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1.
Nanomaterials (Basel) ; 14(5)2024 Feb 20.
Article in English | MEDLINE | ID: mdl-38470722

ABSTRACT

Halide perovskite materials have attracted worldwide attention in the photovoltaic area due to the rapid improvement in efficiency, from less than 4% in 2009 to 26.1% in 2023 with only a nanometer lever photo-active layer. Meanwhile, this nova star found applications in many other areas, such as light emitting, sensor, etc. This review started with the fundamentals of physics and chemistry behind the excellent performance of halide perovskite materials for photovoltaic/light emitting and the methods for preparing them. Then, it described the basic principles for solar cells and light emitting devices. It summarized the strategies including nanotechnology to improve the performance and the application of halide perovskite materials in these two areas: from structure-property relation to how each component in the devices affects the overall performance. Moreover, this review listed the challenges for the future applications of halide perovskite materials.

2.
Micromachines (Basel) ; 15(2)2024 Feb 09.
Article in English | MEDLINE | ID: mdl-38398986

ABSTRACT

Very recently, the synthesis of 2D MoS2 and WS2 through pulsed laser-directed thermolysis can achieve wafer-scale and large-area structures, in ambient conditions. In this paper, we report the synthesis of MoS2 and MoS2 oxides from (NH4)2MoS4 film using a visible continuous-wave (CW) laser at 532 nm, instead of the infrared pulsed laser for the laser-directed thermolysis. The (NH4)2MoS4 film is prepared by dissolving its crystal powder in DI water, sonicating the solution, and dip-coating onto a glass slide. We observed a laser intensity threshold for the laser synthesis of MoS2, however, it occurred in a narrow laser intensity range. Above that range, a mixture of MoS2 and MoO2 is formed, which can be used for a memristor device, as demonstrated by other research groups. We did not observe a mixture of MoS2 and MoO3 in the laser thermolysis of (NH4)2MoS4. The laser synthesis of MoS2 in a line pattern is also achieved through laser scanning. Due to of the ease of CW beam steering and the fine control of laser intensities, this study can lead toward the CW laser-directed thermolysis of (NH4)2MoS4 film for the fast, non-vacuum, patternable, and wafer-scale synthesis of 2D MoS2.

3.
ACS Appl Mater Interfaces ; 16(3): 3640-3653, 2024 Jan 24.
Article in English | MEDLINE | ID: mdl-38268147

ABSTRACT

Two-dimensional (2D) layered materials exhibit great potential for high-performance electronics, where knowledge of their thermal and phononic properties is critical toward understanding heat dissipation mechanisms, considered to be a major bottleneck for current generation nanoelectronic, optoelectronic, and quantum-scale devices. In this work, noncontact Raman spectroscopy was used to analyze thermal properties of suspended 2D WSe2 membranes to access the intrinsic properties. Here, the influence of electron-phonon interactions within the parent crystalline WSe2 membranes was deciphered through a comparative analysis of extrinsic substrate-supported WSe2, where heat dissipation mechanisms are intimately tied to the underlying substrate. Moreover, the excitonic states in WSe2 were analyzed by using temperature-dependent photoluminescence spectroscopy, where an enhancement in intensity of the localized excitons in suspended WSe2 was evident. Finally, phononic and electronic properties in suspended WSe2 were examined through nanoscale local strain engineering, where a uniaxial force was induced on the membrane using a Au-coated cantilever within an atomic force microscope. Through the fundamental analysis provided here with temperature and strain-dependent phononic and optoelectronic properties in suspended WSe2 nanosheets, the findings will inform the design of next-generation energy-efficient, high-performance devices based on WSe2 and other 2D materials, including for quantum applications.

