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The electronic properties of layered materials are directly determined based on their thicknesses. Remarkable progress has been carried out on synthesis of wafer-scale atomically molybdenum disulfi...

We report a novel and facile method to synthesize sulfur-doped titanium oxide sheets and realize TiS2-TiO2 heterostructures by means of a sequential sulfurization and oxidation step in a dual-zone chemical vapor deposition furnace. The inclusion of chlorine and argon gases during the growth of such titanium-based compounds plays a critical role in the formation of desired geometries and crystalline structures. These heterostructures possess nano-whisker and nanosheet configurations, controlled by adjusting the growth parameters such as temperature, carrier gas and the sequencing between different steps of the growth. The evolution of these complex heterostructures has been investigated using Raman spectroscopy and EDS characterization. The presence of chlorine gas during the growth results in local TiS2 formation as well as faceted growth of TiO2 nanosheets through anatase to rutile phase change prohibition. The electron microscopy (TEM) images and diffraction pattern (SAED) characterization reveal the crystallinity and layered nature of grown structures, further demonstrating the 2D characteristics of S-doped nanosheets. The evolution of TiO2 on TiS2 heterostructures has also has been verified using XPS analysis. These highly featured nanostructures are suitable candidates to enhance the photocatalytic behavior of TiO2 nanostructures.

For the first time, the effects of adding hydrazine solution to tin-oxide sol–gel to be used as an electrode in high-performance supercapacitors have been studied. The mixed solution has been spin-coated on stainless steel foils as substrates followed by exposing to hydrogen plasma treatment. The results show the effectiveness of adding hydrazine to tin-oxide sol–gel, compared to pure tin-oxide sol–gel. The electrochemical tests such as cyclic-voltammetry and charge–discharge characteristics have been conducted, and the findings demonstrate the favourable contribution of adding hydrazine in increasing the capacitance of the supercapacitor. The physical properties of the tin-oxide material have been analysed by means of FESEM, XRD, TEM, FT-IR spectroscopy and Raman spectroscopy to have a better understanding of preparation procedure and better insight in material synthesis. The electrochemical tests demonstrate a high capacitance of 18 mF/cm2 for the sample treated with hydrazine during the sol–gel processing which is around 40% higher than the merely prepared tin-oxide sample. The measured values for the capacitance versus rate show a rather linear correlation between these parameters, further corroborating an electric-double layer-based performance for such devices.

Metal-assisted chemical etching process is exploited to realise deep-etched silicon structures. Gold as the noble metal, hydrogen peroxide and hydrofluoric acid solutions are used to achieve deep vertical structures. By controlling the solution concentrations, thickness and morphology of the deposited metal, several hundred micrometre-sized silicon structures can be achieved. This method, upon achieving more controllability and repeatability, can be a good substitute for dry etching, due to its high etch-rate, low-cost materials and non-requirement to complex equipment. In this work, the effect of different etching parameters on the etching process is studied to gain more control over the etching conditions.

Despite many reports on electrical characteristics of carbon nanotubes and the role of defects on their electrical behavior, no special study has been done to understand the influence of entrapped catalyst nanoparticles on the electrical characteristics of CNTs. Since entrapment of Catalytic nano particles within the structure of nanotubes is inevitable in CVD and PECVD growth methods, it is appriciable to realize the effect of these nano-clusters on the electrical parameters of CNTs. Here, we investigated the effect of entrapped Ni nano-catalysts on the resistance and breakdown of MWCNTs grown by the DC-PECVD method. The studied nanotubes ruptured in a few seconds while carrying electric current with current densities lower than that theoretically predicted for ideal CNTs. We demonstrate that entrapped Ni nano particles have the main role in early structural breakdown due to their catalytic behavior. Raman Spectroscopy , transmission electron microscopy and energy dispersive X-ray spectroscopy analyses are exploited to corroborate the existence of Ni nano-clusters and their effects on electrical behavior of CNTs. In addition to undesirable latitudinal rupture of CNTs, Ni grains have the capability to unzip CNTs along their axes in the case of applying unidirectional electric field.

In this paper, fabrication of nanostructures of conducting polypyrrole (PPy) thin films on the surfaces by in situ chemical polymerization in the presence of different anionic dopants including anthraquinone-2-sulfonic acid sodium salt monohydrate/5-sulfosalicylic acid dehydrate (AQSANa/SSCA) and camphor sulfonic acid (CSA) is reported. “Lift-off process” combined with electron beam lithography (EBL) is used for fabrication of nano patterns of conducting PPy thin films down to 100 nm. In addition, the ability to create ordered single PPy nanowires of controlled dimension, with very high aspect ratio, and dendrite free features between Au electrodes for fabricating of field effect transistor (FET) was demonstrated by single wires of PPy-CSA and PPy-(AQSANa,SSCA) with 250 nm widths, up to 12 μm lengths and 100 nm thickness. I–V measurements of both single PPy-CSA (˜ 124 S/cm) and PPy-(AQSANa,SSCA) (˜ 5 S/cm) nanowires indicated Ohmic or space charge limited conduction, depending on the applied bias on the contact electrodes. A considerable modulation in the electrical conductivity of PPy-CSA and PPy-(AQSANa,SSCA) nanowire p-FETs was demonstrated as a result of varying the gate potential. Both PPy-CSA and PPy-(AQSANa,SSCA) nanowire p-FETs provide good performance transistors, nevertheless show different device electrical characteristics due to used different anionic dopants.

