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Photocatalysts for oxidation reactions are crucial for a wide variety of industrial activities. Here, we describe a framework consisting of silver nanomaterials atop Mg-doped lithium niobate. This substrate under white light irradiation is demonstrated to support the oxidation of compounds, such as p-aminothiophenol, through the activation of charge transfer processes. This study highlights the use of doped lithium niobate materials as semiconductor platforms for plasmonic photocatalysis. [ABSTRACT FROM AUTHOR]

In this study, we integrate plasmonic metal nanomaterials with a piezoelectric polyvinylidene fluoride (PVDF) polymer and lithium niobate (LiNbO3) based composite to form an all-solid-state flexible self-energized sensor. We demonstrate that following the application of a load, the film enhances the surface-enhanced Raman spectroscopy (SERS) signal of an analyte molecule up to 14 times. The piezoelectric β-phase of PVDF in the film is optimized through the introduction of multi-walled carbon nanotubes and post-fabrication UV irradiation annealing. Additionally, the SERS signal enhancement can be further increased by the application of in situ UV light irradiation of the sample, resulting in the generation of photoexcited electrons from LiNbO3 microparticles introduced into the composite. Both the application of a mechanical displacement and the UV light-induced charge generation result in an improved charge transfer between the film and an analyte molecule. The piezoelectric PVDF/LiNbO3 film has been shown to be a suitable SERS platform for the detection of important biological molecules, demonstrating the potential of the substrate for fast on-site detection applications. [ABSTRACT FROM AUTHOR]

Enabling an understanding of the optical properties of functional inorganic–organic materials is crucial for driving development in many areas such as medicine and optoelectronics. In particular the use of two-dimensional materials such as hexagonal boron nitride has been recently investigated for the fabrication of nanohybrid composites due to the unique properties of the material. Here we report the use of boron nitride/silver nanoparticle (BN/AgNP) composite templates as an effective substrate for controlling the fluorescence emission of adsorbed organic molecules through applying external electric fields in the range of 0 to 3 × 104 V/m. We report fluorescence quenching in the field and enhancement of fluorescence signal intensity of J-aggregate porphyrins up to 20 min following removal of the applied voltage. We propose that the observed enhancement can be attributed to charge release upon switching off the field due to capacitance effects associated with the BN/AgNP substrate. [ABSTRACT FROM AUTHOR]

Piezoelectric diphenylalanine peptide nanotubes (PNTs) have recently been demonstrated in energy harvesting applications, typically based on vertically aligned PNTs that generate charge when pressed. In this work, we use a wettability difference and an applied electric field to align PNTs and PNT-based composites on flexible substrates. Open-circuit voltages and short-circuit currents exceeding 6 V and 60 nA, respectively, are achieved by bending the substrate, opening up the use of horizontally aligned PNTs as flexible energy harvesting substrates. [ABSTRACT FROM AUTHOR]

Self‐assembling nanostructured peptide gels are promising materials for sensing, drug delivery, and energy harvesting. Of particular interest are short diphenylalanine (FF) peptides modified with 9‐fluorenylmethyloxycarbonyl (Fmoc), which promotes the association of the peptide building blocks. Fmoc‐FF gels generally form fibrous networks and while other structures have been demonstrated, further control of the gelation and resulting ordered three‐dimensional structures potentially offers new possibilities in tissue engineering, sensing, and drug release applications. Herein, we report that the structure tunability of Fmoc‐FF gels can be achieved by controlling the water content and the temperature. We further explore the incorporation of metal nanoparticles in the formation of the gel to enable optical sensing applications based on hybrid Fmoc‐FF‐nanoparticle microspheres. Finally, fluorescence lifetime imaging microscopy reveals a correlation between lifetime and reduced bandgap, in support of a semiconductor‐induced charge transfer mechanism that might also increase the stability of an excited state of a probe molecule. The observations potentially further widen the use of these peptide materials in bioimaging and sensing applications. [ABSTRACT FROM AUTHOR]

Iron-core electromagnets are widely used as applied-field switches in high-temperature superconducting (HTS) flux pumps. It was recently reported that the critical current ( I c ) of the HTS wire is suppressed by up to 45% in the air gap of the iron core. Here, it is reported that the self-field I c of a single tape (unifilar) is suppressed from 357 A to 195 A while in the air gap of an iron core, agreeing closely with the previous study. This is extended by showing that the I c response to a perpendicular magnetic field is asymmetric, with a peak I c of 249 A found to be at 0.16 T of applied magnetic field. This effect can be eliminated using an anti-parallel current configuration (bifilar), which is shown experimentally to recover close to the no-core self-field I c of 357 A with no observed asymmetry. The results of both types of switch configurations are closely replicated in finite-element modelling using COMSOL Multiphysics®. This is caused by the asymmetric interaction between the self-induced magnetic field of the HTS switch element and the magnetic circuit of the iron-core electromagnet. [ABSTRACT FROM AUTHOR]

