Nanometer Length Research Articles

Terpenoids in Early 21st Century: From Renewable Functional Nano-entities to Advanced Materials

Plant metabolites can serve as renewable chemicals for the development of a sustainable society. Terpenoids are the major component of over 500,000 plant secondary metabolites reported till date. Monoterpenoid (C10) to tetraterpenoid (C40) all the terpenoid have recently been shown to have nanometric lengths. Studies on the self-assembly of terpenoids, have drawn the attention of scientific community in recent years due to many of its potential and realized applications in medicine, drug delivery, pollutant capture, metal nanoparticle hybrid material, selective damage of cancer cells, etc. In this review, we have discussed the isolation of seven terpenoids from plants and their self-assembly properties in different liquids, even without functional transformation. The utilization of the resulting supramolecular architectures such as vesicles, spheres, flowers and fibrillar networks of nano- to micro-meter dimensions and gels have also been discussed paving the way for a green, renewable and sustainable world.

Monodisperse N‐Doped Graphene Nanoribbons Reaching 7.7 Nanometers in Length

AbstractThe properties of graphene nanoribbons are highly dependent on structural variables such as width, length, edge structure, and heteroatom doping. Therefore, atomic precision over all these variables is necessary for establishing their fundamental properties and exploring their potential applications. An iterative approach is presented that assembles a small and carefully designed molecular building block into monodisperse N‐doped graphene nanoribbons with different lengths. To showcase this approach, the synthesis and characterisation of a series of nanoribbons constituted of 10, 20 and 30 conjugated linearly‐fused rings (2.9, 5.3, and 7.7 nm in length, respectively) is presented.

Monodisperse N-Doped Graphene Nanoribbons Reaching 7.7 Nanometers in Length.

The properties of graphene nanoribbons are highly dependent on structural variables such as width, length, edge structure, and heteroatom doping. Therefore, atomic precision over all these variables is necessary for establishing their fundamental properties and exploring their potential applications. An iterative approach is presented that assembles a small and carefully designed molecular building block into monodisperse N‐doped graphene nanoribbons with different lengths. To showcase this approach, the synthesis and characterisation of a series of nanoribbons constituted of 10, 20 and 30 conjugated linearly‐fused rings (2.9, 5.3, and 7.7 nm in length, respectively) is presented.

Surface effects on ionic Coulomb blockade in nanometer-size pores

Ionic Coulomb blockade in nanopores is a phenomenon that shares some similarities but also differences with its electronic counterpart. Here, we investigate this phenomenon extensively using all-atom molecular dynamics of ionic transport through nanopores of about one nanometer in diameter and up to several nanometers in length. Our goal is to better understand the role of atomic roughness and structure of the pore walls in the ionic Coulomb blockade. Our numerical results reveal the following general trends. First, the nanopore selectivity changes with its diameter, and the nanopore position in the membrane influences the current strength. Second, the ionic transport through the nanopore takes place in a hopping-like fashion over a set of discretized states caused by local electric fields due to membrane atoms. In some cases, this creates a slow-varying ‘crystal-like’ structure of ions inside the nanopore. Third, while at a given voltage, the resistance of the nanopore depends on its length, the slope of this dependence appears to be independent of the molarity of ions. An effective kinetic model that captures the ionic Coulomb blockade behavior observed in MD simulations is formulated.

The Effect of Eu Doping on Microstructure, Morphology and Methanal-Sensing Performance of Highly Ordered SnO₂ Nanorods Array.

Layered Eu-doped SnO2 ordered nanoarrays constructed by nanorods with 10 nm diameters and several hundred nanometers length were synthesized by a substrate-free hydrothermal route using alcohol and water mixed solvent of sodium stannate and sodium hydroxide at 200 °C. The Eu dopant acted as a crystal growth inhibitor to prevent the SnO2 nanorods growth up, resulting in tenuous SnO2 nanorods ordered arrays. The X-ray diffraction (XRD) revealed the tetragonal rutile-type structure with a systematic average size reduction and unit cell volume tumescence, while enhancing the residual strain as the Eu-doped content increases. The surface defects that were caused by the incorporation of Eu ions within the surface oxide matrix were observed by high-resolution transmission electron microscope (HRTEM). The results of the response properties of sensors based on the different levels of Eu-doped SnO2 layered nanoarrays demonstrated that the 0.5 at % Eu-doped SnO2 layered nanorods arrays exhibited an excellent sensing response to methanal at 278 °C. The reasons of the enhanced sensing performance were discussed from the complicated defect surface structure, the large specific surface area, and the excellent catalytic properties of Eu dopant.