Molybdenum disulfide (MoS2)/reduced Graphene Oxide (rGo)-based photodetector was fabricated based on a convenient method using a novel aligned carbon nanotube (CNT) contact configuration. With this device, one can successfully meet the challenges in device fabrication based on nano-sized 2-D materials. For this purpose, patterned CNTs were grown on a 285-nm SiO2/Si substrate using plasma-enhanced chemical vapor deposition. Then, thermally reduced few-layered go was drop casted on CNTs electrode followed by deposition of MoS2 nanosheets through dispersion. The photo response of the device was investigated under laser illumination with different wavelengths (375, 405, 455, and 532) and various power intensities. Despite adding small portion of MoS2 nanosheets, the results demonstrate an ultra-high photo responsivity of 115 mA/W at ${V}_{\textit {ds}}=\textsf {1}$ V under 405-nm laser illumination, which is quite comparable with other reports.

In this study, we have experimentally investigated the electrical properties of graphene and its derivatives (Exfoliated graphene, CVD synthesized graphene, graphene oxide and hydrogenated graphene oxide) under uniaxial strain. We have used gauge factor as a common representation of the sensitivity of the strain sensors and found that the hydrogenated graphene oxide shows significantly higher responsivity comparing to other samples under study. Reproducibility, reliability and lack of hysteresis in the responses of the graphene based samples make them a good candidate to be used in the strain sensors.

The work reports on the exploitation of semi-sequential deep reactive ion etching (RIE) processes for realisation of deep vertically etched Si structures on Si substrate applicable in fibre-optic sensing systems. These processes employ different mixtures of gases including hexaflourosulphide, hydrogen and oxygen in a RIE system with a programmed passivation and etching sub-cycles. In the so-called semi-sequential processes, the intermediate purging steps are eliminated, which results in remaining little trace of reactant gases from the previous sub-cycle in the RIE machine's chamber, which can participate in the process of current sub-cycle. For the sake of minimum optical losses, which are accomplished by highly smooth vertical sidewalls, several etching processes were applied. In these processes, by controlling the etching parameters such as the flow of gases, plasma power and timing of each subsequence, the process can be controlled for minimum under-etch and surface roughness and maximum verticality of sidewalls. However, time and cost considerations should also be noted in the optimum fabrication process.

In this paper, we have developed an inexpensive and simple method to realize high performance supercapacitor with high specific capacitance of 21 mF/cm2 at a scan rate of 10 mV/s, which is among the highest areal capacitance values reported for SnO2 based devices. Stainless steel foils, coated with a mixture of tin oxide (sol–gel) and multiwall carbon nanotube powder to act as the working electrode, have been employed as substrates for the fabrication of these supercapacitors. The use of hydrogen plasma at a moderate temperature of 300–600 °C has been found to be suitable to functionalize the tin-oxide layer and to incorporate deep porosity in its structure. The application of carbon nanotubes has been a critical step to improve the capacitance of the device and to add to its cycling stability. Comparing the results of tin-oxide with CNT-incorporated structures demonstrates more than two orders of magnitude improvement in the value of areal capacitance. The films have been analyzed using scanning and transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The electrochemical properties of the electrodes have been examined using the cyclic voltammetry and galvanostatic measurements.

This study reports the successful fabrication of high-performance flexible binder-free lithium-ion battery anode and supercapacitor based on the synthesis of 3D hierarchical MnO2 nanoflakes (NFs) on vertically aligned carbon nanotubes (VACNTs) grown upon stainless steel (SS). The experimental results revealed that the prepared electrodes were well served as supercapacitors with a tremendous specific capacitance of MnO2 NFs VACNT/SS 1131 F/g at 0.25 A/g in 0.5 mol.L−1 Na2SO4, 518.8% more than VACNT/SS (218 F/g). Compared to other MnO2 NFs/CNT composites, as-fabricated binder-free MnO2 NFs/VACNTs electrode achieves outstanding performance with high initial discharge and charge capacities of 2438 and 1289 mAhg−1 at a current density of 250 mAg−1, respectively. The fabricated anode anode further demonstrates an extraordinarily high reversible capacity of 803.2 mAhg−1 with columbic efficiency of 98.4% at a current density of 250 mAg−1 over 150 charge/discharge runs. Compared to pure VACNTs electrode, the MnO2/VACNTs has significantly improved cycling stability and lithium storage capability, making this nanocomposite a promising anode for LIBs. Meanwhile, the electrochemical behavior of MnO2 NFs/VACNTs anode was evaluated using a numerical simulation approach. The simulation findings results showed excellent consistency between numerical and experimental results.

