We present an investigation on a coupled system consists of gold nanoparticles and silicon nanocrystals. Gold nanoparticles (AuNPs) embedded into porous silicon (PSi) were prepared using the electrochemical deposition method. Scanning electron microscope images and energy-dispersive X-ray results indicated that the growth of AuNPs on PSi varies with current density. X-ray diffraction analysis showed the presence of cubic gold phases with crystallite sizes around 40 to 58 nm. Size dependence on the plasmon absorption was studied from nanoparticles with various sizes. Comparison with the reference sample, PSi without AuNP deposition, showed a significant blueshift with decreasing AuNP size which was explained in terms of optical coupling between PSi and AuNPs within the pores featuring localized plasmon resonances.
This study introduces a novel titanium dioxide carbon nanofiber (TiO2-CNF) support for anodic catalyst in direct methanol fuel cell. The catalytic synthesis process involves several methods, namely the sol-gel, electrospinning, and deposition methods. The synthesized electrocatalyst is compared with other three electrocatalysts with different types of support. All of these electrocatalysts differ based on a number of physical and electrochemical characteristics. Experimental results show that the TiO2-CNF support gave the highest current density at 345.64 mA mgcatalyst-1, which is equivalent to 5.54-fold that of carbon support while the power density is almost double that of the commercial electrocatalyst.
The aim of this study was to synthesize, characterize, and observe the catalytic activity of Pd1Au1 supported by vapor-grown carbon nanofiber (VGCNF) anode catalyst prepared via the chemical reduction method. The formation of the single-phase compounds was confirmed by X-ray diffraction (XRD) and Rietveld refinement analysis, which showed single peaks corresponding to the (111) plane of the cubic crystal structure. Further analysis was carried out by field emission scanning emission microscopy (FESEM), energy dispersive X-ray analysis (EDX), nitrogen adsorption/desorption measurements, and X-ray photoelectron spectroscopy (XPS). The electrochemical performance was examined by cyclic voltammetry tests. The presence of mesoporous VGCNF as support enables the use of a relatively small amount of metal catalyst that still produces an excellent current density (66.33 mA cm-2). Furthermore, the assessment of the kinetic activity of the nanocatalyst using the Tafel plot suggests that Pd1Au1/VGCNF exerts a strong electrocatalytic effect in glycerol oxidation reactions. The engineering challenges are apparent from the fact that the application of the homemade anode catalyst to the passive direct glycerol fuel cell shows the power density of only 3.9 mW cm-2. To understand the low performance, FESEM observation of the membrane electrode assembly (MEA) was carried out, examining several morphological defects that play a crucial role and affect the performance of the direct glycerol fuel cell.
Head and neck cancer is a heterogeneous disease, originating in the squamous cells lining the larynx (voice box), mouth, pharynx (throat), nasal cavity and salivary glands. Head and neck cancer diagnosis at the later stage is greatly influencing the survival rate of the patient. It makes a mandatory situation to identify this cancer at the earlier stages of development with a suitable biomarker. Squamous cell carcinoma antigen (SCC-Ag) is a circulating serum tumour biomarker, and the elevated level has been found in the head and neck cancer patients and highly correlated with the tumour volume. The present research was carried out to detect and quantify the level of SCC-Ag on titanium oxide (TiO2)-modified interdigitated electrode sensor (IDE) by SCC-Ag antibody. The detection of SCC-Ag was found at the level of 100 fM, while it was improved to 10 fM when the antibody was conjugated with gold nanostar, representing a 10-fold improvement. Interestingly, this enhancement in sensitivity is 1000-folds higher than other substrates. Moreover, the specificity analysis was carried out using two different control proteins and noticed that the antibody only recognised SCC-Ag, indicating the specific detection on IDE-TiO2 sensing surface.
Electrochemical hydrogen evolution reaction (HER) refers to the process of generating hydrogen by splitting water molecules with applied external voltage on the active catalysts. HER reaction in the acidic medium can be studied by different mechanisms such as Volmer reaction (adsorption), Heyrovsky reaction (electrochemical desorption) or Tafel reaction (recombination). In this paper, facile hydrothermal methods are utilized to synthesis a high-performance metal-inorganic composite electrocatalyst, consisting of platinum nanoparticles (Pt) and molybdenum disulfide nanosheets (MoS2) with different platinum loading. The as-synthesized composite is further used as an electrocatalyst for HER. The as-synthesized Pt/Mo-90-modified glassy carbon electrode shows the best electrocatalytic performance than pure MoS2 nanosheets. It exhibits Pt-like performance with the lowest Tafel slope of 41 mV dec-1 and superior electrocatalytic stability in an acidic medium. According to this, the HER mechanism is related to the Volmer-Heyrovsky mechanism, where hydrogen adsorption and desorption occur in the two-step process. According to electrochemical impedance spectroscopy analysis, the presence of Pt nanoparticles enhanced the HER performance of the MoS2 nanosheets because of the increased number of charge carriers transport.
