The binding of imidazolium salts to cucurbit[8]uril, CB[8], triggers a stepwise self-assembly process with semiflexible polymer chains and crystalline nanostructures as early- and late-stage species, respectively. In such a process, which involves the crystallization of the host-guest complexes, the guest plays a critical role in directing self-assembly toward desirable morphologies. These include platelet-like aggregates and two-dimensional (2D) fibers, which, moreover, exhibit viscoelastic and lyotropic properties. Our observations provide a deeper understanding of the self-assembly of CB[8] complexes, with fundamental implications in the design of functional 2D systems and crystalline materials.
The development of easy to use, rapid and sensitive methods for direct detection of foodborne bacterial pathogens has become significantly important due to their impact on human health. In recent years, carbon nanomaterials have been adapted in the fabrication of electrochemical biosensors due to their exceptional combination of intrinsic properties such as high conductivity, stability and biocompatibility that render them as a promising candidate for bio-sensing material. The scope of this review is to provide a brief history of the current methods and different types of electrochemical biosensors used for the detection of bacterial pathogens. We primarily focus on the recent progress and applications of graphene, carbon nanotubes and their derivatives in electrochemical biosensors for foodborne bacterial pathogens detection. Finally, the status and future prospects of carbon-based electrochemical biosensors are also reviewed and discussed.
This paper focuses on the synthesis and mechanism of carbon nanospheres (CNS) coated with few- and multi-layered graphene (FLG, MLG). The graphitic carbon encapsulates the core/shell structure of the Ni/NiO nanoparticles via the chemical vapor deposition (CVD) method. The application of the resulting CNS and hybrids of CNS-FLG and CNS-MLG as reinforcement nanofillers in a polypropylene (PP) matrix were studied from the aspects of mechanical and thermal characteristics. In this research, to synthesize carbon nanostructures, nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and acetylene (C₂H₂) were used as the catalyst source and carbon source, respectively. Besides, the morphology, structure and graphitization of the resulting carbon nanostructures were investigated. On the other hand, the mechanisms of CNS growth and the synthesis of graphene sheets on the CNS surface were studied. Finally, the mechanical and thermal properties of the CNS/PP, CNS-FLG/PP, and CNS-MLG/PP composites were analyzed by applying tensile test and thermogravimetric analysis (TGA), respectively.
Biosensors operating based on electrical methods are being accelerated toward rapid and efficient detection that improve the performance of the device. Continuous study in nano- and material-sciences has led to the inflection with properties of nanomaterials that fit the trend parallel to the biosensor evolution. Advancements in technology that focuses on nano-hybrid are being used to develop biosensors with better detection strategies. In this sense, titanium dioxide (TiO2) nanomaterials have attracted extensive interest in the construction of electrical biosensors. The formation of TiO2 nano-hybrid as an electrical transducing material has revealed good results with high performance. The modification of the sensing portion with a combination (nano-hybrid form) of nanomaterials has produced excellent sensors in terms of stability, reproducibility, and enhanced sensitivity. This review highlights recent research advancements with functional TiO2 nano-hybrid materials, and their victorious story in the construction of electrical biosensors are discussed. Future research directions with commercialization of these devices and their extensive utilizations are also discussed.
Porous ZnO nanostructures have become the subject of research interest--due to their special structures with high surface to volume ratio that may produce peculiar properties for use in optoelectronics, sensing and catalysis applications. A microwave-assisted hydrothermal method has been used for effecting the formation of porous nanostructure of metaloxide materials, such as CoO and SnO2, in solution. Here, by adopting the unique performance of a microwave-assisted-hydrothermal method, we realized the formation of highly porous ZnO nanostructures directly on the substrate surface, instead of in solution. The effects of the ambient reaction conditions and the microwave power on the structural growth of the ZnO nanostructures were studied in detail. Two different ambient reaction conditions, namely refluxed and isolated in autoclave systems, were used in this work. Porous ZnO (PZO) nanostructures with networked-nanoflakes morphology is the typical result for this approach. It was found that the morphology of the ZnO nanostructures was strongly depended on the ambient conditions of the reaction; the isolated-autoclave system may produce reasonably high porous ZnO that is constituted by vertically oriented grainy-flakes structures, whereas the refluxed system produced solid vertically-oriented flake structures. The microwave power did not influence the structural growth of the ZnO. It was also found that both the ambient reaction conditions and the microwave power used influenced the crystallographic orientation of the PZO. For instance, PZO with dominant (002) Bragg plane could be obtained by using refluxed system, whereas PZO with dominant (101) plane could be realized if using isolated system. For the case of microwave power, the crystallographic orientation of PZO prepared using both systems changed from dominant (002) to (101) planes if the power was increased. The mechanism for the formation of porous ZnO nanostructures using the present approach is proposed. The ZnO nanostructures prepared using the present method should find an extensive use in currently existing application due to its property of reasonably high porosity.
