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1.
Bioelectrochemistry ; 126: 92-98, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30530260

RESUMO

In this work, a sandwich-type electrochemical immunosensor was fabricated to quantitatively detect hepatitis B surface antigen (HBsAg). The immunosensor was based on Rh core and Pt shell nanodendrites loaded onto amino group functionalized graphene nanosheet (RhPt NDs/NH2-GS) as label and gold nanoparticles loaded onto polypyrrole nanosheet (Au NPs/PPy NS) as platform. RhPt NDs with abundant catalytic active sites because of the branched core-shell structure, RhPt NDs/NH2-GS as the label displayed high catalytic activity, amplifying the current signal of the immunosensor. Additionally, Au NPs/PPy NS enhanced the electron transfer and provided a good microenvironment to immobilize antibodies effectively, thus improving the sensitivity of the immunosensor. Based on above advantages, the immunosensor emerged a linear concentration ranging from 0.0005 to 10 ng/mL, a low detection limit of 166 fg/mL for HBsAg (S/N = 3) and good stability, selectivity, reproducibility. Furthermore, the satisfactory accuracy in analysis of actual serum samples implied the immunosensor had promising prospect in clinical analysis applications.


Assuntos
Anticorpos Imobilizados/química , Técnicas Eletroquímicas/métodos , Antígenos de Superfície da Hepatite B/sangue , Nanoestruturas/química , Polímeros/química , Pirróis/química , Técnicas Biossensoriais/métodos , Ouro/química , Grafite/química , Hepatite B/sangue , Hepatite B/imunologia , Antígenos de Superfície da Hepatite B/imunologia , Vírus da Hepatite B/imunologia , Humanos , Imunoensaio/métodos , Limite de Detecção , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Nanoestruturas/ultraestrutura , Platina/química , Ródio/química
2.
Nanomaterials (Basel) ; 8(12)2018 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-30513769

RESUMO

The ionic transportation and dielectric properties of YF3:Eu3+ nanocrystals are investigated by AC impedance spectroscopy. The ion diffusion coefficient and conductivity increase along with the doping concentration and reach their highest values at 4% of Eu3+. The difference of ionic radius between Eu3+ and Y3+ leads to the structural disorder and lattice strain, which deduces the increase of the ion diffusion coefficient and conductivity before 4% Eu3+ doping; then the interaction of the neighboring doping ions is dominated, which results in the difficulty of ion migration and decreases of the ion diffusion coefficient and conductivity. The strong dispersion of the permittivity in the low frequency region indicates that the charge carrier transport mechanism is the ion hopping in the system. The low-frequency hopping dispersion is affected by an interfacial polarization, which exhibits a Maxwell-Wagner relaxation process, and its loss peak shifts to higher frequency with the ionic conductivity increasing.

3.
Phys Chem Chem Phys ; 20(38): 24927-24932, 2018 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-30238105

RESUMO

At ambient conditions, the lattice structure of supported ultrathin transition metal dichalcogenides (TMDs) can be effectively modified by a substrate. When compressed, the effect of substrate is far from settled. In this study, the effects of an Si substrate on the lattice structures of compressed monolayer and multilayer ReS2 were investigated by performing high-pressure Raman measurements and first-principle calculations. Our results revealed substrate-affected strain in compressed monolayer ReS2, which resulted in a distorted unit with S atoms sliding within a single layer. This was evidenced by the split of the Ag-5 mode above 1.7 GPa. However, unlike that of the monolayer ReS2, the Ag-5 mode of multilayer ReS2 remained symmetric up to 4.2 GPa, which can be due to weaker substrate-affected strain in compressed multilayer ReS2 when compared with that in the monolayer ReS2. The noticeably different high-pressure responses between multilayer ReS2 and monolayer ReS2 can be due to the effect of interlayer interactions, and the split of the Ag-5 mode provides a clear indication of the prominent strain in compressed supported ReS2.

