We have studied the mechanical properties of a few-layer graphene cantilever (FLGC) using atomic force microscopy (AFM). The mechanical properties of the suspended FLGC over an open hole have been ...derived from the AFM data. Force displacement curves using the Derjaguin-Müller-Toporov (DMT) and the massless cantilever beam models yield a Young modulus of E(c) approximately 37, E(a) approximately 0.7 TPa and a Hamakar constant of approximately 3 x 10( - 18) J. The threshold force to shear the FLGC was determined from a breaking force and modeling. In addition, we studied a graphene nanoribbon (GNR), which is a system similar to the FLGC; using density functional theory (DFT). The in-plane Young's modulus for the GNRs were calculated from the DFT outcomes approximately 0.82 TPa and the results were compared with the experiment. We found that the Young's modulus and the threshold shearing force are dependent on the direction of applied force and the values are different for zigzag edge and armchair edge GNRs.
•Direct growth of aligned ZnO rods on bare SiO2/Si substrate was performed by VPT.•The structure was modified with Au for improving H2S sensing properties.•High sensitivity and selectivity at room ...temperature were achieved.•XPS analysis was used to describe the H2S sensing mechanism.
Pursuing a sensing structure with a large effective surface area, partial ordered arrays of ZnO nanorods with flower-like structures are introduced for gas sensing applications. Room temperature H2S response of the grown structure shows significant enhancement after modification with Au nanoparticles. High response (about 1270 at 6ppm H2S gas) and selectivity were achieved by depositing an Au layer with nominal thickness ∼6nm. X-ray photoelectron spectroscopy (XPS) was utilized to describe the H2S sensing mechanism.
Resting-state functional magnetic resonance imaging is currently the mainstay of functional neuroimaging and has allowed researchers to identify intrinsic connectivity networks (aka functional ...networks) at different spatial scales. However, little is known about the temporal profiles of these networks and whether it is best to model them as continuous phenomena in both space and time or, rather, as a set of temporally discrete events. Both categories have been supported by series of studies with promising findings. However, a critical question is whether focusing only on time points presumed to contain isolated neural events and disregarding the rest of the data is missing important information, potentially leading to misleading conclusions. In this work, we argue that brain networks identified within the spontaneous blood oxygenation level-dependent (BOLD) signal are not limited to temporally sparse burst moments and that these event present time points (EPTs) contain valuable but incomplete information about the underlying functional patterns.
We focus on the default mode and show evidence that is consistent with its continuous presence in the BOLD signal, including during the event absent time points (EATs), i.e., time points that exhibit minimum activity and are the least likely to contain an event. Moreover, our findings suggest that EPTs may not contain all the available information about their corresponding networks. We observe distinct default mode connectivity patterns obtained from all time points (AllTPs), EPTs, and EATs. We show evidence of robust relationships with schizophrenia symptoms that are both common and unique to each of the sets of time points (AllTPs, EPTs, EATs), likely related to transient patterns of connectivity. Together, these findings indicate the importance of leveraging the full temporal data in functional studies, including those using event-detection approaches.
Aim
Increasing the occurrence of non‐albicans Candida species with intrinsic or acquired resistance to antifungals as well as the emergence of multidrug Candida species coupled with the limited ...antifungal agents challenges the treatment of candidiasis. Consequently, a class of secondary metabolites of plants exhibiting decent antifungal activity. Therefore, this study aimed to evaluate the antifungal potential of various monoterpenes including Carvone, Limonene, Pinene, Menthone, Menthol, Camphor, Thujone, Citronellol, and Piperitone against standard and clinical isolates of Candida.
Methods and Results
Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of compounds were determined, using the broth Microdilution method based on M27‐A3 protocol documented by clinical laboratory standard institute (CLSI). Amongst the tested monoterpenes, oxygenated terpenoids showed strong antifungal activity. Specifically, alcoholic terpenoids such as (±)‐Citronellol possess more efficacy than the corresponding ketonic ones with MICs ranging from 0·03 to 2·00 μl ml−1 (0·16–10·80 mmol l−1). Among the examined yeasts, Candida tropicalis was the most susceptible species to (±)‐Citronellol. Moreover, the examined monoterpenes successfully inhibited the growth of fluconazole‐resistant Candida species. Moreover, statistical analysis showed no statistically significant difference between the (+) and (−) isomers, except for (±)‐α‐Pienene and (±) Menthone (ρ‐value < 0·05).
