1D Nanostructures Research Articles

Hierarchical 2D to 3D micro/nano-histology of human dental caries lesions using light, X-ray and electron microscopy

Dental caries is a widespread disease that proceeds by damaging superficial tooth enamel by heterogeneous dissolution. Conventional histology identifies different zones within carious lesions by their optical appearance, but fails to quantify the underlying nanoscale structural changes as a function of specific location, impeding better understanding of the demineralisation process. We employ detailed collocative analysis using different imaging modalities, resolutions and fields of view. Focused ion beam-scanning electron microscopy (FIB-SEM) reveals subsurface 3D nanostructure within milled micro-sized volumes, whilst X-ray tomography allows minimally destructive 3D imaging over large volumes. Correlative combination of these techniques reveals fine detail of enamel rods, inter-rod substance, sheaths, crystallites and voids as a function of location. The degree of enamel demineralisation within the body of the lesion, near its front, and at the surface is visualized and quantified in 3D. We thus establish the paradigm of dental 3D nano-histology as an advanced platform for quantitative evaluation of caries-induced structural modification.

Forming three-dimensional micro-objects using two-dimensional gradient printing

Controllable transformations from two-dimensional (2D) patterns to three-dimensional (3D) geometries independent of materials or external stimuli are being pursued in numerous fields. Here, we present an approach to forming various 3D structures through 2D printing using distributed stress inside a polymer. The key is to establish controlled stress fields by introducing composition and property gradients inside a photocurable polymer by femtosecond laser two-photon polymerization. Structural deformation induced by internal stress is a general bottleneck both in materials processing and 3D printing. In contrast to the significant efforts previously made to reduce stress and deformation, we use them to enable shape transformation to construct various 3D micro-objects through 2D printing with engineered stress fields inside. Multi-mode 2D-to-3D structural transformations, including bending, rolling, coiling, waving, spiraling, and out-of-plane distortions are realized in a shape- and location-specific fashion. This strategy promises a unique way to fabricate delicate 3D objects not feasible through conventional techniques and to circumvent the intrinsic stepping limitations in direct 3D printing using two-photon polymerization. When combined with the standard 2D patterning techniques such as nanoimprint and photolithography, such a 2D-to-3D transformation approach will lay a foundation for high-throughput and cost-effective production of complex 3D nanostructures.

Spatiotemporal-Resolved Hyperspectral Raman Imaging of Plasmon-Assisted Reactions at Single Hotspots.

Raman spectroscopy facilitates the study of reacting molecules on single nanomaterials. In recent years, the temporal resolution of Raman spectral measurement has been remarkably reduced to the millisecond level. However, the classic scan-based imaging mode limits the application in the dynamical study of reactions at multiple nanostructures. In this paper, we propose a spatiotemporal-resolved Raman spectroscopy (STRS) technology to achieve fast (∼40 ms) and high spatial resolution (∼300 nm) hyperspectral Raman imaging of single nanostructures. With benefits of the outstanding electromagnetic field enhancement factor by surface plasmon resonance (∼1012) and the snapshot hyperspectral imaging strategy, we demonstrate the observation of stepwise Raman signals from single-particle plasmon-assisted reactions. Results reveal that the reaction kinetics is strongly affected by not only the surface plasmon-polariton generation but also the density of Raman molecules. In consideration of the spatiotemporal resolving capability of STRS, we anticipate that it provides a potential platform for further extending the application of Raman spectroscopy methods in the dynamic study of 1D or 2D nanostructures.

Organic semiconductor nanostructures: optoelectronic properties, modification strategies, and photocatalytic applications

