One-dimensional Nanostructured Materials Research Articles

MODELING OF THE GEOMETRY AND ELECTRONIC BANDGAP STRUCTURE OF CHIRAL SINGLE WALLED CARBON NANOTUBES

Carbon Nanotubes (CNTs) are one-dimensional nanostructured materials that will play a key role in future electronics. All properties of the carbon nanotubes are determined by its electronic structure. The main focus of this study has been to investigate the basic electronic bandgap structure of the chiral single walled carbon nanotubes (SWCNTs). A simple algorithm is presented in order to model the geometry of the chiral single-walled CNTs with any desired structure. The electronic bandgap structure of the chiral single-walled carbon nanotubes has been studied by employing an extended tight binding model (TBM). The changes in the energy band gap due to the chirality effect in case of metallic (6, 3) SWCNT and in the semiconducting (12, 7) SWCNT are discussed here. The value of the SWCNTs diameter is calculated also. The computed results indicates that the bandgap depends inversely on the diameter of the tube. The present results were found to be in consistent with those reported in the literature and indicated the correctness of the process of simulation technique process.

SiNPLs/CoPc hybrid heterostructures based photodetector with low dark current and enhanced sensitivity

Fabrication of hybrid heterostructures, consisting of two different nanostructured materials are an efficient approach for further improving photodetecting performance over their individual counterparts. In this paper, we demonstrate the fabrication of an inorganic-organic hybrid heterostructure comprising of Si-nanopillars (SiNPLs) and cobalt phthalocyanine (CoPc). Photodetecting performance of SiNPLs/CoPc heterostructure is investigated in photoconductive mode. It exhibits a low dark current of 2.05×10−8 A and enhanced sensitivity (∼4.5 times) in contrast to pristine SiNPLs. Suppression of dark current with enhanced sensitivity is ascribed to the transfer of electrons from SiNPLs to CoPc layer and their trapping in disorder states present in CoPc layer. The process of electron transfer is confirmed by work function measurements. These results indicate that by employing heterostructure method, the trap states originating from the non-uniform molecular packing of organic semiconductors may be used to further improve the photodetecting performance of one-dimensional nanostructured materials. Additionally, the long-term stability of the SiNPLs/CoPc heterostructure was evaluated by exposing it to ambient conditions for 20 days.

One-dimensional nanostructured electrode materials based on electrospinning technology for supercapacitors

Supercapacitors are outstanding electrochemical energy storage devices with high power density, quick charge and discharge and long cycle life. A well-designed structure can significantly increase its electrochemical performance as electrode materials. Carbon nanofibers (CNFs) made by electrospinning technique feature a one-dimensional nanostructure, which can provide directional electron transfer pathways and reduce the internal resistance of materials. This article reviewed the design approaches for one-dimensional nanostructured electrode materials produced from CNFs for supercapacitors, focusing on porous structure design, hollow structure design, surface functional group structure design and core-shell structure design. The porous and hollow structural designs could improve the contact area between electrode and electrolyte, allowing for faster electron/ion transport. Surface functional group structure design had the potential to improve the surface chemical properties of electrode materials, therefore enhancing their capacitance characteristics. The core-shell structure design might result in layered channels, and the diverse components of the core and shell could work together to increase the conductivity and structural stability of electrode materials. The preparation methods and structural properties of these CNF electrode materials with different structural designs were highlighted, as well as their future development.