Isolation of nanocrystalline cellulose from rice straw and preparation of its biocomposites with chitosan: Physicochemical characterization and evaluation of interfacial compatibility

In order to develop high value-added rice straw residue biocomposites, nanocrystalline cellulose (NCC) from rice straw and chitosan (CS) were used as two main raw materials, the CS/NCC biocomposites were prepared by an acid hydrolysis-ultrasonic treatment and blending casting. The physicochemical properties and evaluation of interfacial compatibility on CS/NCC biocomposites were characterized by TEM, ZP analyzer, UV-vis, FTIR, SEM, XRD, TG, DSC, electron mechanical instrument and water absorption testing. The results reveal that a uniform rod-like or filamentary structure of NCC from rice straw, with the width distribution concentrated on the range of 10–15 nm and several hundred nanometers in length, can be effectively obtained by a relatively high ultrasonic power treatment with the same acid hydrolysis conditions. The superior interfacial compatibility of CS/NCC biocomposites with excellent tensile strength can be achieved at 5% NCC addition level due to optimal dispersion of NCC, strong hydrogen bonding and potential electrostatic interactions between CS and NCC. Additionally the thermal stability and water absorption of biocomposites increase, while the transparency rate, elongation at break decrease as the increase of NCC addition amount from 0% to 20%.

Nanostructured TiO<sub>2</sub> Materials: Preparation, Properties and Potential Applications (3P’s)

Nanostructured materials are a new class of materials which provide one of the greatest potentials for improving performance and extended capabilities of products in a number of applications. In particular nanostructured TiO2 was used as photocatalysts, gas sensor, solar cells and nanocomposite biomaterials. For each of these applications, aspects such as surface morphology, crystallinity and chemistry of the titania-based materials are the key parameters to be settled for the process optimization. A series of nanostructured TiO2 materials (TiO2 nanotubes, TiO2 nanorods, TiO2 nanoparticles) was synthesized using simple hydrothermal methods. X-Ray Diffraction (XRD), Field Emission Scanning Electron microscope (FESEM) and Brunauer–Emmett–Teller (BET) surface area characterization was carried out to study the properties of synthesized nanostructured TiO2 materials. The performance of synthesized nanostructured TiO2 was evaluated for various applications such as photocatalyst for methyl orange (MO) degradation and anti-bacterial thin film for biomedical and food packaging. Among the nanostructured TiO2 materials, TiO2 nanotubes shows the highest activity regardless of their applications. This is probably due to their nanotubular morphology in which provided high surface area materials. The surface area of TiO2 nanotubes was found to be 226.52 m2/g. The outer and inner diameters of nanotubes are 4 nm and 10 nm, respectively with several hundred nanometers in length. Anatase TiO2 phase structure and crystallinity of TiO2 nanotubes supports the good performances of the nanostructured materials.

Study of PbBiO2X (X = Cl, Br and I) square nanoplates with efficient visible photocatalytic performance

Abstract Three new type of single crystallite PbBiO 2 X (X = Cl, Br and I) square-like nanoplates with several hundreds nanometers in length are synthesized via a simple hydrothermal method. The band structure and hehavior of charge carriers for the nanoplates are investigated experimentally and theoretically. The halogen elements are closely related to the indirect narrow band gap(2.61 eV, 2.51 eV and 2.38 eV for PbBiO 2 Cl, PbBiO 2 Br and PbBiO 2 I, respectively). The PbBiO 2 X square-like nanoplates exhibit improved photocatalytic performance on degradation of organic pollutant under visible irradiation, owing to their novel nanostructure and efficient photoelectric conversion. This work demonstrates that PbBiO 2 X nanoplates can be considered as a promising photocatalyst and offer a better understanding about other halogen group elements related semiconductors.

