Mass-Based Environmental Factor and Energy Assessment of Microwave-Assisted Synthesized Transition Metal Nanostructures

This paper describes mass-based energy phase-space projection of microwave-assisted synthesis of transition metals (zinc oxide, palladium, silver, platinum, and gold) nanostructures. The projection uses process energy budget (measured in kJ) on the horizontal axes and process density (measured in kJg−1) on the vertical axes. These two axes allow both mass usage efficiency (Environmental-Factor) and energy efficiency to be evaluated for a range of microwave applicator and metal synthesis. The metrics are allied to the: second, sixth and eleventh principle of the twelve principle of Green Chemistry. This analytical approach to microwave synthesis (widely considered as a useful Green Chemistry energy source) allows a quantified dynamic environmental quotient to be given to renewable plant-based biomass associated with the reduction of the metal precursors. Thus allowing a degree of quantification of claimed “eco-friendly” and “sustainable” synthesis with regard to waste production and energy usage.

Ambient-Condition Strategy for Production of Hollow Ga_(2)O_(3)@rGO Crystalline Nanostructures Toward Efficient Lithium Storage

Crystallineγ-Ga_(2)O_(3)@rGO core-shell nanostructures are synthesized in gram scale,which are accomplished by a facile sonochemical strategy under ambient condition.They are composed of uniformγ-Ga_(2)O_(3)nanospheres encapsulated by reduced graphene oxide(rGO)nanolayers,and their formation is mainly attributed to the existed opposite zeta potential between the Ga_(2)O_(3)and rGO.The as-constructed lithium-ion batteries(LIBs)based on as-fabricatedγ-Ga_(2)O_(3)@rGO nanostructures deliver an initial discharge capacity of 1000 mAh g^(-1)at 100 mA g^(-1)and reversible capacity of 600 mAh g^(-1)under 500 mA g^(-1)after 1000 cycles,respectively,which are remarkably higher than those of pristineγ-Ga_(2)O_(3)with a much reduced lifetime of 100 cycles and much lower capacity.Ex situ XRD and XPS analyses demonstrate that the reversible LIBs storage is dominant by a conversion reaction and alloying mechanism,where the discharged product of liquid metal Ga exhibits self-healing ability,thus preventing the destroy of electrodes.Additionally,the rGO shell could act robustly as conductive network of the electrode for significantly improved conductivity,endowing the efficient Li storage behaviors.This work might provide some insight on mass production of advanced electrode materials under mild condition for energy storage and conversion applications.

Controlled Growth of Well-Aligned Carbon Nanotubes, Electrochemical Modification and Electrodeposition of Multiple Shapes of Gold Nanostructures

An efficient method has been developed to synthesize well-aligned multi-walled carbon nanotubes (MWCNTs) on a conductive Ta substrate by chemical vapour deposition (CVD). Free-standing MWCNTs arrays were functionalized through electrochemical oxidation with the formation of hydroxyl and carboxyl functional groups. Using a new oven drying technique, we demonstrate that the unidirectionally aligned and laterally spaced geometry of the CNT arrays can be retained after being subjected to each step of electrochemical modification. Samples were analyzed by using a field emission scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transformed infrared (FTIR) and Raman spectroscopy. Useful electrochemical methods for the synthesis of various gold nanostructures onto the aligned MWCNTs were then presented for the first time. The results demonstrated that flowerlike nanoparticle arrays, nanosheets and nanoflowers were obtained on the aligned CNTs under different experimental conditions. These kinds of aligned-CNT/Au nanostructures hybrid materials introduced by these efficient and simple electrochemical methods could lead to development of a new generation device for ultrasensitive catalytic and biological application.

SELF-ASSEMBLING AMPHIPHILIC POLYELECTROLYTES AND THEIR NANOSTRUCTURES

The self-assembling behavior of random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS)and hydrophobic comonomers possessing dodecyl groups linked by various spacer bonds was discussed with a focus on theeffect of the spacer. The characterization of association behavior of such polymers in water using quasielastic light scattering,capillary electrophoresis, NMR relaxation, various fluorescence, and viscoelastic methods was described. These copolymersform a variety of self-assembled nanostructures depending on the type of the spacer. Random copolymers of AMPS and N-dodecylmethacrylamide show a strong preference for intrapolymer self-association even in concentrated aqueous solutionsforming single-macromolecular self-assemblies (unimolecular micelles). In contrast, random copolymers of AMPS anddodecyl methacrylate are prone to undergo interpolymer associations yielding multipolymer micelles. In random copolymersof AMPS and a methacrylate substituted a nonionic surfactant (HO(CH_2CH_2O)_(25)C_(12)H_(25)) (C_(12)E_(25)), dodecyl groups are muchless restricted by the polymer backbone because they are linked via a long, flexible hydrophilic spacer. Thus, the polymer-bound C_(12)E_(25) surfactant moieties form micelles similar to those formed by discrete surfactants, but they are bridged bypolymer chains forming a network structure.

