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1.
Nanoscale ; 12(6): 3731-3749, 2020 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-31993609

RESUMO

The actin cytoskeleton is required for the maintenance of the cell shape and viability of bacteria. It remains unknown to which extent nanoparticles (NPs) can orchestrate the mechanical instability by disrupting the cytoskeletal network in bacterial cells. Our work demonstrates that Au-Ag NPs disrupt the bacterial actin cytoskeleton specifically, fluidize the inner membrane and lead to killing of bacterial cells. In this study, we have tried to emphasize on the key parameters important for NP-cell interactions and found that the shape, specific elemental surface localization and enhanced electrostatic interaction developed due to the acquired partial positive charge by silver atoms in the aggregated NPs are some of the major factors contributing towards better NP interactions and subsequent cell death. In vivo studies in bacterial cells showed that the NPs exerted a mild perturbation of the membrane potential. However, its most striking effect was on the actin cytoskeleton MreB resulting in morphological changes in the bacterial cell shape from rods to predominantly spheres. Exposure to NPs resulted in the delocalization of MreB patches from the membrane but not the tubulin homologue FtsZ. Concomitant with the redistribution of MreB localization, a dramatic increase of membrane fluid regions was observed. Our studies reveal for the first time that Au-Ag NPs can mediate bacterial killing and disrupt the actin cytoskeletal functions in bacteria.

2.
ACS Appl Mater Interfaces ; 11(51): 48179-48191, 2019 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-31795638

RESUMO

Meticulous surface engineering of layered structures toward new functionalities is a demanding challenge to the scientific community. Here, we introduce defects on varied MoS2 surfaces by suitable doping of nitrogen atoms in a sulfur-rich reaction environment, resulting in stable and scalable phase conversion. The experimental characterizations along with the theoretical calculations within the framework of density functional theory establish the impact of nitrogen doping on stabilization of defects and reconstruction of the 2H to 1T phase. The as-synthesized MoS2 samples exhibit excellent dye removal capacity in the dark, facilitated by a synergistic effect of reactive oxygen species (ROS) generation and adsorption. Positron annihilation spectroscopy and electron paramagnetic resonance studies substantiate the role of defects and associated sulfur vacancies toward ROS generation in the dark. Further, on the basis of its ample ROS generation in the dark and in the light, the commendable antimicrobial activity of the prepared MoS2 samples against fungal pathogen Alternaria alternata has been demonstrated. Thus, the present study opens up a futuristic avenue to develop newer functional materials through defect engineering by suitable dopants toward superior performances in environment issues.

3.
ACS Appl Mater Interfaces ; 11(46): 42998-43017, 2019 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-31664808

RESUMO

Multidrug resistant (MDR) bacteria have emerged as a major clinical challenge. The unavailability of effective antibiotics has necessitated the use of emerging nanoparticles as alternatives. In this work, we have developed carbohydrate-coated bimetallic nanoparticles (Au-AgNP, 30-40 nm diameter) that are nontoxic toward mammalian cells yet highly effective against MDR strains as compared to their monometallic counterparts (Ag-NP, Au-NP). The Au-AgNP is much more effective against Gram-negative MDR Escherichia coli and Enterobacter cloacae when compared to most of the potent antibiotics. We demonstrate that in vivo, Au-AgNP is at least 11000 times more effective than Gentamicin in eliminating MDR Methicillin Resistant Staphylococcus aureus (MRSA) infecting mice skin wounds. Au-AgNP is able to heal and regenerate infected wounds faster and in scar-free manner. In vivo results show that this Au-AgNP is very effective antibacterial agent against MDR strains and does not produce adverse toxicity. We conclude that this bimetallic nanoparticle can be safe in complete skin regeneration in bacteria infected wounds.

