Phosphorus-doped TiO2mesoporous nanocrystals for anodes in high-current-rate lithium ion batteries.

Limited by the intrinsic low electronic conductivity and inferior electrode kinetics, the use of TiO2as an anode material for lithium ion batteries (LIBs) is hampered. Nanoscale surface-engineering strategies of morphology control and particle size reduction have been devoted to increase the lithium storage performances. It is found that the ultrafine nanocrystal with mesoporous framework plays a crucial role in achieving the excellent electrochemical performances due to the surface area effect. Herein, a promising anode material for LIBs consisting of phosphorus-doped TiO2mesoporous nanocrystals (P-TMC) with ultrafine size of 2-8 nm and high specific surface area (234.164 m2g-1) has been synthesized. It is formed through a hydrothermal process and NaBH4assisted heat treatment for anatase defective TiO2(TiO2-x) formation followed by a simple gas phosphorylation process in a low-cost reactor for P-doping. Due to the merits of the large specific surface area for providing more reaction sites for Li+ions to increase the storage capacity and the presence of oxygen vacancies and P-doping for enhancing material's electronic conductivity and diffusion coefficient of ions, the as-designed P-TMC can display improved electrochemical properties. As a LIB anode, it can deliver a high reversible discharge capacity of 187 mAh g-1at 0.2 C and a good long cycling performance with ∼82.6% capacity retention (101 mAh g-1) after 2500 cycles at 10 C with an average capacity loss of only 0.007% per cycle. Impressively, even the current rate increases to 100 times of the original rate, a satisfactory capacity of 104 mAh g-1can be delivered, displaying good rate capacity. These results suggest the P-TMC a viable choice for application as an anode material in LIB applications. Also, the strategy in this work can be easily extended to the design of other high-performance electrode materials with P-doping for energy storage.

High-porosity hybrid bilayer-enabled portable LED plasmonic biosensing.

A TiO2-nanowire/Au-nanoparticle hybrid layer, possessing nanocavities and a plasmonic metasurface, can accomplish an entire visible region absorbance, inducing remarkable photocurrent-extraction efficiency. A blood-glucose strip-like testing protocol assembled using this layer allows nondestructive quantitative alpha-fetoprotein detection in human serum under homemade visible LED illumination, indicating its potential in commercial point-of-care testing applications.

Ultrasensitive label- and amplification-free photoelectric protocols based on sandwiched layer-by-layer plasmonic nanocomposite films for the detection of alpha-fetoprotein.

A label- and amplification-free photoelectric immunosensor based on well-defined layer-by-layer sandwich-structured AuNP/TNW/AuNP composite is proposed for direct and ultrasensitive detection of α-fetoprotein (AFP). The AuNP/TNW/AuNP composite is produced by assembling an Au nanoparticle underlayer and anatase TiO2 nanowires (TNW) onto the FTO substrate, followed by decorating Au nanoparticles onto the TNW surface, through a simple sputtering and hydrothermal process. The resulting AuNP/TNW/AuNP electrode exhibits a 14-fold and 2-fold enhancement in photocurrent density under simulated sunlight compared with that of bare TNW and AuNP/TNW, respectively, which benefits from the SPR-induced photoabsorption increment and charge separation improvement in Au nanoparticle and interfacial charge transfer promotion at the TiO2/substrate interface in the Au underlayer. As a proof of concept, the AFP antigen can be quantitatively detected by the proposed AuNP/TNW/AuNP coupled with anti-AFP through the analysis of the photocurrent change. This novel AFP photoelectric immunosensor exhibited sensitive detection of AFP with an ultrahigh sensitivity of 0.001 ng mL-1 and good specific selectivity. Moreover, the practical determination of AFP in human serum is also investigated, demonstrating its applicability and potential attraction for clinical tests and disease diagnosis.

Green synthesis of carbon quantum dots embedded onto titanium dioxide nanowires for enhancing photocurrent.