Surface enhanced Raman scattering (SERS) systems with large number of active sites exhibit superior capability in detection of low concentration analytes. In this paper, we present theoretical as well as experimental studies on the optical properties of a unique hybrid nanostructure, Ag NPs decorated silicon double nanocones (Si-DNCs) array, which provide high density of hot spots. The Si-DNC array is fabricated by employing electron beam lithography together with plasma etching process. Multipole analysis of the scattering spectra, based on the multipole expansion theory, confirms that the toroidal dipole moment dominates over other electric and magnetic multipole moments in the Si-DNCs array. This response occurs as a result of generating current densities flowing in opposite directions and consequently generating H-field vortexes inside the nanocones. Moreover, SERS applicability of this type of nanostructure is examined. For this purpose, the Si-DNCs array is decorated with Ag nanoparticles (NPs) by means of electroless deposition method. Simulation results indicate that combination of multiple resonances, including LSPR resonance of Ag NPs, longitudinal standing wave resonance of Ag layer and inter-particle interaction in the gap region, result in a significant SERS enhancement. Our experimental results demonstrate that Si-DNC/Ag NPs array substrate provides excellent reproducibility and ultrahigh sensitivity.

In this study, we implemented a functionalization process on the surface of silicon nanowires (SiNWs) which were fabricated by chemical vapour deposition (CVD) method in a low-pressure CVD (LPCVD) chamber. Surface functionalization was carried out in three stages: hydroxylation of the surface with piranha solution, silanization with a solution of 3-Aminopropyl triethoxysilane (APTES) in n-hexane, and finally functionalization with folic acid as a detection agent. Optical spectroscopy and electron microscopy techniques were used to experimentally characterize materials. Surface functionalization was evaluated using Attenuated Total Reflectance Fourier-Transform Infrared spectroscopy (FTIR-ATR), Field Emission Scanning Electron Miscoscopy (FESEM), and Transmission Electron Microscopy (TEM). Cell adhesion to functionalized and non-functionalized silicon nanowires was compared; a cell assay analysis on lung metastatic cells was conducted. Lung cancer metastatic QUDB cells were seeded on a SiNWs surface in RPMI1640 complete medium. To evaluate the adhesion of cancer cells to these surfaces FESEM imaging was used. The number of cancer cells trapped on the folic acid functionalized SiNWs was found to be approximately 3 times higher than that of the non-functionalized ones. This article is protected by copyright. All rights reserved

Photobleaching effect is an immense problem in optical spectroscopy, especially when fluorophores are adsorbed on metal nanoparticles (NPs). Nevertheless, little effort has been assigned to the study of fluorophore photostability under this condition. In this paper, the effect of photobleaching on the Raman signal enhancement factor (RS-EF) of dye molecules on Ag-modified silicon nanowire (SiNW) substrates is investigated. For this purpose, SiNWs are fabricated by using the vapor–liquid–solid growth mechanism and decorated with Ag NPs by means of electroless deposition method. This process provides the possibility of forming uniformly and tightly packed Ag NPs on SiNWs. The effect of photostability of the crystal violet as analyte molecules on surface-enhanced Raman spectroscopy is investigated as a function of time evolution and laser power. The influence of Ag NP deposition time on Raman signal enhancement is explored. Our work shows how we can optimize the excitation power for achievement of higher RS-EF and, consequently, lower detectable concentration. Time evolution of surface-enhanced Raman spectroscopy signal shows an exponential decay behavior, which indicates an almost uniform distribution of EFs. Capability of our nanostructure is assessed for different concentration, and subsequently, limit of detection of 10 pm with RS-EF of 2.4×109 is obtained. Copyright © 2017 John Wiley & Sons, Ltd.

In this study, flakes of molybdenum disulfide (MoS2) with controlled size and thickness are prepared through sequential solvent exchange method by sonication in dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) solvents. While NMP acts more effectively in reducing the thickness of flakes, DMF shows better potential in conserving the lateral size of nanosheets. The distribution of size and thickness of nanoflakes as a function of sonication time verifies that extended sonication results in dramatic drop of the dimension of the exfoliated flakes. This technique leads to the formation of few-layered MoS2 flakes without further drop of their lateral dimensions. It has been observed that by exposing the bulk MoS2 powders to oxygen plasma, the exfoliation process is accelerated without converting to 2H-MoS2 structures. Finally, a phototransistor has been fabricated based on few-layered MoS2 layers with a field effect mobility of ∼2.1 cm2 V–1 s–1 showing a high response to laser excitation of 532 nm wavel...

We report the realization of branched silicon nanowires (SiNWs) by means of controlling the pressure during vapor–liquid–solid growth. Gold nanoparticles migrated from the main catalyst droplet act as seeds for the secondary growth of SiNWs across the trunk sidewall. To have gold nanoparticles migration as well as fewer kinks in the trunks, it is crucial to gradually reduce the pressure, which results in fully covered branched SiNWs. Transmission electron microscopy confirmed the crystallinity of the Si nano-branches by SAED analysis. From optical spectroscopy, it is observed that the light absorption is around 98 % over a wide range of wavelengths from 300 to 600 nm and drops to 90 % for higher wavelengths. It is shown that high absorption is due to the excitation of Mie resonances and waveguide modes in Si nanostructures. In order to confirm the presence of these optical modes, Raman spectroscopy has been used. Raman spectrum of branched SiNWs indicates higher enhancement factor compared to plain SiNWs.