Recently, TiO2/multi-walled carbon nanotube (MWCNT) hybrid nanocatalysts have been a subject of high interest due to their excellent structures, large surface areas and peculiar optical properties, which enhance their photocatalytic performance. In this work, a modified microwave technique was used to rapidly synthesise a TiO2/MWCNT nanocatalyst with a large surface area. X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller measurements were used to characterise the structure, morphology and the surface area of the sample. The photocatalytic activity of the hybrid nanocatalysts was evaluated through a comparison of the degradation of methylene blue dye under irradiation with ultraviolet and visible light. The results showed that the TiO2/MWCNT hybrid nanocatalysts degraded 34.9% of the methylene blue (MB) under irradiation with ultraviolet light, whereas 96.3% of the MB was degraded under irradiation with visible light.
The use of templating method to synthesize the vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO):[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) composite nanotubes is presented here. VOPcPhO is a p-type material and PC71BM is an n-type material which acts as an electron donor and electron acceptor, respectively. Both materials have been studied due to their potential applications as solar energy converter and organic electronics. High-resolution transmission electron microscope (HRTEM) and field emission scanning electron microscope (FESEM) images have shown the replication of the porous template diameter of approximately 200 nm with a superior incorporation of both VOPcPhO and PC71BM. VOPcPhO:PC71BM composite nanotubes showed the significant properties improvement if compared over their bulk heterojunction counterpart. UV-vis spectra of composite nanotubes show a shift to a longer wavelength at the absorption peaks. Significant quenching has been attained by the photoluminescence spectra of VOPcPhO:PC71BM composite nanotubes which supports the redshift of UV-vis absorption spectra. Presumably, the photo-induced charge transfer and charge carrier dissociation can be enhanced from the VOPcPhO:PC71BM composite nanotubes rather than the bulk heterojunction.
Protein corona has became a prevalent subject in the field of nanomedicine owing to its diverse role in determining the efficiency, efficacy, and the ultimate biological fate of the nanomaterials used as a tool to treat and diagnose various diseases. For instance, protein corona formation on the surface of nanoparticles can modify its physicochemical properties and interfere with its intended functionalities in the biological microenvironments. As such, much emphasis should be placed in understanding these complex phenomena that occur at the bio-nano interface. The main aim of this review is to present different factors that are influencing protein-nanoparticle interaction such as physicochemical properties of nanoparticle (i.e., size and size distribution, shape, composition, surface chemistry, and coatings) and the effect of biological microenvironments. Apart from that, the effect of ignored factors at the bio-nano interface such as temperature, plasma concentration, plasma gradient effect, administration route, and cell observer were also addressed.
Verapamil is a calcium channel blocker and highly effective in the treatment of hypertension, angina pectoris, and other diseases. However, the drug has a low bioavailability of 20 to 35% due to the first pass effect. The main objective of this study was to develop hybrid verapamil-dextran nanostructured lipid carriers (HVD-NLCs) in an attempt to increase verapamil cellular uptake. The formulations were successfully prepared by a high-shear homogenization method and statistically optimized using 24 full factorial design. The HVD-NLCs formulations were freeze-dried using trehalose as a cryoprotectant. The results showed that the optimized formula (VER-9) possessed a particle size (PS), polydispersity index (PDI), and the percentage of entrapment efficiency (%EE) of 192.29 ± 2.98, 0.553 ± 0.075, and 93.26 ± 2.66%, respectively. The incorporation of dextran sulfate in the formulation had prolonged the release of verapamil (~ 85% in 48 h) in the simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 6.8). The differential scanning calorimetry analysis showed no chemical interaction between verapamil and the excipients in the formulation. While wide-angle X-ray scattering studies demonstrated the drug in the amorphous form after the incorporation in the NLCs. The transmission electron microscopy and scanning electron microscopy images revealed that the nanoparticles had spherical shape. The cellular uptake study using Caco-2 cell line showed a higher verapamil uptake from HVD-NLCs as compared to verapamil solution and verapamil-dextran complex. The optimized formulation (VER-9) stored in the refrigerated condition (5 °C ± 3 °C) was stable for 6 months. In conclusion, the HVD-NLCs were potential carriers for verapamil as they significantly enhanced the cellular uptake of the drug.