4.
Eur Rev Med Pharmacol Sci ; 27(7): 3150-3158, 2023 04.
Article in English | MEDLINE | ID: mdl-37070918

ABSTRACT

OBJECTIVE: The study aimed to evaluate the Withaferin-A against the drug target α-amylase, revealing its plausible mode of action and molecular-level interactions essential for this specific target inhibitory potential computational approach. MATERIALS AND METHODS: In this scenario, we used computational methods, including docking, molecular dynamics simulation, and model-building simulations, to elucidate the atomic-level details responsible for the inhibitory potential of Withaferin-A derived from W. somnifera. The studio visualizer software was used for the visualization of ligands, structures of the receptor, bond length, and rendering of the image. Absorption, distribution, metabolism, excretion, and toxicity (ADMET) characteristics of phytochemicals were investigated. Crystal structure of protein receptors and ligands were generated. Semi-flexible docking was done using Autodock software. Docking was performed using the Lamarckian Genetic Algorithm (LGA). Molecular descriptors were evaluated, and the pharmacological properties of the phytochemicals were explored. Molecular dynamic simulations were analyzed at the atomic level. All the simulations were conducted under the same temperature, pressure, and volume circumstances over the simulated time scale. RESULTS: Withaferin-A has shown a strong binding affinity towards α-amylase as demonstrated with -9.79 Kcal/mol with 66.61 estimated nanomolecular IC50 value for plausible anti-obesity activity. Molecular-level relationships and knowledge obtained from this study indicate solid interactions with TYR59, ASP197, and HIS299 residues which are of high importance for future works related to computational screening of target-specific α-amylase inhibitors. The results from the analysis have revealed potential molecular-level interactions useful for further designing/discovering novel α-amylase inhibitors. CONCLUSIONS: The framework of the studied phytochemicals enables the rapid development of subsequent modifications that could result in more lead-like compounds with better inhibitory efficacy and selectivity for α-amylase.


Subject(s)
Molecular Dynamics Simulation , alpha-Amylases , Molecular Docking Simulation , alpha-Amylases/metabolism
5.
Sci Rep ; 12(1): 18574, 2022 Nov 03.
Article in English | MEDLINE | ID: mdl-36329076

ABSTRACT

Perovskite solar cells (PSCs), particularly based on the methyl ammonium lead iodide (MAPbI3) formulation, have been of intense interest for the past decade within the photovoltaics (PV) community, given the stupendous rise in power conversion efficiencies (PCEs) attributed to these perovskite formulations, where PCEs have exceeded 25%. However, their long-term stability under operational conditions and environmental storage are still prime challenges to be overcome towards their commercialization. Although studies on the intrinsic perovskite absorber stability have been conducted previously, there are no clear mechanisms for the interaction of electrode-induced absorber degradation pathways, which is the focus of this study. In this report, we have conducted a comprehensive analysis on the impact of the electrode collector layer, specifically Ag and Au, on the degradation mechanism associated with the MAPbI3 and a triple cation absorber, Cs0.05FA0.79MA0.16PbI2.45Br0.55. Notably, Au-based PSCs for both absorbers in an n-i-p architecture showed superior PCE over Ag-based PSCs, where the optimized PCE of MAPbI3 and triple cation-based PSCs was 15.39% and 18.21%, respectively. On the other hand, optimized PCE of MAPbI3 and triple cation-based PSCs with Ag electrodes was 3.02% and 16.44%, respectively. In addition, the Ag-based PSCs showed a rapid decrease in PCE over Au-based PSCs through operational stability measurements. We hypothesize the mechanism of degradation, arising from the Ag interaction with the absorber through the formation of AgI in the PSCs, leads to corrosion of the perovskite absorber, as opposed to the benign AuI when Au electrodes are used in the solar cell stack. Additionally, novel use of photoluminescence spectroscopy (PL) here, allowed us to access key features of the perovskite absorber in situ, while it was in contact with the various layers within the n-i-p solar cell stack. A quenching in the PL peak in the case of Ag-contacted MAPbI3 provided direct evidence of the Ag corrupting the optical properties of the absorber through the formation of AgI which our X-ray diffraction (XRD) results confirmed. This was supported by the fact that an emission peak was still present in the triple cation Ag-device. For the Au-contacted MAPbI3 the presence of a well-defined PL peak, though attenuated from the triple cation Au-device, suggested the AuI does not quell the emission spectrum for either the triple cation or the MAPbI3 absorber. The findings should aid in the understanding and design of new electrode materials with PSCs, which will help accelerate their introduction into the commercial sector in the future.