Nanotextured gate ion-sensitive field-effect transistors have been realized for high-sensitivity DNA detection. The formation of doped poly-Si rods decorated with ultrafine features is believed to be responsible for higher sensitivities of such devices. Owing to their high sensitivities, such devices can detect charge variations during various functionalization, DNA immobilization, and hybridization steps. An analytical model has been proposed to correlate the high sensitivity with a structural parameter, ${\beta }$ , varying between zero and one. For small values of ${\beta }$ , high sensitivities have been obtained.

An integrated nano-electromechanical chip (NELMEC) has been developed for the label-free distinguishing of both epithelial and mesenchymal circulating tumor cells (ECTCs and MCTCs, respectively) from white blood cells (WBCs). This nanoelectronic microfluidic chip fabricated by silicon micromachining can trap large single cells (>12 µm) at the opening of the analysis microchannel arrays. The nature of the captured cells is detected using silicon nanograss (SiNG) electrodes patterned at the entrance of the channels. There is an observable difference between the membrane capacitance of the ECTCs and MCTCs and that of WBCs (measured using SiNG electrodes), which is the key indication for our diagnosis. The NELMEC chip not only solves the problem of the size overlap between CTCs and WBCs but also detects MCTCs without the need for any markers or tagging processes, which has been an important problem in previously reported CTC detection systems. The great conductivity of the gold-coated SiNG nanocontacts as well as their safe penetration into the membrane of captured cells, facilitate a precise and direct signal extraction to distinguish the type of captured cell. The results achieved from epithelial (MCF-7) and mesenchymal (MDA-MB231) breast cancer cells circulated in unprocessed blood suggest the significant applications for these diagnostic abilities of NELMEC.

One-dimensional heterostructures, based on functionalities of dissimilar materials within a monolithic structure, are promising building blocks for different applications. Herein, utilizing surface decoration of multiwalled carbon nanotubes (MWCNTs) with hydrogenated graphitic carbon layers (HGCLs), the realization of a vertically aligned MWCNT/amorphous-silicon (a-Si) core/shell heterostructure is reported. The proposed method enables the formation of conformal, continuous, and all-around silicon deposition on the carbon nanotube and eliminates any signature of line-of-sight deposition problem, even for thicknesses as low as a few nanometers. Precise elaboration using comparative Raman analysis reveals that the HGCLs play a major role in the construction of such structures. Evidence of direct binding between Si and C, a missing remarkable feature in previous reports, has been observed in high-resolution transmission electron microscope images and X-ray photoelectron spectroscopy. Monitoring time evolution during the formation of the silicon shell declares a diffusive mechanism for the deposition of Si on the surface of MWCNTs. Furthermore, the electro-optical proficiency of the MWCNT/a-Si heterostructure was studied by fabrication of a photodiode. Unlike previous attempts, a naturally formed Schottky junction at the high-quality a-Si/nanotube interface is exploited for charge separation in this photodiode, which provides a sensitivity of >10 7 % in the reverse saturation current for a wavelength of λ = 405 nm.

High aspect ratio zinc oxide (ZnO) nanotubes (NT) were synthesized based on a two-steps approach. In the first step, ZnO nanorod (NR) arrays were prepared by chemical bath deposition from an aqueous of zinc nitrate. In the second step, the cores of ZnO NRs were carved selectively in a KCl solution, resulting in the formation of a tubular structure. The influence of KCL concentration, temperature, and immersion time on the ZnO NT formation process was completely characterized and investigated. 12.5 μm NRs and NTs have been utilized to manufacture dye-sensitized solar cells (DSSCs) and as a result, conversion efficiencies of 1.06% and 2.87% were obtained, respectively. Electrochemical impedance spectroscopy measurements have demonstrated that the NTs could acquire a higher electron lifetime compared to NRs which causes a faster electron collection. The overall improvement in NT-based DSSC performance demonstrates a new approach to enhance the efficiency of dye-sensitized solar cells.

Cancerous transformation may be dependent on correlation between electrical disruptions in the cell membrane and mechanical disruptions of cytoskeleton structures. Silicon nanotube (SiNT)-based electrical probes, as ultra-accurate signal recorders with subcellular resolution, may create many opportunities for fundamental biological research and biomedical applications. Here, we used this technology to electrically monitor cellular mechanosensing. The SiNT probe was combined with an electrically activated glass micropipette aspiration system to achieve a new cancer diagnostic technique that is based on real-time correlation between mechanical and electrical behaviour of single cells. Our studies demonstrated marked changes in the electrical response following increases in the mechanical aspiration force in healthy cells. In contrast, such responses were extremely weak for malignant cells. Confocal microscopy results showed the impact of actin microfilament remodelling on the reduction of the electrical response for aspirated cancer cells due to the significant role of actin in modulating the ion channel activity in the cell membrane.