Organic semiconductors (OSCs) possess diverse chemical structures and tailored optoelectronic properties via simple chemical modifications, so increasing use of them are found in efficient visible-light photocatalysis. However, the weak chemical bonds and the poor charge behavior (e.g., low concentration of free charge carriers, low carrier mobility) intrinsic in them, always incur quite limited stability and efficiency. Therefore, the assembly of them into refined nanostructures or nanocomposites is usually proposed to enhance their optoelectronic properties, as well as the photocatalytic efficiency and reliability. Zero-dimensional (0D) nanoparticles are low in size and hence high specific surface area (SSA); One-dimensional (1D) nanostructures are usually arranged in an orderly long range thus leading to low surface defect density and increased carrier mobility; Two-dimensional (2D) nanostructures are particularly capable of enhancing the photogenerated charge utilization because of their large reaction sites and shortened charge transport length. Furthermore, the building of heterogeneous interfaces in the nanocomposites can effectively facilitate the special charge separation. All these highlight the importance of organic nanostructures in improving the photocatalytic activity and stability. Therefore, organic semiconductor nanostructures (OSNs) have been increasingly used in the photocatalytic water splitting into H2 and O2, CO2 reduction, pollutant decomposition, disinfection, etc. In this review, we first examine the important optoelectronic properties of OSNs that govern the photocatalytic processes; we then analyze different classes of OSNs and their mechanistic pathways, with an emphasis on the structure-property relationships; we also introduced various photocatalytic applications of OSNs; we lastly propose the challenges and future outlook in real use.

Facile preparation of nanostructured ZnO via low-temperature hydrothermal method upon changing the precursor anion: The study of structural, morphological, and optical properties

The synthesis of ZnO nanostructures was carried out via a low-temperature hydrothermal route; using three different zinc precursors: ZnSO4, ZnCl2, and Zn(ac)2. X-ray diffraction analysis confirmed that all synthesized samples have high purity wurtzite hexagonal structure. The calculation of lattice parameters indicated that the precursor’s anion and the hydrothermal time strongly affected the lattice parameters. The SO42- anion capped the polar surface growth, which leads to 2D nanostructures. However, the Cl- anion boosted growth along the c axis and inhibited the lateral axes, which lead to 1D nanostructures. The microstrain and crystallite size of the samples were determined using the Williamson-Hall (W-H), Size-Strain Plot, and Halder-Wagner (H-W) methods. The SEM images indicated morphological differences in the formation of the synthesized samples, confirming that the anion of the precursor and the hydrothermal time play a determining role in the shape of the ZnO nanostructures. All the ZnO samples show strong absorption in the ultraviolet region with an onset of absorbance in the range 250–335 nm; blue shifting was observed for all samples indicating a large bandgap, such as Eg(Cl-) > Eg(SO42-) > Eg(C2H3O2-) and the Urbach energy that reflects the disorder was calculated, such thatEu(ZA6) > Eu(ZS6) > Eu(ZC6). There was a correlation between optical and structural proprieties: the bandgap decreased with increasing microstrain, however, Urbach energy increased.

The role of defects in the nonlinear optical absorption behavior of pristine and Co-doped V2O5 layered 2D nanostructures

V2O5 nanostructures doped with 1% Co have been successfully synthesized by simple hydrothermal method. Structural and morphological aspects, vibrational spectra and optical properties (linear and nonlinear) of pristine as well as Co-doped V2O5 (V2O5:Co) nanoparticles are investigated. X-ray diffraction patterns indicate that both V2O5 and Co doped V2O5 are stabilized in an orthorhombic structure. Energy band gaps measured using the Tauc plot give 2.24 eV for V2O5 and 2.16 eV for Co doped V2O5. When excited using 5 ns laser pulses at 532 nm in the open aperture Z-scan configuration, pristine as well as Co-doped V2O5 nanoparticles are found to show excellent nonlinear absorption, which arises from strong reverse saturable absorption occurring in the sample at this wavelength. The corresponding effective two-photon absorption coefficients are in the range of 10−11 to 10−12 m/W, and effective three-photon absorption coefficients are in the range of 10−22 to 10−23 m3/W2. When excited at the same wavelength using a continuous wave laser beam, the effective two-photon absorption coefficient gets enhanced to 10−6 m/W. These results confirm the suitability of V2O5 and Co-doped V2O5 nanoparticles for the fabrication of optical limiter devices for the protection of human eyes and sensitive optical detectors from hazardous laser radiation.