The bactericidal properties of chemically patterned lithium niobate substrates under a super-bandgap UV light source is established. UV irradiation of lithium niobate surfaces inoculated with bacteria leads to antimicrobial activity compared to a glass substrate under similar conditions, as determined by surface enhanced Raman spectroscopy and corroborated with a fluorescence-based live/dead assay. This finding may expand the possible biomedical applications of lithium niobate. [ABSTRACT FROM AUTHOR]

We examine the potential of cadmium sulfide when combined with plasmonic nanostructures to support photo-induced catalysis. Super-bandgap irradiation of a silver nanowire and cadmium sulfide composite for the probe molecule p-aminothiophenol (PATP) showed the formation of dimercaptoazobenzene (DMAB) from PATP. Our results demonstrate that cadmium sulfide can be used as an alternative material to semiconductors, such as titanium dioxide, for plasmonic photocatalysis applications. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) is a sensitive and nondestructive technique used for the detection of molecules, traditionally applied on noble-metal or semiconductor substrates. Point defect introduction has been applied to increase the enhancement of semiconductor templates due to more efficient charge transfer; however, they are still limited by low detection sensitivity and inferior SERS enhancement. Here we propose a universal approach of oxygen incorporation into metal oxide nanowire/metal nanoparticle templates that allows for greater SERS enhancement due to localized surface plasmon resonance excitation, point defect-induced optical gap shrinking, and wettability change of the substrate. We report up to 5-fold Raman relative peak intensity enhancement after annealing-induced oxygen introduction. This approach is applied to defect formation in metal oxide semiconductor nanowires such as ZnO, WO3, TiO2, and NiO and is applicable for a wide variety of probe molecules, making the method suitable for medical, security, and environmental applications. [ABSTRACT FROM AUTHOR]

Mapping of the potential energy surface of the torsions of the phenyl groups of C[sub 70]Ph[sub 8] and C[sub 70]Ph[sub 10] by molecular mechanics reveals the existence of two conformers for each molecule. Energetically, both pairs are quasi- degenerate and therefore they could be experimentally detectable despite the low activation barriers for the inter-conversion (2.4 kcal mol[sup -1] for C[sub 70]Ph[sub 8] and 3.9 kcal mol[sup -1] for C[sub 70]Ph[sub 10], respectively). In an effort to pin down the existence of the conformers, the laser induced luminescence spectra of C[sub 70]Ph[sub 8] and C[sub 70]Ph[sub 10] were recorded in several solid solutions. The spectral features for C[sub 70]Ph[sub 8] are rather independent of the nature of the environment and closely resemble those observed before in liquid solution with two main bands separated by more than 2000 cm[sup -1]. For C[sub 70]Ph[sub 10], two new low-energy bands appear which were previously undetected in the liquid phase studies and which depend on the matrix. It is proposed that the doublet bands are fingerprints of the presence of the conformers. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Precise control over the arrangement of plasmonic nanomaterials is critical for label-free single-molecule surface-enhanced Raman spectroscopy (SERS)-based sensing applications. SERS templates should provide high sensitivity and reproducibility and be cost-effective and easy to prepare. Additive manufacturing by extrusion-based three-dimensional (3D) printing is an emerging technique for the spatial arrangement of nanomaterials and is a method that may satisfy these SERS template requirements. In this work, we use 3D printing to produce sensitive and reproducible SERS templates using a fluorenylmethyloxycarbonyl diphenylalanine (Fmoc-FF) hydrogel loaded with silver or gold nanoparticles. The Fmoc-FF template allows the detection of low Raman cross-section molecules such as adenine at concentrations as low as 100 pM. [ABSTRACT FROM AUTHOR]

Nanocomposites of diphenylalanine (FF) and carbon based materials provide an opportunity to overcome drawbacks associated with using FF micro- and nanostructures in nanobiotechnology applications, in particular their poor structural stability in liquid solutions. In this study, FF/graphene oxide (GO) composites were found to self-assemble into layered micro- and nanostructures, which exhibited improved thermal and aqueous stability. Dependent on the FF/GO ratio, the solubility of these structures was reduced to 35.65% after 30 min as compared to 92.4% for pure FF samples. Such functional nanocomposites may extend the use of FF structures to e.g. biosensing, electrochemical, electromechanical or electronic applications. [ABSTRACT FROM AUTHOR]