In this research, polyaniline (PANI)/unzipped carbon nanotube (UCNT) composites were synthesized by in situ chemical oxidative polymerization method. The UCNTs were synthesized via longitudinal unzipping of multi-walled CNTs (MWCNTs) through chemical treatments. Different unzipping levels in UCNTs were obtained by regulating the introduced amount of oxidant (KMnO4) into reaction solutions. Transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and X-ray diffraction were applied in order to characterize the synthesized samples. Electrochemical properties of electrodes were studied by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy techniques in 1 M HCl aqueous solution. The electrochemical measurements of electrode materials confirmed that composition of PANI with the partially UCNT exhibited much higher specific capacitance (762 Fg−1) compared to the pure PANI (295 Fg−1) at a scan rate of 30 mV s−1. In addition, this composite electrode showed better cycling stability with 81% capacitance retention after 1000 cycles. These improvements could be mainly attributed to the presence of CNT/UCNT mixture in the composite structure, resulting from partially unzipping of CNTs, which greatly facilitates electrolyte ions accessibility to the electrode material during charge/discharge process and also maintains the mechanical strength. These results can introduce PANI/UCNT composite as a promising electrode material for supercapacitor applications.

A Co-Ni oxide/vertically aligned carbon nanotube (VACNT) composite was prepared by thermal decomposition of cobalt-nickel nitrate precursor on the surface of VACNT electrode. VACNTs were used as 3D nanoporous substrate and were grown by plasma-enhanced chemical vapor deposition from a mixture of H2 and C2H2. The specific capacitance of Co-Ni oxide (5:5)/VACNT (with equal Co+2/Ni+2 mole ratio) was measured to be 1050 Fg−1, which is about 1.9- and 3-fold that of Ni oxide/VACNT (540 Fg−1) and Co oxide/VACNT (341 Fg−1), respectively. The results show Co-Ni oxide (5:5)/VACNT composite electrode has excellent specific capacitance because of porous network structure, good electrical conduction pathways, high access for the electrolyte solution, and consequently increased composite/solution interfacial contact area. The capacitance property of the Co-Ni oxide/VACNT composite electrode with different Co+2/Ni+2 mole ratios was also investigated and the highest specific capacitance is achieved at equal Co+2/Ni+2 mol...

In this paper, patterning ability of ultra-thin films of conducting polypyrrole deposited on silicon wafer surfaces by in situ chemical polymerization in the presence of different anionic dopants including α-naphthalene sulfonic acid, anthraquinone-2-sulfonic acid sodium salt monohydrate/5-sulfosalicylic acid dehydrate and camphor sulfonic acid has been studied. “Lift-off process” combined with photolithography is the used method for large-area and easy fabrication of micro patterns of conducting PPy thin films. In this procedure, a self-assembled mono layer of Py-silane is deposited on a patterned surface of a positive photoresist, followed by immersion of the surface into polymerization solution. After polymerization, positive micro pattern of the conducting PPy thin film appears on the surface by lifting-off the post baked positive photo resist by THF. The results showed deposition and patterning of conducting PPy thin films with nanometer thickness and relatively high range of conductivity with features as small as 3–4.5 µm in lateral dimensions on silicon wafer.

The capacitive properties of graphene nanoribbons (GNRs) with different reduction levels were investigated. GNRs have been synthesized through thermal reduction of oxidized GNRs in the temperature range 100–400 °C. Oxidized GNRs were synthesized by longitudinal unzipping of multi-walled carbon nanotubes (MWCNTs) by means of chemical treatments. Scanning electron microscopy and transmission electron microscopy observations showed, that the efficient tube unzipping yielded improved effective surface area without any tube annihilation by the unzipping process of MWCNTs. Electrochemical studies indicated that through unzipping of MWCNTs, specific capacitance increased from 8 to 28 F g −1 at discharge current density of 0.5 A g −1 , confirming increased active surface area and increased defect density in the MWCNTs surface. Unzipping of MWCNTs resulted in decreased rate capability of the electrode because of low electrical conductivity due to oxidization during the unzipping process. Thermal reduction of unzipped sample affected both specific capacitance and rate capability of electrodes. The highest specific capacitance of 62 F g −1 at discharge current density of 0.5 A g −1 was obtained for the sample unzipped and thermally annealed at about 150 °C. The amount of oxygen-containing groups was shown to be an important factor influencing the performance of the GNRs. These results make unzipped MWCNTs promising electrode materials for supercapacitor applications.