6.
Eur Rev Med Pharmacol Sci ; 26(19): 7245-7255, 2022 10.
Article in English | MEDLINE | ID: mdl-36263535

ABSTRACT

OBJECTIVE: The aim of the study is to design N5-(1H-pyrazol-3-yl)-3H-benzo[d]imidazole-2,5-diamine derivatives and evaluate its anti-obesity activity. MATERIALS AND METHODS: A few pyrazole-fused benzimidazole derivatives were designed as potential Pancreatic Lipase (PL) inhibitors. The designed N5-(1H-pyrazol-3-yl)-3H-benzo[d]imidazole-2,5-diamine derivatives have been screened using the Lipinski rule of five, ADMET analysis, acute toxicity prediction, and molecular docking. Later on, the derivatives which possess the most drug-likeness properties and displayed the most potent inhibition of the enzyme in molecular docking were synthesized. Then, in vitro enzyme assay was performed. RESULTS: Orlistat used as the standard exhibited 91±1.68% inhibition of the enzyme, displayed binding affinity (BA) of only -4.5 kcal/mol with Pancreatic Lipase (PL), and made only one salt bridge attractive charge and carbon-hydrogen bond with ASP79 and TRP252, respectively. Compound 9 displayed the most potent activity (93±1.12% inhibition of P.L. and -9.5 kcal/mol BA). It has formed five conventional H- bonds with GLU253, ILE78, ASP79, PHE258, and one Pi-donor H- bond with ILE78. From the present investigation, we hereby reported (E)-N2-((naphthalene-1-yl)methylene)-N5-(1H-pyrazol-3-yl)-3H-benzo[d]imidazole-2,5-diamine as most potent PL inhibitor for the treatment of obesity, which can be further optimized by undergoing more studies using in vivo and in vitro models. CONCLUSIONS: (E)-N2-((naphthalene-1-yl)methylene)-N5-(1H-pyrazol-3-yl)-3H-benzo[d]imidazole-2,5-diamine as most potent PL inhibitor for the treatment of obesity which can be further optimized better using more in vivo and in vitro models. PL plays a critical role in digesting dietary fat. Therefore, PL inhibitors are verified as a potential therapy for treating obesity.


Subject(s)
Diamines , Lipase , Molecular Docking Simulation , Orlistat/pharmacology , Pyrazoles/pharmacology , Imidazoles , Benzimidazoles/pharmacology , Naphthalenes , Dietary Fats , Carbon , Structure-Activity Relationship
7.
J Investig Med High Impact Case Rep ; 9: 23247096211001659, 2021.
Article in English | MEDLINE | ID: mdl-33733898

ABSTRACT

We report the case of a 71-year-old female who was incidentally found to have nonoliguric acute kidney injury on a routine workup for new-onset visual hallucination. Further history revealed inadvertent usage of nitrofurantoin for 3 months for an anticipated urological procedure. Renal biopsy demonstrated acute granulomatous interstitial nephritis. The renal function significantly improved following discontinuation of nitrofurantoin and corticosteroid administration. We highlight a rare association of nitrofurantoin with acute granulomatous interstitial nephritis through this case report.


Subject(s)
Acute Kidney Injury , Nephritis, Interstitial , Aged , Female , Granuloma/chemically induced , Humans , Nephritis, Interstitial/chemically induced , Nitrofurantoin/adverse effects
8.
ACS Appl Mater Interfaces ; 13(4): 5379-5389, 2021 Feb 03.
Article in English | MEDLINE | ID: mdl-33471523

ABSTRACT

The hybrid structure of zero-dimensional (0D) graphene quantum dots (GQDs) and semiconducting two-dimensional (2D) MoS2 has been investigated, which exhibit outstanding properties for optoelectronic devices surpassing the limitations of MoS2 photodetectors where the GQDs extend the optical absorption into the near-UV regime. The GQDs and MoS2 films are characterized by Raman and photoluminescence (PL) spectroscopies, along with atomic force microscopy. After outlining the fabrication of our 0D-2D heterostructure photodetectors comprising GQDs with bulk MoS2 sheets, their photoresponse to the incoming radiation was measured. The hybrid GQD/MoS2 heterostructure photodetector exhibits a high photoresponsivity R of more than 1200 A W-1 at 0.64 mW/cm2 at room temperature T. The T-dependent optoelectronic measurements revealed a peak R of ∼544 A W-1 at 245 K, examined from 5.4 K up to 305 K with an incoming white light power density of 3.2 mW/cm2. A tunable laser revealed the photocurrent to be maximal at lower wavelengths in the near ultraviolet (UV) over the 400-1100 nm spectral range, where the R of the hybrid GQDs/MoS2 was ∼775 A W-1, while a value of 2.33 × 1012 Jones was computed for the detectivity D* at 400 nm. The external quantum efficiency was measured to be ∼99.8% at 650 nm, which increased to 241% when the wavelength of the incoming laser was reduced to 400 nm. Time-resolved measurements of the photocurrent for the hybrid devices resulted in a rise time τrise and a fall time τfall of ∼7 and ∼25 ms, respectively, at room T, which are 10× lower compared to previous reports. From our promising results, we conclude that the GQDs exhibit a sizable band gap upon optical excitation, where photocarriers are injected into the MoS2 films, endowing the hybrids with long carrier lifetimes to enable efficient light absorption beyond the visible and into the near-UV regime. The GQD-MoS2 structure is thus an enabling platform for high-performance photodetectors, optoelectronic circuits, and quantum devices.