Self-assembly offers potential routes for large-scale, rapid, and cost-effective surface-enhanced Raman scattering (SERS) substrate designs. Here, a highly sensitive SERS template is reported, which utilizes aligned diphenylalanine nanotubes to form a dense packing arrangement of plasmon-active silver nanoparticles. The template is stable under high laser illumination with a power density of ~6.25 MW/cm2 in comparison to only silver nanoparticles and enables picomolar and femtomolar probe molecule concentrations to be probed, indicative of single-molecule SERS detection. [ABSTRACT FROM AUTHOR]

Nano-bio interfaces play a significant role in assay device design and performance, here we study the use of a combined plasmonic and ferroelectric active substrate design for protein assemblies on a plasmon active array. We demonstrate that biotinylation and protein assemblies can be made on metal nanoparticles patterned on ferroelectric substrates. These results in turn demonstrate that ferroelectric substrates combined with active plasmonics is potentially applicable as substrates for biological assays. [ABSTRACT FROM PUBLISHER]

Nanocomposites of diphenylalanine (FF) and carbon based materials provide an opportunity to overcome drawbacks associated with using FF micro- and nanostructures in nanobiotechnology applications, in particular their poor structural stability in liquid solutions. In this study, FF/graphene oxide (GO) composites were found to self-assemble into layered micro- and nanostructures, which exhibited improved thermal and aqueous stability. Dependent on the FF/GO ratio, the solubility of these structures was reduced to 35.65% after 30 min as compared to 92.4% for pure FF samples. Such functional nanocomposites may extend the use of FF structures to e.g. biosensing, electrochemical, electromechanical or electronic applications. [ABSTRACT FROM AUTHOR]

Here, we demonstrate that quasi self-standing Au nanorod arrays prepared with plasma polymerisation deposited SiO2 dielectric spacers support surface enhanced fluorescence (SEF) while maintaining high signal reproducibility. We show that it is possible to find a balance between enhanced radiative and non-radiative decay rates at which the fluorescent intensity is maximized. The SEF signal optimised with a 30 nm spacer layer thickness showed a 3.5-fold enhancement with a signal variance of <15% thereby keeping the integrity of the nanorod array. We also demonstrate the decreased importance of obtaining resonance conditions when localized surface plasmon resonance is positioned within the spectral region of Au interband transitions. Procedures for further increasing the SEF enhancement factor are also discussed. [ABSTRACT FROM AUTHOR]

Subcellular chemical heterogeneity plays a key role in cell organization and function. However the biomechanics underlying the structure-function relationship is governed by cell substructures which are poorly resolved using conventional chemical imaging methods. To date, advances in sub-diffraction limited infrared (IR) nanoscopy have permitted intracellular chemical mapping. In this work we report how image analysis applied to a combination of IR absorption nanoimaging and topographic data permits quantification of chemical complexity at the nanoscale, enabling the analysis of biochemical heterogeneity in mammalian cancer cells on the scale of subcellular features. [ABSTRACT FROM AUTHOR]

We examine here a series of meso-phenyl porphyrin micro- and nanostructures. Optical absorption and emission spectroscopy imaging and atomic force microscopy are used to investigate the effect of peripheral groups in nano- and microstructures of 5,10,15,20-tetraphenylporphyrin (H2TPP) compared to three other phenylporphyrins, i.e. 5,10,15-triphenylporphyrin (H2-Tri-PP), 5,10-diphenylporphyrin (H25,10-BPP) and 5,15-diphenylporphyrin (H25,15-BPP) molecules. We show that nanospheres and nanorods are formed, the occurrence and properties of which are influenced by the number and position of the phenyl substituents. [ABSTRACT FROM AUTHOR]

Ag nanopatterned arrays prepared using periodically proton exchanged templates have been demonstrated to support surface enhanced luminescence. Fluorescence lifetime imaging reveals that luminescence intensity is greatest on Ag and that the lifetime of the molecular probe is reduced, in line with a surface enhanced luminescence mechanism. Studies establish that the substrate simultaneously supports surface enhanced luminescence and Raman scattering. Spatial dependence along the nanopatterned arrays shows <7% variation in Raman scattering signal intensity, offering high reproducibility for practical applications. Fluorophores emitting near the plasmon absorption maxima are enhanced 4-fold. [ABSTRACT FROM AUTHOR]

