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1.
Nanoscale Adv ; 6(5): 1507-1523, 2024 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-38419879

RESUMO

In advanced electronics, supercapacitors (SCs) have received a lot of attention. Nevertheless, it has been shown that different electrode designs that are based on metal sulfides are prone to oxidation, instability, and poor conductance, which severely limits their practical application. We present a very stable, free-standing copper-cobalt sulfide doped with polyaniline as an electrode coated on nickel foam (CuCoS/PANI). The lightweight nickel foam encourages current collection as well as serving as a flexible support. The CuCoS-PANI electrode had a substantially greater 1659 C g-1 capacity at 1.0 A g-1. The asymmetric supercapacitor (ASC) can provide an impressive 54 W h kg-1 energy density while maintaining 1150 W kg-1 power. Additionally, when employed as an electrocatalyst in the oxygen evolution reaction, CuCoS/PANI exhibited a 200 mV overpotential and 55 mV dec-1 Tafel slope, demonstrating its effectiveness in facilitating the reaction.

2.
RSC Adv ; 13(50): 35468-35480, 2023 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-38058556

RESUMO

In recent years, energy storage and conversion tools have evolved significantly in response to rising energy demands. Owing to their large surface area, superior electric and chemical stabilities, and thermal conductivities, barium copper phosphate (BaCuPO4) materials are promising electrode materials for electrochemical energy storage systems. In this study, the synthesis of nanostructures (NSs) using hydrothermal and chemical precipitation methods and exploring the electrochemical characteristics of BaCuPO4 in asymmetric supercapacitors provides a comparative investigation. Systematic characterization shows that nanomaterials prepared by applying the hydrothermal method have a more crystalline and large surface area than chemical precipitation. In the three cell arrangements, the hydrothermally prepared BaCuPO4 NSs delivered a high specific capacity (764.4 C g-1) compared to the chemical precipitation route (660 C g-1). Additionally, the supercapattery associated with the two electrode assemblages delivers an optimum specific capacity of 77 C g-1. The energy and power density of BaCuPO4//AC NSs were 52.13 W h kg-1 and 950 W kg-1, respectively. A durability test was also performed with BaCuPO4//AC NSs for 5000 consecutive cycles. Further, the coulombic efficiency and capacity retention of BaCuPO4//AC after 5000 cycles were 81% and 92%, respectively. Bimetallic phosphate is comparatively suggested for future perspectives towards HER to overcome the performance of single metal phosphate materials. This is the first approach, we are aware of, for investigating the electrochemical behavior of BaCuPO4, and our results suggest that it may be useful as an electrode material in electrochemical systems requiring high energy and rate capabilities.

3.
Nanomaterials (Basel) ; 13(17)2023 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-37686950

RESUMO

This review article attempts to provide a comprehensive review of the recent progress in cerium oxide (CeO2)-based resistive random-access memories (RRAMs). CeO2 is considered the most promising candidate because of its multiple oxidation states (Ce3+ and Ce4+), remarkable resistive-switching (RS) uniformity in DC mode, gradual resistance transition, cycling endurance, long data-retention period, and utilization of the RS mechanism as a dielectric layer, thereby exhibiting potential for neuromorphic computing. In this context, a detailed study of the filamentary mechanisms and their types is required. Accordingly, extensive studies on unipolar, bipolar, and threshold memristive behaviors are reviewed in this work. Furthermore, electrode-based (both symmetric and asymmetric) engineering is focused for the memristor's structures such as single-layer, bilayer (as an oxygen barrier layer), and doped switching-layer-based memristors have been proved to be unique CeO2-based synaptic devices. Hence, neuromorphic applications comprising spike-based learning processes, potentiation and depression characteristics, potentiation motion and synaptic weight decay process, short-term plasticity, and long-term plasticity are intensively studied. More recently, because learning based on Pavlov's dog experiment has been adopted as an advanced synoptic study, it is one of the primary topics of this review. Finally, CeO2-based memristors are considered promising compared to previously reported memristors for advanced synaptic study in the future, particularly by utilizing high-dielectric-constant oxide memristors.