9.
J Investig Med High Impact Case Rep ; 8: 2324709620948407, 2020.
Article in English | MEDLINE | ID: mdl-32762368

ABSTRACT

Recent reports have suggested an increased risk of QT prolongation and subsequent life-threatening ventricular arrhythmias, particularly torsade de pointes, in patients with coronavirus disease-2019 (COVID-19) treated with hydroxychloroquine and azithromycin. In this article, we report the case of a 75-year-old female with a baseline prolonged QT interval in whom the COVID-19 illness resulted in further remarkable QT prolongation (>700 ms), precipitating recurrent self-terminating episodes of torsade de pointes that necessitated temporary cardiac pacing. Despite the correction of hypoxemia and the absence of reversible factors, such as adverse medication effects, electrolyte derangements, and usage of hydroxychloroquine/azithromycin, the QT interval remained persistently prolonged compared with the baseline with subsequent degeneration into ventricular tachycardia and death. Thus, we highlight that COVID-19 illness itself can potentially lead to further prolongation of QT interval and unmask fatal ventricular arrhythmias in patients who have a prolonged QT and low repolarization reserve at baseline.


Subject(s)
Betacoronavirus , Coronavirus Infections/physiopathology , Long QT Syndrome/physiopathology , Pneumonia, Viral/physiopathology , Tachycardia, Ventricular/physiopathology , Aged , Azithromycin/therapeutic use , COVID-19 , Coronavirus Infections/complications , Coronavirus Infections/diet therapy , Coronavirus Infections/drug therapy , Coronavirus Infections/metabolism , Fatal Outcome , Female , Humans , Hydroxychloroquine/therapeutic use , Long QT Syndrome/drug therapy , Pandemics , Pneumonia, Viral/complications , Pneumonia, Viral/diet therapy , SARS-CoV-2 , Tachycardia, Ventricular/etiology , COVID-19 Drug Treatment
10.
J Investig Med High Impact Case Rep ; 8: 2324709620947577, 2020.
Article in English | MEDLINE | ID: mdl-32762374

ABSTRACT

A 66-year-old male patient with coronavirus disease-19 (COVID-19) developed cardiogenic shock with echocardiographic evidence of decreased left ventricular ejection fraction and global hypokinesia concomitant with a robust systemic inflammatory response. Following the administration of convalescent plasma therapy and inotropic support, left ventricular function recovered fully in accordance with the decrease in the concentration of the inflammatory markers. Thus, we demonstrate the presence of transient reversible cardiomyopathy in a patient with severe COVID-19 and illustrate the association of acute cardiac dysfunction with profound systemic inflammation among COVID-19 patients.


Subject(s)
Betacoronavirus , Cardiomyopathies/therapy , Coronavirus Infections/therapy , Pneumonia, Viral/therapy , Aged , COVID-19 , Cardiomyopathies/complications , Cardiomyopathies/immunology , Coronavirus Infections/complications , Coronavirus Infections/immunology , Coronavirus Infections/metabolism , Humans , Immunization, Passive/methods , Male , Pandemics , Pneumonia, Viral/complications , Pneumonia, Viral/immunology , SARS-CoV-2 , Stroke Volume , Treatment Outcome , Ventricular Function, Left , COVID-19 Serotherapy
11.
Beilstein J Nanotechnol ; 11: 782-797, 2020.
Article in English | MEDLINE | ID: mdl-32509492