Kinetic study of methane hydrate formation in the presence of carbon nanostructures

The effect of synthesized nanostructures,including graphene oxide,chemically reduced graphene oxide with sodium dodecyl sulfate(SDS),chemically reduced graphene oxide with polyvinylpyrrolidone,and multi-walled carbon nanotubes,on the kinetics of methane hydrate formation was investigated in this work.The experiments were carried out at a pressure of 4.5 MPa and a temperature of 0 ℃ in a batch reactor.By adding nanostructures,the induction time decreases,and the shortest induction time appeares at certain concentrations of reduced graphene oxide with SDS and graphene oxide,that is,at a concentration of 360 ppm for reduced graphene oxide with SDS and 180 ppm for graphene oxide,with a 98% decrease in induction time compared to that in pure water.Moreover,utilization of carbon nanostructures increases the amount and the rate of methane consumed during the hydrate formation process.Utilization of multi-walled carbon nanotubes with a concentration of 90 ppm showes the highest amount of methane consumption.The amount of methane consumption increases by 173% in comparison with that in pure water.The addition of carbon nanostructures does not change the storage capacity of methane hydrate in the hydrate formation process,while the percentage of water conversion to hydrate in the presence of carbon nanotubes increases considerably,the greatest value of which occurres at a 90 ppm concentration of carbon nanotubes,that is,a 253% increase in the presence of carbon nanotubes compared to that of pure water.

Morphology and Crystallinity-controlled Synthesis of Manganese Cobalt Oxide/Manganese Dioxides Hierarchical Nanostructures for High-Performance Supercapacitors

We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanowires to form core-shell heterostructures.Detailed electrochemical characterization reveals that MnCo_2O_(4.5)@δ-MnO_2 pattern exhibits not only high specific capacitance of 357.5 F g^(-1)at a scan rate of 0.5 A g^(-1),but also good cycle stability(97%capacitance retention after 1000 cycles at a scan rate of 5 A g^(-1)),which make it have a promising application as a supercapacitor electrode material.

Recent Advances in Visible-Light-Driven Photoelectrochemical Water Splitting: Catalyst Nanostructures and Reaction Systems

Photoelectrochemical(PEC) water splitting using solar energy has attracted great attention for generation of renewable hydrogen with less carbon footprint, while there are enormous challenges that still remain for improving solar energy water splitting efficiency, due to limited light harvesting, energy loss associated to fast recombination of photogenerated charge carriers, as well as electrode degradation. This overview focuses on the recent development about catalyst nanomaterials and nanostructures in different PEC water splitting systems. As photoanode, Au nanoparticle-decorated TiO_2 nanowire electrodes exhibited enhanced photoactivity in both the UV and the visible regions due to surface plasmon resonance of Au and showed the largest photocurrent generation of up to 710 nm. Pt/Cd S/CGSe electrodes were developed as photocathode. With the role of p–n heterojunction, the photoelectrode showed high stability and evolved hydrogen continuously for more than 10 days. Further, in the Z-scheme system(Bi_2S_3/TNA as photoanode and Pt/Si PVC as photocathode at the same time), a self-bias(open-circuit voltage Voc= 0.766 V) was formed between two photoelectrodes, which could facilitate photogenerated charge transfers and enhance the photoelectrochemical performance, and which might provide new hints for PEC water splitting. Meanwhile, the existing problems and prospective solutions have also been reviewed.

Electronic and Optical Properties of Nanostructures and Its Relationship with Harari Index

The topological index of molecular graph is a number that attributed to the molecular graph and is valid than graph isomorphism, this number can reflect the properties of the molecules. In this study, Harari index in family phenacenes was calculated with some electronic and optical properties desired for a number of elements of the family, a model for predicting the electronic and optical properties by Harari index was prepared. To offer this model using mathematical software, electronic and optical properties of phenacenes calculated and compared with the data sources.