Integrating Highly Luminescent Lanthanides with Strongly Coupled Dye J-Aggregates on Nanotubes for Efficient Cascade Energy Transfer

Photoluminescent one-dimensional hybrid nanostructured materials having outstanding inorganic–organic advantages are gaining significant attention on account of their intriguing applications in nanoscale optoelectronic devices, (bio)sensors, and energy harvesting and conversion technologies. Here, we first report on the development of highly photoluminescent lanthanide organic hybrid nanotubular assemblies through in situ incorporation of a trivalent lanthanide ion, terbium (Tb3+), along with organic photosensitizers 2,3-dihydroxynaphthalene (DHN) or 1,10-phenanthroline (Phen) into the self-assembled nanotubes of sodium lithocholate (NaLC). Both the photosensitizers (DHN/Phen) are effective in sensitizing intense narrow emission peaks of Tb3+ on the nanotubes. Next, we utilize these luminescent lanthanides containing hybrid nanotubular assemblies as templates for spontaneous integration of strongly coupled pseudoisocyanine (PIC) dye J-aggregates with a sharp J-band absorption at 555 nm and strong fluorescence emission at 570 nm. The presence of the significant spectral overlap between the luminescence peak of Tb3+ at 545 nm and the J-aggregate absorption band results in efficient cascade energy transfer from photosensitizers to Tb3+ to the coherently coupled PIC dye J-aggregates. These NaLC nanotube-templated photosensitizer-Tb3+-J-aggregate hybrid systems have great potential for sensing and optoelectronic applications.

Hydrogen free direct growth carbon nanorod as a promising electrode in symmetric supercapacitor applications

Carbon nanorods (CNRs) are significant one-dimensional carbon-based nanostructured materials. A new method to prepare direct growth fast-standing carbon nanorod as a promising electrode in symmetric supercapacitor applications has been explored. In this study, the CNRs are directly grown on SS plate in the three-zone horizontal chemical vapor deposition unit. The hydrogen free environment is used to grow the CNRs. The substrate position was studied by controlling the substrate temperature, time and precursor gas flow rate. Raman, Fourier transform infrared spectra (FTIR), high-resolution transmission electron microscopy (HR-TEM) explored CNRs formation. The CNRs are well assembled in the substrate and showed excellent electrical contact with it. The biological SP-150 instrument measured electrochemical activity of CNR-developed electrodes. The symmetric device was fabricated with two same electrodes and the device energy and power density was studied. Symmetric supercapacitor devices expressed 22 W h/kg energy density at low 1 A/g. The 96.65% capacity is maintained for 10,000 charge discharge cycles in symmetrical supercapacitor device.

Fast growth of highly ordered porous alumina films based on closed bipolar electrochemistry

Highly ordered porous anodic alumina (PAA) is widely used as a template for preparing one-dimensional nanostructured materials. At present, research efforts to prepare PAA templates with straight channels mainly focus on improving their regularity or increasing the efficiency of the preparation methods. Herein, we introduce a novel anodization method to fabricate highly ordered PAA films based on closed bipolar electrochemistry. To the best of our knowledge, there have been no reports of the use of closed bipolar electrochemistry in PAA film fabrication. Compared to traditional anodization, a faster PAA film growth rate of 1.67 μm min−1 was obtained in 0.75 M oxalic acid when a voltage of 62 V was applied to the driving electrodes. Furthermore, different electrolyte solutions can be employed in the anodic and cathodic cells in the closed bipolar electrochemical system. In addition, no direct electrical connection to the aluminum sheets is required in this approach.

Electrospun CoSe@N-doped carbon nanofibers with highly capacitive Li storage

Abstract One-dimensional nano-structured materials have attracted attention due to its unique properties afforded such as the across-linked structures and large aspect ratios. In this work, one-dimensional CoSe@N-doped carbon nanofibers (CoSe@NC NFs) are successfully by combining the techniques of electrospinning and annealing. Selenium powder are directly dispersed in the polyacrylonitrile /N,N-Dimethylformamide (DMF) solution containing cobalt salt to form the product. The performance of these materials was investigated in Li-ion batteries after the annealing at different temperatures. The CoSe@NC nanofibers annealed at 550 °C (CoSe@NC-550) and displayed excellent storage properties, affording a high capacity of 796 mAh·g−1 at a current density of 1 A·g−1 for 100 cycles. Moreover, it is confirmed that the pseudocapacitive contribution of CoSe@NC-550 is up to 72.8% at the scan rate of 1 mV/s through the cyclic voltammetry analysis.