The green synthesis of nanowired photocatalyst composed of carbon quantum dots-titanium hybrid-semiconductors, CQDs/TiO2, are reported. Where graphite-based CQDs with a size less than 5 nm are directly synthesized in pure water electrolyte by a one-step electrochemistry approach and subsequently electrodeposited onto as-prepared TiO2 nanowires through a voltage-driven reduction process. Electron paramagnetic resonance studies show that the CQDs can generate singlet oxygen and/or oxygen radicals to decompose the kinetic H2O2 intermediate species upon UV light illumination. With the effect of peroxidase-like CQDs, photocurrent density of CQDs/TiO2 is remarkably enhanced by a 6.4 factor when compared with that of as-prepared TiO2.

Plasmon-Enhanced Photocurrent using Gold Nanoparticles on a Three-Dimensional TiO2 Nanowire-Web Electrode.

In this study, an anatase/rutile mixed-phase titanium dioxide (TiO2) hierarchical network deposited with Au nanoparticles (Au/TiO2 ARHN) was synthesized using a facile hydrothermal method followed by a simple calcination step. Such a unique structure was designed for improving the light harvest, charge transportation/separation, and the performance of photo-electro-chemical (PEC) cells. The properties of the as-synthesized Au/TiO2 ARHN in PEC cells were investigated by electrochemical measurements using a three-electrode system in a 1 M NaOH electrolyte. Remarkably, a 4.5-folds enhancement of the photocurrent for Au/TiO2 ARHN was observed as compared to that for TiO2 nanowire (NW), under AM1.5G solar illumination, suggesting its potential application in PEC cells. A mechanism has been proposed to explain the high photocurrent of Au/TiO2 ARHN in PEC water splitting.

Porous honeycomb structures formed from interconnected MnO2 sheets on CNT-coated substrates for flexible all-solid-state supercapacitors.

The use of lightweight and easily-fabricated MnO2/carbon nanotube (CNT)-based flexible networks as binder-free electrodes and a polyvinyl alcohol/H2SO4 electrolyte for the formation of stretchable solid-state supercapacitors was examined. The active electrodes were fabricated from 3D honeycomb porous MnO2 assembled from cross-walled and interconnected sheet-architectural MnO2 on CNT-based plastic substrates (denoted as honeycomb MnO2/CNT textiles).These substrates were fabricated through a simple two-step procedure involving the coating of multi-walled carbon nanotubes (MWCNTs) onto commercial textiles by a dipping-drying process and subsequent electrodeposition of the interconnected MnO2 sheets onto the MWCNT-coated textile. With such unique MnO2 architectures integrated onto CNT flexible films, good performance was achieved with a specific capacitance of 324 F/g at 0.5 A/g. A maximum energy density of 7.2 Wh/kg and a power density as high as 3.3 kW/kg were exhibited by the honeycomb MnO2/CNT network device, which is comparable to the performance of other carbon-based and metal oxide/carbon-based solid-state supercapacitor devices. Specifically, the long-term cycling stability of this material is excellent, with almost no loss of its initial capacitance and good Coulombic efficiency of 82% after 5000 cycles. These impressive results identify these materials as a promising candidate for use in environmentally friendly, low-cost, and high-performance flexible energy-storage devices.

Plasmon-induced efficiency enhancement on dye-sensitized solar cell by a 3D TNW-AuNP layer.

A new 3D TNW-AuNP plasmonic electrode consists of antireflective (AR) TiO2 nanowires (TNWs) (∼600 nm thickness) serving as light-harvesting antennae coupling with Au nanoparticles (NPs). A huge red-shift of 55 nm is observed in surface plasmon spectra for the Au (11 nm) plasmonic electrode that has 11 nm size Au NPs, whereby (111) lattice planes have a specific bonding with the TiO2 (101) planes. Remarkable red-shift is mainly attributed to the localized electric field improvement resulting from the plasmonic coupling effect between the Au NPs and the Au-TiO2 hybrids. After TiCl4 treatment, this favorable Au (11 nm) nanostructure takes advantage of harvesting photons to increase the conversion efficiency of dye-sensitized solar cells (DSSCs) from 6.25% to 9.73%.