ABSTRACT

Phonon dynamics is explored in mechanically exfoliated two-dimensional WSe2 using temperature-dependent and laser-power-dependent Raman and photoluminescence (PL) spectroscopy. From this analysis, phonon lifetime in the Raman active modes and phonon concentration, as correlated to the energy parameter E 0, were calculated as a function of the laser power, P, and substrate temperature, T. For monolayer WSe2, from the power dependence it was determined that the phonon lifetime for the in-plane vibrational mode was twice that of the out-of-plane vibrational mode for P in the range from 0.308 mW up to 3.35 mW. On the other hand, the corresponding relationship for the temperature analysis showed that the phonon lifetime for the in-plane vibrational mode lies within 1.42× to 1.90× that of the out-of-plane vibrational mode over T = 79 K up to 523 K. To provide energy from external stimuli, as T and P were increased, peak broadening in the PL spectra of the A-exciton was observed. From this, a phonon concentration was tabulated using the Urbach formulism, which increased with increasing T and P; consequently, the phonon lifetime was found to decrease. Although phonon lifetime decreased with increasing temperature for all thicknesses, the decay rate in the phonon lifetime in the monolayer (1L) material was found to be 2× lower compared to the bulk. We invoke a harmonic oscillator model to explain the damping mechanism in WSe2. From this it was determined that the damping coefficient increases with the number of layers. The work reported here sheds fundamental insights into the evolution of phonon dynamics in WSe2 and should help pave the way for designing high-performance electronic, optoelectronic and thermoelectric devices in the future.

12.
ACS Appl Mater Interfaces ; 12(9): 10809-10819, 2020 Mar 04.
Article in English | MEDLINE | ID: mdl-32068396

ABSTRACT

The synthesis of solution-processed two-dimensional (2D) layered organohalide (CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (n = 2, 3, and 4) perovskites is presented, where inkjet printing was used to fabricate heterostructure flexible photodetector (PD) devices on polyimide (PI) substrates. Inks for the n = 4 formulation were developed to inkjet-print PD devices that were photoresponsive to broadband incoming radiation in the visible regime, where the peak photoresponsivity R was calculated to be ∼0.17 A/W, which is higher compared to prior reports, while the detectivity D was measured to be ∼3.7 × 1012 Jones at a low light intensity F ≈ 0.6 mW/cm2. The ON/OFF ratio was also high (∼2.3 × 103), while the response time τ on the rising and falling edges was measured to be τrise ≈ 24 ms and τfall ≈ 65 ms, respectively. Our strain-dependent measurements, conducted here for the first time for inkjet-printed perovskite PDs, revealed that the Ip decreased by only ∼27% with bending (radius of curvature of ∼0.262 cm-1). This work demonstrates the tremendous potential of the inkjet-printed, composition-tunable, organohalide 2D perovskite heterostructures for high-performance PDs, where the techniques are readily translatable toward flexible solar cell platforms as well.

13.
ACS Appl Mater Interfaces ; 11(27): 24349-24359, 2019 Jul 10.
Article in English | MEDLINE | ID: mdl-31141336

ABSTRACT

Fullerene (C60) and multilayer graphene hybrid devices were fabricated using electrophoretic deposition, where the C60 clusters are electrically charged upon the application of an external bias in a polar solvent, acetonitrile, mixed with toluene, which facilitates their deposition on the graphene membranes. Raman spectroscopy unveiled the unique vibrational fingerprints associated with the A2g mode of the C60 molecules at ∼1453 cm-1, while blue shifts of ∼6 and ∼17 cm-1 were also attributed to the G- and 2D-bands of the hybrids relative to bare graphene, suggestive of p-doped graphene. The intensity ratio of the G- and the 2D-bands I2D/IG (hybrid) dropped to ∼0.18 from ∼0.3 (bare graphene), and this reduction in I2D/IG is also a signature of hole-doped graphene, consistent with the relatively strong electron accepting nature of C60. The electronic conductance of the two-terminal hybrid devices increased relative to bare graphene at room temperature which was attributed to the increased carrier density, and temperature-dependent electronic transport measurements were also conducted from ambient down to ∼5.8 K. Additionally, a low energy shift in the Fermi level, EF ≈ 140 meV, was calculated for the hybrids. When the hybrid devices were irradiated with a broadband white light source and a tunable laser source (with a wavelength λ ranging from ∼400-1100 nm), a strong photoresponse was evident, in contrast to the bare graphene devices which appeared unresponsive. The responsivity R of the hybrids was measured to be ∼109 A/W at λ ≈ 400 nm and ∼298 K, while the detectivity and external quantum efficiency were also exceptional, ∼1015 jones and ∼109%, respectively, at ∼1 V and a light power density of ∼3 mW/cm2. The R values are ∼10 times higher compared to other hybrid devices derived from graphene reported previously, such as quantum dot-graphene and few-layer MoS2-graphene heterostructures. The strong photoresponse of the C60-graphene hybrids reported here is attributed to the doping enhancement arising in graphene upon the adsorption of C60. This work demonstrates the exceptional potential of such hybrid nanocarbon-based structures for optoelectronics.