Solution Processable Carbon Nanotube Biosensors with Multisensing Capability

The rapid development of nano-biosensors, combining nanomaterials (as detectors) and biological components (as receptors), offers great opportunities for enhancing the efficiency of biomarkers’ detection. Establishing a practical platform with low cost processability and multi-sensing capability is of significance to both fundamental biology and practical diagnosis. Devices consisting of one-dimensional nanostructured materials and bioreceptors, in particular single walled carbon nanotubes (SWCNTs) and aptamers, have been used to fabricate nanoscale biosensors. CNTs have been considered as one of the best nanomaterials for the fabrication of nanoscale biosensors, because of their intrinsic nanoscale size and their low charge carrier density. Additionally, due to their high affinity and specificity to biotargets, aptamers can improve the selectivity of biosensing devices. In this regard, efforts have been dedicated to fabricate CNT-aptamer based biosensors. However, it is still challenging to fabricate CNT-aptamer biosensing devices possessing both low cost processability (i.e. ideally from solution) and multi-sensing capability. Herein, we report a solution processable strategy for the fabrication of ultra-sensitive, selective and reconfigurable nanoscale biosensors, based on SWCNTs and aptamers (Figure 1). Briefly, SWCNTs wrapped with DNA (therefore water-soluble) were functionalized with aptamers in solution, which were then used as selective bioreceptors for particular analytes of interest. Atomic Force Microscopy (AFM) images demonstrated the successful formation of SWCNT-aptamer hybrids; these SWCNT-aptamer hybrids were then immobilized in a device configuration between electrodes via dielectrophoresis (DEP). We initially verified whether the nucleotide recognition element within the SWCNT-aptamer hybrids was accessible, by exposing these devices to the aptamers’ complementary strands. The change in source-drain current indicated the successful hybridization between the aptamers in the devices and the complementary strands. This specific hybridization was further confirmed by a control experiment employing a non-complementary ss-DNA. Moreover, the denaturation of the hybridized DNA induced by a simple cleaning procedure, demonstrated the re-configurability of our devices. We finally investigated the electrical response of our devices for the detection of biomarkers indicative to stress and neuro-trauma conditions. Our results showed that these devices are able to detect concentrations of relevant analytes from pM to µM, with high selectivity and reversibility. We extended this idea towards the fabrication of a multi-sensing platform, by immobilizing on the same chip different SWCNT-aptamer hybrids selective to distinct biomarkers. Notably, we obtained evidence of selective recognition without any crosstalk nor false-positive signals; detection in serum and real time measurement further demonstrated the potential of our multi-sensing nanoscale devices. In conclusion, we present an environmentally friendly and low-cost strategy for the fabrication of label-free biosensing devices that allow for the real time and reversible electrical detection of biomolecules. Because we assembled SWCNT-aptamer hybrids with distinct bio-recognition elements on the same chip, the devices exhibit multi-sensing capability in addition to high sensitivity and selectivity. The general applicability of this solution-processable method makes it suitable for different practical applications, including for point of care clinical diagnosis. Figure 1

Insights into the multistep transformation of titanate nanotubes into nanowires and nanoribbons

Abstract Different types of titanate one-dimensional nanostructured materials were synthesized and characterized using scanning and transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The results presented in this work unquestionably showed dependence of morphology and structure of the titanate nanopowders on parameters of hydrothermal synthesis. It was found that nanotubes, nanowires and nanoribbons are three unavoidable kinetic products of hydrothermal reaction. Moreover, increasing temperature of reaction or hydrothermal treatment duration results in acceleration of nanotube-nanowire-nanoribbon transformation. However, the sequence of titanate morphology transformation is invariable. The detailed studies further revealed that the crystal structure of hydrothermally prepared nanotubes and nanowires are indistinguishable but the determination of the exact structure is practically impossible. Because of higher crystallinity, the structure of nanoribbons can be established. It was shown that it corresponds to the monoclinic layered trititanic acid H2Ti3O7 and is isostructural with sodium derivatives Na2_xHxTi3O7.nH20 (with x near 2).

