varying the size of the multilayer gold islands that were deposited on the tip of the SERS active nanoimaging probe, it is possible to tune the optimal SERS excitation wavelength accurately and predictably over the range of approximately 450 to 600 nm, without coating the entire surface of the probe and significantly reducing the transmission and resulting signal-to-noise ratio of the images obtained.  相似文献   

11.
12.
Chen  Meijie  He  Yurong  Zhu  Jiaqi 《Plasmonics (Norwell, Mass.)》2019,14(4):1019-1027
Plasmonics - In this work, the finite element method and two-temperature model were used to optimize the near electric field, photothermal conversion efficiency, and local heating of SiO2@Au...  相似文献   

13.
Hierarchical hollow NiCo2S4 microspheres with a tunable interior architecture are synthesized by a facile and cost‐effective hydrothermal method, and used as a cathode material. A three‐dimensional (3D) porous reduced graphene oxide/Fe2O3 composite (rGO/Fe2O3) with precisely controlled particle size and morphology is successfully prepared through a scalable facile approach, with well‐dispersed Fe2O3 nanoparticles decorating the surface of rGO sheets. The fixed Fe2O3 nanoparticles in graphene efficiently prevent the intermediates during the redox reaction from dissolving into the electrolyte, resulting in long cycle life. KOH activation of the rGO/Fe2O3 composite is conducted for the preparation of an activated carbon material–based hybrid to transform into a 3D porous carbon material–based hybrid. An energy storage device consisting of hollow NiCo2S4 microspheres as the positive electrode, the 3D porous rGO/Fe2O3 composite as the negative electrode, and KOH solution as the electrolyte with a maximum energy density of 61.7 W h kg?1 is achieved owing to its wide operating voltage range of 0–1.75 V and the designed 3D structure. Moreover, the device exhibits a high power density of 22 kW kg?1 and a long cycle life with 90% retention after 1000 cycles at the current density of 1 A g?1.  相似文献   

14.
Zhengfeng Xie  Hao  Yunpeng  Li  Zhen  Sun  Fanghua  Ma  Junchi  Chen  Xin  Shi  Wei  Feng  Shun 《Russian Journal of Bioorganic Chemistry》2020,46(4):627-641
Russian Journal of Bioorganic Chemistry - —A novel 2-phenyl-1,2,3-triazole derived fluorescent probe HPTC ((2-hydroxybenzylidene)-2-phenyl-2H-1,2,3-triazole-4-carbohydrazide) has been...  相似文献   

15.
Sb2Se3 has recently spurred great interest as a promising light‐absorbing material for solar energy conversion. Sb2Se3 consists of 1D covalently linked nanoribbons stacked via van der Waals forces and its properties strongly depend on the crystallographic orientation. However, strategies for adjusting the anisotropy of 1D Sb2Se3 nanostructures are rarely investigated. Here, a novel approach is presented to fabricate 1D Sb2Se3 nanostructure arrays with different aspect ratios on conductive substrates by simply spin‐coating Sb‐Se solutions with different molar ratios of thioglycolic acid and ethanolamine. A relatively small proportion of thioglycolic acid induces the growth of short Sb2Se3 nanorod arrays with preferred orientation, leading to fast carrier transport and enhanced photocurrent. After the deposition of TiO2 and Pt, an appropriately oriented Sb2Se3 nanostructure array exhibits a significantly enhanced photoelectrochemical performance; the photocurrent reaches 12.5 mA cm?2 at 0 V versus reversible hydrogen electrode under air mass 1.5 global illumination.  相似文献   