4.
Biosens Bioelectron ; 122: 231-238, 2018 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-30267981

RESUMO

The quantitative detection of carcinoembryonic antigen (CEA) is significant to assess tumor status and therapeutic efficiency. In this study, a sandwich-type amperometric immunosensor for CEA detection sensitively was fabricated by novel signal amplification system. The signal amplification system was formed by gold nanoparticles loaded on amino functionalized graphene sheet (Au NPs/NH2-GS) and gold@palladium nanodendrites loaded on ferrous-chitosan functionalized polypyrrole nanotubes (Au@Pd NDs/Fe2+-CS/PPy NTs). Au NPs/NH2-GS as platform enhanced the electron transfer proven by apparent electron transfer rate constant. Au@Pd NDs/Fe2+-CS/PPy NTs nanocomposite as label appeared high catalytic activity to hydrogen peroxide reduction. Thus, the immunosensor showed wide linear concentration range (50 fg/mL to 50 ng/mL) and low detection limit of 17 fg/mL via amperometric i-t curve (i-t). Significantly, the nanocomposite can act as electroactive substance, which provided a good method to detect CEA without additional electroactive substance via square wave voltammetry (SWV). An overlapping linear concentration range (500 fg/mL to 5.0 ng/mL) was obtained compared i-t with SWV. The good reliability was verified mutually by i-t and SWV in actual sample analysis under overlapping linear concentration range. The detection method of without additional electroactive substance has vast potential for future development, due to simple testing condition.


Assuntos
Técnicas Biossensoriais/métodos , Antígeno Carcinoembrionário/sangue , Quitosana/análogos & derivados , Ouro/química , Nanoestruturas/química , Paládio/química , Polímeros/química , Pirróis/química , Anticorpos Imobilizados/química , Técnicas Eletroquímicas/métodos , Grafite/química , Humanos , Imunoensaio/métodos , Limite de Detecção , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Nanoestruturas/ultraestrutura
5.
Nanomaterials (Basel) ; 8(7)2018 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-30011931

RESUMO

Calcium fluoride (CaF2) nanoparticles with various terbium (Tb) doping concentrations were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and alternating current (AC) impedance measurement. The original shape and structure of CaF2 nanoparticles were retained after doping. In all the samples, the dominant charge carriers were electrons, and the F- ion transference number increased with increasing Tb concentration. The defects in the grain region considerably contributed to the electron transportation process. When the Tb concentration was less than 3%, the effect of the ionic radius variation dominated and led to the diffusion of the F- ions and facilitated electron transportation. When the Tb concentration was greater than 3%, the increasing deformation potential scattering dominated, impeding F- ion diffusion and electron transportation. The substitution of Ca2+ by Tb3+ enables the electron and ion hopping in CaF2 nanocrystals, resulting in increased permittivity.

6.
Sci Rep ; 8(1): 5086, 2018 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-29572527

RESUMO

The electrical transport and structural properties of tin oxide nanoparticles under compression have been studied by in situ impedance measurements and synchrotron X-ray diffraction (XRD) up to 27.9 GPa. It was found that the conduction of SnO2 can be improved significantly with compression. Abnormal variations in resistivity, relaxation frequency, and relative permittivity were observed at approximately 12.3 and 25.0 GPa, which can be attributed to pressure-induced tetragonal- orthorhombic-cubic structural transitions. The dielectric properties of the SnO2 nanoparticles were found to be a function of pressure, and the dielectric response was dependent on frequency and pressure. The dielectric constant and loss tangent decreased with increasing frequency. Relaxation-type dielectric behaviour dominated at low frequencies. Whereas, modulus spectra indicated that charge carrier short-range motion dominated at high frequencies.

7.
Phys Chem Chem Phys ; 20(13): 8917-8923, 2018 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-29557428

RESUMO

Hydride ions (H-) have an appropriate size for fast transport, which makes the conduction of H- attractive. In this work, the H- transport properties of BaH2 have been investigated under pressure using in situ impedance spectroscopy measurements up to 11.2 GPa and density functional theoretical calculations. The H- transport properties, including ionic migration resistance, relaxation frequency, and relative permittivity, change significantly with pressure around 2.3 GPa, which can be attributed to the structural phase transition of BaH2. The ionic migration barrier energy of the P63/mmc phase decreases with pressure, which is responsible for the increased ionic conductivity. A huge dielectric constant at low frequencies is observed, which is related to the polarization of the H- dipoles. The current study establishes general guidelines for developing high-energy storage and conversion devices based on hydride ion transportation.

8.
J Phys Condens Matter ; 30(14): 144008, 2018 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-29498357

RESUMO

Fe3+ doped chrysotile nanotubes (NTs) have been synthesized under controlled hydrothermal conditions, and have been characteristic of layered-walls and room-temperature ferromagnetism. High-pressure in situ impedance spectra and synchrotron XRD measurements are performed on Fe-doped chrysotile NTs to reveal the electrical transport and structural properties under compression. Sample resistance (R sum) was found to increase with the pressure elevation, accompanying the step decrease in the grain boundary relaxation frequency (f gb), which reflects the bandgap broadening and dipoles polarization weakening due to the application of pressure. Furthermore, it is found that both R sum and f gb change their pressure dependences at ~5.0 GPa, which is attributed to the nonlinear compressibility of c-axis and even the underlying lattice distortion of monoclinic structure obtained in the XRD observations.