4.
Nanoscale Adv ; 5(18): 4735-4751, 2023 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-37705774

RESUMO

The implementation of battery-like electrode materials with complicated hollow structures, large surface areas, and excellent redox properties is an attractive strategy to improve the performance of hybrid supercapacitors. The efficiency of a supercapattery is determined by its energy density, rate capabilities, and electrode reliability. In this study, a magnesium copper phosphate nanocomposite (MgCuPO4) was synthesized using a hydrothermal technique, and silver phosphate (Ag3PO4) was decorated on its surface using a sonochemical technique. Morphological analyses demonstrated that Ag3PO4 was closely bound to the surface of amorphous MgCuPO4. The MgCuPO4 nanocomposite electrode showed a 1138 C g-1 capacity at 2 A g-1 with considerably improved capacity retention of 59% at 3.2 A g-1. The increased capacity retention was due to the fast movement of electrons and the presence of an excess of active sites for the diffusion of ions from the porous Ag3PO4 surface. The MgCuPO4-Ag3PO4//AC supercapattery showed 49.4 W h kg-1 energy density at 550 W kg-1 power density and outstanding capacity retention (92% after 5000 cycles). The experimental findings for the oxygen evolution reaction reveal that the initial increase in potential required for MgCuPO4-Ag3PO4 is 142 mV, indicating a clear Tafel slope of 49 mV dec-1.

5.
RSC Adv ; 13(38): 26528-26543, 2023 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-37674488

RESUMO

In this work, a novel bimetallic Fe-Mg/MOF was synthesized through a cost-effective and rapid hydrothermal process. The structure, morphology, and composition were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy. Further, the Brunauer-Emmett-Teller (BET) measurement showed a 324 m2 g-1 surface area for Fe-Mg/MOF. The Fe-Mg/MOF achieved 1825 C g-1 capacity at 1.2 A g-1 current density, which is higher than simple Fe-MOF (1144 C g-1) and Mg-MOF (1401 C g-1). To assess the long-term stability of the asymmetric device, the bimetallic MOF supercapattery underwent 1000 charge/discharge cycles and retained 85% of its initial capacity. The energy and power densities were calculated to be 57 W h kg-1 and 2393 W kg-1, respectively. Additionally, Fe-Mg/MOF showed superior electrocatalytic performance in hydrogen evolution reaction (HER) by demonstrating a smaller Tafel slope of 51.43 mV dec-1. Our research lays the foundation for enhancing the efficiency of energy storage technologies, paving the way for more sustainable and robust energy solutions.

6.
RSC Adv ; 13(31): 21236-21248, 2023 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-37456536

RESUMO

A supercapattery is a device that combines the properties of batteries and supercapacitors, such as power density and energy density. A binary composite (zinc cobalt sulfide) and rGO are synthesized using a simple hydrothermal method and modified Hummers' method. A notable specific capacity (Cs) of 1254 C g-1 is obtained in the ZnCoS@rGO case, which is higher than individual Cs of ZnS (975 C g-1) and CoS (400 C g-1). For the asymmetric (ASC) device (ZnCoS@rGO//PANI@AC), the PANI-doped activated carbon and ZnCoS@rGO are used as the cathode and anode respectively. A high Cm of 141 C g-1 is achieved at 1.4 A g-1. The ASC is exhibited an extraordinary energy density of 45 W h kg-1 with a power density 5000 W kg-1 at 1.4 A g-1. To check the stability of the device, the ASC device is measured for 2000 charging/discharging cycles. The device showed improved coulombic efficiency of 94%. These findings confirmed that the two-dimensional materials provide the opportunities to design battery and supercapacitor hybrid devices.

7.
Molecules ; 28(12)2023 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-37375293

RESUMO

Electrolytes are one of the most influential aspects determining the efficiency of electrochemical supercapacitors. Therefore, in this paper, we investigate the effect of introducing co-solvents of ester into ethylene carbonate (EC). The use of ester co-solvents in ethylene carbonate (EC) as an electrolyte for supercapacitors improves conductivity, electrochemical properties, and stability, allowing greater energy storage capacity and increased device durability. We synthesized extremely thin nanosheets of niobium silver sulfide using a hydrothermal process and mixed them with magnesium sulfate in different wt% ratios to produce Mg(NbAgS)x)(SO4)y. The synergistic effect of MgSO4 and NbS2 increased the storage capacity and energy density of the supercapattery. Multivalent ion storage in Mg(NbAgS)x(SO4)y enables the storage of a number of ions. The Mg(NbAgS)x)(SO4)y was directly deposited on a nickel foam substrate using a simple and innovative electrodeposition approach. The synthesized silver Mg(NbAgS)x)(SO4)y provided a maximum specific capacity of 2087 C/g at 2.0 A/g current density because of its substantial electrochemically active surface area and linked nanosheet channels which aid in ion transportation. The supercapattery was designed with Mg(NbAgS)x)(SO4)y and activated carbon (AC) achieved a high energy density of 79 Wh/kg in addition to its high power density of 420 W/kg. The supercapattery (Mg(NbAgS)x)(SO4)y//AC) was subjected to 15,000 consecutive cycles. The Coulombic efficiency of the device was 81% after 15,000 consecutive cycles while retaining a 78% capacity retention. This study reveals that the use of this novel electrode material (Mg(NbAgS)x(SO4)y) in ester-based electrolytes has great potential in supercapattery applications.