Nanophase-segregation in the dielectric layer enhances the charge storage capacity of polymeric electrochemical supercapacitors

Properties related with the charge storage capacity have been evaluated for three-layered films made with two sheets of poly(3,4-ethylenedioxythiophene) separated by a sheet of poly(N-methylpyrrole) or poly(3,4-ethylenedioxythiophene-co-N-methylpyrrole) (3l-PEDOT/PNMPy or 3l-PEDOT/P(EDOT-co-NMPy), respectively). The most distinctive trend of the copolymer, which shows electrochemical properties intermediate between those of the two homopolymers, is the formation of a biphasic structure, EDOT- and NMPy-rich blocks organizing separately. The ability to exchange charge reversibly is higher for 3l-PEDOT/P(EDOT-co-NMPy) than for 3l-PEDOT/PNMPy, the electroactivity and electrostability of such two 3-layered films being significantly better than that of single-layered PEDOT. Advantages of 3l-PEDOT/P(EDOT-co-NMPy) are mainly based on the nanophase-segregated structure of the copolymer. Thus, the intermediate layer can be considered as random disposition of ultrathin dielectrics having nanometric length and width. In terms of charge storage, the intermediate layer of 3l-PEDOT/P(EDOT-co-NMPy) can be viewed as a thin reservoir filled of heterogeneously distributed nanometric supercapacitors that are connected in series among them and in parallel to the PEDOT layers. The superiority of 3l-PEDOT/P(EDOT-co-NMPy) as organic electrochemical supercapacitor compared to other 3-layered systems, has been proved by powering a red LED bulb.

Reactive supramolecular filler for elastomer reinforcement

A reactive amphiphile, SA1, which comprises a mercaptodecyl oleophilic tail and a β-alanine oleophobic moiety, has been introduced to serve as the building block for supramolecular filler. At least a fraction of SA1 reacts in situ during mechanically mixing and vulcanization with SBR via thiol-ene reaction. Some oxidative dimerization also concomitantly occurs to give DSA1. The chemical coupling between SA1 and SBR results in drastically improved filler domain dispersion. Short fibrous crystalline domains, which are likely composed of SA1, SA1 grafted to SBR, and DSA1, less than 10 nm in width and a few tens to one hundred nanometers in length are observed by TEM. The filler domains are evenly distributed in the SBR. In contrast, the simple filler PA1 forms large irregular aggregates on the length scale of hundreds of nanometers. The improved filler dispersion and filler-rubber interaction allow effective energy dissipation and result in significantly improved mechanical properties.A solution-mixing method proves feasible for mixing SA1 and SBR and actually has resulted in better mechanical properties than the mechanical mixing method. Since the conventional mechanical mixing method for rubber compounding is highly energy-intensive, avoidance of the mechanical mixing method is another practical advantage for the novel strategy of supramolecular reinforcement.

Novel Nanoscale Materials and Devices for Wireless Communication and Networking Applications

In the last decade, there have been immense technological developments throughout the world leading to much advancement in the technologies used in wireless communication systems. Massive ongoing research at nanometer length is set to meet the rising demand of the communication industry. So nanoscale materials and devices will play a major role in intelligent communication system. In this paper, we envisage the current and future applications of nanoscale materials and devices for wireless communication systems. It discusses about novel materials and devices that are being designed to provide enhanced and improved quality of service in terms of long range communication, improved performance, less power consumption, smaller size, energy efficient and robustness. We harness the properties and applications of materials at nanoscale dimensions by integrating them with the current technological requirements in terms of extremely high speed, intelligence, large capacity and swift interconnections. Such materials and devices would certainly leverage the future direction of research in wireless communication systems.

Fabrication of a Graphene@TiO2@Porphyrin Hybrid Material and Its Photocatalytic Properties under Simulated Sunlight Irradiation

AbstractThe fabrication of a nanostructured graphene@TiO2@porphyrin composite was achieved via surfactant‐assisted self‐assembly. The obtained nanostructures were fully characterized by UV‐vis, fluorescence emission spectroscopy, SEM, XRD and FTIR techniques. The graphene@TiO2@porphyrin composite reveals good incorporation of TiO2 particles with a diameter of 15–30 nm, and aggregated porphyrin nanorods with 50–60 nm width and several hundreds of nanometers in length on the graphene surface. The applications of three components (graphene@TiO2@porphyrin) based nanostructure in photocatalytic pollutant degradation Rhodamine B is reported, where TiO2 and porphyrin aggregates are shown to be activated for UV and visible light respectively, resulting in a high performing composite. The possible photocatalytic mechanism of RhB degradation by graphene@TiO2@porphyrins composite is discussed.

