Nanobelts Research Articles

Synthesis of belt-like BiOBr hierarchical nanostructure with high photocatalytic performance

One-dimensional (1D) bismuth oxyhalide (BiOX) hierarchical nanostructures are always difficult to prepare. Herein, we report, for the first time, a simple synthesis of BiOBr nanobelts (NBs) via a facile solvothermal route, using bismuth subsalicylate as the template and bismuth source. The BiOBr nanobelts are composed of irregular single crystal nanoparticles with highly exposed (010) facets. Compared with the BiOBr nanosheets (NSs) with dominant exposed (001) facets, they exhibit higher photocatalytic activity toward degradation of Rhodamine B and Methylene Blue under visible light irradiation. The higher photocatalytic performance of BiOBr NBs arises from their larger specific surface area and higher photoabsorption capability. This study provides a simple route for synthesis of belt-like Bi-based hierarchical nanostructures.

Contribution of oligomer/carbon dots hybrid semiconductor nanoribbon to surface-enhanced Raman scattering property

The hybrid Ag-(PS-PSS)/C-dots nanobelts (NBs) have been prepared by decorating Ag nanoparticles (NPs) on surface of the ultra-long, semiconducting (PS-PSS)/C-dots nanoribbons (NRs) via an electroless plating method. The as-prepared Ag-(PS-PSS)/C-dots NB has been demonstrated to be an excellent substrate for surface-enhanced Raman scattering (SERS) with a detection limit of 10−14M and an enhancement factor of 3.35×108 while using rhodamine 6G as probe molecules. Moreover, we have investigated the application of Ag-(PS-PSS)/C-dots NBs as SERS substrate for detection of coumarins. Further, the Ag-(PS-PSS)/C-dots NB could be used as a sacrificial template to form a novel kind of hollow porous Ag nanotubes (NTs) by simply removing the inner NR in tetrahydrofuran. However, the obtained Ag NTs show a weaker SERS effect compared to that of the Ag-(PS-PSS)/C-dots NBs, which indicates that the inner organic/C-dots NR plays an essential role in SERS property of the Ag-(PS-PSS)/C-dots NBs. Here the organic (PS-PSS)/C-dots NR not only acts as a dielectric support for Ag NPs to reduce the surface plasmon damping at the Ag-NR interface due to the high electrical conductivity but also their large surface area are favorable for creating more “hot-spots”. In addition, the embedded sp2-hybridized C-dots in NR can adsorb more aromatic R6G molecules via π–π interaction, which also drives R6G molecules approaching to the “hot-spots”, thus enhancing the SERS signals. Based on our results, it is believed that the employment of semiconducting organic (PS-PSS)/C-dots ribbon-like structures to fabricate sensitive SERS substrates is an interesting new approach.

Constructing Ru/TiO2 Heteronanostructures Toward Enhanced Photocatalytic Water Splitting via a RuO2/TiO2 Heterojunction and Ru/TiO2 Schottky Junction

Photocatalysts based on metallic Ru and RuO2 dual co‐catalysts modified TiO2 nanobelts (NBs) are constructed through a wet‐impregnation reduction method with post thermal oxidation. The samples are characterized carefully and their photocatalytic activities for the half reactions of water splitting as well as full water splitting are evaluated systematically under solar light irradiation. The detailed characterizations and analyses clearly reveal the formation of a Schottky junction at the Ru‐TiO2 interface and of RuO2/TiO2 heterojunctions. The results of the photocatalytic tests show that both Ru and RuO2 can improve the photocatalytic activity for H2/O2 evolution and water splitting. Moreover, the photocatalytic activity of the TiO2 NBs can be further enhanced by co‐modification with dual Ru and RuO2 co‐catalysts. The RuO2/TiO2 heterojunction improves the transfer of the photogenerated holes from the TiO2 to the RuO2, where water can be oxidized by the holes to evolve O2, and the Ru/TiO2 Schottky junction promotes the transfer of photogenerated electrons from the TiO2 NBs to the metallic Ru for proton reduction into H2. These two processes are involved in the overall water splitting. This work provides an important reference for designing highly efficient photocatalysts for water splitting through loading of dual co‐catalysts containing the same element but with different valence structures.