Comparison between inorganic geomimetic chrysotile and multiwalled carbon nanotubes in the preparation of one-dimensional conducting polymer nanocomposites

The aim of this study was to examine the role of the nanofillers spatial arrangement in the electrical properties of hybrid organic-inorganic fibers. In this paper, we have presented experimental results for preparation of fibers with a nanometric diameter based on a polyaniline/poly(ethylene oxide) doped blend and geomimetic chrysotile nanotubes. The nanostructured material was prepared using electrospinning techniques. Electrospun fibers made by pristine polymers and by the same blend loaded with carbon nanotubes were used as reference materials to compare the structural, and electrical properties of the novel organic-inorganic material. Generally, electrical properties were improved by the addition of materials that have high conductivity. Electrospun fibers filled with a traditional insulator like chrysotile have shown higher electrical conductivity than the pristine materials. In order to fully understand how structural variations impact upon the electrical conductivity the materials were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), differential scanning calorimetry (DSC) and four-point probe method. The results suggest that the occurred electrical conductivity gain could be attributed to parallel orientation of the chrysotile nanotubes and higher crystallinity induced by the one-dimensional nanostructured filler materials. The obtained results bring us one step closer to using intrinsically conducting polymers (ICPs) in the creation of functionalized polymeric nanocomposites for nanotechnology.

Review of one-dimensional and two-dimensional nanostructured materials for hydrogen generation.

Hydrogen is an attractive alternative to fossil fuels in terms of environmental and other advantages. Of the various production methods for H2, photocatalysis requires further development so that it can be applied economically on an industrial scale. One- and two-dimensional nanostructures in both pristine and modified forms have shown great potential as catalysts in the generation of H2. We review here recent developments in these nanostructure catalysts and their efficiency in the generation of H2 under UV/visible/simulated solar light. Despite much research effort, many photocatalysts do not yet meet the practical requirements for the generation of H2, such as visible light activity. H2 production is dependent on a variety of parameters and factors. To meet future energy demands, several challenges in H2 production still need to be solved. We address here the factors that influence the efficiency of H2 production and suggest alternatives. The nanostructures are classified based on their morphology and their efficiency is considered with respect to the influencing parameters. We suggest effective ways of engineering catalyst combinations to overcome the current performance barriers.

One-dimensional nanostructures for flexible supercapacitors

We review the recent research progress in one-dimensional nanostructured materials for different structured flexible supercapacitors.

High-performance epoxy/silica coated silver nanowire composites as underfill material for electronic packaging

Abstract Silver nanowires (AgNWs), as one-dimensional nanostructured materials, possess high aspect ratio and intrinsically high thermal conductivity. However, AgNWs are difficult to disperse homogeneously in epoxy resin, and their high electrical conductivity also limits their applications for electronic packaging. Herein, silica-coated silver nanowires (AgNWs@SiO2) were synthesized by a flexible sol–gel method and then incorporated into epoxy. The less stiff silica intermediate nanolayer on AgNWs not only alleviated the mismatch between AgNWs and epoxy, but also enhanced their interfacial interaction. Hence, the thermal conductivity of an epoxy/AgNWs@SiO2 composite with 4 vol.% filler loading was increased to 1.03 W/mK from 0.19 W/mK of neat epoxy compared to 0.57 W/mK of an epoxy/AgNWs composite with identical nanowire loading. Simultaneously, the insulating silica nanolayer effectively avoided formation of an electrically conductive network of AgNWs in epoxy, leading to high electrical insulation of the composite. AgNWs@SiO2 nanowires with core–shell structure also improved the dielectric properties of epoxy. In addition, these composites possessed a viscosity suitable for the underfill process in electronic packaging.