Green Chemistry Allometry Test of Microwave-Assisted Synthesis of Transition Metal Nanostructures

Microwave irradiation is considered an important approach to Green Chemistry, because of its ability to rapidly increase the internal temperature of polar-organic compounds that lead to synthesis times of minutes rather than hours when compared to conventional thermal heating. This works describes a dual allometry test for the discrimination between the solvents and reagents used in the microwave-assisted synthesis of transition metal (zinc oxide, palladium silver, platinum, and gold) nanostructures. The test is performed in log-log process energy phase-space projection, where the synthesis data (kJ against kJ·mol-1) has a power-law signature. The test is shown to discriminate between recommended Green Chemistry, problematic Green Chemistry, and Green Chemistry hazardous solvents. Typically, recommended Green chemistry exhibits a broad y-axes distribution within an upper exponent = 1 and lower exponent = 0.5. Problematic Green Chemistry exhibits a y-axes narrower distribution with an upper exponent = 0.94 and lower exponent = 0.64. Non-Green Chemistry hazardous data exhibits a further narrowing of the y-axes distribution within upper exponent = 0.87 and lower exponent = 0.66. In all three cases, the y-axes is aligned to original database power-law signature. It is also shown that in the x-axes direction (process energy budget) the grouped order of magnitude decreases from four orders for recommended Green Chemistry solvent and reagent data, through two orders for non-Green Chemistry hazardous material and down to one order for problematic Green Chemistry.

Anodized metal oxide nanostructures for photoelectrochemical water splitting

Photoelectrochemical(PEC) water splitting offers the capability of harvesting, storing, and converting solar energy into clean and sustainable hydrogen energy. Metal oxides are appealing photoelectrode materials because of their easy manufacturing and relatively high stability. In particular, metal oxides prepared by electrochemical anodization are typical of ordered nanostructures, which are beneficial for light harvesting, charge transfer and transport, and the adsorption and desorption of reactive species due to their high specific surface area and rich channels. However, bare anodic oxides still suffer from low charge separation and sunlight absorption efficiencies. Accordingly, many strategies of modifying anodic oxides have been explored and investigated. In this review, we attempt to summarize the recent advances in the rational design and modifications of these oxides from processes before, during, and after anodization. Rational design strategies are thoroughly addressed for each part with an aim to boost overall PEC performance. The ongoing efforts and challenges for future development of practical PEC electrodes are also presented.

Piezoresistive behavior of elastomer composites with segregated network of carbon nanostructures and alumina

Electrically conductive elastomer composites(CECs)with segregated networks of conductive nanofillers show high potential in stretchable strain sensors due to balanced mechanical and electrical properties,yet the sensitivity at low strain is generally insufficient for practical application.Herein,we report an easy and effective way to improve the resistive response to low strain for CECs with segregated network structure via adding stiff alumina into carbon nanostructures(CNS).The CEC containing 0.7 wt%CNS and 5 wt%Al_(2)O_(3) almost sustains the same elasticity(elongation at break of~900%)and conductivity(0.8 S/m)as the control,while the piezoresistive sensitivity is significantly improved.Thermoplastic polyurethane(TPU)composites with a segregated network of hybrid nanofillers(CNS and Al_(2)O_(3))show much higher strain sensitivity(Gauge factor,GF-566)at low strain(45%strain)due to a local stress concentration effect,this sensitivity is superior to that of TPU/CNS composites(GF-11).Such a local stress concentration effect depends on alumina content and its distribution at the TPU particle interface.In addition,CECs with hybrid fillers show better reproducibility in cyclic piezoresistive behavior testing than the control.This work offers an easy method for fabricating CECs with a segregated filler network offering stretchable strain sensors with a high strain sensitivity.