Since the discovery of carbon nanotubes (CNTs) in 1991, a fundamental question still remained on how to control morphologically the synthesis of CNTs. This task has always been a challenge. In this paper, we report the results that we have published previously with the aim of sharing the possible controlled synthesis approach via this novel production method. Findings demonstrated that various CNTs could be synthesized by using specially developed supported catalysts from the catalytic decomposition of methane. These synthesized CNTs include carbon nanofibres, single-walled and multi-walled CNTs, Y-junction CNTs and CNTs with special morphologies. It was also revealed that catalyst composition and reaction parameters played an important role in controlling the morphology and type of CNTs formed. The synthesis of CNTs with various morphologies is important because this can enrich the nanostructures of the carbon family. This finding also provides useful data for better understanding of the parameters that govern the growth mechanism of CNTs which may be required in the near future for enhanced controlled synthesis of CNTs.
This paper presents a straightforward plasma treatment modification of graphene with an enhanced piezoresistive effect for the realization of a high-performance pressure sensor. The changes in the graphene in terms of its morphology, structure, chemical composition, and electrical properties after the NH3/Ar plasma treatment were investigated in detail. Through a sufficient plasma treatment condition, our studies demonstrated that plasma-treated graphene sheet exhibits a significant increase in sensitivity by one order of magnitude compared to that of the unmodified graphene sheet. The plasma-doping introduced nitrogen (N) atoms inside the graphene structure and was found to play a significant role in enhancing the pressure sensing performance due to the tunneling behavior from the localized defects. The high sensitivity and good robustness demonstrated by the plasma-treated graphene sensor suggest a promising route for simple, low-cost, and ultrahigh resolution flexible sensors.
Silicon nanomaterial was prepared using the peroxide/acid/salt technique in which an aqueous silicon-based salt solution was added to H2O2/HF etchants. In order to optimize the experimental conditions for silicon nanomaterial production, the amount of nanomaterial produced was studied as a function of the volume of the silicon salt solution used in the synthesis. A set of samples was prepared using: 0, 5, 10, 15, and 20 mL of an aqueous 1 mg/L metasilicate solution. The area under the corresponding peaks in the infrared (ir) absorption spectra was used as a qualitative indicator to the amount of the nanomaterial present. The results indicated that using 10 mL of the metasilicate solution produced the highest amount of nanomaterial. Furthermore, the results demonstrated that the peroxide/acid/salt technique results in the enhancement of the production yield of silicon nanomaterial at a reduced power demand and with a higher material to void ratio. A model in which the silicon salt forms a secondary source of silicon nanomaterial is proposed. The auxiliary nanomaterial is deposited into the porous network causing an increase in the amount of nanomaterial produced and a reduction in the voids present. Thus a reduction in the resistance of the porous layer, and consequently reduction in the power required, are expected.
Poly-vinyl-pyrrolidone (PVP)/polyaniline based surface acoustic wave (SAW) sensors were fabricated and characterized and their performances towards hydrogen gas were investigated. The PVP/polyaniline fibers composite were prepared by electrospinning of the composite aqueous solution deposited directly onto the active area of SAW transducers. Via scanning electron microscopy (SEM), the morphology of the deposited nanostructure material was observed. From the dynamic response, frequency shifts of 6.243 kHz (1% H2) and 8.051 kHz (1% H2) were recorded for the sensors deposited with PVP/ES and PVP/EB, respectively.
Quantum dots being an interesting class of nanostructures are considered potential prototype systems for novel nano-devices such as single electron transistor (sET). Here in this research, we present an analysis of the electron trajectory in the vicinity of gallium arsenide (GaAs) quantum dot. To perform this study, DFT based methodology is employed to optimize structure of quantum dot and determining the electrostatic potential around the dot. Under the influence of obtained electrostatic potential, trajectory of the moving electron towards the dot is investigated. The results showed that GaAs quantum dot have negative and positive potential surfaces that influence the electron interaction with the dot. These results motivate the development of SET electrode channel where the electron moves towards the dot on the surface with positive potential rather than negative potential surface.