16.
Quantification of brassinosteroids is essential and extremely important to study the molecular mechanisms of their physiological roles in plant growth and development. Herein, we present a simple, material and cost-saving high-performance method for determining endogenous brassinosteroids (BRs) in model plants. This new method enables simultaneous enrichment of a wide range of bioactive BRs such as brassinolide, castasterone, teasterone, and typhasterol with ion exchange solid-phase extraction and high-sensitivity quantitation of these BRs based on isotope dilution combined with internal standard approach. For routine analysis, the consumption of plant materials was reduced to one-twentieth of previously reported and the overall process could be completed within 1 day compared with previous 3 to 4 days. The strategy was validated by profiling BRs in different ecotypes and mutants of rice (Oryza sativa) and Arabidopsis (Arabidopsis thaliana), and the BR distributions in different model plants tissues were determined with the new method. The method allows plant physiologists to monitor the dynamics and distributions of BRs with 1 gram fresh weight of model plant tissues, which will speed up the process for the molecular mechanism research of BRs with these model plants in future work.Brassinosteroids (BRs) have been considered as the sixth class of endogenous plant hormones with wide occurrence across the plant kingdom (Bajguz and Tretyn, 2003). BRs play a key role in a variety of physiological processes, such as cell elongation, vascular differentiation, reproductive development, photomorphogenesis, stress tolerance, and so on (Hayat, 2010). Recently, it was found that BR deficiency could increase grain yield in rice (Oryza sativa) by more than 30%, which showed a food security-enhancing potential and guided new green revolution in the future (Sakamoto et al., 2006; Wu et al., 2008). Since BRs were first isolated and identified from rape (Brassica napus) pollen in 1970s (Mitchell et al., 1970; Grove et al., 1979), the natural occurrence of more than 60 BRs in a large quantity of plant species has been reported (Hayat, 2010). To date, research on the occurrence of BRs in different plants, physiological properties, and their action modes has made much progress (Fujioka and Yokota, 2003; Symons et al., 2008; Kim and Wang, 2010; Tang et al., 2010; Tong and Chu, 2012). However, so far, only limited information was obtained to understand the molecular mechanism of the physiological role of BRs. For example, although the biosynthetic pathway of C28 BRs has been well established, the biosynthesis of C27 and C29 BRs remains unclear, and some intermediates on their biosynthetic pathways still need to be elucidated (Noguchi et al., 2000; Fujita et al., 2006). The plant physiology research of BRs is speeded up by employing BR mutants on biosynthesis and signaling pathways (Yamamuro et al., 2000; Hong et al., 2003; Kwon and Choe, 2005; Tanabe et al., 2005); however, a simple, high-sensitivity screening, detection, and quantification method for BR analysis is still a bottleneck technique for in-depth studying of the role of BRs during the life cycle of plants.In the past 20 years, most of the detection and identification processes of BRs could be described briefly as the following steps. The harvested plant materials were lyophilized and then ground to a fine powder, followed by the CH3OH/CHCl3 extraction. The concentrate was then partitioned with the CHCl3/H2O system three times. After that, the CHCl3 fraction was subjected to a silica gel column for BR enrichment, and the collected BRs-containing fraction was purified with Sephadex LH-20 column and Sep-Pak Plus C18 cartridge in sequence. At last, the collected fractions were purified with preparative HPLC and then derivatized for analysis with gas chromatography-mass spectrometry (MS) under selected ion monitoring mode (Hong et al., 2005; Nomura et al., 2005; Kim et al., 2006). So far, this protocol has been proven to be workable in most cases and provided a great quantity of valuable data for plant physiological research (Hwang et al., 2006; Lee et al., 2010). However, at least more than 20 g of plant materials were consumed for quantifying/identifying BRs in one plant sample without replicates (Hong et al., 2005; Bancos et al., 2006; Kim et al., 2006), and it is difficult to collect sufficient plant tissues for BR measurement in some rare model plant mutants. In addition, the method involved multiple tedious and labor-intensive steps, which might result in poor recovery and low sensitivity, especially for some labile BR intermediates. The traditional method took one person about 3 to 4 d to treat one batch of samples. Most of the BR measurement experiments were performed without biological replicates using traditional methods due to the disadvantages mentioned above, which discounted the reliability of the results. Therefore, a simple, rapid, and sensitive analysis method for BRs is in urgent need, along with the development of BR research.Recently, several efforts were made to improve the BR determination (Svatos et al., 2004; Huo et al., 2012). The consumption of plant material was reduced to 2 g after modifying the BRs with a new derivatization reagent for further ultra-performance liquid chromatography (UPLC)-multiple reaction monitoring (MRM)-MS detection. However, the purification process consisting of deproteinization and multiple solid-phase extraction (SPE) steps was still quite tedious and couldn’t guarantee covering the four most important bioactive BRs, including brassinolide (BL), castasterone (CS), teasterone (TE), and typhasterol (TY; Fig. 1). In our previous study (Xin et al., 2013), we reported a simple, convenient, and high-sensitivity method for detection of endogenous BRs from real plant materials based on the dual role of specific boronate affinity. Although it was the first time to measure multiple BRs in subgram plant materials and the time duration of the method decreased to one-third of that previously reported, the synthesis of boronate affinity-functionalized magnetic nanoparticles made the method difficult to follow in biological laboratories for routine analysis.Open in a separate windowFigure 1.Chemical structure of four major bioactive BRs.BRs are neutral steroid compounds with a common four-ring cholestane skeleton and hydroxyl groups on A ring and/or the side chain linked to D ring. Especially, the vicinal diol moieties on C22 and C23 sites of BL, CS, TY, and TE allow these bioactive BRs to be derivatized with ionizable reagents for MS response enhancement. Considering the unique physicochemical properties of BRs, we herein developed a simplified high-sensitivity analytical method based on mixed-mode anion exchange (MAX)-cation exchange (MCX) solid phase extraction (SPE) purification, vicinal diol derivatization combined with UPLC-MRM3-MS detection for quantification of BL, CS, TE, and TY in model plants (Fig. 2). The performance of the method was demonstrated by determination of BRs in different tissues of both wild-type and mutant Arabidopsis (Arabidopsis thaliana) and rice.Open in a separate windowFigure 2.Simplified high-sensitivity protocol for quantitative analysis of BRs. IS, Internal standards. [See online article for color version of this figure.]  相似文献   