Ru nanoparticles decorated TiO2 nanobelts: A heterostructure towards enhanced photocatalytic activity and gas-phase selective oxidation of benzyl alcohol

One-dimensional (1D) TiO2 nanostructures can be used as the support of metal particles to form the heterostructures, which can prevent the metal agglomeration and enhance the activity of metal in various applications. Here, well-dispersed Ru nanoparticles (NPs) supported on 1D TiO2 nanobelts (NBs) are firstly synthesized by a facile photo-reduction method. The as-synthesized Ru/TiO2 NB heterostructures exhibit an improved photocatalytic performance compared with P25 and TiO2 under both UV and visible light irradiation. Our mechanistic investigation reveals that the enhanced photocatalytic activity can be attributed to the Schottky barrier effect of Ru NPs, which efficiently harvest the electrons of TiO2 and enhance the separation of photogenerated electron–hole pairs. Moreover, the Ru/TiO2 NB heterostructures are assembled into the porous nanopaper via a modified paper-making process, which can be applied in heterogeneous catalysis. The formed Ru/TiO2 NB heterostructure nanopapers exhibit enhanced activity and selectivity for catalyzing aerobic oxidation of benzyl alcohol. Ru NPs are well dispersed with the average size of about 1.5nm on the TiO2 NBs support, which could contribute to the high catalytic activity of Ru/TiO2 catalyst.

Growth of β‐gallium oxide films and nanostructures by atmospheric‐ pressure CVD using gallium and water as source materials

AbstractFilms and nanostructures of β‐Ga2O3 were successfully grown by atmospheric‐pressure CVD (AP‐CVD) using metal Ga and H2O as source materials. It was confirmed that highly (‐201) oriented polycrystalline β‐Ga2O3 films can be obtained on c ‐plane sapphire (c ‐Al2O3) substrates by optimizing growth temperature (Tg) and source supply ratio of H2O to Ga. The optical gap energy of the β‐Ga2O3 film with a relatively flat surface was estimated to be ∼4.9 eV. Photoluminescence (PL) measurements for the β‐Ga2O3 films revealed the existence of at least three emission bands with their peaks at ∼370 nm, ∼440 nm and ∼520 nm. Various shapes of quasi 1D nanostructures, such as nanowires (NWs), nanorods (NRs), tapered NRs and nanobelts (NBs), were obtained on the c ‐Al2O3 substrates coated with the Au films by utilizing vapour‐liquid‐solid (VLS) growth mechanism. The diversity of the quasi 1D nanostructures is probably due to the contribution of vapour‐solid (VS) growth mechanism and/or the coalescence between the neighbouring Au metal particles before initiating the NW (or NR) growth. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural Origin of the Band Gap Anomaly of Quaternary Alloy Cd(x)Zn(1-x)S(y)Se(1-y) Nanowires, Nanobelts, and Nanosheets in the Visible Spectrum.