Nanomaterial-based sensors with high sensitivity, fast response and recovery time, large detection range, and high chemical stability are in immense demand for the detection of hazardous gas molecules. Graphene nanoribbons (GNRs) which have exceptional electrical, physical, and chemical properties can fulfil all of these requirements. The detection of gas molecules using gas sensors, particularly in medical diagnostics and safety applications, is receiving particularly high demand. GNRs exhibit remarkable changes in their electrical characteristics when exposed to different gases through molecular adsorption. In this paper, the adsorption effects of the target gas molecules (CO and NO) on the electrical properties of the armchair graphene nanoribbon (AGNR)-based sensor are analytically modelled. Thus, the energy dispersion relation of AGNR is developed considering the molecular adsorption effect using a tight binding (TB) method. The carrier velocity is calculated based on the density of states (DOS) and carrier concentration (n) to obtain I-V characteristics and to monitor its variation in the presence of the gas molecules. Furthermore, the I-V characteristics and energy band structure of the AGNR sensor are simulated using first principle calculations to investigate the gas adsorption effects on these properties. To ensure the accuracy of the proposed model, the I-V characteristics of the AGNR sensor that are simulated based both on the proposed model and first principles calculations are compared, and an acceptable agreement is achieved.
Photocatalytic CO2 reduction is a revolutionary approach to solve imminent energy and environmental issues by replicating the ingenuity of nature. The past decade has witnessed an impetus in the rise of two-dimensional (2D) structure materials as advanced nanomaterials to boost photocatalytic activities. In particular, the use of 2D carbon-based materials is deemed as highly favorable, not only as a green material choice, but also due to their exceptional physicochemical and electrical properties. This Review article presents a diverse range of alterations and compositions derived from 2D carbon-based nanomaterials, mainly graphene and graphitic carbon nitride (g-C3 N4 ), which have remarkably ameliorated the photocatalytic CO2 performance. Herein, the rational design of the photocatalyst systems with consideration of the aspect of dimensionality and the resultant heterostructures at the interface are systematically analyzed to elucidate an insightful perspective on this pacey subject. Finally, a conclusion and outlook on the limitations and prospects of the cutting-edge research field are highlighted.
Dendrimers are novel nanoarchitectures with unique properties including a globular 3D shape, a monodispersed unimicellar nature and a nanometric size range. The availability of multiple peripheral functional groups and tunable surface engineering enable the facile modification of the dendrimer surface with different therapeutic drugs, diagnostic agents and targeting ligands. Drug encapsulation, and solubilizing and passive targeting also equally contribute to the therapeutic use of dendrimers. In this review, we highlight recent advances in the delivery of anticancer drugs using dendrimers, as well as other biomedical and diagnostic applications. Taken together, the immense potential and utility of dendrimers are envisaged to have a significant positive impact on the growing arena of drug delivery and targeting.
The present study examines the synthesis of Co3O4 ultra-nanosheets (Co3O4 UNSs) and Co3O4 ultra-nanosheet-Ni(OH)2 (Co3O4 UNS-Ni(OH)2) via solvothermal process and their application as non-enzymatic electrochemical sensors for glucose detection. X-ray diffraction and transmission electron microscopy results confirmed the Co3O4 UNS deposition on Ni(OH)2 surface. The presence of Co3O4 UNSs on Ni (OH) 2 surface improved the sensitivity of glucose detection, from the increase of glucose oxidation peak current at the Co3O4 UNS-Ni(OH)2/glassy carbon electrode (current density: 2000μA·cm(-2)), compared to the Co3O4 UNSs. These results confirmed that Ni(OH)2 on glassy carbon electrode is a sensitive material for glucose detection, moreover the Co3O4 UNSs can increase the interaction and detection of glucose due to their high surface area. The estimated limit of detection (S/N=3) and limit of quantification (S/N=10) of the linear segment (5-40μM) are 1.08μM and 3.60μM respectively. The reproducibility experiments confirmed the feasibility of Co3O4 UNS-Ni(OH)2 for the quantitative detection of certain concentration ranges of glucose.
In this letter, we investigate the fabrication of Silicon nanostructure patterned on lightly doped (10(15) cm(-3)) p-type silicon-on-insulator by atomic force microscope nanolithography technique. The local anodic oxidation followed by two wet etching steps, potassium hydroxide etching for silicon removal and hydrofluoric etching for oxide removal, are implemented to reach the structures. The impact of contributing parameters in oxidation such as tip materials, applying voltage on the tip, relative humidity and exposure time are studied. The effect of the etchant concentration (10% to 30% wt) of potassium hydroxide and its mixture with isopropyl alcohol (10%vol. IPA ) at different temperatures on silicon surface are expressed. For different KOH concentrations, the effect of etching with the IPA admixture and the effect of the immersing time in the etching process on the structure are investigated. The etching processes are accurately optimized by 30%wt. KOH +10%vol. IPA in appropriate time, temperature, and humidity.