9.
Phys Chem Chem Phys ; 20(11): 7492-7497, 2018 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-29508875

RESUMO

The electrical transport behavior of the superionic conductor AgBr was systematically studied under high pressure up to 30.0 GPa with electrochemical impedance spectra measurements and first-principles calculations. From impedance spectra measurements, a pressure-induced abnormal ionic-polaronic-ionic transition was found. Herein, the ionic to polaronic transition at 5.0 GPa occurs with the absence of a structural phase transition. At 8.6 GPa, the ionic state of AgBr can be reactivated after a structural phase transition. Previous structural studies based on X-ray diffraction data cannot provide strong evidence to support the ionic-polaronic transition in AgBr at 5.0 GPa. In this paper, based on first-principles calculations, a localized-electron-soup model was proposed to explain the physical origin of the ionic-polaronic transition. In this model, more localized electrons around the Br atoms are pressed into interstitial spaces and, simultaneously, polarons are formed between Ag+ ions and the localized electron background at 5.0 GPa. Therefore, the diffusion of Ag+ ions is effectively screened by the movement of the localized electron background from its equilibrium position, much like beans completely trapped in a cup of thick soup.

10.
Phys Chem Chem Phys ; 19(39): 26758-26764, 2017 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-28948241

RESUMO

We report on the intriguing structural and electrical transport properties of compressed InN. Pronounced anomalies of the resistivity, Hall coefficient, electron concentration, and mobility are observed at ∼11.5 GPa, accompanied by a wurtzite-rocksalt structural transition confirmed using high-pressure XRD measurements and first-principles calculations. The pressure-tuned electrical properties of wurtzite and rocksalt InN are also studied, respectively. Particularly, compression pressure significantly decreases the electron concentration of rocksalt InN by two orders of magnitude and increases the mobility by ten fold. The obvious variations in electrical parameters can be rationalized by our band structure simulations, which reveal a direct-indirect energy crossover at 10 GPa, followed by the rapidly increasing patterns of the energy gap with a pressure coefficient of 33 meV GPa-1. Moreover the electron effective mass and energy gap are found to well satisfy with the k·p model. Definite correlation between the structural change and the electrical transport properties should shed a new light on building InN-based applications in the future.

11.
Adv Mater ; 29(34)2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28692745

RESUMO

An unexpected superconductivity enhancement is reported in decompressed In2 Se3 . The onset of superconductivity in In2 Se3 occurs at 41.3 GPa with a critical temperature (Tc ) of 3.7 K, peaking at 47.1 GPa. The striking observation shows that this layered chalcogenide remains superconducting in decompression down to 10.7 GPa. More surprisingly, the highest Tc that occurs at lower decompression pressures is 8.2 K, a twofold increase in the same crystal structure as in compression. It is found that the evolution of Tc is driven by the pressure-induced R-3m to I-43d structural transition and significant softening of phonons and gentle variation of carrier concentration combined in the pressure quench. The novel decompression-induced superconductivity enhancement implies that it is possible to maintain pressure-induced superconductivity at lower or even ambient pressures with better superconducting performance.

12.
J Phys Chem Lett ; 8(15): 3648-3655, 2017 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-28731712

RESUMO

The transition metal dichalcogenide (TMD) ReS2 is a promising material for optoelectronic devices because of its remarkable quantum yield. Pressure can effectively tune the optoelectronic properties of TMDs through control of the atomic displacement. Here, we systematically investigated the lattice and electronic structural evolutions of compressed multilayer ReS2. Both Raman spectra and first-principles calculations suggest the occurrence of an intralayer phase transition followed by an interlayer transition. A transition from one indirect to another indirect bandgap at 2.7 GPa was revealed by both high-pressure photoluminescence (PL) measurements and first-principles calculations, this behavior was elucidated by considering the fundamental relationship between lattice variation and electronic evolution. Moreover, by comparing the high-pressure behavior of MoS2 and ReS2, we demonstrated interlayer coupling plays a critical role in determining the lattice and electronic structures in compressed TMDs. Our findings suggest the potential application of ReS2 in fabricating various stacking devices with tailored properties.