Dense high aspect ratio nanostructures for cell chip applications - Fabrication, replication, and cell interactions

Culturing human cells on the surface of a microchip brings living cells in direct contact with artificial microstructured surfaces. This work focuses on the effect of high aspect ratio nanostructures – dense nanoneedle arrays – on the mechanical response and proliferation of fibroblasts. We present a fabrication process for micropatterned chips that feature areas with hierarchical high aspect ratio nanostructures directly adjacent to flat chip areas. The chip was pre-patterned by conventional lithography. We have fabricated “black silicon” arrays of densely packed, sharp, vertical nano-needles for high aspect ratio structures by cryogenic reactive ion etching in an SF 6 /O 2 plasma. An essential requirement for many real-life applications is to make such complex high aspect ratio 3D nanostructures available in larger areas. We have successfully demonstrated the 3D replication of black silicon by a UV- nanoimprint lithography process. This study provides insight into the extent to which such nanoneedle arrays influence the growth of human fibroblasts. We have investigated microstructured samples featuring a combination of (i) smooth surfaces and (ii) nanoneedle surfaces for the mechanical behavior and proliferation of fibroblasts. Our results show that the bonding viability and proliferation of the fibroblast on the high aspect ratio nano-needle surfaces differ significantly from flat surfaces. The nanoneedles only provide a minimum area for cell attachment compared to the neighboring flat, unstructured chip areas. • Development of a fabrication process for a dense nano-needle array. • Reproduction of black silicon using nanoimprint lithography. • Black silicon structures were investigated with regard to NIL replication and cell proliferation.

Nanohybrids of hematite nanoparticles and reduced graphene oxide nanosheets: Anode materials for lithium ion batteries

The nanohybrids of hematite (α–Fe2O3) nanoparticles and reduced graphene oxide (rGO) nanosheets were prepared by a facial two-step chemical method. The αFe2O3 nanoparticles prepared by a sol-gel technique were hybridized with the pristine rGO nanosheets by ultra-sonication-assisted method. The rGO and α–Fe2O3 nanoparticles were dispersed in toluene to prepare (rGO)x/α–Fe2O3 nanohybrids. The crystal structure, vibrational modes, surface morphology, and elemental composition of these (rGO)x/α–Fe2O3 nanohybrids were investigated. The 3D nanostructure of α–Fe2O3 nanoparticles were randomly anchored on cross-linking rGO nanosheets. These rGO nanosheets functioned as mechanical support and an efficient electron conducting pathway in the (rGO)x/α–Fe2O3 nanohybrids. X-ray diffraction (XRD) spectra confirmed the crystal structure and phase purity while scanning electron microscopy (SEM) images showed the dispersion of α–Fe2O3 nanoparticles over rGO nanosheets. The hybridization of rGOs nanosheets with α–Fe2O3 nanoparticles significantly enhanced the electrochemical storage performance as anode material for LIBs. The first discharge capacity for the (rGO)x/α–Fe2O3 nanohybrids of 1469 mAh/gwas much better than that of the bare α–Fe2O3 nanoparticles of 895 mAh/g. Cyclic stability was enhanced as the discharge capacity was retained after 100 cycles for the (rGO)x/α–Fe2O3 nanohybrids. Moreover, the improved rate capability that was also observed for the (rGO)x/α–Fe2O3 nanohybrids further authenticates the use of these nanohybrids as anode materials for LIBs.

Ceramic Ti/TiO2/AuNP Film with 1-D Nanostructures for Selfstanding Supercapacitor Electrodes

Herein we have fabricated AuTiO2 from a one-dimensional (1D) nanocomposite by the simple oxidation method of the Ti sheet for supercapacitor applications. We intended on fabricating a microlayer extended into the sheet body to form a selfstanding electrode. Raman spectra and XRD patterns confirmed the formation of the rutile phase of the TiO2 bulk, and FESEM confirmed the growth of the 1D nanostructure made of Au/TiO2, where the Au nanoparticles reside on the tip of the TiO2 nanorods. The growth of 1D TiO2 by this method is supported by a growth mechanism during the oxidation process. Three electrodes were fabricated based on pure and doped TiO2. These electrodes were used as a selfstanding supercapacitor electrode. The Au-doped TiO2 exhibited a great improvement in the electrochemical performance at low Au concentrations, whereas the excessive Au concentration on the TiO2 surface exhibited a negative effect on the capacitance value. The highest areal capacitance of 72 mFcm−2 at a current density of 5 µAcm−2 was recorded for TiO2 doped with a low Au concentration. The mechanism of the electrochemical reaction was proposed based on Nyquist and Bode plots. The obtained results point out that the effect of Au on the TiO2 surface makes Au/TiO2 ceramic electrodes a promising material as selfstanding energy storage electrodes.

