Ordered arrays of copper nanostructures were fabricated and modified with porphyrin molecules in order to evaluate fluorescence enhancement due to the localized surface plasmon resonance. The nanostructures were prepared by thermally depositing copper on the upper hemispheres of two-dimensional silica colloidal crystals. The wavelength at which the surface plasmon resonance of the nanostructures was generated was tuned to a longer wavelength than the interband transition region of copper (>590 nm) by controlling the diameter of the underlying silica particles. Immobilization of porphyrin monolayers onto the nanostructures was achieved via self-assembly of 16-mercaptohexadecanoic acid, which also suppressed the oxidation of the copper surface. The maximum fluorescence enhancement of porphyrin by a factor of 89.2 was achieved as compared with that on a planar Cu plate (CuP) due to the generation of the surface plasmon resonance. Furthermore, it was found that while the fluorescence from the porphyrin was quenched within the interband transition region, it was efficiently enhanced at longer wavelengths. It was demonstrated that the enhancement induced by the proximity of the fluorophore to the nanostructures was enough to overcome the highly efficient quenching effects of the metal. From these results, it is speculated that the surface plasmon resonance of copper has tremendous potential for practical use as high functional plasmonic sensor and devices.

Silver nanocolloid, a dense suspension of ligand-encapsulated silver nanoparticles, is an important material for printing-based device production technologies. However, printed conductive patterns of sufficiently high quality and resolution for industrial products have not yet been achieved, as the use of conventional printing techniques is severely limiting. Here we report a printing technique to manufacture ultrafine conductive patterns utilizing the exclusive chemisorption phenomenon of weakly encapsulated silver nanoparticles on a photoactivated surface. The process includes masked irradiation of vacuum ultraviolet light on an amorphous perfluorinated polymer layer to photoactivate the surface with pendant carboxylate groups, and subsequent coating of alkylamine-encapsulated silver nanocolloids, which causes amine–carboxylate conversion to trigger the spontaneous formation of a self-fused solid silver layer. The technique can produce silver patterns of submicron fineness adhered strongly to substrates, thus enabling manufacture of flexible transparent conductive sheets. This printing technique could replace conventional vacuum- and photolithography-based device processing.

The optical diffusion of transmitted or refl ected light via a deformable wrinkled surface with a periodicity in the range of hundreds of micrometers is studied. Without strain, the sample shows no wrinkles and no optical diffusion. With uniaxial strain, the surface shows aligned wrinkles and anisotropically diffuses incident light in a manner that depends on the degree of applied strain. The relationship between the sinusoidal microstructure and the diffused state is successfully explained in the context of geometric optics. The present system can be used as a mechanically tunable optical diffuser.

Sensors based on surface plasmons or waveguide modes are at the focus of interest for applications in biological or environmental chemistry. Waveguide-mode spectra of 1 mum-thick pure and perforated silica films comprising isolated nanometric holes with great aspect ratio were measured before and after adhesion of streptavidin at concentrations of 500 nM. The shift of the angular position for guided modes was nine times higher in perforated films than in bulk films. Capturing of streptavidin in the nanoholes is at the origin of that largely enhanced shift in the angular position as the amplitude of the guided mode in the waveguide perfectly overlaps with the perturbation caused by the molecules. Hence, the device allows for strongly confined modes and their strong perturbation to enable ultra-sensitive sensor applications.

We describe efficient visible- and near-infrared (vis/NIR) light-driven photocatalytic properties of hybrids of CuO and plasmonic Cu arrays. The CuO/Cu arrays were prepared simply by allowing a Cu half-shell array to stand in an oxygen atmosphere for 3 h, which was prepared by depositing Cu on two-dimensional colloidal crystals with a diameter of 543 or 224 nm. The localized surface plasmon resonances (LSPRs) of the arrays were strongly excited at 866 and 626 nm, respectively, at which the imaginary part of the dielectric function of Cu is small. The rate of photodegradation of methyl orange was 27 and 84 times faster, respectively, than that with a CuO/nonplasmonic Cu plate. The photocatalytic activity was demonstrated to be dominated by Cu LSPR excitation. These results showed that the inexpensive CuO/Cu arrays can be excellent vis/NIR-light-driven photocatalysts based on the efficient excitation of Cu LSPR.

Harvesting of ambient renewable energy resources, such as indoor light, is a viable solution for the development of autonomous, “install-and-forget”, environmental nanosensors. In this work we fabricated and characterized photovoltaic cells based on AgBiI4 rudorffites as promising indoor photovoltaic energy harvesters demonstrating photoconversion efficiency of 5.17% and power output of 1.76 μW cm−2 measured under white LED light of 1000 lux. Considering that modern low-power wireless transmitters consume <1 μJ per bit for data transmission, the indoor rudorffite photovoltaic cell combined with a supercapacitor can be used for sensor readout and reliable intermittent data transmission.

Surface plasmon excitation provides stronger enhancement of the fluorescence intensity and better sensitivity than other sensing approaches but requires optimal positioning of a prism to ensure optimum output of the incident light. Here we describe a simple, highly sensitive optical sensing system combining surface plasmon excitation and fluorescence to address this limitation. V-shaped fluidic channels are employed to mimic the functions of a prism, sensing plate, and flow channel in a single setup. Superior performance is demonstrated for different biomolecular recognition reactions on a self-assembled monolayer, and the sensitivity reaches 100 fM for biotin-streptavidin interactions. Using an antibody as a probe, we demonstrate the detection of intact influenza viruses at 0.2 HA units ml À 1 levels. The convenient sensing system developed here has the advantages of being prism-free and requiring less sample (1-2 ml), making this platform suitable for use in situations requiring low sample volumes.

Mechanisms, materials, and processes of high-resolution printing techniques dedicated to printed electronics are reviewed. Advanced printing methods, including reverse offset printing and adhesion contrast planography, use absorption of ink solvents by polydimethylsiloxane (PDMS) to semi-solidify inks before ink-transfer. The patterning principle transforms from wetting to adhesion and fracture; resolution problems encountered during the patterning of liquid inks (e.g. spreading, splitting, coalescence, bulges, and coffee ring shapes) can be avoided, and single-μm features can be achieved. After summarizing the fundamentals of reverse offset printing, details on the patterning mechanism and contact mechanics encountered during the process are shown together with the design concept of the ink formulation. Complementary processes for multilayered electronic devices (e.g. wet-on-wet for high-throughput production, buried electrode formation, taper formation, and vertical interconnections) and the prediction of pattern size integrity are presented.