Chain-network anatase/TiO2 (B) thin film with improved photocatalytic efficiency.

A 3-dimensional chain-network anatase/TiO2 (B) was obtained via the basic hydrothermal treatment of a sandwich Ti/TiO2/Ti film on a glass substrate that was prepared from 16 nm anatase TiO2 nanoparticles. The Ti film was converted to the TiO2 (B) phase in a Teflon vessel containing a 10 M NaOH aqueous solution that was encapsulated in a stainless-steel autoclave and heated at 130 °C for 2 h. The TiO2 (B) then served as a binder layer that enabled the formation of pearl-necklace chains made of anatase TiO2 nanoparticles, and these chain-like structures thoroughly interpenetrated into the textured layer. Decomposition tests using methylene blue indicated that the chain-network anatase/TiO2 (B) mixed-phase film had a photocatalytic half-life that was 0.84 and 0.69 times shorter than those of as-prepared anatase TiO2 and P25, respectively. In addition, the intensity of the room temperature photoluminescence spectra of anatase TiO2 was 2.55-fold higher than that of the chain-network anatase/TiO2 (B). We thus conclude that the remarkable photocatalytic activity of the chain-network anatase/TiO2 (B) is attributed to the chain-network structural characteristics and a synergistic effect of the matching band gap potentials, which increases the transfer of photogenerated electrons and reduces electron-hole recombination.

Towards a high-throughput label-free detection system combining localized-surface plasmon resonance and microfluidics.

This work reports an integrated platform combining localized-surface plasmon resonance (LSPR) and microfluidic chips to carry out multiplexed and label-free protein analysis. We fabricated an optical bench to enable detection using only a laboratory UV-Vis spectrophotometer. This assay not only improves throughput, but also allows quantitative analysis.

Hydrothermally processed TiO2 nanowire electrodes with antireflective and electrochromic properties.

Dual functionalities of antireflective and electrochromic properties-based anatase TiO(2) nanowire devices with a high-porosity cross-linked geometry directly grown onto transparent conductive glass was achieved for the first time through a simple one-step hydrothermal process under mild alkali conditions. Devices fashioned from these TiO(2) nanowires were found to display enhanced optical transparency in the visible range, better color contrast, and faster color-switching time in comparison to devices made from nanoparticles. These improvements can be attributed to the low refractive index and high porosity of the TiO(2) nanowires and their larger accessible surface area for Li(+) intercalation and deintercalation, leading to enhanced capabilities for transparent electrochromic smart windows.

Nonvolatile gating effects on radicals-containing vanadium oxide nanowires by gas molecule absorption and diffusion.

The charge conduction of a single nanowire of radicals-containing vanadium oxides was experimentally studied and found to be modulated by different gas exposures, showing a gating effect by the adsorption and absorption of different gas molecules. After N(2) and O(2) gas are introduced, the nanowires show an abrupt increase of the resistance but show the opposite trend within a longer timescale of several ks. The introduction of N(2) and O(2) can respectively 'write' the nanowire into high and low resistance states, which are metastable in a high vacuum. The long-term gating effect which was attributed to the interlayer diffusion of the gas molecules can be registered on the nanowire in the high vacuum environment.

High sensitivity and selectivity of human antibody attachment at the interstices between substrate-bound gold nanoparticles.

Durable Au-patterning nanostructures with uniform spacing having an average nanoparticle size of 8 nm and an interparticle gap of 11 nm were fabricated using a microwave-plasma oven. Single molecules of immunoglobulin G (IgG) are individually occupied at the space constraints so that the extinction response of localized surface plasmon resonance (LSPR) can be observed when detecting human anti-IgG molecules, affording a detection limit of 66.7 pM.

Erratum to: Architectural Growth of Cu Nanoparticles Through Electrodeposition.

[This corrects the article DOI: 10.1007/s11671-009-9424-5.].

Growth of copper phthalocyanine rods on Au plasmon electrodes through micelle disruption methods.