4.
Microsc Microanal ; 25(6): 1407-1415, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31514761

RESUMO

Herein, we report an efficient method to produce silver (Ag) nanoparticle-decorated silicon (Si) nanowire (NW) arrays on a pyramidal Si (P-Si) substrate by using a pure chemical method and rapid thermal annealing in different atmospheres. A metal-assisted chemical etching technique was used to produce vertical Si NW arrays on pyramidal Si. The etching was observed to be heavily dependent on the substrate type. On planar Si (100), the etching was observed to occur in a uniform manner. However, the etching rate was observed to increase from the top to the base of the Si pyramid. The Si NWs produced from P-Si have zig-zag sidewalls as observed from high-resolution transmission electron microscopy images. However, for the same oxidant concentration, Si NWs produced from planar Si (100) consist of straight and amorphous sidewalls. Local variation of oxidant concentration is responsible for the formation of different sidewalls. The substrates are both surface-enhanced Raman scattering (SERS) active and hydrophobic. The hydrophobicity is due to the dual scale of roughness contributed to by both pyramidal and NW structures. Finite-difference time-domain simulation shows that the gap between two Ag spheres and also the gap between Si NWs and Ag spheres contributed to SERS enhancement.

5.
Nanotechnology ; 30(43): 435705, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31342941

RESUMO

In ferromagnetic (FM) metal/organic semiconductor (OSC) heterostructures charge transfer can occur which leads to induction of magnetism in the non-magnetic OSC. This phenomenon has been described by the change in the density of states in the OSC which leads to a finite magnetic moment at the OSC interface and it is called the 'spinterface'. One of the main motivations in this field of organic spintronics is how to control the magnetic moment in the spinterface. In this regard, there are several open questions such as (i) which combination of FM and OSC can lead to more moment at the spinterface? (ii) Is the thickness of OSC also important? (iii) How does the spinterface moment vary with the FM thickness? (iv) Does the crystalline quality of the FM matter? (v) What is the effect of spinterface on magnetization reversal, domain structure and anisotropy? In this context, we have tried to answer the last four issues in this paper by studying Fe/C60 bilayers of variable Fe thickness deposited on Si substrates. We find that both the induced moment and thickness of the spinterface vary proportionally with the Fe thickness. Such behavior is explained in terms of the growth quality of the Fe layer on the native oxide of the Si (100) substrate. The magnetization reversal, domain structure and anisotropy of these bilayer samples were studied and compared with their respective reference samples without the C60 layer. It is observed that the formation of spinterface leads to a reduction in uniaxial anisotropy in Fe/C60 on Si (100) in comparison to their reference samples.

6.
ChemSusChem ; 12(14): 3383-3389, 2019 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-31124304

RESUMO

The design of an efficient and highly selective organic polymeric semiconductor photocatalyst consisting of Earth-abundant elements for solar fuel generation using seawater, and also deionized water, as a proton source is reported. The mesoporous g-C3 N4 synthesized using a conventional precursor (urea) shows significant H2 generation (ca. 33 000 µmol h-1 g-1 ) and drives the photoreduction of CO2 to CH4 , along with trace amount of methanol. However, when the chosen precursor cyanamide is used, drastic improvement in H2 generation (ca. 41 600 µmol h-1 g-1 ) and CO2 photoreduction is observed. The introduction of a surface nitrogen deficiency and modification of the surface with Cu0 further enhances solar H2 generation (ca. 50 000 µmol h-1 g-1 ) and CO2 photoreduction (3.12 µmol h-1 g-1 ) activity, respectively, owing to improvement in light harvesting and charge separation, as revealed by a shorter average lifetime of 3.52 ns and higher Stern-Volmer quenching constant value of approximately 11.2 m-1 . In addition, improved selectivity in CO2 photoreduction to only CH4 is also observed. The designed photocatalytic system is stable, with the solar H2 generation rate increasing even after 20 h under continuous illumination with a turnover number of 6500. When seawater used instead of deionized water, the overall solar fuel generation efficiencies of all photocatalysts marginally decreased owing to a decrease in the photogenerated charge-carrier separation efficacy.

7.
ACS Appl Mater Interfaces ; 11(4): 4193-4202, 2019 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-30596233

RESUMO

Organic field-effect transistors (OFETs) with hexagonal barium titanate nanocrystals (h-BTNCs) in amorphous matrix as one of the bilayer dielectric systems have been fabricated on a highly flexible 10 µm thick poly(ethylene terephthalate) substrate. The device current and mobility remain constant up to a bending radius of 4 mm, which makes the substrate suitable for wearable e-skin applications. h-BTNC films are found to be highly temperature-sensitive, and the OFETs designed based on this material showed ultraprecision measurement (∼4.3 mK), low power (∼1 µW at 1.2 V operating voltage), and ultrafast response (∼24 ms) in sensing temperature over a range of 20-45 °C continuously. The sensors are highly stable around body temperature and work at various extreme conditions, such as under water and in solutions of different pH values and various salt concentrations. These properties make this sensor unique and highly suitable for various healthcare and other applications, wherein a small variation of temperature around this temperature range is required to be measured at an ultrahigh speed.