Generating micro/nanostructures on magnesium alloy surface using ultraprecision diamond surface texturing process

The lightness and high strength-to-weight ratio of the magnesium alloy have attracted more interest in various applications.However,micro/nanostructure generation on their surfaces remains a challenge due to the flammability and ignition.Motivated by this,this study proposed a machining process,named the ultraprecision diamond surface texturing process,to machine the micro/nanostructures on magnesium alloy surfaces.Experimental results showed the various microstructures and sawtooth-shaped nanostructures were successfully generated on the AZ31B magnesium alloy surfaces,demonstrating the effectiveness of this proposed machining process.Furthermore,sawtooth-shaped nanostructures had the function of inducing the optical effect and generating different colors on workpiece surfaces.The colorful letter and colorful flower image were clearly viewed on magnesium alloy surfaces.The corresponding cutting force,chip morphology,and tool wear were systematically investigated to understand the machining mechanism of micro/nanostructures on magnesium alloy surfaces.The proposed machining process can further improve the performances of the magnesium alloy and extend its functions to other fields,such as optics.

Atomic-Scale AES-EELS Analysis of Structure-Phase State and Growth Mechanism of Layered Nanostructures

A review of our experience in range of electron spectroscopy of the physical vapor-phase deposition and growth of single- and multilayer nanostructures with atomic scale interfaces is presented. The foundation of an innovative methodology for the combined AES-EELS analysis of layered nanostructures is developed. The methodology includes: 1) determination of the composition, thickness, and the mechanism of phase transitions in nanocoatings under the probing depth most appropriated for the range of film thickness 1 - 10 ML;2) quantitative iteration Auger-analysis of the composition, thickness and growth mechanism of nanocoating;3) structural and phase analysis of nanocoatings with use of the analysis of position, shape and energy of the plasmon EELS peak and with subtracting the contribution from the substrate;4) analysis of phase transitions with use of the shift of the plasmon Auger-satellite and 5) non-destructive profiling of the composition of nanocoatings over depth with use of a dependence of the intensity and energy of EELS peaks on the value of the primary electron energy.

Vertical 3D Nanostructures Boost Efficient Hydrogen Production Coupled with Glycerol Oxidation Under Alkaline Conditions

Hydrogen production from electrolytic water is an important sustainable technology to realize renewable energy conversion and carbon neutrality.However,it is limited by the high overpotential of oxygen evolution reaction(OER)at the anode.To reduce the operating voltage of electrolyzer,herein thermodynamically favorable glycerol oxidation reaction(GOR)is proposed to replace the OER.Moreover,vertical Ni O flakes and NiMoNH nanopillars are developed to boost the reaction kinetics of anodic GOR and cathodic hydrogen evolution,respectively.Meanwhile,excluding the explosion risk of mixed H_2/O_(2),a cheap organic membrane is used to replace the expensive anion exchange membrane in the electrolyzer.Impressively,the electrolyzer delivers a remarkable reduction of operation voltage by 280 mV,and exhibits good long-term stability.This work provides a new paradigm of hydrogen production with low cost and good feasibility.

Tailored BiVO_(4)/In_(2)O_(3)nanostructures with boosted charge separation ability toward unassisted water splitting

The development of new heterostructures with high photoactivity is a breakthrough for the limitation of solar-driven water splitting.Here,we first introduce indium oxide(In_(2)O_(3))nanorods(NRs)as a novel electron transport layer for bismuth vanadate(BiVO_(4))with a short charge diffusion length.In_(2)O_(3)NRs reinforce the electron transport and hole blocking of BiVO_(4),surpassing the state-of-the-art photoelectrochemical performances of BiVO_(4)-based photoanodes.Also,a tannin-nickel-iron complex(TANF)is used as an oxygen evolution catalyst to speed up the reaction kinetics.The final TANF/BiVO_(4)/In_(2)O_(3)NR photoanode generates photocurrent densities of 7.1 mAcm^(−2) in sulfite oxidation and 4.2 mA cm^(−2) in water oxidation at 1.23 V versus the reversible hydrogen electrode.Furthermore,the“artificial leaf,”which is a tandem cell with a perovskite/silicon solar cell,shows a solar-to-hydrogen conversion efficiency of 6.2%for unbiased solar water splitting.We reveal significant advances in the photoactivity of TANF/BiVO_(4)/In_(2)O_(3)NRs from the tailored nanostructure and band structure for charge dynamics.

Multiple Fano resonances in nanorod and nanoring hybrid nanostructures

Multiple Fano resonances of plasmonic nanostructures have attracted much attention due to their potential applications in multicomponent biosensing. In this paper, we propose a series of hybridized nanostructures consisting of a single nanoring and multiple nanorods to generate multiple Fano resonances. One to three Fano resonances are achieved through tuning the number of nanorods. The interaction coupling process between different components of the nanostructures is recognized as the mechanism of multiple Fano resonances. We also theoretically investigate the applications of the produced multiple Fano resonances in refractive index sensing. The specific properties of multiple Fano resonances will make our proposed nanostructures beneficial to high-sensitivity biosensors.