13.
J Phys Chem Lett ; 8(13): 2944-2950, 2017 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-28613889

RESUMO

The electrical transport properties of CH3NH3PbBr3 (MAPbBr3) polycrystals were in situ investigated by alternating-current impedance spectroscopy under high pressures up to 5.6 GPa. It is confirmed that ionic and electronic conductions coexist in MAPbBr3. As pressure below 3.3 GPa ions migration is the predominant process, while above 3.3 GPa electronic conduction becomes the main process. An obvious ionic-electronic transition can be observed. The pressure dependent photo responsiveness of MAPbBr3 was also studied by in situ photocurrent measurements up to 3.8 GPa. The mixed conduction can be clearly seen in photocurrent measurement. Additionally, the photocurrents remain robust below 2.4 GPa, while they are suppressed with pressure-induced partial amorphization. Interestingly, the photoelectric response of MAPbBr3 can be enhanced by high pressure, and the strongest photocurrent value appears in the high-pressure phase II at 0.7 GPa, which is similar to previous results in both MAPbI3 and MASnI3.

14.
Sci Rep ; 7(1): 2656, 2017 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-28572598

RESUMO

The high-pressure metallization and electrical transport behaviors of GaSb were systematically investigated using in situ temperature-dependent electrical resistivity measurements, Hall effect measurements, transmission electron microscopy analysis, and first-principles calculations. The temperature-dependent resistivity measurements revealed pressure-induced metallization of GaSb at approximately 7.0 GPa, which corresponds to a structural phase transition from F-43m to Imma. In addition, the activation energies for the conductivity and Hall effect measurements indicated that GaSb undergoes a carrier-type inversion (p-type to n-type) at approximately 4.5 GPa before metallization. The first-principles calculations also revealed that GaSb undergoes a phase transition from F-43m to Imma at 7.0 GPa and explained the carrier-type inversion at approximately 4.5 GPa. Finally, transmission electron microscopy analysis revealed the effect of the interface on the electrical transport behavior of a small-resistance GaSb sample and explained the discontinuous change of resistivity after metallization. Under high pressure, GaSb undergoes grain refinement, the number of interfaces increases, and carrier transport becomes more difficult, increasing the electrical resistivity.

15.
Sci Rep ; 7: 41256, 2017 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-28120949

RESUMO

Tropical forests have essential functions in global C dynamics but vulnerable to changes in land cover land use (LCLUC) and climate. The tropics of Caribbean are experiencing warming and drying climate and diverse LCLUC. However, large-scale studies to detect long-term trends of C and mechanisms behind are still rare. Using MODIS Enhanced Vegetation Index (EVI), we investigated greenness trend in the Greater Antilles Caribbean during 2000-2015, and analyzed trend of vegetation patches without LCLUC to give prominence to climate impacts. We hypothesized that night warming and heavy cloudiness would reduce EVI in this mountainous tropical region. Over the 15 years, EVI decreased significantly in Jamaica, Haiti, Dominican Republic, and Puerto Rico, but increased in Cuba partly due to its strong reforestation. Haiti had the largest decreasing trend because of continuous deforestation for charcoals. After LCLUC was excluded, EVI trend still varied greatly, decreasing in the windward but increasing in the leeward of Puerto Rico. Nighttime warming reinforced by spatially heterogeneous cloudiness was found to significantly and negatively correlate with EVI trend, and explained the spatial pattern of the latter. Although cooled daytime and increased rainfall might enhance EVI, nighttime warming dominated the climate impacts and differentiated the EVI trend.

16.
Sci Rep ; 6: 38566, 2016 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-27924843

RESUMO

Raman spectroscopy, synchrotron angle-dispersive X-ray diffraction (ADXRD), first-principles calculations, and electrical resistivity measurements were carried out under high pressure to investigate the structural stability and electrical transport properties of metavanadate MgV2O6. The results have revealed the coordination change of vanadium ions (from 5+1 to 6) at around 4 GPa. In addition, a pressure-induced structure transformation from the C2/m phase to the C2 phase in MgV2O6 was detected above 20 GPa, and both phases coexisted up to the highest pressure. This structural phase transition was induced by the enhanced distortions of MgO6 octahedra and VO6 octahedra under high pressure. Furthermore, the electrical resistivity decreased with pressure but exhibited different slope for these two phases, indicating that the pressure-induced structural phase transitions of MgV2O6 was also accompanied by the obvious changes in its electrical transport behavior.