8.
Sci Rep ; 8(1): 14870, 2018 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-30291264

RESUMO

In this study, the synthesis of a novel ternary intermetallic compound Pr2Ni0.95Si2.95 forming in single phase only by deliberately introducing vacancies in Ni/Si site is reported. The detailed studies on dc magnetization, heat capacity, ac magnetization & associated dynamical scaling, different types of non-equilibrium dynamical behaviour, viz., magnetic relaxation behaviour as a function of wait time and temperature, aging phenomena, and magnetic memory effect firmly establish that the compound exhibits spin freezing behaviour below 3.3 K (Tf). However, below Tf, temperature dependence of ac susceptibility data exhibit an additional peak that shows reverse frequency dependence to that generally observed in a glassy system. The unusual bidirectional frequency dependence in a single magnetic system is of significant interest and rarely reported in literature. Competing exchange interaction arising from c/a ~ 1 and crystallographic randomness driven magnetic phase separation has been argued to be responsible for such observation. The reverse frequency shift of the low temperature peak has been described on the basis of a simple phenomenological model proposed in this work.

9.
Biosens Bioelectron ; 119: 10-17, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-30098461

RESUMO

Fabrication of Molybdenum disulfide (MoS2) nanostructures and surface functionalization with noble metal nano particles is an emerging field of research as it has potential applications in electronic devices and chemical sensing. Here we report application of gold nanoparticles (AuNPs) decorated MoS2 nanoflowers (Au-MoS2 NFs) as an efficient bio-sensor. MoS2 NFs, synthesized using green synthesis process, are further functionalized with AuNPs to tune their physical properties and make them more appropriate for biological applications. The abundant 'hot-spots' created by AuNPs through localization of electromagnetic field endows the Au-MoS2 hybrid structure as an excellent substrate for biochemical sensing through surface enhanced Raman scattering (SERS). The sensing efficiency of the SERS substrate is examined using Rh6G as probe molecule with concentration as low as 10-12 M. Main emphasis is given in detecting free bilirubin, an important component of human blood, using SERS technique. Au-MoS2 NF SERS substrate exhibits high sensitivity, stability and excellent reproducibility in sensing bilirubin from high level (10-3 M) to picomolar level. The concentration (C) dependent SERS intensity (I) is found to follow the general relationship I = Cα, with α ranging from 0.09 to 0.12. The substrate shows excellent selectivity and reliability while sensing of free bilirubin performed in human serum in the presence of crucial interferences such as dextrose, cholesterol and phosphate. In the present study, this Au-MoS2 hybrid offers a new potential biosensing technology for free bilirubin detection and is anticipated to be applied for clinic diagnosis.


Assuntos
Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , Ouro/química , Nanopartículas Metálicas/química , Nanoestruturas/química , Análise Espectral Raman/instrumentação , Humanos , Reprodutibilidade dos Testes
10.
Sci Rep ; 8(1): 10527, 2018 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-30002469

RESUMO

TaSb2 has been predicted theoretically to be a weak topological insulator. Whereas, the earlier magnetotransport experiment has established it as a topological semimetal. In the previous works, the Shubnikov-de Haas oscillation has been analyzed to probe the Fermi surface, with magnetic field along a particular crystallographic axis only. By employing a sample rotator, we reveal highly anisotropic transverse magnetoresistance by rotating the magnetic field along different crystallographic directions. To probe the anisotropy in the Fermi surface, we have performed magnetization measurements and detected strong de Haas-van Alphen (dHvA) oscillations for the magnetic field applied along a and b axes as well as perpendicular to ab plane of the crystals. Three Fermi pockets have been identified by analyzing the dHvA oscillations. With the application of magnetic field along different crystal directions, the cross-sectional areas of the Fermi pockets have been found significantly different, i.e., the Fermi pockets are highly anisotropic in nature. Three-band fitting of electrical and Hall conductivity reveals two high mobility electron pockets and one low mobility hole pocket. The angular variation of transverse magnetoresistance has been qualitatively explained using the results of dHvA oscillations and three-band analysis.