Multilevel Ultrafast Flexible Nanoscale Nonvolatile Hybrid Graphene Oxide–Titanium Oxide Memories

Graphene oxide (GO) resistive memories offer the promise of low-cost environmentally sustainable fabrication, high mechanical flexibility and high optical transparency, making them ideally suited to future flexible and transparent electronics applications. However, the dimensional and temporal scalability of GO memories, i.e., how small they can be made and how fast they can be switched, is an area that has received scant attention. Moreover, a plethora of GO resistive switching characteristics and mechanisms has been reported in the literature, sometimes leading to a confusing and conflicting picture. Consequently, the potential for graphene oxide to deliver high-performance memories operating on nanometer length and nanosecond time scales is currently unknown. Here we address such shortcomings, presenting not only the smallest (50 nm), fastest (sub-5 ns), thinnest (8 nm) GO-based memory devices produced to date, but also demonstrate that our approach provides easily accessible multilevel (4-level, 2-bit per cell) storage capabilities along with excellent endurance and retention performance-all on both rigid and flexible substrates. Via comprehensive experimental characterizations backed-up by detailed atomistic simulations, we also show that the resistive switching mechanism in our Pt/GO/Ti/Pt devices is driven by redox reactions in the interfacial region between the top (Ti) electrode and the GO layer.

Influence of hydrofluoric acid treatment on electroless deposition of Au clusters

The morphology of gold nanoparticles (AuNPs) deposited on a (100) silicon wafer by simple immersion in a solution containing a metal salt and hydrofluoric acid (HF) is altered by HF treatment both before and after deposition. The gold clusters are characterized by the presence of flat regions and quasispherical particles consistent with the layer-by-layer or island growth modes, respectively. The cleaning procedure, including HF immersion prior to deposition, affects the predominantly occurring gold structures. Flat regions, which are of a few tens of nanometers long, are present after immersion for 10 s. The three-dimensional (3D) clusters are formed after a cleaning procedure of 4 min, which results in a large amount of spherical particles with a diameter of ≈15 nm and in a small percentage of residual square layers of a few nanometers in length. The samples were also treated with HF after the deposition and we found out a general thickening of flat regions, as revealed by TEM and AFM analysis. This result is in contrast to the coalescence observed in similar experiments performed with Ag. It is suggested that the HF dissolves the silicon oxide layer formed on top of the thin flat clusters and promotes the partial atomic rearrangement of the layered gold atoms, driven by a reduction of the surface energy. The X-ray diffraction investigation indicated changes in the crystalline orientation of the flat regions, which partially lose their initially heteroepitaxial relationship with the substrate. A postdeposition HF treatment for almost 70 s has nearly the same effect of long duration, high temperature annealing. The process presented herein could be beneficial to change the spectral response of nanoparticle arrays and to improve the conversion efficiency of hybrid photovoltaic devices.

Graphene flakes obtained by local electro-exfoliation of graphite with a STM tip.

Graphite surfaces can be manipulated by several methods to create graphene structures of different shapes and sizes. Scanning tunneling microscopy (STM) can be used to create these structures either through mechanical contact between the tip and the surface or through electro-exfoliation. In the latter, the mechanisms involved in the process of exfoliation at an applied voltage are not fully understood. Here, we show how a graphite surface can be locally exfoliated in a systematic manner by applying an electrostatic force with a STM tip at the edge of a terrace, forming triangular flakes several nanometers in length. We demonstrate, through experiments and simulations, how these flakes are created by a two-step process: first a voltage ramp must be applied at the edge of the terrace, and then the tip must be scanned perpendicular to the edge. Ab initio electrostatic calculations reveal that the presence of charges on the graphite surface weakens the interaction between layers allowing for exfoliation at voltages in the same range as those used experimentally. Molecular dynamics simulations show that a force applied locally on the edge of a step produces triangular flakes such as those observed under STM. Our results provide new insights into surface modification that can be extended to other layered materials.

Terpenoids as Renewable Nano-Sized Building Blocks

Terpenoids are a large and structurally group of natural products containing multiple five carbon containing isoprene units. Previously we have reported that irrespective of their acyclic or alicyclic nature, all the triterpenoids containing 30C’s have nano-metric lengths. In the current studies, detailed computations have been carried out with 120 naturally occurring mono- (C10), sesqui- (C15), di- (C20), sester- (C25), sesqua- (C35) and tetra- (C40) terpenoids using Gaussian 09 software with Gauss view 07 and molecular mechanics calculation using Serena software. The heat of formation and the calculated molecular lengths obtained by the two methods were compared. Interestingly, monoterpenoid to tetraterpenoid all the terpenoids (except three monoterpenoid and one sesqui-terpenoid) have molecular lengths above one nanometer making them useful as nano-sized building blocks.