Nanocrystalline Oxides: CdS nanowires synthesized by solvothermal method

Recent advances in the field of nanotechnology produced an assortment of one-dimensional (1D) structures, such as nanowires and nanorods. These fascinating materials are the potential building blocks for a wide range of nanoscale electronics, optoelectronics, magnetoelectronics, or sensing devices [1]. Parallel to the success with group IV and groups III–V compounds semiconductor nanostructures, semiconducting metal oxide materials with wide band gaps are attracting attention [2-3]. The main aim of this communication is to report our results on the application of several new techniques, particularly the use of hydrothermal synthesis, to fabricate single crystal one-dimensional nanostructured materials, study their growth processes, understand the growth mechanisms and investigate their physical properties. A wide range of remarkable features are then presented, to cover a number of metal oxides, such as ZnO, Sb2O3, CdS, MgO, α-Fe2O3, or TiO2, describing their structures, optical, magnetic, mechanical and chemical sensing properties. These studies constitute the basis for developing versatile applications based on metal oxide 1D systems as well as highlighting the current progress in device development. To exemplify, the as-prepared CdS nanowires have average 28 nm in diameter and length up to several micrometres. The direct band gap of the CdS nanowires is 2.56 eV calculated by the UV-vis absorption spectra. The PL spectrum has two distinct emission bands at 502 nm and 695 nm, which are associated with the near-band-edge emission and defect emission, respectively. These synthesized single-crystal CdS nanowires have a high potential in the optoelectronic applications of nanolasers, solar cells, lighting-emitting diodes or photodetectors. Acknowledgments: Erasmus Mundus MEDASTAR (Mediterranean Area for Science, Technology and Research) Programme, 2011–4051/002–001-EMA2, Spanish MINECO (MAT2010-15094, Factoría de Cristalización – Consolider Ingenio 2010) and ERDF.

Synthesis of one-dimensional nanostructured anode materials with high-yield, low-cost and their application in lithium ion batteries

The electrochemical performances of lithium-ion batteries are highly dependent on their electrode materials. The currently used graphite anode is limited by the low theoretical capacity and cant meet the demand of the next generation lithium-ion batteries with higher energy and power density. Although great progress has been achieved with the development of new anode materials instead of graphite, it is still far from realizing commerce success. One of the most important points is the large-scale production of the new anode materials with high-yield and low-cost. This short article reviews the recent progress in large scale synthesis of one dimensional nanostructured anode materials in our research group, including one dimensional porous α-Fe2O3, Co3O4, anhydrous oxalates and zinc ferrite.

Synthesis and influence of alkaline concentration on α-FeOOH nanorods shapes

α-FeOOH nanorods having uniform morphology were synthesized by water bath process. X-ray diffraction and transmission electron microscopy revealed that the single-crystalline orthorhombic α-FeOOH nanorods are about 10 nm in diameter and hundreds of nanometer in length. The effect of concentration of KOH on morphology of α-FeOOH nanorods was investigated. pH values of solution play an important role in the process of transformation of ferrihydrite into goethite. The inconsistent growth rate along different facets can be effected by pH values of the solution. The influence and growth mechanism of α-FeOOH nanorods were discussed in detail. This method may be widely used as reference to fabricate other inorganic one-dimensional nanostructured materials and easily realized in industrial-scale synthesis.

The effects of physicochemical parameters on the synthesis of silver nanowires via polyol method

The potential applications of one-dimensional nanostructured materials widely depend on their shape and size. This paper deals with a method for synthesizing and characterizing silver nanowires through an organic solution. The so-called polyol method was used to synthesize silver nanowires in which ethylene glycol was used as both media and the reducing agent. Adequate CuCl2/ethylene glycol solution is used to prohibit chemical etching by the oxygen on nanowires surfaces. The effects of CuCl2 concentration and the addition rate of AgNO3 were examined. It was revealed that by optimizing the parameters, silver nanowires with aspect ratios of up to 32 are accessible. To characterize the structure and morphology of nanowires, X-ray powder diffraction, UV–Vis spectroscopy, scanning electron microscopy and atomic force microscopy were used.