11.
Nanoscale ; 10(28): 13792, 2018 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-29978174

RESUMO

Correction for 'Crystal-defect-induced facet-dependent electrocatalytic activity of 3D gold nanoflowers for the selective nanomolar detection of ascorbic acid' by Sandip Kumar De, et al., Nanoscale, 2018, 10, 11091-11102.

12.
Nanoscale ; 10(23): 11091-11102, 2018 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-29872830

RESUMO

Understanding and exploring the decisive factors responsible for superlative catalytic efficiency is necessary to formulate active electrode materials for improved electrocatalysis and high-throughput sensing. This research demonstrates the ability of bud-shaped gold nanoflowers (AuNFs), intermediates in the bud-to-blossom gold nanoflower synthesis, to offer remarkable electrocatalytic efficiency in the oxidation of ascorbic acid (AA) at nanomolar concentrations. Multicomponent sensing in a single potential sweep is measured using differential pulse voltammetry while the kinetic parameters are estimated using electrochemical impedance spectroscopy. The outstanding catalytic activity of bud-structured AuNF [iAuNFp(Bud)/iGCp ≅ 100] compared with other bud-to-blossom intermediate nanostructures is explained by studying their structural transitions, charge distributions, crystalline patterns, and intrinsic irregularities/defects. Detailed microscopic analysis shows that density of crystal defects, such as edges, terraces, steps, ledges, kinks, and dislocation, plays a major role in producing the high catalytic efficiency. An associated ab initio simulation provides necessary support for the projected role of different crystal facets as selective catalytic sites. Density functional theory corroborates the appearance of inter- and intra-molecular hydrogen bonding within AA molecules to control the resultant fingerprint peak potentials at variable concentrations. Bud-structured AuNF facilitates AA detection at nanomolar levels in a multicomponent pathological sample.


Assuntos
Ácido Ascórbico/análise , Ouro , Nanoestruturas , Espectroscopia Dielétrica , Eletrodos
13.
Nanotechnology ; 29(20): 205604, 2018 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-29498935

RESUMO

Coplanar heterojunctions composed of van der Waals layered materials with different structural polymorphs have drawn immense interest recently due to low contact resistance and high carrier injection rate owing to low Schottky barrier height. Present research has largely focused on efficient exfoliation of these layered materials and their restacking to achieve better performances. We present here a microwave assisted easy, fast and efficient route to induce high concentration of metallic 1T phase in the original 2H matrix of exfoliated MoS2 layers and thus facilitating the formation of a 1T-2H coplanar superlattice phase. High resolution transmission electron microscopy (HRTEM) investigations reveal formation of highly crystalline 1T-2H hybridized structure with sharp interface and disclose the evidence of surface ripplocations within the same exfoliated layer of MoS2. In this work, the structural stability of 1T-2H superlattice phase during HRTEM measurements under an electron beam of energy 300 keV is reported. This structural stability could be either associated to the change in electronic configuration due to induction of the restacked hybridized phase with 1T- and 2H-regions or to the formation of the surface ripplocations. Surface ripplocations can act as an additional source of scattering centers to the electron beam and also it is possible that a pulse train of propagating ripplocations can sweep out the defects via interaction from specific areas of MoS2 sheets.

14.
ACS Appl Mater Interfaces ; 10(5): 4582-4589, 2018 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-29338178

RESUMO

Herein we have engineered a smart nuclear targeting thiol-modified riboflavin-gold nano assembly, RfS@AuNPs, which accumulates selectively in the nucleus without any nuclear-targeting peptides (NLS/RGD) and shows photophysically in vitro DNA intercalation. A theoretical model using Molecular Dynamics has been developed to probe the mechanism of formation and stability as well as dynamics of the RfS@AuNPs in aqueous solution and within the DNA microenvironment. The RfS@AuNPs facilitate the binucleated cell formation that is reflected in the significant increase of DNA damage marker, γ-H2AX as well as the arrest of most of the HeLa cells at the pre-G1 phase indicating cell death. Moreover, a significant upregulation of apoptotic markers confirms that the cell death occurs through the apoptotic pathway. Analyses of the microarray gene expression of RfS@AuNPs treated HeLa cells show significant alterations in vital biological processes necessary for cell survival. Taken together, our study reports a unique nuclear targeting mechanism through targeting the riboflavin receptors, which are upregulated in cancer cells and induce apoptosis in the targeted cells.