Single-crystalline alloy II-VI semiconductor nanostructures have been used as functional materials to propel photonic and optoelectronic device performance in a broad range of the visible spectrum. Their functionality depends on the stable modulation of the direct band gap (Eg), which can be finely tuned by controlling the properties of alloy composition, crystallinity, and morphology. We report on the structural correlation of the optical band gap anomaly of quaternary alloy CdxZn1-xSySe1-y single-crystalline nanostructures that exhibit different morphologies, such as nanowires (NWs), nanobelts (NBs), and nanosheets (NSs), and cover a wide range of the visible spectrum (Eg = 1.96-2.88 eV). Using pulsed laser deposition, the nanostructures evolve from NWs via NBs to NSs with decreasing growth temperature. The effects of the growth temperature are also reflected in the systematic variation of the composition. The alloy nanostructures firmly maintain single crystallinity of the hexagonal wurtzite and the nanoscale morphology, with no distortion of lattice parameters, satisfying the virtual crystal model. For the optical properties, however, we observed distinct structure-dependent band gap anomalies: the disappearance of bowing for NWs and maximum and slightly reduced bowing for NBs and NSs, respectively. We tried to uncover the underlying mechanism that bridges the structural properties and the optical anomaly using an empirical pseudopotential model calculation of electronic band structures. From the calculations, we found that the optical bowings in NBs and NSs were due to residual strain, by which they are also distinguishable from each other: large for NBs and small for NSs. To explain the origin of the residual strain, we suggest a semiempirical model that considers intrinsic atomic disorder, resulting from the bond length mismatch, combined with the strain relaxation factor as a function of the width-to-thickness ratio of the NBs or NSs. The model agreed well with the observed optical bowing of the alloy nanostructures in which a mechanism for the maximum bowing for NBs is explained. The present systematic study on the structural-optical properties correlation opens a new perspective to understand the morphology- and composition-dependent unique optical properties of II-VI alloy nanostructures as well as a comprehensive strategy to design a facile band gap modulation method of preparing photoconverting and photodetecting materials.

Synthesis of vanadium pentoxide (V2O5) nanobelts with high coverage using plasma assisted PVD approach

Cost-saving, easy-handling, and eco-affable plasma assisted sublimation process (PASP) is proposed to synthesize vanadium pentoxide (V2O5) nanobelts (NBs) with excellent coverage on Si [100] wafer using oxygen plasma without using surfactants/catalysts. Pure orthorhombic V2O5 NBs having average length of few hundred of microns with quite uniform width nearly of 100nm are formed at 500°C. No film is deposited on Si in presence of oxygen gas without exciting plasma at 500°C. HRTEM analysis with SAED pattern confirm that all V2O5 NBs are single crystalline in nature with the fringe width of 0.33nm corresponding to [010] crystal plane. The XPS analysis shows the compositional purity and sub-stoichiometric nature of V2O5 NBs. The sub-stoichiometric nature of NBs is manifested through an appearance of low intensity peak corresponding to low oxidation state of V (i.e. V4+) at the binding energy of 514.8eV. The micro-Raman and FTIR analysis of NBs are carried out to study the different vibrational modes exhibited by V and O atoms coordinated in distinct fashions. The nanobelts exhibit room temperature PL emission in UV–visible realm with a broad hump in the range of 450–750nm, which confirms the presence of oxygen defects in NBs and strongly supports the XPS results as well. The possible growth mechanism of α-V2O5 NBs is proposed in this paper briefly.

Size and Temperature Dependence of Electron Transfer between CdSe Quantum Dots and a TiO2 Nanobelt

Understanding charge transfer reactions between quantum dots (QD) and metal oxides is fundamental for improving photocatalytic, photovoltaic, and electronic devices. The complexity of these processes makes it difficult to find an optimum QD size with rapid charge injection and low recombination. We combine time-domain density functional theory with nonadiabatic molecular dynamics to investigate the size and temperature dependence of the experimentally studied electron transfer and charge recombination at CdSe QD–TiO2 nanobelt (NB) interfaces. The electron injection rate shows strong dependence on the QD size, increasing for small QDs. The rate exhibits Arrhenius temperature dependence, with the activation energy of the order of millielectronvolts. The charge recombination process occurs due to coupling of the electronic subsystem to vibrational modes of the TiO2 NB. Inelastic electron–phonon scattering happens on a picosecond time scale, with strong dependence on the QD size. Our simulations demonstrate t...