Sepsis is an extreme condition involving a physical response to severe microbial infection and causes fatal and life-threatening issues. Sepsis generates during the chemicals release with the immune system into the bloodstream for fighting against an infection, which causes the inflammation and leads to the medical emergency. A complexed longitudinal zeolite and iron oxide nanocomposite was extracted from coal mine fly ash and utilized to improve the surface characteristics of the capacitance biosensor to identify sepsis attacks. Anti-interleukin-3 (anti-IL-3) antibody was attached to the zeolite- and iron oxide-complexed capacitance electrode surface through an amine linker to interact with the sepsis biomarker IL-3. The morphological and chemical components of the nanocomplex were investigated by FESEM, FETEM, and EDX analyses. At approximately 30 nm, the longitudinal zeolite and iron oxide nanocomposite aided in attaining the limit of IL-3 detection of 3 pg/mL on the linear curve, with a regression coefficient (R2) of 0.9673 [y = 1.638x - 1.1847]. A lower detection limit was achieved in the dose-dependent range (3-100 pg/mL) due to the higher amount of antibody immobilization on the sensing surface due to the nanomaterials and the improved surface current. Furthermore, control experiments with relevant biomolecules did not show capacitance changes, and spiked IL-3 in human serum increased capacitance, indicating the specific and selective detection of IL-3. This study identifies and quantifies IL-3 via potentially useful methods and helps in diagnosing sepsis attack.
This paper presents a unique synergistic behavior between a graphene oxide (GO) and graphene nanoplatelet (GnP) composite in an aqueous medium. The results showed that GO stabilized GnP colloid near its isoelectric point and prevented rapid agglomeration and sedimentation. It was considered that a rarely encountered charge-dependent electrostatic interaction between the highly charged GO and weakly charged GnP particles kept GnP suspended at its rapid coagulation and phase separation pH. Sedimentation and transmission electron microscope (TEM) micrograph images revealed the evidence of highly stable colloidal mixtures while zeta potential measurement provided semi-quantitative explanation on the mechanism of stabilization. GnP suspension was confirmed via UV-vis spectral data while contact angle measurement elucidated the close resemblance to an aqueous solution indicating the ability of GO to mediate the flocculation prone GnP colloids. About a tenfold increase in viscosity was recorded at a low shear rate in comparison to an individual GO solution due to a strong interaction manifested between participating colloids. An optimum level of mixing ratio between the two constituents was also obtained. These new findings related to an interaction between charge-based graphitic carbon materials would open new avenues for further exploration on the enhancement of both GO and GnP functionalities particularly in mechanical and electrical domains.
In this report, we experimentally investigate the formation of "flower-like silver structures" on graphene. Using an electrochemical deposition technique with deposition times of 2.5 and 5 min, agglomerations of silver nanoparticles (AgNPs) were deposited on the graphene surfaces, causing the formation of "flower-like structures" on the graphene substrate. Localized surface plasmon resonance (LSPR) was observed in the interaction between the structures and the graphene substrate. The morphology of the samples was observed using a field-emission scanning electron microscope (FESEM) and Raman spectroscopy. Thereafter, the potential of the flower-like Ag microstructures on graphene for use in Raman spectroscopic applications was examined. The signal showed a highest intensity value after a deposition time of 5 min, as portrayed by the intense local electromagnetic fields. For a better understanding, the CST Microwave Studio software, based on the finite element method (FEM), was applied to simulate the absorption characteristics of the structures on the graphene substrate. The absorption peak was redshifted due to the increment of the nanoparticle size.