Atomic Layer Assembly Based on Sacrificial Templates for 3D Nanofabrication.

Three-dimensional (3D) nanostructures have attracted widespread attention in physics, chemistry, engineering sciences, and biology devices due to excellent functionalities which planar nanostructures cannot achieve. However, the fabrication of 3D nanostructures is still challenging at present. Reliable fabrication, improved controllability, and multifunction integration are desired for further applications in commercial devices. In this review, a powerful fabrication method to realize 3D nanostructures is introduced and reviewed thoroughly, which is based on atomic layer deposition assisted 3D assembly through various sacrificial templates. The aim of this review is to provide a comprehensive overview of 3D nanofabrication based on atomic layer assembly (ALA) in multifarious sacrificial templates for 3D nanostructures and to present recent advancements, with the ultimate aim to further unlock more potential of this method for nanodevice applications.

TiO2 nanoflower photocatalysts: Synthesis, modifications and applications in wastewater treatment for removal of emerging organic pollutants

Titanium dioxide (TiO2) has been considered as one of the most promising photocatalysts nanomaterials and is being used in a variety of fields of energy and environment under sunlight irradiation via photocatalysis. Highly efficient photocatalytic materials require the design of the proper structure with excellent morphology, interfacial structures, optical and surface properties, etc. Which are the key points to realize effective light-harvesting for photocatalytic applications. Hierarchical TiO2 based nanoflower structures (i.e., 3D nanostructures) possess such characteristics and have attracted much attention in recent years. The uniqueness of TiO2 nanoflowers (NFs) with a coarse texture and arranged structures demonstrates higher photocatalytic activity. This review deals with the hydrothermal synthesis of 3D TiO2 NFs and effect of shape/size as well as various key synthesis parameters to improve their optoelectronic and photocatalytic properties. Furthermore, to improve their photocatalytic properties, various strategies such as doping engineering and heterojunction/nanocomposite formation with other functional nanomaterials have been discussed followed by their potential applications in photocatalytic degradation of various emerging pollutants discharged into the wastewater from various sources. Importance of such 3D nanoarchitecutres and future research in other fields of current interest in environments are discussed.

Structures, Electronic Properties, and Gas Permeability of 3D Pillared Silicon Carbide Nanostructures.

Silicon carbide (SiC) is recognized as excellent material for high power/temperature applications with a wide-band gap semiconductor. With different structures at the nanosize scale, SiC nanomaterials offer outstanding mechanical, physical, and chemical properties leading to a variety of applications. In this work, new 3D pillared SiC nanostructures have been designed and investigated based on self-consistent charge density functional tight-binding (SCC-DFTB) including Van der Waals dispersion corrections. The structural and electronic properties of 3D pillared SiC nanostructures with effects of diameters and pillar lengths have been studied and compared with 3D pillared graphene nanostructures. The permeability of small gas molecules including H2O, CO2, N2, NO, O2, and NO2 have been demonstrated with different orientations into the 3D pillared SiC nanostructures. The promising candidate of 3D pillared SiC nanostructures for gas molecule separation application at room temperature is highlighted.

Fast, Sensitive, and Highly Selective Room-Temperature Hydrogen Sensing of Defect-Rich Orthorhombic Nb2O5-x Nanobelts with an Abnormal p-Type Sensor Response.