17.

In this study, a numerical investigation was done on the optical properties of silver nanostructures using the boundary element method (BEM) and finite element method (FEM). The BEM simulation was done using a freely available code called MNBEM in MATLAB with minor modifications. The FEM simulation was done by Comsol Multiphysics, a commercial software package. Silver nanostructures in the sphere, rod, and triangle geometries and the presence of different polarization angles were compared between these two methods. According to the obtained results, the absorption cross-sections for both BEM and FEM were consistent with their actual optical properties. For instance, both longitudinal and transverse resonance modes were observed in the case of nanorods, and all three in–plane dipole, in–plane quadrupole, and out–plane quadrupole plasmon resonances were observed successfully obtained for triangular nanostructures. Although both BEM and FEM results were similar to each other (from the number and position of the peaks in the final spectra), this similarity was decreased as the anisotropy was increased in the structure. For example, nearly 40 nm difference was observed between the BEM and FEM results in the triangular nanostructures, even though the trends and shape of the peaks were similar. It was revealed that specific points should be considered in the discretization process (especially the corner fillets) to close the gap in the obtained results from BEM and FEM. According to the obtained results, BEM significantly reduces the computational cost and time by discretizing only the boundary of the domain. A self-written software was developed to predict the optical cross-section of a plasmonic-ensemble consisting of spherical, rod-shaped, and triangular nanostructures, which can be used in different disciplines such as plasmon-enhanced solar cells, plasmon-enhanced photocatalysis, and plasmon-enhanced fluorescence.