8.
RSC Adv ; 13(19): 12634-12645, 2023 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-37101525

RESUMO

A supercapattery is a hybrid device that is a combination of a battery and a capacitor. Niobium sulfide (NbS), silver sulfide (Ag2S), and niobium silver sulfide (NbAg2S) were synthesized by a simple hydrothermal method. NbAg2S (50/50 wt% ratio) had a specific capacity of 654 C g-1, which was higher than the combined specific capacities of NbS (440 C g-1) and Ag2S (232 C g-1), as determined by the electrochemical investigation of a three-cell assembly. Activated carbon and NbAg2S were combined to develop the asymmetric device (NbAg2S//AC). A maximum specific capacity of 142 C g-1 was delivered by the supercapattery (NbAg2S//AC). The supercapattery (NbAg2S/AC) provided 43.06 W h kg-1 energy density while retaining 750 W kg-1 power density. The stability of the NbAg2S//AC device was evaluated by subjecting it to 5000 cycles. After 5000 cycles, the (NbAg2S/AC) device still had 93% of its initial capacity. This research indicates that merging NbS and Ag2S (50/50 wt% ratio) may be the best choice for future energy storage technologies.

9.
ACS Appl Mater Interfaces ; 14(19): 22082-22094, 2022 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-35522907

RESUMO

Reverse microemulsion method was implemented to synthesize a CuO/γ-Al2O3 catalyst (18 wt % Cu) with a specific surface area (SSA) of 328 m2/g (after calcination at 400 °C). Catalytic performance was evaluated in the range of temperatures and space velocities (300-600 °C and 10,000-200,000 mL/(g h)). The catalyst was 100% selective to CO generation while attaining a nearly equilibrium CO2 conversion at 500 °C (ca. 50% at 10,000 mL/(g h) and H2/CO2 = 4). Despite the initial reduction of surface area under the reaction conditions, the reduced Cu/γ-Al2O3 catalyst demonstrated a stable performance for 80 h on stream, attaining a nearly equilibrium CO2 conversion at 600 °C (ca. 60% at 60,000 mL/(g h) and H2/CO2 = 4). The selectivity to CO generation remained complete during the stability test, and no significant carbon deposition was detected.

10.
RSC Adv ; 12(3): 1278-1286, 2022 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-35425203

RESUMO

Transition metal dichalcogenides (TMDs) have received significant attention owing to their thickness-dependent folded current-voltage (I ds-V ds) characteristics, which offer various threshold voltage values. Owing to these astonishing characteristics, TMDs based negative differential resistance (NDR) devices are preferred for the realization of multi-valued logic applications. In this study, an innovative and ground-breaking germanium selenide/hafnium disulfide (p-GeSe/n-HfS2) TMDs van der Waals heterostructure (vdWH) NDR device is designed. An extraordinary peak-to-valley current ratio (≈5.8) was estimated at room temperature and was used to explain the tunneling and diffusion currents by using the tunneling mechanism. In addition, the p-GeSe/n-HfS2 vdWH diode was used as a ternary inverter. The TMD vdWH diode, which can exhibit different band alignments, is a step forward on the road to developing high-performance multifunctional devices in electronics.