Conclusion
Among the tested monoterpenes, (±)‐Citronellol was the most potent compounds followed by (+)‐α‐Pinene and Menthol. Considering the significant antifungal activity of the examined monoterpenes, they could be used in controlling or treating candidiasis. Those potent antifungal monoterpenes with GRAS status in addition to their pleasant taste and odour make them appropriate additive or preservative compounds in food and cosmetics products. Furthermore, these data might help researchers to predict EOs antifungal activities, after determining its constituents.
Significance and Impact of the Study
This study provides new information about the antifungal activities of monoterpenes and their isomers presented widely in essential oils. Screening results against pathogenic yeasts confirm the correlation between the chemical structure of tested monoterpenes and their antifungal effects. The present findings might be helpful to anticipate the antifungal activity of essential oils
This paper describes the photoluminescence study of titanium dioxide (TiO2) nanorods grown by a hydrothermal synthesis method on the surface of fluorine doped tin oxide (FTO) coated glass. The ...effects of growth conditions including: reaction time, precursor concentration and adding NaCl to hydrothermal solution on the structural and optical properties of productions are examined by using SEM, XRD, TEM and room temperature photoluminescence measurements. Also, the performance of the TiO2 nanorods as a photoanode of dye sensitized solar cells is investigated. The different excitation energies and intensities are chosen to verify the discrete electronic state of radiative recombination centers in nanorods. The photoluminescence studies show the profound effect of the excitation light energy and intensity on the emission spectra. The nanorods have extended emission spectra from UV to visible region. The near band edge emission is observed at 3.04±0.01eV. Also, the spectra consist of high emission peaks around at 3.44 and 3.14eV and other emissions at 2.90±0.01, 2.83±0.02, 2.70±0.01, 2.56, 2.36±0.03, 2.30±0.02, 2.03, and 1.66eV. The photoluminescence study of TiO2 nanorods and photoconversion efficiency of dye sensitized solar cells indicate a correlation among some PL emission peaks, the aspect ratio and efficiency of photoanode based solar cells.
•TiO2 nanorods were grown directly on fluorine doped tin oxide coated glass by a hydrothermal synthesis method.•The effect of adding NaCl to hydrothermal solution for limiting the diameter growth of nanorods was studied.•The radiative recombination processes were investigated by photoluminescence spectroscopy under different excitation energies and intensities.•The performance of TiO2 nanorods as photoanode of dye sensitized solar cells was examined.•A correlation among aspect ratio of nanorods, photovoltaic properties of dye sensitized solar cells and photoluminescence spectra of photoanodes was observed.
•TiO2–graphene doped with noble metals was synthesized using photoreduction method.•The surface area of TiO2 increased by addition of graphene and noble metals.•The activity of M-TiO2–GR was ...evaluated for the photodegradation of pollutants.•The highest photocatalytic activity was observed for the Pt–TiO2–GR.
TiO2–graphene (TiO2–GR) nanocomposites were synthesized using photocatalytic reduction method. TiO2–GR nanocomposites were thereafter doped with noble metals (Pt and Pd) by chemical reduction of the corresponding cations. The samples were characterized by different techniques. The addition of GR to TiO2 decreases the crystalline size of TiO2 due to the homogeneous dispersion of the TiO2 nanoparticles on GR sheets and prevention of coagulation of TiO2 nanoparticles during synthesis process. In addition, the surface area of TiO2 was increased by addition of GR and deposition of noble metals which helps to prevent agglomeration of graphene sheets and TiO2 nanoparticles. Red shifts to the higher wavelength have been detected for both TiO2–GR and M-TiO2–GR nanocomposites. X-ray photoelectron spectroscopy demonstrated that graphene oxide is reduced to GR by the UV irradiated TiO2 nanoparticles, TiC bonds are formed, and Ti3+ sites are also present on the surface of photocatalyst. The photocatalytic activity of all samples was evaluated for the photodegradation of two pollutants (2,4-dichlorophenoxyacetic acid and Reactive Red 195) in aqueous medium under UV and visible irradiations. The M-TiO2–graphene nanocomposites exhibited excellent photocatalytic activity within both UV and visible regions. The results confirm that the addition of GR as well as noble metal to TiO2 nanoparticles increases electron transport, thus impeding the charge recombination of the excited TiO2. The highest photocatalytic activity was observed for Pt–TiO2–GR nanocomposites due to its high photonic efficiency.