In the present study, stable homogeneous graphene nanoplatelet (GNP) nanofluids were prepared without any surfactant by high-power ultrasonic (probe) dispersion of GNPs in distilled water. The concentrations of nanofluids were maintained at 0.025, 0.05, 0.075, and 0.1 wt.% for three different specific surface areas of 300, 500, and 750 m2/g. Transmission electron microscopy image shows that the suspensions are homogeneous and most of the materials have been well dispersed. The stability of nanofluid was investigated using a UV-visible spectrophotometer in a time span of 600 h, and zeta potential after dispersion had been investigated to elucidate its role on dispersion characteristics. The rheological properties of GNP nanofluids approach Newtonian and non-Newtonian behaviors where viscosity decreases linearly with the rise of temperature. The thermal conductivity results show that the dispersed nanoparticles can always enhance the thermal conductivity of the base fluid, and the highest enhancement was obtained to be 27.64% in the concentration of 0.1 wt.% of GNPs with a specific surface area of 750 m2/g. Electrical conductivity of the GNP nanofluids shows a significant enhancement by dispersion of GNPs in distilled water. This novel type of nanofluids shows outstanding potential for replacements as advanced heat transfer fluids in medium temperature applications including solar collectors and heat exchanger systems.
Nanoparticle science is rapidly changing the landscape of various scientific fields and defining new technological platforms. This is perhaps even more evident in the field of nanomedicine whereby nanoparticles have been used as a tool for the treatment and diagnosis of many diseases. However, despite the tremendous benefit conferred, common pitfalls of this technology is its potential short and long-term effects on the human body. To understand these issues, many scientific studies have been carried out. This review attempts to shed light on some of these studies and its outcomes. The topics that were examined in this review include the different possible uptake pathways of nanoparticles and intracellular trafficking routes. Additionally, the effect of physicochemical properties of nanoparticle such as size, shape, charge and surface chemistry in determining the mechanism of uptake and biological function of nanoparticles are also addressed.
Synthesis of nanocrystalline strontium ferrite (SrFe12O19) via sol-gel is sensitive to its modification parameters. Therefore, in this study, an attempt of regulating the pH as a sol-gel modification parameter during preparation of SrFe12O19 nanoparticles sintered at a low sintering temperature of 900 °C has been presented. The relationship of varying pH (pH 0 to 8) on structural, microstructures, and magnetic behaviors of SrFe12O19 nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning microscope (FESEM), and vibrating sample magnetometer (VSM). Varying the pH of precursor exhibited a strong effect on the sintered density, crystal structure and magnetic properties of the SrFe12O19 nanoparticles. As the pH is 0, the SrFe12O19 produced relatively largest density, saturation magnetization, Ms, and coercivity, Hc, at a low sintering temperature of 900 °C. The grain size of SrFe12O19 is obtained in the range of 73.6 to 133.3 nm. The porosity of the sample affected the density and the magnetic properties of the SrFe12O19 ferrite. It is suggested that the low-temperature sintered SrFe12O19 at pH 0 displayed Ms of 44.19 emu/g and Hc of 6403.6 Oe, possessing a significant potential for applying in low-temperature co-fired ceramic permanent magnet.
In this research, a facile co-precipitation method was used to synthesize pure and Mg-doped ZnO nanoparticles (NPs). The structure, morphology, chemical composition, and optical and antibacterial activity of the synthesized nanoparticles (NPs) were studied with respect to pure and Mg-doped ZnO concentrations (0-7.5 molar (M) %). X-ray diffraction pattern confirmed the presence of crystalline, hexagonal wurtzite phase of ZnO. Scanning electron microscope (SEM) images revealed that pure and Mg-doped ZnO NPs were in the nanoscale regime with hexagonal crystalline morphology around 30-110 nm. Optical characterization of the sample revealed that the band gap energy (Eg) decreased from 3.36 to 3.04 eV with an increase in Mg2+ doping concentration. Optical absorption spectrum of ZnO redshifted as the Mg concentration varied from 2.5 to 7.5 M. Photoluminescence (PL) spectra showed UV emission peak around 400 nm. Enhanced visible emission between 430 and 600 nm with Mg2+ doping indicated the defect density in ZnO by occupying Zn2+ vacancies with Mg2+ ions. Photocatalytic studies revealed that 7.5% Mg-doped ZnO NPs exhibited maximum degradation (78%) for Rhodamine B (RhB) dye under UV-Vis irradiation. Antibacterial studies were conducted using Gram-positive and Gram-negative bacteria. The results demonstrated that doping with Mg ions inside the ZnO matrix had enhanced the antibacterial activity against all types of bacteria and its performance was improved with successive increment in Mg ion concentration inside ZnO NPs.