Vertically aligned carbon nanotubes (VACNTs) were grown on highly n -doped silicon substrates by direct current plasma enhanced chemical vapor deposition to be used as supercapacitor electrodes from a gas mixture of acetylene and hydrogen on nickel islands as the catalyst particles. Scanning electron microscopy and transmission electron microscopy have been exploited to characterize the VACNTs. Electrochemical properties of electrodes were studied by cyclic voltammetry, galvanostatic charge–discharge and impedance spectroscopy technique. According to SEM and TEM images growth mechanism was tip-initiated. Capacitances for four different growth durations of 20, 40, 60 and 120 min were measured to be 1.5, 5.8, 7.5 and 15 mF cm −2 , respectively, at 1 mA discharge current. VACNT electrodes fabricated by this method contributed to better electrode capacitance as compared with results of similar previous studies. Furthermore the rate capability of electrodes was found to be excellent. The specific capacitances of a fabricated VACNT electrode and an entangled carbon nanotube (ECNT) electrode in 0.5 M KCl aqueous solution electrolyte were 70 and 8 Fg −1 , respectively. Compared with ECNT electrode, VACNT electrode achieved higher specific capacitance. The higher specific capacitance of VACNT was attributed to the high surface area as well as to defects on the VACNTs, which may be formed by the H 2 -plasma during growth. The maximum specific energy and power of the VACNT electrode were 3.5 Wh kg −1 and 22 kW kg −1 , respectively. The results indicate that the VACNTs are promising candidates as electrode materials in supercapacitors.

Bioinspired materials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. In this study, biomimetic micro/nanoenvironments were fabricated by cell-imprinted substrates based on mature human keratinocyte morphological templates. The data obtained from atomic force microscopy and field emission scanning electron microscopy revealed that the keratinocyte-cell-imprinted poly(dimethylsiloxane) casting procedure could imitate the surface morphology of the plasma membrane, ranging from the nanoscale to the macroscale, which may provide the required topographical cell fingerprints to induce differentiation. Gene expression levels of the genes analyzed (involucrin, collagen type I, and keratin 10) together with protein expression data showed that human adipose-derived stem cells (ADSCs) seeded on these cell-imprinted substrates were driven to adopt the specific shape and characteristics of keratinocytes. The observed morphology of the ADSCs grown on the keratinocyte casts was noticeably different from that of stem cells cultivated on the stem-cell-imprinted substrates. Since the shape and geometry of the nucleus could potentially alter the gene expression, we used molecular dynamics to probe the effect of the confining geometry on the chain arrangement of simulated chromatin fibers in the nuclei. The results obtained suggested that induction of mature cell shapes onto stem cells can influence nucleus deformation of the stem cells followed by regulation of target genes. This might pave the way for a reliable, efficient, and cheap approach of controlling stem cell differentiation toward skin cells for wound healing applications.

Metal-assisted etching of silicon in HF/H2O2 aqueous solutions has been used to fabricate luminescent silicon nanowires (SiNWs) and porous silicon. The impact of the gold catalyst layer thickness and the etching solution on the morphology of the synthesized nanostructures and the diameter of the obtained nanowires were systematically investigated. Scanning electron microscopy (SEM) analyses reveal that the morphology of the fabricated structures strongly depends on the composition of the solution and the thickness of the catalyst layer. It has been observed that SiNWs are formed in solutions with H2O2 ratios (ξ) below 10 %; increasing the H2O2 concentration above this critical value leads to mesoporous (10 % < ξ < 14 %) and macroporous (14 % < ξ < 17 %) structures. Photoluminescence measurements show that SiNWs emit light at about 430 nm. Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) analyses were utilized to determine the origin of the emission in the silicon nanostructures. TEM imaging demonstrates that SiNWs are covered by a thin layer of porous silicon, which is assumed to be responsible for their light emission.

Metal-assisted chemical etching is applied to fabricate deep, high aspect ratio nanopores in silicon. The authors’ simple and cost-effective fabrication process has proven capable of generating nanopores with diameters as small as 30 nm, over the whole wafer surface (50.8 mm in diameter). The process uses a thin layer of DC-sputtered gold and H 2 O 2 / H 2 O / HF treatment to generate Au nanoislands. The formation of these nanoislands is confirmed by scanning electron microscopy. In this paper, the authors study the effect of Au-layer thickness on the diameter and morphology of the fabricated nanopores. The resulting structures have wide applications in optical sensing and filtering.

Here, controlled growth of vertically aligned carbon nanotubes (VACNTs) on free-standing porous activated reduced graphene oxide (a-rGO) paper was fabricated using plasma-enhanced chemical vapor deposition method. The electrochemical performance of prepared film was investigated to provide effective electrode for 3D flexible high-performance lithium-ion batteries (LIBs) and supercapacitors. The results revealed that the prepared electrode exhibited a high specific capacitance of 347 F/g at 0.5 A/g in 1 M KOH electrolyte, 60% more than non-activated rGO-paper (218 F/g). The VACNTs on a-rGO have increased the accessible surface area and acted as efficient electrical conducting paths, which improved the power density. The free-standing flexible supercapacitor fabricated using such a film exhibited a sufficient electrochemical behaviour with high power density of 407 kW kg−1 at 5 Wh.kg−1 at a current density of 0.5 A/g. Since VACNTs with low sp2 hybridization defect lead to cyclic stability, suitable for high-performance LIB anodes. This 3D flexible anode electrode demonstrated a high initial discharge capacity of 1401 mAhg−1 with a large reversible charge capacity of 958 mAhg−1 at 150 mAg−1. The charge and discharge capacity have reached a stable value of 459 mAhg−1 after 100 cycles with a coulombic efficiency of ∼100% which is much higher than most carbon structures.