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•TEMPO-oxidized cellulose nanofibrils (TOCNFs), as a natural polymer based sensing films, were prepared through spin-coating on quartz crystal Microbalance (QCM) chips.•Detection of ...aqueous L-lysine (Lys), glycine (Gly) and L-leucine (Leu) was performed without further sensing film modification.•The fabricated biodetector is low cost, simple and label-free and more sensitive to Lys.
Developing a simple, cost effective and accurate detection method for L-lysine (Lys), L-leucine (Leu) and glycine (Gly) as the important analytes in clinical diagnostics, biological processes and food industries is of great significance. Herein, we prepared spin-coated TEMPO-oxidized cellulose nanofibrils (TOCNFs) on Quartz Crystal Microbalance (QCM) chip to achieve QCM biodetectors. The coated QCMs were carefully characterized before and after interaction with amino acids (AA) using water contact angle (WCA), Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), Raman spectroscopy, and scanning electron microscopy (SEM). In addition, to study the response of the fully covered QCM chips to the aqueous AA, the frequency reductions of the detectors in proportion to different AA concentrations (10–1000 μg/mL) were recorded. The data showed a linear range of detection R2 = 0.9987, 0.9933, 0.9833 and a calculated limit of detection (LOD) equal to 49, 113 and 178 µg/ml for Lys, Gly and Leu, respectively. We observed the highest frequency shifts (the strongest interaction with TOCNFs) for Lys detection while response to Leu was negligible.
Modified tungsten oxide films by vanadium oxide provide neutrally coloring electrochromic electrodes for smart windows technology. In this study W–V–O mixed oxide films were fabricated by Nd:YAG ...pulsed laser deposition (PLD),
λ=1064
nm, from mixed pressed powders of (WO
3)
1−
x
(V
2O
5)
x
,
x=0, 0.09, 0.17, 0.23, 0.29 and 0.33, at 13.3
Pa oxygen partial pressure and 200
°C temperature on glass substrates. X-ray photoelectron spectroscopy (XPS) revealed V
5+, V
4+, W
6+ and W
5+ surface oxide states, where the ratio of W
5+/W
6+ enhances by the amount of vanadium in the films. Surface morphology was studied by scanning electron microscope (SEM) and optical properties by transmission-reflection spectra. Results showed that films with a low amount of vanadium oxide have better porosity and higher optical band gaps. The gasochromic response to hydrogen gas exposure was found better for
x=0.09 in the sense of both deeper and faster coloring. Weak responses of samples with more vanadium oxide were attributed to higher amounts of W
5+ in the films and also to lower porosity.
► The UV photodetection of ZnO rods grown on porous silicon substrates are reported. ► The I–V characteristics have linear behavior, indicating space charge effect. ► The device exhibits photocurrent ...response of 0.027A/W for 325nm UV light under −5V bias. ► The rise and decay time constants under these conditions are 19 and 62s, respectively.
Here, the UV photodetection of ZnO rods grown on porous silicon substrates are reported. Laterally interconnected ZnO rods have been synthesized by chemical vapor transport and condensation method on porous silicon substrates. As characterized by current–voltage measurements the I–V characteristics have linear behavior, indicating space charge effect. The device exhibits photocurrent response of 0.027A/W for 325nm UV light under −5V bias. The rise and decay time constants under these conditions are 19 and 62s, respectively.
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