Exceptional performance of TiNb₂O₇ anode in all one-dimensional architecture by electrospinning.

We report the extraordinary performance of an Li-ion battery (full-cell) constructed from one-dimensional nanostructured materials, i.e. nanofibers as cathode, anode, and separator-cum-electrolyte, by scalable electrospinning. Before constructing such a one-dimensional Li-ion battery, electrospun materials are individually characterized to ensure its performance and balancing the mass loading as well. The insertion type anode TiNb2O7 exhibits the reversible capacity of ∼271 mAh g(-1) at current density of 150 mA g(-1) with capacity retention of ∼82% after 100 cycles. Under the same current density, electrospun LiMn2O4 cathode delivered the discharge capacity of ∼118 mAh g(-1). Gelled electrospun polyvinylidene fluoride-co-hexafluoropropylene (PVdF-HFP) nanofibers membrane is used as the separator-cum-electrolyte in both half-cell and full-cell assembly which exhibit the liquid like conductivity of ∼2.9 mS cm(-1) at ambient conditions. Full-cell, LiMn2O4|gelled PVdF-HFP|TiNb2O7 is constructed by optimized mass loading of cathode with respect to anode and tested between 1.95 and 2.75 V at room temperature. The full-cell delivered the reversible capacity of ∼116 mAh g(-1) at current density of 150 mA g(-1) with operating potential and energy density of ∼2.4 V and ∼278 Wh kg(-1), respectively. Further, excellent cyclability is noted for such configuration irrespective of the applied current densities.

Pressure-controlled growth of piezoelectric low-dimensional structures in ternary fullerene C60/carbon nanotube/poly (vinylidene fluoride) based hybrid composites

Hybrid composites, consisting of polymers and nanostructured carbon allotropes, can exhibit different properties than their constituent components. In this work, the synergistic action of fullerene C60 and carbon nanotube (CNT) on poly (vinylidene fluoride) (PVDF) was evaluated, in terms of the dispersion of the carbonaceous fillers in the polymer matrix during the composite preparation, and the control of crystalline morphology of the polymer at high pressure. The synergistic effect of the zero-dimensional and one-dimensional carbon materials resulted in a well dispersed ternary C60/CNT/PVDF based composite, which was simply fabricated by a physical and mechanical route. Furthermore, the pressure-controlled growth of piezoelectric low-dimensional crystalline structures of PVDF, including hollow nanowires and extended-chain lamellae, was achieved by the simultaneous introduction of C60 and CNT. Especially, PVDF nanowires with folded- and extended-chain lamellae as their substructures were obtained respectively by controlling the crystallization conditions of the ternary composite at high pressure. Under specific conditions, composite samples, which crystalline structures were totally with extended-chain β- or γ-form lamellae, further self-reinforced with extended-chain β-form nanowires, were successfully crystallized. The present study provides a facile and effective approach for the fabrication and the multi-level control of polar crystalline structures of a polymer based hybrid composite, with an overall good dispersion of zero- and one-dimensional nanostructured carbonaceous materials.

One-dimensional nanostructured materials for solar energy harvesting

As the energy demand is rapidly increasing worldwide compared with the supply, there is an urgent need to develop alternative energy-harvesting technologies to sustain the economic growth. Among them, solar energy is one of the most promising sources as it is clean, abundant and renewable. Due to the unique optical and electrical properties, one-dimensional (1D) nanostructured semiconductors are attractive materials for the construction of active energy-harvesting devices. In this review article, applications of 1D nanostructured materials – including photovoltaics, photoelectrochemical cells and solar hydrogen production – in solar energy harvesting are summarized. With the efficiency enhancement and cost reduction, 1D nanostructured solar energy harvesting devices are found to be promising to tackle the future energy issue.