We report a facile method to realize large area two-dimensional tungsten disulfide nanosheets. The formation of such large WS2 sheets is feasible through sonication in water and dimethyl-sulfoxide (DMSO) solutions, leading to well-separated mono and few layer flakes. The exfoliation has been improved by extensive immersion in near-freezing water prior to probe sonication and subsequent addition of DMSO. By applying oxygen plasma before exfoliation, the size and distribution of sheets become more uniform and larger mono and double-layered structures with sizes of the order of 1 μm are achieved. Different analyses such as SEM, TEM, AFM, DLS and Raman spectroscopy have been employed to understand the mechanism of the exfoliation and study the effects of various parameters such as water temperature, duration and plasma power. The optical properties of WS2 sheets have been examined with a 532 nm laser illumination and demonstrate superior responsivity and detectivity of 0.59 A W-1 and 6.5 × 1010 cm Hz1/2 W-1, respectively.

A simple microfabrication process to make an uncooled aluminum/silicon dioxide bi-material microcantilever infrared (IR) detector using silicon bulk micromachining technology is presented in this work. This detector is based on high banding of the microcantilever due to the large dissimilar in thermal expansion coefficients between the two materials. It consists of a 1 μm SiO2 layer deposited by 200 nm thin Al layer. Since no sacrificial layer is used in this process, complexity related to releasing sacrificial layer is avoided. Moreover Al is protected in Si etchant using dual-doped tetramethyl ammonium hydroxide. The other advantage of this process is that only three masks are used with four photolithography process. Thermal and thermal mechanical behaviors of this structure are obtained using finite element analysis, and the maximum temperature and displacement at the end of cantilever at 100 pW/μm2 absorbed IR power density on top surface are 7.82°K and 1.924 μm, respectively.

In this work we have developed a novel method to place previously grown CNTs on desired nano-textured and micro-machined substrates. Once the desired structures are created on a given substrate (silicon here) the already grown nanotubes are planted on the created holes either by a mechanical rubbing or solution dispersing approach. The main idea of this work is to plant partially vertical nanostructures on textured substrates.

Green tea-reduced graphene oxide (GT-rGO) sheets have been exploited for high efficiency near infrared (NIR) photothermal therapy of HT29 and SW48 colon cancer cells. The biocompatibility of GT-rGO sheets was investigated by means of MTT assays. The polyphenol constituents of GT-rGO act as effective targeting ligands for the attachment of rGO to the surface of cancer cells, as confirmed by the cell granularity test in flow cytometry assays and also by scanning electron microscopy. The photo-thermal destruction of higher metastatic cancer cells (SW48) is found to be more than 20% higher than that of the lower metastatic one (HT29). The photo-destruction efficiency factor of the GT-rGO is found to be at least two orders of magnitude higher than other carbon-based nano-materials. Such excellent cancer cell destruction efficiency provided application of a low concentration of rGO (3 mg/L) and NIR laser power density (0.25 W/cm(2)) in our photo-thermal therapy of cancer cells.

In this paper Electrochromic based micro-mirrors fabrication has been investigated on silicon substrates using a highlyprogrammable deep reactive ion etching technique. Silicon based micro structures have been used as micro containers for Li+ based electrolyte.Covering these micro vessels with WO3 coated ITO electrodes as electrochromic layer, leads to transparent or opaque interfaces which later will be used as image pixels. Passive addressing of micro-mirrors if feasible between mentioned ITO electrodes on top and silicon n+ doped lines at the bottom of micro structures. Desired image can be achieved by addressing each or a cluster of pixels.

We report the realization of graphene nanosheets by means of unzipping carbon nanotubes grown on silicon substrates. The formation of carbon nanotubes is possible with a gas mixture of methane and hydrogen in a direct-current plasma enhanced chemical vapor deposition reactor at a temperature of 700 °C. To avoid the undesired agglomeration of nickel islands as the catalyst layer, a hydrogen-assisted pre-treatment has been used. Vertically aligned CNTs are placed horizontally on a silicon substrate and unzipped using a sequential passivation and etching process in a reactive ion etching unit. A mixture of hydrogen, oxygen and SF6 gases are used to result in proper unzipping of horizontal CNTs. Scanning electron microscopy, transmission electron microscopy, atomic force microscopy and Raman spectroscopy have been exploited to investigate the physical properties of the grown nano-structures. In addition, the composition of the passivation layer has been examined using energy dispersive spectroscopy. Multilayered graphene sheets with a height of 3 nm have been obtained.

We report a novel method to achieve high-sensitivity capacitive humidity sensors based on silicon nanowires. Silicon nanowires have been grown by means of a vapor–liquid–solid technique. It has been observed that the doping of nanowires leads to a significant improvement in the sensitivity of the device. A circuit model, supported by infrared spectroscopy, is proposed to explain the mechanism of the doping effects on the sensitivity. We have observed that by changing the growth pressure, nanowires with different thicknesses and densities could be achieved. Furthermore, it is demonstrated that nanowires with higher densities result in a constructive effect on the response of the sensor.