Assuntos
Dano ao DNA , Apoptose , Linhagem Celular Tumoral , Ouro , Células HeLa , Humanos , Riboflavina
15.
Sci Rep ; 8(1): 868, 2018 01 17.
Artigo em Inglês | MEDLINE | ID: mdl-29343696

RESUMO

Decoupling of different plasmon resonance modes (in-plane, and out-of-plane dipole and quadrupole resonances) by tuning nanoparticle's size and shape offers a new field of plasmonics as colorimetric assay-based optical-ruler for ultra-trace sensing. Driven by its low cost, easy to perform and efficient way to measure trace level (up to 30 ppt in presence of common mining elements in natural gold ore) abundance, this study develops a highly selective and ultrasensitive turn-on colorimetric sensor to detect gold-ion from environmental samples. Different level of gold-ion tracer makes size variable spherical- and disc-shaped silver nanoparticles when added to a 'growth solution' which results decoupling of in-plane dipole resonance from in-plane quadrupole and out-of-plane dipole resonances with a wide range of in-plane dipole plasmon tunability to generate different colors. This color-coded sensing of gold-ion shows high selectivity and ultrasensitivity over other metal ions in the ppt level with an impurity aberration limit of 1 ppm. A plausible explanation explains the possible role of catalytic gold-ion to initiate unfavorable silver ion (Ag+) reduction by ascorbic acid to generate silver nanoparticles. Proposed technology has been applied in real mining sample (Bugunda Gold Deposit, Tajikistan) to detect gold concentration from ores to find potential application in mining technology.

16.
ACS Omega ; 3(7): 7944-7954, 2018 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31458934

RESUMO

Selective catalytic oxidation of carbohydrate-derived 5-hydroxymethylfurfural, furfuryl alcohol, and various aromatic and aliphatic compounds to the corresponding aldehyde is a challenging task. The development of a sustainable heterogeneous catalyst is crucial in achieving high selectivity for the desired aldehyde, especially using O2 or air. In this study, a RuO2-supported Mn3O4 catalyst is reported for the selective oxidation reaction. Treatment of MnO2 molecular sieves with RuCl3 in aqueous formaldehyde solution gives a new type of RuO2-supported Mn3O4 catalyst. Detailed catalyst characterization using powder X-ray diffraction, N2 adsorption, scanning and transmission electron microscopes, diffuse reflectance UV-visible spectrometer, and X-ray photoelectron spectroscopy proves that the RuO2 species are dispersed on the highly crystalline Mn3O4 surface. This catalytic conversion process involves molecular oxygen or air (flow, 10 mL/min) as an oxidant. No external oxidizing reagent, additive, or cocatalyst is required to carry out this transformation. This oxidation protocol affords 2,5-diformylfuran, 2-formylfuran, and other aromatic and aliphatic aldehydes in good to excellent yield (70-99%). Moreover, the catalyst is easily recycled and reused without any loss in the catalytic activity.

17.
ACS Appl Mater Interfaces ; 9(44): 38931-38942, 2017 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-29019387

RESUMO

Point sources exhibit low threshold electron emission due to local field enhancement at the tip. In the case of silicon, however, the realization of tip emitters has been hampered by unwanted oxidation, limiting the number of emission sites and the overall current. In contrast to this, here, we report the fascinating low threshold (∼0.67 V µm-1) cold cathode electron emission from silicon nanofacets (Si-NFs). The ensembles of nanofacets fabricated at different time scales, under low energy ion impacts, yield tunable field emission with a Fowler-Nordheim tunneling field in the range of 0.67-4.75 V µm-1. The local probe surface microscopy-based tunneling current mapping in conjunction with Kelvin probe force microscopy measurements revealed that the valleys and a part of the sidewalls of the nanofacets contribute more to the field emission process. The observed lowest turn-on field is attributed to the absence of native oxide on the sidewalls of the smallest facets as well as their lowest work function. In addition, first-principle density functional theory-based simulation revealed a crystal orientation-dependent work function of Si, which corroborates well with our experimental observations. The present study demonstrates a novel way to address the origin of the cold cathode electron emission sites from Si-NFs fabricated at room temperature. In principle, the present methodology can be extended to probe the cold cathode electron emission sites from any nanostructured material.