11.
Dalton Trans ; 51(3): 797-816, 2022 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-34874382

RESUMO

With perovskite materials, rapid progress in power conversion efficiency (PCE) to reach 25% has gained a significant amount of attention from the solar cell industry. Since the development of solid-state perovskite solar cells, rapid research development and investigation on structure design, device fabrication and fundamental studies have contributed to solid-state perovskite solar cells to be a strong candidate for next-generation solar energy. The promising efficiency with low-cost materials is the key point over the other material-based solar cells. The power conversion efficiency (PCE) of two-dimensional (2D) perovskite materials is yet to be enhanced in order to contest with the 3D perovskite-based solar cells. Their enormous variety compromises better prospects and possibilities for research. Two-dimensional (2D) perovskites play a multi-functional role within a solar cell, such as a capping layer, passivating layer, prime cell absorber, and in a hybrid 3D/2D perovskite-based solar cell absorber. This review summarizes the evolution of solar cells that are based on 2D perovskites and their prominent character in solar cells, along with the significant trends. The fundamental configuration and the optoelectronic characteristics, including the band orientation and the transportation of the charges, are discussed in detail. The 2D perovskites are analyzed to study the confined charges within the inorganic structure due to the dielectric and quantum confinement influence. Furthermore, the importance of cesium cation (Cs+) doped with 2D substance (BA)2(MA3) PbI3 approach has been discussed to attain high power conversion efficiency (PCE). These attributes offer an efficient step towards air-stable and small-sized perovskites as a new group of renewable energy sources.

12.
J Colloid Interface Sci ; 603: 511-517, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34214725

RESUMO

The Fermi level alignment between electrodes and two-dimensional (2D) materials is significant in characterizing sensors based on their reversibility, response time, sensitivity, and long-term stability. Here, we have demonstrated that the modulation of the Schottky barrier height between the interface of metal (Pd/Au) and multilayered ReSe2 nanoflakes caused the change in the transfer curve (Ids-Vbg) of FETs based devices and rectifying characteristics (Ids-Vds) of the Schottky diodes at various hydrogen concentrations at T = 22 °C, fluctuating from 50 to 350 ppm with a response (R%) from 669 to 1198%, respectively. Sensors based on a mono- or bilayer system did not exhibit sensitivity to hydrogen gas owing to metal electrodes diffused into materials. The value of the ideality factor of the Schottky diode-based sensor changed from 4 to 1.6 as the hydrogen concentration was changed from 50 to 900 ppm, while the relative response increased from 0 to 3.5 as the hydrogen concentration was increased from 0 to 900 ppm. This research can offer a real solution for developing cost-effective, faster, and room temperature sensors based on 2D materials.

13.
Nanotechnology ; 32(28)2021 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-33535197

RESUMO

Two-dimensional (2D) materials can be implemented in several functional devices for future optoelectronics and electronics applications. Remarkably, recent research on p-n diodes by stacking 2D materials in heterostructures or homostructures (out of plane) has been carried out extensively with novel designs that are impossible with conventional bulk semiconductor materials. However, the insight of a lateral p-n diode through a single nanoflake based on 2D material needs attention to facilitate the miniaturization of device architectures with efficient performance. Here, we have established a physical carrier-type inversion technique to invert the polarity of MoTe2-based field-effect transistors (FETs) with deep ultraviolet (DUV) doping in (oxygen) O2and (nitrogen) N2gas environments. A p-type MoTe2nanoflake transformed its polarity to n-type when irradiated under DUV illumination in an N2gaseous atmosphere, and it returned to its original state once irradiated in an O2gaseous environment. Further, Kelvin probe force microscopy (KPFM) measurements were employed to support our findings, where the value of the work function changed from ∼4.8 and ∼4.5 eV when p-type MoTe2inverted to the n-type, respectively. Also, using this approach, an in-plane homogeneous p-n junction was formed and achieved a diode rectifying ratio (If/Ir) up to ∼3.8 × 104. This effective approach for carrier-type inversion may play an important role in the advancement of functional devices.

14.
Nanoscale ; 12(35): 18171-18179, 2020 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-32856027

RESUMO

A two-dimensional (2D) layered material-based p-n diode is an essential element in the modern semiconductor industry for facilitating the miniaturization and structural flexibility of devices with high efficiency for future optoelectronic and electronic applications. Planar devices constructed previously required a complicated device structure using a photoresist, as they needed to consider non-abrupt interfaces. Here, we demonstrated a WSe2 based lateral homojunction diode obtained by applying a photo-induced effect in BN/WSe2 heterostructures upon illumination via visible and deep UV light, which represents a stable and flexible charge doping technique. We have discovered that with this technique, a field-effect transistor (FET) based on p-type WSe2 is inverted to n-WSe2 so that a high electron mobility is maintained in the h-BN/n-WSe2 heterostructures. To confirm this hypothesis, we deduced the work function values of p-WSe2 and n-WSe2 FETs by conducting Kelvin probe force microscopy (KPFM) measurements, which revealed the decline of the Fermi level from 5.07 (p-WSe2) to 4.21 eV (n-WSe2). The contact potential difference (CPD) between doped and undoped junctions was found to be 165 meV. We employed ohmic metal contacts for the planar homojunction diode by utilizing an ionic liquid gate to achieve a diode rectification ratio up to ∼105 with n = 1. An exceptional photovoltaic performance is also observed. The presence of a built-in potential in our devices leads to an open-circuit voltage (Voc) and short-circuit current (Isc) without an external electric field. This effective doping technique is promising to advance the concept of preparing future functional devices.