We report the hydrogenation-assisted unzipping of multiwall carbon nanotubes grown on silicon substrates. Carbon nanotubes are formed using hydrogen and acetylene or methane in a direct-current plasma enhanced chemical vapor deposition chamber at a temperature of 650 °C. By patterning the nickel prior to the growth of CNTs, desired patterns are feasible which can be used for unzipping purposes. The unrolling of CNTs is feasible using a mixture of hydrogen and oxygen plasma treatments at temperatures ranging from 200 to 600 °C and in the presence of plasma powers of around 0.3–0.7 watt cm−2. By the extended exposure of CNTs to hydrogen plasma at low powers, an anomalous swelling of CNTs has been observed. We believe that the swelling of CNTs is due to the incorporation of H atoms into CNT structure. Scanning electron microscopy, transmission electron microscopy; atomic force microscopy, Raman Spectroscopy and X-ray diffraction analyses have been exploited to investigate the physical properties of the synthesized nano-structures.

We report on the fabrication of graphene/Zno nanocomposite supercapacitor electrodes. Laser-scribing process was implemented in order to reduce the graphene oxide (GO)/ZnO mixture on a DVD disk. With reduced graphene oxide (rGO)/ZnO composite prepared by a mass ratio of 1:25 of Zn(NO3)2·6H2O to GO constituents, nanoparticles of ZnO with sizes ranging from 20 to 50 nm are obtained. Consequently, 12 times improvement in the specific capacitance was achieved at a current density of 0.1 mA/cm2 compared with pristine rGO electrodes. In addition, flexible microsupercapacitor was fabricated by spin coating of the gel electrolyte, showing high stack capacitance of 9 F/cm3 at a current density of 150 mA/cm2. This microsupercapacitor delivers power density of 70 mW/cm3 and energy density of 1.2 mWh/cm3. Furthermore, the performance of device was investigated at different bending angles. The resulted characteristics demonstrate that LSG/ZnO nanocomposite is a promising electrode material for high-performance supercapacitors. .

We report the use of a silicon microfabricated device as a new spinneret for electrospinning purposes. This device has been realized on silicon substrates using a deep reactive ion etching process. To make proper holes in the center of microneedles, a rotating angle deposition method followed by vertical etching of silicon is employed. By using these needles as fluid nozzles in the electrospinning process, poly vinyl alcohol solution with a concentration of 7 % has been converted into nanofibers. The formation of nanofibers has been investigated using field emission scanning electron microscopy. Using this process, nanofibers with a diameter of 100–200 nm are realized where the dispersion is less than 50 nm. Finally, the effects of needle size and the applied voltage have been investigated on the diameter of nanofibers.

In this paper, we report on the realization of miniaturized projection displays on silicon substrates using a highly programmable deep reactive ion etching technique. The micro-machined silicon substrates have been used to incorporate Liionic electro-chromic solutions. The use of tungsten oxide (WO3) in conjunction with the ITO electrodes, leads to a transparent or opaque interfaces which can be used as a method to distinguish different spots in an image, provided an external light source is exploited. The formation of highly complex three-dimensional structures is feasible during the deep reactive ion etching of silicon wafers, while desired under-etching is achieved by controlling the etching parameters. The evolution of cup-like micro-mirrors can be carried out at micrometer sizes leading to ultra-high resolution projection systems. A passive addressing is feasible between the top ITO-lines placed on a glass substrate and the bottom cavity-holding substrate. By addressing individual or clusters of pixels one can achieve desired images.

Vertically aligned multi-wall carbon nanotube (CNT) arrays were fabricated in tip-growth mode on Ni/Si substrates using plasma enhanced chemical vapor deposition. In a purification process including hydrogenation and acid washing of the Ni/CNTs, the oxygen-containing functional groups were substantially reduced and a wide hollow core at the tip of the CNTs was formed by removing the Ni seeds. Sol–gel silver nanoparticles were deposited on the surface of the unpurified Ni/CNTs, while they could also be embedded within the hollow core of the Ni-removed CNTs. The persistency of the silver ions in the Ni-removed Ag–CNTs in comparison to the release of the silver ions from the Ag–Ni/CNTs in a dilute HNO3 solution confirmed the effective embedding of the Ag nanoparticles within the hollow core of the Ni-removed CNTs. The Ni-removed Ag–CNTs showed a strong antibacterial activity against Escherichia coli bacteria in the dark (inactivation of 99.8 ± 0.1% of the bacteria as compared to the Ni-removed CNTs and the Ag–Ni/CNTs with 62 ± 11 and 47 ± 18% inactivation in 120 min), while the bacteria even exhibited some proliferation on the surface of the unpurified Ni/CNT arrays. In the context of cell membrane rupture of the bacteria through a direct contact mechanism, it was proposed that the Ni seeds acted as obstacles for an effective contact between the bacteria and the tips of the CNT arrays.