Sub diffraction limited infrared absorption imaging of hemoglobin was performed by coupling IR optics with an atomic force microscope. Comparisons between the AFM topography and IR absorption images of micron sized hemoglobin features are presented, along with nanoscale IR spectroscopic analysis of the metalloprotein. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Presented here are angle dependence studies on the surface enhanced Raman (SER) signal obtained from dye placed on plasmon active nanocavity arrays. A comparative study was carried out between two modified array supports. One array had dye placed only on the interior walls of the cavities in the array. The other array had dye placed only on its top flat surface. Results show that Raman intensities as a function of angle depend on the location of the dye on the array; this was interpreted to arise from the presence of different plasmon polariton modes in these sites. [ABSTRACT FROM AUTHOR]

Presented here are studies of the impact of excitation angle on surface enhanced Raman and luminescence spectroscopy of dye immobilized on a plasmon active nanocavity array support. Results show that both Raman and luminescence intensities depend on the angle of incidence consistent with the presence of cavity supported plasmon modes. Dependence of scattering or emission intensity with excitation angle occurs over the window of observation. [ABSTRACT FROM AUTHOR]

The effect of an externally applied lateral electric field upon an exciton confined in a single InGaN quantum dot is studied using microphotoluminescence spectroscopy. The quantum-confined Stark effect causes a shift in the exciton energy of more than 5 meV, accompanied by a reduction in the exciton oscillator strength. The shift has both linear and quadratic terms as a function of the applied field. [ABSTRACT FROM AUTHOR]

We have investigated the behavior of excitons in GaN nanocolumns using time-integrated and time-resolved micro-photoluminescence measurements. In the weak confinement limit, the model of fractional-dimensional space gives an intermediate dimensionality of 2.14 for GaN nanocolumns, with an average diameter of 80 nm. Enhanced exciton and donor binding energies are deduced from a fractional-dimensional model and a phenomenological description. Time-integrated photoluminescence spectra as a function of temperature show a curved emission shift. Recombination dynamics are deduced from the temperature dependence of the PL efficiency and decay times. [ABSTRACT FROM AUTHOR]

We report measurements of optical transitions in single III/V (InGaN) quantum dots as a function of time. Temporal fluctuations in microphotoluminescence peak position and linewidth are demonstrated and attributed to spectral diffusion processes. The origin of this temporal variation is ascribed to randomly generated local electric fields inducing a Stark shift in the optical emission peaks of the InGaN quantum dots. [ABSTRACT FROM AUTHOR]

We present measurements of photoluminescence decay dynamics for single InGaN quantum dots. The recombination is shown to be characterized by a single exponential decay, in contrast to the nonexponential recombination dynamics seen in the two-dimensional wetting layer. The lifetimes of single dots in the temperature range 4 to 60 K decrease with increasing temperature. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We describe the growth of InGaN quantum dots (QDs) by metalorganic vapor phase epitaxy. A thin InGaN epilayer is grown on a GaN buffer layer and then annealed at the growth temperature in molecular nitrogen inducing quantum dot formation. Microphotoluminescence studies of these QDs reveal sharp peaks with typical linewidths of ∼700 µeV at 4.2 K, the linewidth being limited by the spectral resolution. Time-resolved photoluminescence suggests that the excitons in these structures have lifetimes in excess of 2 ns at 4.2 K. [ABSTRACT FROM AUTHOR]

The development of new catalysts for oxidation reactions is of central importance for many industrial processes. Plasmonic catalysis involves photoexcitation of templates/chips to drive and enhance oxidation of target molecules. Raman-based sensing of target molecules can also be enhanced by these templates. This provides motivation for the rational design, characterization, and experimental demonstration of effective template nanostructures. In this paper, we report on a template comprising silver nanoparticles on aligned peptide nanotubes, contacted with a microfabricated chip in a dry environment. Efficient plasmonic catalysis for oxidation of molecules such as p-aminothiophenol results from facile trans-template charge transfer, activated and controlled by application of an electric field. Raman detection of biomolecules such as glucose and nucleobases are also dramatically enhanced by the template. A reduced quantum mechanical model is formulated, comprising a minimum description of key components. Calculated nanotube-metal-molecule charge transfer is used to understand the catalytic mechanism and shows this system is well-optimized. Plasmonic nanomaterials offer new frontiers as photocatalysis and sensor materials, yet elucidating factors controlling each is a challenge. Here, authors examine the role of electric fields in photocatalysis and biomolecule sensing abilities of peptide-nanotubesupported silver nanoparticles. [ABSTRACT FROM AUTHOR]

A correction to the article "Surface enhanced luminescence and Raman scattering from ferroelectrically defined Ag nanopatterned arrays," by Signe Damm and colleagues that was published in the August 20, 2013 issue is presented.