Shell Structure Control of PPy-Modified CuO Composite Nanoleaves for Lithium Batteries with Improved Cyclic Performance

Polypyrrole (PPy)-modified CuO nanocomposites (NCs) with various shell structures have been synthesized by controlling the polymerization time of pyrrole in the presence of leaf-like CuO nanobelts (NBs) as wire templates. The synthesized CuO/PPy NCs and CuO NBs are characterized by XRD, FT–IR, TGA, SEM, TEM, STEM, and EDX line analysis/elemental mapping. The formation mechanism of CuO/PPy core–shell NCs is also illustrated. Electrochemical lithium-storage properties of all the products are evaluated by using them as anode materials for Li-ion batteries (LIBs). It is found that the polymerization time of pyrrole plays a significant role in affecting the shell structures and subsequent lithium-storage properties of the hybrid CuO/PPy NCs. With the extension of polymerization time, CuO/PPy NCs gradually form typical core–shell structures, where the doped PPy with increasing content is steadily and uniformly coated on the CuO surface. Correspondingly, the discharge/charge capacity and cyclic durability of CuO...

In situ synthesis of Ni(OH)2nanobelt modified electroactive poly(vinylidene fluoride) thin films: remarkable improvement in dielectric properties

A facile and low cost synthesis of Ni(OH)2 nanobelt (NB) modified electroactive poly(vinylidene fluoride) (PVDF) thin films with excellent dielectric properties has been reported via in situ formation of Ni(OH)2 NBs in the PVDF matrix. The formation and morphology of the NBs are confirmed by UV-visible spectroscopy and field emission scanning electron microscopy respectively. A remarkable improvement in electroactive β phase nucleation (∼82%) and the dielectric constant (ε ∼ 3.1 × 10(6) at 20 Hz) has been observed in the nanocomposites (NCs). The interface between the NBs and the polymer matrix plays a crucial role in the enhancement of the electroactive β phase and the dielectric properties of thin films. Strong interaction via hydrogen bonds between Ni(OH)2 NBs and the PVDF matrix is the main reason for enhancement in β phase crystallization and improved dielectric properties. The NC thin films can be utilized for potential applications as high energy storage devices like supercapacitors, solid electrolyte batteries, self-charging power cells, piezoelectric nanogenerators, and thin film transistors and sensors.

VO2(B)/Graphene Forest for High-Rate Li-Ion Battery

ABSTRACT2D nanomaterials, when assembled into an ordered macrostructure, will present many great opportunities, including for Li-ion batteries (LIBs). We report densely-packed vertically-aligned VO2(B) nanobelts (NBs)-based forest structure synthesized on edge-oriented graphene (EOG) network. Using a EOG/Ni foam as a 3D scaffold, aligned VO2(B) NBs can be further synthesized into a folded 3D forest structure to construct a freestanding electrode for LIBs. Electrochemical studies found that such a freestanding VO2(B)/EOG electrode, which combines the unique merits of 2D VO2(B) NBs and 2D graphene sheets, has excellent charge-discharge rate performance. A discharge capacity of 178 mAh g-1 at a rate of 59 C and 100 mAh g-1 at 300 C was measured. A good charge-discharge cycling stability under a high current density was also demonstrated. The results indicate VO2(B)/EOG forest based freestanding electrode is very promising for developing high-rate LIBs.

AgI/TiO2 nanobelts monolithic catalyst with enhanced visible light photocatalytic activity

AgI nanoparticles (NPs) have been decorated on the TiO2 nanobelts (NBs) immobilized on a metal Ti substrate by a simple impregnating-precipitation method. The as-achieved AgI/TiO2 monolithic catalyst exhibits a high and stable visible photocatalytic activity toward acid orange II (AO-II) degradation, which is attributed to the suitable energy band match of AgI NPs and TiO2 NBs, leading to the efficient transfer of photo-generated electrons. In addition, it was found that O2− radicals and h+ are the main reactive species for the degradation of AO-II under visible light irradiation. A reasonable photocatalytic mechanism of AgI/TiO2 photocatalyst toward AO-II degradation was discussed. This monolithic catalyst provides an advantage over the drawback encountered with powder suspension.