15.
Dalton Trans ; 49(29): 10017-10027, 2020 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-32643710

RESUMO

Vertical integration of two dimensional (2D) layered materials is indispensable in making van der Waals (vdWs) heterostructures for promising electronic and optoelectronic devices. Herein, we report excellent electrical and photoelectrical measurements where the current ON & OFF ratio of FET is increased by decreasing the temperature in the graphene/ReSe2/graphene heterojunction. We investigated the photoresponsivity in broad spectral range (UV-Vis-NIR) and achieved high photoresponsivity of 1.5 × 107 A W-1 and external quantum efficiency of ∼64% at λ = 220 nm. Further, the photovoltaic effect was examined, which significantly modulated the short circuit current (Isc) from 4.2 × 10-8 A to 2.6 × 10-7 A and open-circuit voltage (Voc) from 0.21 V to 0.44 V at different wavelengths (1064, 840, 514 and 220 nm), attributed to the photo-generation and recombination rate of the carriers. Moreover, photoresponsivity was observed near 1.2 × 106, 8.6 × 106 and 1.5 × 107 A W-1 by applying different gate biases (0, 20 and 40 V), respectively. Further, we have explored the photocurrent and photoresponsivity at different intensities of incident light (200, 260, 400, 620 and 850 µW cm-2). In addition, we calculated the rise and decay response times of photodetectors at different wavelengths and power densities, which depend upon the trap sites in the energy band of ReSe2. These devices opened up new ways to improve the performance of photodetectors from the UV to the NIR region.

16.
Nanoscale ; 12(29): 15687-15696, 2020 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-32672307

RESUMO

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) are layered semiconductor materials that have recently emerged as promising candidates for advanced nano- and photoelectronic applications. Previously, various doping methods, such as surface functionalization, chemical doping, substitutional doping, surface charge transfer, and electrostatic doping, have been introduced, but they are not stable or efficient. In this study, we have developed carrier polarity modulation of molybdenum ditelluride (MoTe2) for the development of phototransistors and switching photodiodes. Initially, we treated p-MoTe2 in a N2 environment under DUV irradiation and found that the p-type MoTe2 changed to n-type MoTe2. However, the treated devices exhibited environmental stability over a long period of 60 days. Kelvin probe force microscopy (KPFM) measurements demonstrated that the values of the work function for p-MoTe2 and n-MoTe2 were ∼4.90 and ∼4.49 eV, respectively, which confirmed the carrier tunability. Also, first-principles studies were performed to confirm the n-type carrier polarity variation. Interestingly, the n-type MoTe2 reversed its polarity to p-type after the irradiation of the devices under DUV in an O2 environment. Additionally, a lateral homojunction-based p-n diode of MoTe2 with a rectification ratio of ∼2.5 × 104 was formed with the value of contact potential difference of ∼400 mV and an estimated fast rise time of 29 ms and decay time of 38 ms. Furthermore, a well self-biased photovoltaic behavior upon illumination of light was achieved and various photovoltaic parameters were examined. Also, VOC switching behavior was established at the p-n diode state by switching on and off the incident light. We believe that this efficient and facile carrier polarity modulation technique may pave the way for the development of phototransistors and switching photodiodes in advanced nanotechnology.

17.
J Mol Model ; 26(6): 158, 2020 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-32468317

RESUMO

Density functional theoretical (DFT) calculations were carried out to explore the electronic and optical properties of double ordered Ba2NaReO6, Ba2LiReO6, and Sr2LiReO6 perovskites by employing the state-of-the-art exchange-correlation potential, i.e., Tran-Blaha modified Becke-Johnson for the electronic system. The calculated electronic band structures show an indirect band gap along with a semiconductor nature. Total and partial densities of state peaks were analyzed in light of effective contributions of various electronic states. The significant optical parameters, including the components of dielectric constant, the energy loss function, the absorption coefficient, the reflectivity spectra, the refractive index, and the extinction coefficient, were computed and discussed in details for radiation up to 14 eV. Finally, we studied the inter-band contributions from the optical characteristics. Our present study might be considered as first theoretical quantitative calculations of the optical and electronic behavior in the cubic phase of double perovskite materials based on rhenium.