A novel samarium-doped spherical-like ZnO hierarchical nanostructure (Sm/ZnO) was synthesized via a facile and surfactant-free chemical solution route. The as-synthesized products were characterized by X-ray diffraction, Brunauer-Emmett-Teller surface area analysis, field emission scanning electron microscopy together with an energy dispersion X-ray spectrum analysis, transmission electron microscopy, UV-visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The results revealed that Sm ion was successfully doped into ZnO. It was also observed that the Sm doping increased the visible light absorption ability of Sm/ZnO and a red shift for Sm/ZnO appeared when compared to pure ZnO. The photocatalytic studies revealed that the Sm/ZnO exhibited excellent photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) compared with the pure ZnO and commercial TiO2 under visible light irradiation. The photocatalytic enhancement of Sm/ZnO products was attributed to their high charge separation efficiency and ·OH generation ability as evidenced by the photoluminescence spectra. The photocatalytic investigation also showed that various parameters exerted their individual influence on the degradation rate of 2,4-DCP. By using a certain of radical scavengers, ·OH was determined to play a pivotal role for the 2,4-DCP degradation. Moreover, the Sm/ZnO could be easily separated and reused, indicating great potential for practical applications in environmental cleanup.
In the present investigation, the operating efficiency of a bench-top air-driven microfluidizer has been compared to that of a bench-top high power ultrasound horn in the production of pharmaceutical grade nanoemulsions using aspirin as a model drug. The influence of important process variables as well as the pre-homogenization and drug loading on the resultant mean droplet diameter and size distribution of emulsion droplets was studied in an oil-in-water nanoemulsion incorporated with a model drug aspirin. Results obtained show that both the emulsification methods were capable of producing very fine nanoemulsions containing aspirin with the minimum droplet size ranging from 150 to 170 nm. In case of using the microfluidizer, it has been observed that the size of the emulsion droplets obtained was almost independent of the applied microfluidization pressure (200-600 bar) and the number of passes (up to 10 passes) while the pre-homogenization and drug loading had a marginal effect in increasing the droplet size. Whereas, in the case of ultrasound emulsification, the droplet size was generally decreased with an increase in sonication amplitude (50-70%) and period of sonication but the resultant emulsion was found to be dependent on the pre-homogenization and drug loading. The STEM microscopic observations illustrated that the optimized formulations obtained using ultrasound cavitation technique are comparable to microfluidized emulsions. These comparative results demonstrated that ultrasound cavitation is a relatively energy-efficient yet promising method of pharmaceutical nanoemulsions as compared to microfluidizer although the means used to generate the nanoemulsions are different.
Herbicides, namely 4-(2,4-dichlorophenoxy) butyrate (DPBA) and 2-(3-chlorophenoxy) propionate (CPPA), were intercalated simultaneously into the interlayers of zinc layered hydroxide (ZLH) by direct reaction of zinc oxide with both anions under aqueous environment to form a new nanohybrid containing both herbicides labeled as ZCDX. Successful intercalation of both anions simultaneously into the interlayer gallery space of ZLH was studied by PXRD, with basal spacing of 28.7 Å and supported by FTIR, TGA/DTG and UV-visible studies. Simultaneous release of both CPPA and DPBA anions into the release media was found to be governed by a pseudo second-order equation. The loading and percentage release of the DPBA is higher than the CPPA anion, which indicates that the DPBA anion was preferentially intercalated into and released from the ZLH interlayer galleries. This work shows that layered single metal hydroxide, particularly ZLH, is a suitable host for the controlled release formulation of two herbicides simultaneously.
Hydroxyapatite powder was mechanochemically synthesized from calcium pyrophosphate (Ca2P2O7) and calcium carbonate (CaCO3) using a solid-state reaction. The two powders were mixed in distilled water, milled for 8 hours, dried and calcined at 1100 degrees C for 1 hour. The phase(s) formed was analyzed by x-ray diffraction (XRD). It was found that hydroxyapatite was not the only one formed. This result will be used as the starting point to produce a single-phase hydroxyapatite in terms of excess hydroxyl group in a mechanochemical reaction.
Hybrid gold nanostructures seeded into nanotextured zinc oxide (ZnO) nanoflowers (NFs) were created for novel biosensing applications. The selected 'spotted NFs' had a 30-nm-thick gold nanoparticle (AuNP) layer, chosen from a range of AuNP thicknesses, sputtered onto the surface. The generated nanohybrids, characterized by morphological, physical and structural analyses, were uniformly AuNP-seeded onto the ZnO NFs with an average length of 2-3 μm. Selective capture of molecular probes onto the seeded AuNPs was evidence for the specific interaction with DNA from pathogenic Leptospirosis-causing strains via hybridization and mis-match analyses. The attained detection limit was 100 fM as determined via impedance spectroscopy. High levels of stability, reproducibility and regeneration of the sensor were obtained. Selective DNA immobilization and hybridization were confirmed by nitrogen and phosphorus peaks in an X-ray photoelectron spectroscopy analysis. The created nanostructure hybrids illuminate the mechanism of generating multiple-target, high-performance detection on a single NF platform, which opens a new avenue for array-based medical diagnostics.