Graphical Abstract
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18.
A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological research. Perhaps the most widely used physical force to achieve noninvasive manipulation of small particles has been dielectrophoresis(DEP).1 However, DEP on its own lacks the versatility and precision that are desired when manipulating cells since it is traditionally done with stationary electrodes. Optical tweezers, which utilize a three dimensional electromagnetic field gradient to exert forces on small particles, achieve this desired versatility and precision.2 However, a major drawback of this approach is the high radiation intensity required to achieve the necessary force to trap a particle which can damage biological samples.3 A solution that allows trapping and sorting with lower optical intensities are optoelectronic tweezers (OET) but OET''s have limitations with fine manipulation of small particles; being DEP-based technology also puts constraint on the property of the solution.4,5This video article will describe two methods that decrease the intensity of the radiation needed for optical manipulation of living cells and also describe a method for orientation control. The first method is plasmonic tweezers which use a random gold nanoparticle (AuNP) array as a substrate for the sample as shown in Figure 1. The AuNP array converts the incident photons into localized surface plasmons (LSP) which consist of resonant dipole moments that radiate and generate a patterned radiation field with a large gradient in the cell solution. Initial work on surface plasmon enhanced trapping by Righini et al and our own modeling have shown the fields generated by the plasmonic substrate reduce the initial intensity required by enhancing the gradient field that traps the particle.6,7,8 The plasmonic approach allows for fine orientation control of ellipsoidal particles and cells with low optical intensities because of more efficient optical energy conversion into mechanical energy and a dipole-dependent radiation field. These fields are shown in figure 2 and the low trapping intensities are detailed in figures 4 and 5. The main problems with plasmonic tweezers are that the LSP''s generate a considerable amount of heat and the trapping is only two dimensional. This heat generates convective flows and thermophoresis which can be powerful enough to expel submicron particles from the trap.9,10 The second approach that we will describe is utilizing periodic dielectric nanostructures to scatter incident light very efficiently into diffraction modes, as shown in figure 6.11 Ideally, one would make this structure out of a dielectric material to avoid the same heating problems experienced with the plasmonic tweezers but in our approach an aluminum-coated diffraction grating is used as a one-dimensional periodic dielectric nanostructure. Although it is not a semiconductor, it did not experience significant heating and effectively trapped small particles with low trapping intensities, as shown in figure 7. Alignment of particles with the grating substrate conceptually validates the proposition that a 2-D photonic crystal could allow precise rotation of non-spherical micron sized particles.10 The efficiencies of these optical traps are increased due to the enhanced fields produced by the nanostructures described in this paper.Download video file.(57M, mov)  相似文献   

19.
The ecological study design suffers from a broad range of biases that result from the loss of information regarding the joint distribution of individual-level outcomes, exposures, and confounders. The consequent nonidentifiability of individual-level models cannot be overcome without additional information; we combine ecological data with a sample of individual-level case-control data. The focus of this article is hierarchical models to account for between-group heterogeneity. Estimation and inference pose serious computational challenges. We present a Bayesian implementation based on a data augmentation scheme where the unobserved data are treated as auxiliary variables. The methods are illustrated with a dataset of county-specific infant mortality data from the state of North Carolina.  相似文献   

20.
The photothermal properties of solid and hollow gold nanostructures represented by colloidal solutions of spherical nanoparticles, nanoshells, and nanocages upon irradiation with a 100 mW 808 nm continuous-wave laser for the first time were experimentally compared under identical optical density and nanoparticle concentration conditions. Accompanying computer modeling of light absorption by the studied gold nanostructures revealed the general parameters influencing the photothermal efficiency, which is of significance for nanomedical applications. The spectral position of localized plasmonic excitations of the studied nanostructures ranged from 518 nm for solid gold nanoparticles to 718 nm for gold nanocages, which provided a possibility to observe a direct influence of the wavelength proximity between the localized surface plasmon resonance and laser line on the heat generation capability of the nanostructures. As a result, the best photothermal efficiency was registered for gold nanocages, which proves them as an efficient photothermal treatment agent and a possible candidate to build a nanocarrier platform for drug delivery with a controlled release. Light absorption modeling demonstrated an existence of optimal wall thickness for gold nanoshells that should lead to the maximum photothermal efficiency when irradiated with 808 nm light, which varied from about 0.1 to 0.4 in units of external nanoshell radius with an increase of the wall porosity. Additionally, computer modeling results show that increased wall porosity should lead to enhanced photothermal efficiency of polydisperse colloidal solutions of hollow gold nanostructures.  相似文献   

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