14.
RSC Adv ; 9(44): 25805-25816, 2019 Aug 13.
Article in English | MEDLINE | ID: mdl-35530073

ABSTRACT

In the present work, various chemical exfoliation routes for semiconducting two-dimensional (2D) layered material WS2 are explored, which include magnetic stirring (MS), shear mixing (SM), and horn-tip (HT) sonication. Current-voltage measurements, Raman spectroscopy, and photoluminescence (PL) spectroscopy were used to characterize the drop-casted WS2 nanosheets produced by these three techniques and our analysis revealed that HT sonication produced the most optimal dispersions. Heterostructure photodetector devices were then fabricated using inkjet printing of the HT sonicated dispersions of WS2 and graphene. The photodetector device performance was measured using a stream of ON/OFF light pulses generated using a red laser with wavelength λ ∼ 660 nm, and an arbitrary waveform generator. From this analysis, the photoresponsivity and detectivity of the graphene-WS2-graphene heterostructure devices were calculated to be ∼0.86 A W-1 and ∼1013 Jones, respectively. Capacitance-voltage (C-V) and C-frequency (f) measurements were also conducted, where the V was swept from -6 V to +6 V, while the change in C was measured from f ∼ 20 kHz up to 3 MHz to gain insights into the nature of the graphene-WS2 interface. From the C-V measurements, the C plateaued at ∼324.3 pF from ∼-4 V to +4 V for the lowest f of 20 kHz and it reduced to ∼200 pF from -6 V to ∼-4 V, and similarly from ∼4 V to 6 V, C was ∼190 pF. The decrease in C for V > +4 V and V < -4 V was attributed to the reduction of the interfacial barrier at the electrodes which is suggestive of a Schottky-based photodiode at the graphene-WS2 interface. A sharp decrease in C from ∼315.75 pF at 25.76 kHz to ∼23.79 pF at 480 kHz (at 0 V bias) from the C-f measurements suggests a strong effect of interface trap density on C built-up at the graphene-WS2 interface and the ensuing Schottky barrier height. Our work confirms the excellent potential of solution-cast, trilayer graphene-WS2-graphene heterostructures as a promising photodetector platform using additively manufactured inkjet printing.

15.
Sci Rep ; 8(1): 1276, 2018 01 19.
Article in English | MEDLINE | ID: mdl-29352140

ABSTRACT

The design, fabrication, and characterization of ultra-high responsivity photodetectors based on mesoscopic multilayer MoS2 is presented, which is a less explored system compared to direct band gap monolayer MoS2 that has received increasing attention in recent years. The device architecture is comprised of a metal-semiconductor-metal (MSM) photodetector, where Mo was used as the contact metal to suspended MoS2 membranes. The photoresponsivity [Formula: see text] was measured to be ~1.4 × 104 A/W, which is > 104 times higher compared to prior reports, while the detectivity D* was computed to be ~2.3 × 1011 Jones at 300 K at an optical power P of ~14.5 pW and wavelength λ of ~700 nm. In addition, the dominant photocurrent mechanism was determined to be the photoconductive effect (PCE), while a contribution from the photogating effect was also noted from trap-states that yielded a wide spectral photoresponse from UV-to-IR (400 nm to 1100 nm) with an external quantum efficiency (EQE) ~104. From time-resolved photocurrent measurements, a decay time τ d ~ 2.5 ms at 300 K was measured from the falling edge of the photogenerated waveform after irradiating the device with a stream of incoming ON/OFF white light pulses.