The research and development of low-power-consumption and room-temperature hydrogen sensors are of great significance for the safe application of hydrogen energy. Herein, orthorhombic Nb2O5-x nanobelts are prepared through a combined procedure of hydrothermal, ion exchange, and annealing treatment in Ar. The topological transformation process results in the formation of abundant surface defects including chemical defects such as Nb4+, oxygen vacancies, and disordered microregions, which lead to the abnormal p-type conducting and hydrogen sensing behavior. Moreover, the orthorhombic Nb2O5-x nanobelts exhibit fast and sensitive room-temperature hydrogen sensing performance, which shows greater advancement than the monoclinic, tetragonal, and hexagonal Nb2O5 one-dimensional (1D) nanostructures. The response time and lowest limit of detection of the as-fabricated room-temperature sensor decrease to 28 s and 3.5 ppm, respectively. The sensor also exhibits a highly selective hydrogen response against CO, CH4, ethanol, H2S, and NH3. The hydrogen response of the Nb2O5-x nanobelts can be attributed to the redox reaction between hydrogen and preadsorbed oxygens. The defective surface structure and the prolonged dimension of the nanobelts give rise to the highly reactive surface and the suppression of the negative nanojunction effect, which greatly improves the sensing performance. The orthorhombic lattice structure can also promote gas adsorption and diffusion behavior due to its specific catalytic and pathway effect. The results of this work can be helpful for the rational design and defect engineering of the Nb2O5-based 1D nanostructures for room-temperature hydrogen sensing applications.

Severe carbon accumulation on black phosphorous flakes induced by synchrotron x-ray radiation

Two-dimensional (2D) materials, such as black phosphorus (BP) and transition metal dichalcogenide, recently gained much interest due to their unique electronic, photonic, and mechanical properties. Synchrotron-based scanning photoelectron microscopy (s-SPEM) with a spatial resolution (down to 70 nm) has actively applied for exploring the relationship between chemical information and electronic structure of 2D materials on concerned local surface area. Here, we compare carbon accumulation on the surface of BP and MoS2 during synchrotron beam irradiation. During the BP characterization, carbon was rapidly accumulated on BP surface as irradiation progress, while MoS2 demonstrated better resistance to carbon accumulation in comparison to BP. Our work suggests that the higher surface reactivity of BP results in the formation of even BP-carbide structure upon the irradiation, while MoS2 with relatively low reactivity is rather stable against carbon accumulation. This photon-induced carbon accumulation causes the misleading result of surface chemical information and electronic structure in highly reactive 2D materials or nanostructures.

High‐Aspect‐Ratio Nanoelectrodes Enable Long‐Term Recordings of Neuronal Signals with Subthreshold Resolution

The further development of neurochips requires high-density and high-resolution recordings that also allow neuronal signals to be observed over a long period of time. Expanding fields of network neuroscience and neuromorphic engineering demand the multiparallel and direct estimations of synaptic weights, and the key objective is to construct a device that also records subthreshold events. Recently, 3D nanostructures with a high aspect ratio have become a particularly suitable interface between neurons and electronic devices, since the excellent mechanical coupling to the neuronal cell membrane allows very high signal-to-noise ratio recordings. In the light of an increasing demand for a stable, noninvasive and long-term recording at subthreshold resolution, a combination of vertical nanostraws with nanocavities is presented. These structures provide a spontaneous tight coupling with rat cortical neurons, resulting in high amplitude sensitivity and postsynaptic resolution capability, as directly confirmed by combined patch-clamp and microelectrode array measurements.

Recent progress on microfluidic devices with incorporated 1D nanostructures for enhanced extracellular vesicle (EV) separation

Recent progress on microfluidic devices with incorporated 1D nanostructures for enhanced extracellular vesicle (EV) separation

Fusion Growth of Two-Dimensional Disklike Micelles via Liquid-Crystallization-Driven Self-Assembly

Liquid-crystallization-driven self-assembly (LCDSA) is an emerging strategy for constructing nanoassemblies, such as 1D cylindrical micelles with LC-like micellar cores. However, it is still unknown whether LCDSA can be applied to higher-dimensional self-assembly. Herein, we realize the growth of two-dimensional (2D) disklike micelles via LCDSA and reveal its mechanism. Disklike seeds are constructed through the self-assembly of poly(γ-benzyl l-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) block copolymers in solution. In the micellar core, the PBLG rod blocks take a smectic LC-like packing manner. After PBLG-b-PEG unimers are added into the seed solution, they first self-assemble into small aggregates. The aggregates then fuse with the seed edges to achieve the epitaxial growth of the disklike micelles. Brownian dynamic simulations reveal that the rod blocks in the small aggregates rearrange themselves to match the LC-like structure of the seed core in the growth process. The contour area of the disklike micelles is dependent on the unimer-to-seed ratio, and the 2D growth kinetics can be well controlled to construct concentric disklike micelles. The observed growth behavior of disklike micelles extends the LCDSA from 1D to 2D and can address the challenge of the precise manipulation of 2D nanostructures.