17.
Nanoscale ; 8(45): 19014-19024, 2016 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-27808315

RESUMO

The combination of upconversion nanocrystals with a wide-bandgap semiconductor is an efficient strategy to develop near-infrared (NIR)-responsive photocatalysts. The photocatalytic activity of the hybrid structures is greatly determined by the efficiency of the energy transfer on the interface between upconversion nanocrystals and the semiconductor. In this work, we demonstrate the interface design of a NaYF4:Yb,Tm-BiOCl hybrid structure based on the choice of suitable BiOCl facets in depositing NaYF4:Yb,Tm upconversion nanocrystals. It was found that the selective deposition of NaYF4:Yb,Tm nanocrystals on the BiOCl(110) facet can greatly enhance the photocatalytic performance in dye degradation compared with the sample with NaYF4:Yb,Tm nanocrystals loaded on the BiOCl(001) facet. Two effects were believed to contribute to this enhancement: (1) a stronger UV emission absorption ability of the BiOCl(110) facet from NaYF4:Yb,Tm in generating more photo-induced charge carriers resulted from the narrower bandgap; (2) a shorter diffusion distance of photogenerated charge carriers to the BiOCl(110) reactive facet for surface catalytic reactions owing to the spatial charge separation between different facets. This work highlights the rational interfacial design of an upconversion nanocrystal-semiconductor hybrid structure for enhanced energy transfer in photocatalysis.

18.
Phys Chem Chem Phys ; 18(48): 33109-33114, 2016 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-27886297

RESUMO

In situ impedance measurements were employed to investigate the electrical transport properties of BaMoO4 under pressures of up to 20.0 GPa. Two anomalous changes in the electrical parameters were found, related to the pressure-induced structural phase transitions. The dielectric performance of BaMoO4 was improved by pressure. The dispersion in the real part of dielectric constant versus frequency weakens with increasing pressure. Based on the first-principles calculations, the increases of resistance with increasing pressure in the tetragonal and monoclinic phases were mainly caused by the increasing defect levels. The decrease of the relative permittivity in the tetragonal phase was attributed to pressure-induced strengthening in electronic localization around Mo atoms, which hindered the polarization of Mo-O electric dipoles.

19.
ACS Appl Mater Interfaces ; 8(43): 29334-29342, 2016 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-27726331

RESUMO

For effective gene therapy, nonviral gene carriers with low toxicity and high transfection efficiency are of much importance. In this work, we developed a facile strategy to prepare hyperbranched hydroxyl-rich polycations (denoted by TE) by the one-pot method involving ring-opening reactions between two commonly used reagents, ethylenediamine (ED) with two amino groups and 1,3,5-triglycidyl isocyanurate (TGIC) with three epoxy groups. The hyperbranched TEs with different molecular weights were investigated on their DNA condensation ability, protein absorption property, biocompatibility, transfection efficiency, and in vivo cancer therapy and toxicity. TE exhibited low cytotoxicity and protein absorption property due to the plentiful hydroxyl groups. The optimal transfection efficiency of TE was significantly higher than that of the gold standard polycationic gene carrier branched polyethylenimine (PEI, 25 kDa). Furthermore, TE was applied for in vivo tumor inhibition by the delivery of antioncogene p53, which showed good antitumor efficiency with low adverse effects. The present work provides a new concept for the facile preparation of hyperbranched hydroxyl-rich polycationic carriers with good transfection performances.


Assuntos
Poliaminas/química , DNA , Terapia Genética , Polietilenoimina , Transfecção
20.
Nanoscale ; 8(22): 11426-31, 2016 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-26880393

RESUMO

Recent scientific advances on organic-inorganic hybrid perovskites are mainly focused on the improvement of power conversion efficiency. So far, how compression tunes their electronic and structural properties remains less understood. By combining in situ photocurrent, impedance spectroscopy, and X-ray diffraction (XRD) measurements, we have studied the electrical transport and structural properties of compressed CH3NH3PbI3 (MAPbI3) nanorods. The visible light response of MAPbI3 remains robust below 3 GPa while it is suppressed when it becomes amorphous. Pressure-induced electrical transport properties of MAPbI3 including resistance, relaxation frequency, and relative permittivity have been investigated under pressure up to 8.5 GPa by in situ impedance spectroscopy measurements. These results indicate that the discontinuous changes of these physical parameters occur around the structural phase transition pressure. The XRD studies of MAPbI3 under high pressure up to 20.9 GPa show that a phase transformation below 0.7 GPa, could be attributed to the tilting and distortion of PbI6 octahedra. And pressure-induced amorphization is reversible at a low density amorphous state but irreversible at a relatively higher density state. Furthermore, the MAPbI3 nanorods crush into nanopieces around 0.9 GPa which helps us to explain why the mixed phase of tetragonal and orthorhombic was observed at 0.5 GPa. The pressure modulated changes of electrical transport and visible light response properties open up a new approach for exploring CH3NH3PbI3-based photo-electronic applications.

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