From bulk to nano metal phthalocyanine by recrystallization with enhanced nucleation

A recrystallization process with enhanced nucleation by a dilute KOH aqueous solution is used to create nano from bulk metal phthalocyanines (MPcs). Cobalt phthalocyanine (CoPc) nanorods (∼20 nm in width and ∼60 nm in length) and copper phthalocyanine (CuPc) nanorods (∼30 nm in width and several hundred nano meters in length) are prepared from bulk CoPc and CuPc, respectively. It indicates the strength of the interaction force between MPcs and H2O molecules possibly affects the size of the nano particles. The formation of nano MPcs and purification were accomplished simultaneously, providing a facial way to turn bulk MPcs into nano with high purity.

Dissolution-reprecipitation and self-assembly of serpentine nanoparticles preceding chrysotile formation: Insights into the structure of proto-serpentine

Any poorly crystalline serpentine-type mineral with a lack of recognizable textural or diffraction features for typical serpentine varieties (i.e., chryotile, lizardite, and antigorite) is usually referred to as proto-serpentine. The formation of the so-called proto-serpentine seems ubiquitous in serpentinization reactions. It is related to dissolution-precipitation of strongly reactive particles prior to true serpentine formation (e.g., in veins where both chrysotile and proto-serpentine are described). However, the structural characteristics of proto-serpentine and its relation with serpentine crystalline varieties remain unclear. In this study a model describing the transformation from proto-serpentine to chrysotile is presented based on experimental chrysotile synthesis using thermogravimetric analyses, transmission electron microscopy, and high-energy X-ray diffraction with pair distribution function analyses. The combination of the high-resolution TEM and high-energy X-ray diffraction enables to resolve the local order of neo-formed particles and their structuration processes occurring during pure chrysotile formation (i.e., during the first three hours of reaction). The formation of individual nanotubes is preceded by the formation of small nanocrystals that already show a chrysotile short-range order, forming porous anastomosing features of hydrophilic crystallites mixed with brucite. This is followed by a hierarchical aggregation of particles into a fiber-like structure. These flake-like particles subsequently stack forming concentric layers with the chrysotile structure. Finally, the individualization of chrysotile nanotubes with a homogeneous distribution of diameter and lengths (several hundreds of nanometer in length) is observed. The competitive precipitation of brucite and transient serpentine during incipient serpentinization reaction indicates that both dissolution-precipitation and serpentine-particle aggregation processes operate to form individual chrysotile. This study sheds light into mineralization processes and sets a first milestone toward the identification of the factors controlling polymorph selection mechanisms in this fascinating system.

Sub-10 fs Time-Resolved Vibronic Optical Microscopy.

We introduce femtosecond wide-field transient absorption microscopy combining sub-10 fs pump and probe pulses covering the complete visible (500–650 nm) and near-infrared (650–950 nm) spectrum with diffraction-limited optical resolution. We demonstrate the capabilities of our system by reporting the spatially- and spectrally-resolved transient electronic response of MAPbI3–xClx perovskite films and reveal significant quenching of the transient bleach signal at grain boundaries. The unprecedented temporal resolution enables us to directly observe the formation of band-gap renormalization, completed in 25 fs after photoexcitation. In addition, we acquire hyperspectral Raman maps of TIPS pentacene films with sub-400 nm spatial and sub-15 cm–1 spectral resolution covering the 100–2000 cm–1 window. Our approach opens up the possibility of studying ultrafast dynamics on nanometer length and femtosecond time scales in a variety of two-dimensional and nanoscopic systems.

Fabrication of sharp atomic force microscope probes using in situ local electric field induced deposition under ambient conditions.

We demonstrate a simple method to significantly improve the sharpness of standard silicon probes for an atomic force microscope or to repair a damaged probe. The method is based on creating and maintaining a strong, spatially localized electric field in the air gap between the probe tip and the surface of conductive sample. Under these conditions, nanostructure growth takes place on both the sample and the tip. The most likely mechanism is the decomposition of atmospheric adsorbate with subsequent deposition of carbon structures. This makes it possible to grow a spike of a few hundred nanometers in length on the tip. We further demonstrate that probes obtained by this method can be used for high-resolution scanning. It is important to note that all process operations are carried out in situ, in air and do not require the use of closed chambers or any additional equipment beyond the atomic force microscope itself.