16.
Nanoscale ; 9(33): 11864-11870, 2017 Aug 24.
Article in English | MEDLINE | ID: mdl-28805881

ABSTRACT

Carbon nanofibers (CNFs) synthesized using a plasma-enhanced chemical vapor deposition (PECVD) process are investigated as a new class of building blocks for high-frequency vibrating nanomechanical resonators. The CNF resonators are prototyped by using vertically oriented few-µm-long cantilever-structured CNFs grown by PECVD. Undriven thermomechanical motions and photothermally driven resonances are measured in the frequency range of ∼3-10 MHz, which exhibit quality (Q) factors of ∼140-350 in moderate vacuum (milliTorr) at room temperature. Further, characteristics of CNF resonators after platinum deposition and intensive electron beam exposure are investigated, and resonance frequency shifts due to mass loading on the CNFs are clearly observed. In addition, extensive material characterization of the CNFs using techniques such as X-ray electron dispersive spectroscopy (XEDS) with spatial element-mapping reveals the structure and growth mechanism of the CNFs.

17.
Nanotechnology ; 27(48): 485602, 2016 Dec 02.
Article in English | MEDLINE | ID: mdl-27805909

ABSTRACT

Stable ink dispersions of two-dimensional-layered-materials (2DLMs) MoS2 and graphite are successfully obtained in organic solvents exhibiting a wide range of polarities and surface energies. The role of sonication time, ink viscosity and surface tension is explored in the context of dispersion stability using these solvents, which include N-methyl-2-pyrrolidone (NMP), N,N-Dimethylacetamide (DMA), dimethylformamide (DMF), Cyclohexanone (C), as well as less-toxic and more environmentally friendly Isopropanol (IPA) and Terpineol (T). The ink viscosity is engineered through the addition of Ethyl-Cellulose (EC) which has been shown to optimize the jettability of the dispersions. In contrast to prior work, the addition of EC after sonication-instead of prior to it-is noted to be effective in generating a high-density dispersion, yielding a uniform film morphology. High-quality inks are obtained using C/T and NMP as solvents for MoS2 and graphite, respectively, as gauged through optical absorption spectroscopy. Electronic transport data on the solution-cast inks is gathered at room temperature. Arrays of 2D graphite-rod based inks are printed on rigid Si, as well as flexible and transparent polyethylene terephthalate (PET) substrates. The results clearly show the promise of ink-jet printing for casting 2DLMs into hierarchically assembled structures over a range of substrates for flexible and printed-electronics applications.

18.
Eur Heart J Acute Cardiovasc Care ; 5(5): 455-60, 2016 Sep.
Article in English | MEDLINE | ID: mdl-26450780

ABSTRACT

AIMS: Cardiac outcomes after acute coronary syndrome (ACS) are worse in patients with depression, but identifying which depressed patients are at increased risk, and by what means, remains difficult. METHODS AND RESULTS: We analyzed inpatient electrocardiograms (ECGs) from 955 patients admitted with non-ST elevation ACS (NSTE-ACS) in the Prescription Use, Lifestyle, and Stress Evaluation (PULSE) study. Patients with QRS duration ⩾120 ms or whose rhythm was not normal sinus were excluded (sample size=769). Depressive symptoms were measured by Beck Depression Inventory score ⩾10. ECG markers included Cornell product-left ventricular hypertrophy (CP-LVH) and strain pattern in the lateral leads. In multivariable logistic regression models, depressive symptoms were associated with increased odds of CP-LVH, ECG-strain, and the combination of the two (odds ratios 1.74-2.33, p values <0.01). The combination of both CP-LVH and ECG-strain was predictive of one-year risk of myocardial infarction (MI) or death among patients with depressive symptoms (hazard ratio 4.91, 95% CI 1.55-15.61, p=0.007), but not among those without depressive symptoms (p value for interaction 0.043). CONCLUSION: In our non-ST elevation (NSTE)-ACS cohort, ECG markers of hypertrophy were both more common, and more predictive of MI/mortality, among those with depressive symptoms. Cardiac hypertrophy is a potential target for therapy to improve outcomes among depressed NSTE-ACS patients.