TiO2 nanobelts with a uniform coating of g-C3N4 as a highly effective heterostructure for enhanced photocatalytic activities

A novel g-C3N4/TiO2 nanobelt (NB) heterostructure was successfully designed and prepared. The as-prepared g-C3N4/TiO2 NB heterostructure exhibited high photocatalytic activity not only in the photodegradation of Rhodamine B (RhB) but also in photocatalytic H2 production. The g-C3N4/TiO2 NB heterostructure with a mass ratio of 1:1 demonstrated the best performance in the photodegradation of RhB, whereas a mass ratio of 3:1 demonstrated the highest H2 production rate of 46.6μmolh−1 in photocatalytic H2 production. We conclude that the synergistic effect between g-C3N4 and TiO2 NBs promotes the photogenerated carrier separation in space. This valuable insight into the rational architectural design of nanostructure-based photocatalysts is expected to shed light on other photocatalytic reaction systems in the future.

Construction of high-quality CdSe NB/graphene Schottky diodes for optoelectronic applications

High-quality CdSe nanobelts (NBs) and monolayer graphene were synthesized via a chemical vapor deposition (CVD) method. Schottky diodes based on CdSe NBs/graphene have been fabricated and investigated. The as-fabricated Schottky diodes exhibit excellent rectification characteristic with rectification ratio up to 103 within ±2V in the dark and distinctive photoresponse to light switching between on and off. Further analysis reveals that the Schottky diodes were highly sensitive to light illumination with very good stability, reproducibility and fast response speeds of 47/122μs. Our results suggest that CdSe NBs/graphene Schottky diodes have potential future application in integrated nano-optoelectronic systems.

Antimony doped cadmium selenium nanobelts with enhanced electrical and optoelectrical properties

Abstract Intrinsic and Sb-doped CdSe nanobelts (NBs) were synthesized via a thermal evaporation technique. The electrical transport properties of field effect transistors (FETs) fabricated using the NBs were investigated. The results indicate that the Sb-doped NBs behave as n-type semiconductors with improved electrical conductivity (10 −1 to 100 S/cm) compared with the intrinsic CdSe. Photodetectors made of single NB were also fabricated and investigated. The results show that Sb-doped NB photodetectors exhibit much higher responsivity (1.5 × 10 4 A/W) and external quantum efficiency (1.2 × 10 5 ) but lower on/off current ratio (∼253) and longer response time (≤40 ms). Furthermore, both electrical transport and optoelectrical properties of the as-synthesized CdSe NBs can be tuned by changing the doping concentration. The results indicate that the as-synthesized NBs are excellent building blocks for constructing electronic and optoelectronic devices.

Growth mechanism and room temperature ferromagnetism property of the Zn1−xCrxS nanobelts

In this paper, the wurtzite-type Zn1−xCrxS nanobelts (NBs) were obtained by a simple hydrothermal process with the ethanol amine as the oriented-assembly agent at 180 °C. The results showed that the Cr3+ ions substituted for the Zn2+ sites in the host zinc sulfide (ZnS), and the maximum concentration of the Cr3+ ions in the ZnS NBs was 4.80 %. The Zn1−xCrxS NBs were constructed by the nanowires, and the growth mechanism of the NBs was investigated in detail. The Zn1−xCrxS NBs showed the ferromagnetism property at room temperature and the magnetic saturation value was increased as the Cr3+ doped ratio increased.

Sn self-doped α-Fe2O3 nanobranch arrays supported on a transparent, conductive SnO2 trunk to improve photoelectrochemical water oxidation

We produced hierarchically branched Fe2O3 nanorods on a Sb:SnO2 transparent conducting oxide (TCO) nanobelt structure as photoanodes for photoelectrochemical water splitting. Single-crystalline SnO2 nanobelts (NBs) surrounded by Fe2O3 nanorods (NRs) were synthesized by thermal evaporation, then underwent chemical bath deposition and annealing. When Fe2O3 was crystallized by annealing, Sn was diffused from SnO2 NBs and incorporated to Fe2O3 NRs, which was confirmed through Energy dispersive spectroscopy. Unlike previous high temperature sintering (∼800 °C), Sn doped hematite NRs were obtained at a low temperature (∼650 °C). This occurred since SnO2 NBs directly connected to Fe2O3 NRs are an abundant source of Sn dopant. The 3D hematite NRs on SnO2 NBs annealed at 650 °C produce a photocurrent density of 0.88 mA/cm2 at 1.23 V vs. RHE, which is 3 times higher than that of hematite NRs on a fluorine doped tin oxide (FTO) glass substrate annealed at the same temperature. The enhanced photocurrent is attributed to the improved electrical conductivity of Fe2O3 NRs by Sn doping, the efficient electron transport pathway by TCO nanowire and the increased surface area by hierarchically branched structure.