To improve the efficiency of the photocurrent conversion process, we have utilized copper phthalocyanine (CuPc) rods, which are capable of enhancing the interfacial area of electron transport and plasmonic gold nanoparticles (Au NPs), which can increase the separation and photogeneration of excitons, to produce a more effective system. In-plane horizontal CuPc rods, with diameters ranging from 0.2 to 1.5 microm, were electrodeposited onto the surface of plasmonic (Au NP) monolayers predeposited onto ITO substrates through electrolytic micelle disruption (EMD) methods.

Direct observation of multiple pathways of single-stranded DNA stretching.

We observed multiple pathways of stretching single-stranded polydeoxynucleotides, poly(dA). Poly(dA) has been shown to undergo unique transitions under mechanical force, and such transitions were attributed to the stacking characteristics of poly(dA). Using single-molecule manipulation studies, we found that poly(dA) has two stretching pathways at high forces. The previously observed pathway has a free energy that is less than what is expected of single-stranded DNA with a random sequence, indicating the existence of a novel conformation of poly(dA) at large extensions. We also observed stepwise transitions between the two pathways by pulling the molecule with constant force, and found that the transitions are cooperative. These results suggest that the unique mechanical property of poly(dA) may play an important role in biological processes such as gene expression.

The facile fabrication of tunable plasmonic gold nanostructure arrays using microwave plasma.

Fabrication of isolated noble metal nanoparticles embedded in transparent substrates is the fasting growing demand for innovative plasmonic technologies. Here we report a simple and effective methodology for the preparation of highly stable plasmonic nanoparticles embedded in a glass surface. Size-controllable (10-70 nm) Au nanoparticles were rapidly prepared when subjected to the home-microwave plasma. Accordingly, the optical extinction maximum of the localized surface plasmon resonance (LSPR) can be systematically tuned in the range 532-586 nm. We find that the plasmonic structures are exceedingly stable toward immersion in ethanol solvents and pass successfully the adhesive tape test, which makes our system highly promising for efficient transmission-LSPR nanosensors. Besides, the attractive features of substrate-bound plasmonic nanostructures include its low cost, versatility, robustness, reusability and a promising ability to make a multi-arrayed LSPR biochip.

Well-aligned multi-walled carbon nanotubes emitting natural white-light under microwave irradiation.

Low-cost black coating with freestanding well-aligned carbon nanotubes (CNTs), fabricated from CNT-dispersive in water-soluble poly(vinyl alcohol) (PVA) matrix, exhibits a bright white-light emission with narrow-band RGB (red, green, blue) colors having CIE (0.327, 0.349) chromaticity coordinate when subjected to the microwave irradiation.

Temperature and chemical denaturant dependence of forced unfolding of titin I27.

Single-molecule force measurement opens a new door for investigating detailed biomolecular interactions and their thermodynamic properties by pulling molecules apart while monitoring the force exerted on them. Recent advances in the nonequilibrium work theorem allows one to determine the free-energy landscapes of these events. Such information is valuable for understanding processes such as protein and RNA folding and receptor-ligand binding. Here, we used force as a physical parameter under the traditional chemical and temperature denaturing environment to alter the protein folding energy landscape and compared the change in the unfolding free-energy barrier of the I27 domain of human cardiac titin. We found that the trends in protein unfolding free-energy barriers are consistent for single-molecule force measurements and bulk chemical and temperature studies. The results suggest that the information from single-molecule pulling experiments are meaningful and useful for understanding the mechanism of folding of titin I27.

Quantifying DNA melting transitions using single-molecule force spectroscopy.

We stretched a DNA molecule using atomic force microscope and quantified the mechanical properties associated with B and S forms of double-stranded DNA (dsDNA), molten DNA, and single-stranded DNA (ssDNA). We also fit overdamped diffusion models to the AFM time series and used these models to extract additional kinetic information about the system. Our analysis provides additional evidence supporting the view that S-DNA is a stable intermediate encountered during dsDNA melting by mechanical force. In addition, we demonstrated that the estimated diffusion models can detect dynamical signatures of conformational degrees of freedom not directly observed in experiments.