Passive alkaline-direct ethanol fuel cells (alkaline-DEFCs) appear to be suitable for producing sustainable energy for portable devices. However, ethanol crossover is a major challenge for passive alkaline-DEFC systems. This study investigated the performance of a crosslinked quaternized poly (vinyl alcohol)/graphene oxide (QPVA/GO) composite membrane to reduce ethanol permeability, leading in enhancement of passive alkaline-DEFC performance. The chemical and physical structure, morphology, ethanol uptake and permeability, ion exchange capacity, water uptake, and ionic conductivity of the composite membranes were characterized and measured to evaluate their applicability in fuel cells. The transport properties of the membrane were affected by GO loading, with an optimal loading of 15 wt.% and doped with 1 M of KOH showing the lowest ethanol permeability (1.49 × 10-7 cm2 s-1 and 3.65 × 10-7 cm2 s-1 at 30 °C and 60 °C, respectively) and the highest ionic conductivity (1.74 × 10-2 S cm-1 and 6.24 × 10-2 S cm-1 at 30 °C and 60 °C, respectively). In the passive alkaline-DEFCs, the maximum power density was 9.1 mW cm-2, which is higher than commercial Nafion 117/KOH (7.68 mW cm-2) at 30 °C with a 2 M ethanol + 2 M KOH solution. For the 60 °C, the maximum power density of composite membrane achieved was 11.4 mW cm-2.
ZnO nanorods were synthesized using a low-cost sol-gel spin coating technique. The synthesized nanorods were consisted of hexagonal phase having c-axis orientation. SEM images reflected perpendicular ZnO nanorods forming bridging network in some areas. The impact of different hydrogen concentrations on the Pd-sensitized ZnO nanorods was investigated using an impedance spectroscopy (IS). The grain boundary resistance (Rgb) significantly contributed to the sensing properties of hydrogen gas. The boundary resistance was decreased from 11.95 to 3.765 kΩ when the hydrogen concentration was increased from 40 to 360 ppm. IS gain curve showed a gain of 6.5 for 360 ppm of hydrogen at room temperature. Nyquist plot showed reduction in real part of impedance at low frequencies on exposure to different concentrations of hydrogen. Circuit equivalency was investigated by placing capacitors and resistors to identify the conduction mechanism according to complex impedance Nyquist plot. Variations in nanorod resistance and capacitance in response to the introduction of various concentrations of hydrogen gas were obtained from the alternating current impedance spectra.
This paper presents a functionalized, horizontally oriented carbon nanotube network as a sensing element to enhance the sensitivity of a pressure sensor. The synthesis of horizontally oriented nanotubes from the AuFe catalyst and their deposition onto a mechanically flexible substrate via transfer printing are studied. Nanotube formation on thermally oxidized Si (100) substrates via plasma-enhanced chemical vapor deposition controls the nanotube coverage and orientation on the flexible substrate. These nanotubes can be simply transferred to the flexible substrate without changing their physical structure. When tested under a pressure range of 0 to 50 kPa, the performance of the fabricated pressure sensor reaches as high as approximately 1.68%/kPa, which indicates high sensitivity to a small change of pressure. Such sensitivity may be induced by the slight contact in isolated nanotubes. This nanotube formation, in turn, enhances the modification of the contact and tunneling distance of the nanotubes upon the deformation of the network. Therefore, the horizontally oriented carbon nanotube network has great potential as a sensing element for future transparent sensors.
Hydrothermal zinc oxide (ZnO) thick films were successfully grown on the chemical vapor deposition (CVD)-grown thick ZnO seed layers on a-plane sapphire substrates using the aqueous solution of zinc nitrate dehydrate (Zn(NO3)2). The use of the CVD ZnO seed layers with the flat surfaces seems to be a key technique for obtaining thick films instead of vertically aligned nanostructures as reported in many literatures. All the hydrothermal ZnO layers showed the large grains with hexagonal end facets and were highly oriented towards the c-axis direction. Photoluminescence (PL) spectra of the hydrothermal layers were composed of the ultraviolet (UV) emission (370 to 380 nm) and the visible emission (481 to 491 nm), and the intensity ratio of the former emission (I UV) to the latter emission (I VIS) changed, depending on both the molarity of the solution and temperature. It is surprising that all the Hall mobilities for the hydrothermal ZnO layers were significantly larger than those for their corresponding CVD seed films. It was also found that, for the hydrothermal films grown at 70°C to 90°C, the molarity dependences of I UV/I VIS resembled those of mobilities, implying that the mobility in the film is affected by the structural defects. The highest mobility of 166 cm(2)/Vs was achieved on the hydrothermal film with the carrier concentration of 1.65 × 10(17) cm(-3) grown from the aqueous solution of 40 mM at 70°C.