Subject(s)
Depression/complications , Hypertrophy, Left Ventricular/diagnosis , Non-ST Elevated Myocardial Infarction/mortality , Aged , Electrocardiography/methods , Female , Hospitalization , Humans , Hypertrophy, Left Ventricular/etiology , Logistic Models , Male , Middle Aged , Non-ST Elevated Myocardial Infarction/complications , Risk Factors
19.
Mol Microbiol ; 98(3): 473-89, 2015 Oct.
Article in English | MEDLINE | ID: mdl-26192205

ABSTRACT

Phenotypic heterogeneity is commonly observed between isolates of a given pathogen. Epidemiological analyses have identified that some serotypes of the group A Streptococcus (GAS) are non-randomly associated with particular disease manifestations. Here, we present evidence that a contributing factor to the association of serotype M3 GAS isolates with severe invasive infections is the presence of a null mutant allele for the orphan kinase RocA. Through use of RNAseq analysis, we identified that the natural rocA mutation present within M3 isolates leads to the enhanced expression of more than a dozen immunomodulatory virulence factors, enhancing phenotypes such as hemolysis and NAD(+) hydrolysis. Consequently, an M3 GAS isolate survived human phagocytic killing at a level 13-fold higher than a rocA complemented derivative, and was significantly more virulent in a murine bacteremia model of infection. Finally, we identified that RocA functions through the CovR/S two-component system as levels of phosphorylated CovR increase in the presence of functional RocA, and RocA has no regulatory activity following covR or covS mutation. Our data are consistent with RocA interfacing with the CovR/S two-component system, and that the absence of this activity in M3 GAS potentiates the severity of invasive infections caused by isolates of this serotype.


Subject(s)
Streptococcus pyogenes/genetics , Streptococcus pyogenes/pathogenicity , Animals , Antigens, Bacterial/genetics , Antigens, Bacterial/metabolism , Bacteremia/microbiology , Bacterial Outer Membrane Proteins/genetics , Bacterial Outer Membrane Proteins/metabolism , Base Sequence , Carrier Proteins/genetics , Carrier Proteins/metabolism , Gene Deletion , Humans , Mice , Mice, Hairless , Molecular Sequence Data , Mutation , Serogroup , Streptococcal Infections/microbiology , Streptococcus pyogenes/classification , Trans-Activators/genetics , Trans-Activators/metabolism , Virulence/genetics , Virulence Factors/genetics , Virulence Factors/metabolism
20.
J Fluoresc ; 24(6): 1687-99, 2014 Nov.
Article in English | MEDLINE | ID: mdl-25238802

ABSTRACT

Mixed-ligand Cu(II), Co(II) complexes of formulae [Co(NSALT)(A.A)(H2O)](1), [Co(OHAPT)(A.A)H2O](2), and [Cu(ESALT)(ABPH)H2O] (3) were obtained by refluxing methanol solutions of copper, cobalt chlorides with the appropriate ligands. The complexes were characterized by the ESI-MASS, vibrational spectroscopy (Fourier transform-IR), (1)H-NMR spectroscopy, UV-vis spectroscopy, TGA, ESR, SEM and powder XRD. The preliminary DNA-binding activity of the complexes was studied by recording electronic absorption spectra of the complexes in presence of CT-DNA. The binding constants of three complexes towards calf thymus DNA (CT-DNA) [1.2 × 10(4) M(-1) for 1, 2.5 × 10(4) M(-1) for 2, and 3.0 × 10(4) M(-1) for 3] indicate strong interaction of 3. Changes in the fluorescence of ethidium bromide in the presence of DNA suggest intercalation into or electrostatic interactions with CT DNA. The quenching constants, KSV towards-DNA calculated through fluorescence spectra are 2.9 × 10(4) M(-1)for 1, 1.8 × 10(4) M(-1) for 2, and 3.2 × 10(4) M(-1) for 3. Docking studies on DNA complexes confirm the binding of 1 and 2 in the major groove of CT-DNA (CTP-1 Endonuclease). Moreover, the antibacterial effect of 1-3 against the five bacterial species was evaluated. The metal complexes have cleavage affinity towards PBR322 plasmid. Furthermore, the antioxidant activities of the complexes were determined by DPPH scavenging activity method.


Subject(s)
Anti-Bacterial Agents/pharmacology , Antioxidants/pharmacology , Bacteria/drug effects , Cobalt/chemistry , Coordination Complexes/pharmacology , Copper/chemistry , DNA Cleavage/drug effects , DNA/metabolism , Animals , Anti-Bacterial Agents/chemistry , Antioxidants/chemistry , Cattle , Coordination Complexes/chemistry , Electron Spin Resonance Spectroscopy , Ligands , Magnetic Resonance Spectroscopy , Models, Molecular , Molecular Structure , Spectrometry, Mass, Electrospray Ionization , Spectroscopy, Fourier Transform Infrared
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