18.
J Mol Graph Model ; 92: 296-302, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31430680

RESUMO

We performed ab initio calculations to study the structural and optoelectronic properties of simple and slab phase TaNO using density functional theory (DFT), in which the full potential augmented plane wave (FP-LAPW) method was implemented using the computational code Wien 2k. The modified Becke-Johnson potential (mBJ-GGA) was used for these calculations. The calculated band structure and electronic properties revealed an indirect bandgap for simple TaNO (3.2 eV) and a direct bandgap for slab TaNO (1.5 eV). The interband electronic transitions were investigated from the band structure, and transition peaks were observed from the imaginary part of the dielectric function. These transitions are due to Ta-p, N-p and O-p orbitals for simple TaNO and Ta-p, N-s as well as O-p orbitals for slab TaNO. The plasmon energy was related to the main peak of the energy loss function, which was approximately 10 eV. The static value of the dielectric constant and the refraction were close to the experimental values. In general, slab TaNO shows different properties and is more suitable for optoelectronic applications due to direct bandgap.


Assuntos
Elétrons , Estrutura Molecular , Óxido Nítrico/química , Tantálio/química , Algoritmos , Teoria da Densidade Funcional , Modelos Moleculares , Análise Espectral
19.
RSC Adv ; 9(18): 10017-10023, 2019 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-35520896

RESUMO

Schottky-barrier diodes have great importance in power management and mobile communication because of their informal device technology, fast response and small capacitance. In this research, a p-type molybdenum ditelluride (p-MoTe2) based Schottky barrier diode was fabricated using asymmetric metal contacts. The MoTe2 nano-flakes were mechanically exfoliated using adhesive tape and with the help of dry transfer techniques, the flakes were transferred onto silicon/silicon dioxide (Si/SiO2) substrates to form the device. The Schottky-barrier was formed as a result of using ultra-low palladium/gold (Pd/Au) and high resistive chromium/gold (Cr/Au) metal electrodes. The Schottky diode exhibited a clear rectifying behavior with an on/off ratio of ∼103 and an ideality factor of ∼1.4 at zero gate voltage. In order to check the photovoltaic response, a green laser light was illuminated, which resulted in a responsivity of ∼3.8 × 103 A W-1. These values are higher than the previously reported results that were obtained using conventional semiconducting materials. Furthermore, the barrier heights for Pd and Cr with a MoTe2 junction were calculated to be 90 meV and 300 meV, respectively. In addition, the device was used for rectification purposes revealing a stable rectifying behavior.

20.
Cureus ; 10(6): e2858, 2018 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-30148011

RESUMO

BACKGROUND: Rheumatic diseases are referred to as conditions affecting joints, muscles, ligaments, tendons, and bones. According to a report by World Health Organization, rheumatic and musculoskeletal diseases were labeled as the second most reported cause of disability around the globe. The purpose of this study was to estimate the prevalence of rheumatic diseases in a tertiary care hospital of Karachi; additionally, associations with age groups, gender and comorbidities were obtained as well. METHODS: A cross-sectional study was conducted at the Orthopedic Out Patient Department (OPD) of Dr. Ruth KM Pfau Civil Hospital, Karachi over a span of three months in 2018 (February till May). All 346 patients were follow-up diagnosed cases in the age range of 11-90 years, divided into groups of adolescents, young adults, adults, and older adults. The subjects were questioned about their symptoms, duration of illness, presence of comorbidities, genetic background and the therapy they are undergoing along with compliance. Simple statistical analysis of frequency was done, whereas chi-square test was applied to study associations with gender, age groups, and comorbidities. RESULTS: During the study period, a total of 2000 patients visited the orthopedic OPD, 346 of which were diagnosed cases of rheumatic diseases, yielding a prevalence of 17.3%. The mean age of rheumatic patients who partook in the study was 46.15 ± 15.49 (Range: 12 - 84). Osteoarthritis was recorded as the most prevalent condition, followed by non-specific low back pain and rheumatoid arthritis. Osteoarthritis was statistically significant in young adults, adults, and older adults, while non-specific low back pain had significant associations with gender, young adults, and adults. Diabetes was significantly associated with osteoarthritis, non-specific low back pain, shoulder pain syndrome and psoriatic arthritis, while hypertension significantly co-existed with systemic lupus erthematosus. CONCLUSION: Rheumatic diseases constitute a major disease burden in almost all of the age groups, especially in young patients (18-40 years) within our setup.

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