Solution processed films and nanobelts of substituted zinc phthalocyanine as room temperature ppb level Cl2 sensors

Room temperature Cl2 sensing characteristics of highly selective spin coated Zn (II) 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (ZnPc(OBu)8) film and self-assembled nanobelts (NBs) have been studied in the concentration range of 5–1500ppb. UV–Visible absorption spectroscopic studies indicate the formation of J-type aggregates in case of ZnPc(OBu)8 film and H-type aggregates in NBs. The electrical conductance of NBs is found to be 60% more than ZnPc(OBu)8 film. For 1500ppb of Cl2, the response of ZnPc(OBu)8 film and NBs is 522% and 655% with a response time of 25s and 15s, respectively. The detection limit of ZnPc film is lowered from 50ppb to 5ppb by making butoxy substitution. X-ray photoelectron spectroscopic studies reveal that absorption sites predominantly are the central metal ions of ZnPc(OBu)8 molecules. The results obtained are compared with Cl2 sensing characteristics of unsubstituted ZnPc film to show the effect of butoxy substitution and NBs formation.

A Cu2+ ion–F Center Complex View on the Photoluminescence Quenching and Correlating Ferrimagnetism in (Cu2+/Cu12+)0.044Zn0.956O Electrospun Nanobelts

Unlike to the most previous reports, mixed-cation Cu(+)/Cu(2+) doping-induced novel nanoscale phenomena, including photoluminescence quenching and a correlating ferrimagnetism with Néel temperature ≈ 14 K, were found in the as-calcined (Cu2(+)/Cu1(2+))0.044Zn0.956O electrospun nanobelts (NBs). There is also high strain (up to 1.98%) and shrunk lattice distortion (ΔV/V0 ∼ 0.127%) in the (Cu2(+)/Cu1(2+))0.044Zn0.956O NBs, leading to broken lattice symmetry in conjunction with nonstoichiometry (i.e., oxygen vacancies or accurate F centers), which could be possible origins of ferrimagnetism in the Cu-doped ZnO NBs. Electron paramagnetic resonance spectra reveal that there are giant and anisotropic g factors, suggesting that there is strong anisotropic spin-orbit interaction between the Cu(2+) ion and F center (i.e., forming Cu(2+)-F(+) complexes) in the (Cu2(+)/Cu1(2+))0.044Zn0.956O NBs. The above correlation enables the potential application of tuning of the optical and ferrimagnetic properties through strain and F-center engineering.

Dimensionality of Nanoscale TiO2 Determines the Mechanism of Photoinduced Electron Injection from a CdSe Nanoparticle

Assumptions about electron transfer (ET) mechanisms guide design of catalytic, photovoltaic, and electronic systems. We demonstrate that the mechanism of ET from a CdSe quantum dot (QD) into nanoscale TiO2 depends on TiO2 dimensionality. The injection into a TiO2 QD is adiabatic due to strong donor-acceptor coupling, arising from unsaturated chemical bonds on the QD surface, and low density of acceptor states. In contrast, the injection into a TiO2 nanobelt (NB) is nonadiabatic, because the state density is high, the donor-acceptor coupling is weak, and multiple phonons accommodate changes in the electronic energy. The CdSe adsorbant breaks symmetry of delocalized TiO2 NB states, relaxing coupling selection rules, and generating more ET channels. Both mechanisms can give efficient ultrafast injection. However, the dependence on system properties is very different for the two mechanisms, demonstrating that the fundamental principles leading to efficient charge separation depend strongly on the type of nanoscale material.