The BOLS-NEP theory reconciling the attributes of undercoordinated adatoms,defects,surfaces and nanostructures

This article describes a theory unifying the unusual performance of the undercoordinated adatoms,point defects,terrace edges,surfaces,and nanostructures of various shapes.The ideas of bond order-length-strength correlation and the associated nonbonding electron polarization(BOLS-NEP)feature that bonds between undercoordinated atoms contract spontaneously.Bond contraction raises the local density of charge and energy.Bond strength gain deepens the interatomic potential well to trap the core and bonding electrons deeply.In turn,the locally and densely entrapped electrons polarize those partially occupying the valence band and above pertaining to the lower-coordinated atoms.The BOLS-NEP theory reconciles the unusual behaviors of undercoordinated systems and the size dependency of nanostructures in their lattice oscillating dynamics,mechanical strength,thermal stability,photon emissivity,chemical reactivity,dielectric permeability,associated with generation of polarized Dirac fermions,serving as carriers for extraordinary catalysis,hydrophobicity,fluidity,lubricity,as well as monolayer high-TC superconductivity and topological insulator conductivity.

Laser additive manufacturing of Si/ZrO_(2)tunable crystalline phase 3D nanostructures

The current study is directed to the rapidly developing field of inorganic material 3D object production at nano-/micro scale.The fabrication method includes laser lithography of hybrid organic-inorganic materials with subsequent heat treatment leading to a variety of crystalline phases in 3D structures.In this work,it was examined a series of organometallic polymer precursors with different silicon(Si)and zirconium(Zr)molar ratios,ranging from 9:1 to 5:5,prepared via sol-gel method.All mixtures were examined for perspective to be used in 3D laser manufacturing by fabricating nano-and micro-feature sized structures.Their spatial downscaling and surface morphology were evaluated depending on chemical composition and crystallographic phase.The appearance of a crystalline phase was proven using single-crystal X-ray diffraction analysis,which revealed a lower crystallization temperature for microstructures compared to bulk materials.Fabricated 3D objects retained a complex geometry without any distortion after heat treatment up to 1400℃.Under the proper conditions,a wide variety of crystalline phases as well as zircon(ZrSiO_(4)-a highly stable material)can be observed.In addition,the highest new record of achieved resolution below 60 nm has been reached.The proposed preparation protocol can be used to manufacture micro/nano-devices with high precision and resistance to high temperature and aggressive environment.

Morphological features and nanostructures generated during SiC graphitization process

Surface morphological features and nanostructures generated during SiC graphitization process can significantly affect fabrication of high-quality epitaxial graphene on semiconductor substrates.In this work,we investigate the surface morphologies and atomic structures during graphitization process of 4H-SiC(0001) using scanning tunneling microscopy.Our high-magnified scanning-tunneling-microscope images exhibit the appearance and gradual developments of SiC(1 × 1)nanostructures after 1100℃ cleaning treatments,irregularly distributed among carbon nanocaps and(√3×√3) reconstruction domains.A model for the formation and growth progression of SiC(1 × 1) nanostructures has been proposed.When post-annealing temperature reaches 1300 ℃,the nanoholes and nanoislands can be observed on the surface,and multilayer graphene is often detected lying on the top surface of those nanoislands.These results provide profound insights into the complex evolution process of surface morphology during SiC thermal decomposition and will shed light on fabrication of SiC nanostructures and graphene nanoflakes.

Unidirectional plasmonic Bragg reflector based on longitudinally asymmetric nanostructures

Plasmonic Bragg reflectors are essential components in plasmonic circuits.Here we propose a novel type of plasmonic Bragg reflector, which has very high reflectance for the right-side incidence and meanwhile has extremely large absorption for the left-side incidence.This device is composed of longitudinally asymmetric nanostructures in a metal–insulator–metal waveguide.In order to efficiently analyze, design, and optimize the reflection and transmission characteristics of the proposed device, we develop a semi-analytic coupled-mode model.Results show that the reflectance extinction ratio between plasmonic modes incident from the right-side and the left-side reaches 11 dB.We expect this device with such striking unidirectional reflection performance can be used as insulators in nanoplasmonic circuits.