18.
ACS Appl Mater Interfaces ; 9(46): 40831-40845, 2017 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-29072442

RESUMO

Nanoparticles of Li0.3Zn0.3Co0.1Fe2.3O4 (LZC) were prepared by the sol-gel method and dried in a furnace at ∼200 °C. The dried sample was annealed at 500, 600, 700, and 800 °C for 5 h each. Rietveld analysis of X-ray diffraction patterns confirms the cubic Fd3̅m phase formation with lattice parameters ranged from 8.376 up to 8.390 Å and allows the crystallite sizes (dcryst) to be estimated. To enhance microwave (MW) absorption as well as the effectiveness for hyperthermia treatment, nanoparticles are taken in the matrix of multiwalled carbon nanotubes (MWCNTs) and the morphology of the so-prepared samples (LZC@MWCNT) was studied by scanning electron microscopy and transmission electron microscopy analyses. Both static and dynamic magnetic properties were investigated on the samples of LZC nanoparticles and compared to those of the samples of LZC@MWCNT. The samples annealed at 500, 600, and 800 °C are excellent candidates in cancer treatment as ac magnetic heating analysis shows that the hyperthermia temperature (42 °C) was successfully achieved for an applied ac magnetic field of 420 Oe and 300 kHz frequency. MW absorption study also reveals that the samples of LZC@MWCNT could be used as a potential MW absorbing material for which a maximum reflection loss (RL) of ∼-21 dB was achieved at a frequency of 15.27 GHz for only 1 mm layer thickness.

19.
ACS Appl Mater Interfaces ; 9(39): 34405-34415, 2017 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-28901125

RESUMO

This paper reports on a simple and cost-effective process of developing a stable surface-enhanced Raman scattering (SERS) substrate based on silver (Ag) nanoparticles deposited on silicon (Si) surface. Durability is an important issue for preparing SERS active substrate as silver nanostructures are prone to rapid surface oxidation when exposed to ambient conditions, which may result in the loss of the enhancement capabilities in a short period of time. Here, we employ the galvanic displacement method to produce Ag nanoparticles on Si(100) substrate prepatterned with arrays of micropyramids by chemical etching, and subsequently, separate pieces of such substrates were annealed in oxygen and nitrogen environments at 550 °C. Interestingly, while nitrogen-annealed Si substrates were featured by spherical-shaped Ag particles, the oxygen annealed Si substrates were dominated by the formation of triangular shape particles attached with the spherical one. Remarkably, the oxygen-annealed substrate thus produced shows very high SERS enhancement compared to the either unannealed or nitrogen annealed substrate. The hitherto unobserved coexistence of triangular morphology with the spherical one and the gap between the two (source of efficient hot-spots) are the origin of enhanced SERS activity for the oxygen-annealed Ag particle-covered Si substrate as probed by the combined finite-difference time domain (FDTD) simulation and cathodoluminesensce (CL) experiment. As the substrate has already been annealed in an oxygen environment, further probability of oxidation is reduced in the present synthesis protocol that paves the way for making a novel long-lived thermally stable SERS substrate.

20.
Sci Rep ; 7(1): 6321, 2017 07 24.
Artigo em Inglês | MEDLINE | ID: mdl-28740199

RESUMO

Novel topological state of matter is one of the rapidly growing fields in condensed matter physics research in recent times. While these materials are fascinating from the aspect of fundamental physics of relativistic particles, their exotic transport properties are equally compelling due to the potential technological applications. Extreme magnetoresistance and ultrahigh carrier mobility are two such major hallmarks of topological materials and often used as primary criteria for identifying new compounds belonging to this class. Recently, LaBi has emerged as a new system, which exhibits the above mentioned properties. However, the topological nature of its band structure remains unresolved. Here, using the magnetotransport and magnetization measurements, we have probed the bulk and surface states of LaBi. Similar to earlier reports, extremely large magnetoresistance and high carrier mobility have been observed with compensated electron and hole density. The Fermi surface properties have been analyzed from both Shubnikov-de Haas and de Haas-van Alphen oscillation techniques. In the magnetization measurement, a prominent paramagnetic singularity has been observed, which demonstrates the non-trivial nature of the surface states in LaBi. Our study unambiguously confirms that LaBi is a three-dimensional topological insulator with possible linear dispersion in the gapped bulk band structure.

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