Rational construction of phosphate layer to optimize Cu-regulated Fe3O4 as anode material with promoted energy storage performance for rechargeable Ni-Fe batteries

Flexible aqueous energy storage devices with high security and flexibility are crucial for the progress of wearable energy storage. Particularly, aqueous rechargeable Ni-Fe batteries owning a large theoretical capacity, low cost and outstanding safety characteristics have emerged as a promising candidate for flexible aqueous energy storage devices. Herein, Cu-doped Fe 3 O 4 (CFO) with 3D coral structure was prepared by doping Cu 2+ based on Fe 3 O 4 nanosheets (FO). Furthermore, the Fe-based anode material (CFPO) grown on carbon fibers was obtained by reconstructing the surface of CFO to form a low-crystallization shell which can enhance the ion transport. Excitingly, the newly developed CFPO electrode as an innovative anode material further exhibited a high capacity of 117.5 mAh g −1 (or 423 F g −1 ) at 1 A g −1 . Then, the assembled aqueous Ni-Fe batteries with a high cell-voltage output of 1.6 V deliver a high capacity of 49.02 mAh g −1 at 1 A g −1 and retention ratio of 96.8% for capacitance after 10 000 continuous cycles. What's more, the aqueous quasi-solid-state batteries present a remarkable maximal energy density of 45.6 Wh kg −1 and a power density of 12 kW kg −1 . This work provides an innovative and feasible way and optimization idea for the design of high-performance Fe-based anodes, and may promote the development of a new generation of flexible aqueous Ni-Fe batteries. The cationic doping strategy can construct unique 3D coral nanostructures, optimize the interface, leading to the electrode with a significant reaction active center, stable structure. Among them, the mass capacity of the as-assembled Ni-Fe battery is 49.02 mAh g −1 , the energy density is 45.6 Wh kg −1 , the power density is 12 kW kg −1 , which is better than numerous Fe-based batteries reported recently.

Polymer/graphene nanofoam nanocomposites: Properties and potential

Graphene is a nano-allotrope of carbon. It is a two dimensional (2D) one atom thick single layer of sp2 hybridized carbon atoms. An important form of graphene is the three dimensional (3D) graphene, also known as graphene nanofoam. This review article précises progress in the field of 3D graphene-based polymeric nanocomposites. The 3D macroscopic graphene nanostructures when used to reinforce polymer matrices attain superior structural and physical properties. This article considers the design, fabrication, characteristics, and promising applications of polymer/graphene nanofoam nanocomposites. The graphene nanofoam and polymer/graphene nanofoam nanocomposites have been prepared through advance approaches. The microstructure, electrical conductivity, specific capacitance, radiation shielding, mechanical properties, and other physical properties of the polymer/graphene nanofoam architectures have been studied. Interactions between the polymers and 3D graphene architecture are essential to enhance the nanocomposite performance. Polymer/graphene nanofoam nanocomposites applications are for solar cells, fuel cells, supercapacitors, and electromagnetic interference (EMI) shielding.

ATP-Triggered Drug Release of Self-Assembled 3D DNA Nanostructures for Fluorescence Imaging and Tumor Therapy.

Stimulus-responsive materials are ideal carriers for precisely controlled drug delivery due to their high selectivity. However, the complex physiological environment hinders its development in clinical medicine. Here, we aim to design a self-assembled three-dimensional (3D) DNA nanostructure drug delivery system with adenosine-5'-triphosphate (ATP)-triggered drug release for tumor fluorescence imaging analysis and targeted drug delivery. Dox@3D DNA nanostructures are self-assembled by a simple one-pot annealing reaction and embedded with drugs, which are structurally stable but can be induced using high concentrations of ATP in tumor cells to cleave and release drugs rapidly, facilitating the rapid accumulation of drugs in tumors and exerting therapeutic effects, thus effectively avoiding damage to normal tissues. This work demonstrates that 3D DNA nanostructures can be used as efficient drug nanocarriers with promising applications in tumor therapy.