Ordered nanocone arrays of the electroactive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) were fabricated by the simultaneous oxygen plasma etching of an electrodeposited PEDOT thin film coated with a hexagonally closed packed polystyrene bead monolayer. PEDOT nanocone arrays with an intercone spacing of 200 nm and an average nanocone height of 350 nm exhibited a low broadband reflectivity of <1.5% from 550 to 800 nm. Electrochemical modulation of the oxidation state of the PEDOT nanocone array film was used to change both its ex situ absorption spectrum (electrochromism) and reflection spectrum (electroreflectivity). The sign of the PEDOT nanocone array electroreflectivity was opposite to that observed from unmodified PEDOT thin films; this significant difference is attributed to the unique optical behavior of nanostructured surfaces with an interfacial layer that contains a graded mix of air and highly absorptive nanocones. The combined electrochromic and electroreflective behavior of the antireflective PEDOT nanocone array films should find promising applications in solar energy cells, sensors and other optical devices.
N-Isopropylacrylamide-based hydrogel nanoparticles (HNPs) that incorporate 30 mer single-stranded DNA (ssDNA) oligonucleotides were synthesized and characterized with single-nanoparticle surface plasmon resonance imaging (SPRI) microscopy, dynamic light scattering, transmission electron microscopy, and fluorescence measurements. The synthesized HNPs had an averaged diameter of 230 nm and exhibited a large (5−10×) increase in the average single-nanoparticle SPRI refractive index (Δ% R NP ), as compared with HNPs without DNA. A combination of SPRI and fluorescence measurements was used to measure the uptake of approximately 20 000 complementary ssDNA into each HNP, resulting in a Langmuir isotherm adsorption coefficient of 4.89 × 10 8 M −1 . Single-nanoparticle SPRI measurements also showed that approximately 35% of the incorporated ssDNA was accessible for both hybridization uptake and enzymatic hydrolysis using exonuclease I. We attribute the presence of an inactive ssDNA population in the nanoparticle to a combination of acrylamide Michael addition reactions with adenine, cytosine, and guanine nucleotides, as well as the possible formation of self-complementary secondary structures in the polymerized ssDNA.
International audienceNovel broadband ultra-antireflective surfaces were created via the electrodeposition of a nanostructured zinc oxide thin film onto conductive, light absorbing periodic nanocone arrays. Nanocone arrays of (i) fluorinated ethylene propylene (FEP) coated with a 50 nm plasmonic gold thin film and (ii) the electroactive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) exhibited a very low broadband reflectivity of less than 0.1% from 475 to 800 nm at a wide range of incident angles after the electrodeposition of a nanostructured ZnO thin film onto the surface. SEM images reveal the formation of ZnO nanoflowers and nanorods on both nanocone array surfaces; these additional ZnO nanostructures enhance the coupling of the incident visible light into the absorptive gold or PEDOT nanocones to significantly reduce the reflectivity of these surfaces. The ZnO-coated nanocone array surfaces also exhibited an enhanced photoreactivity for the oxidative degradation of methylene blue, suggesting their potential to be used as a self-cleaning antireflective surface
To quantitatively
characterize the optical coupling between ZnO
(a high refractive index but nonabsorptive material) and an electrochromic
material (either tungsten oxide (WO3) or poly(3,4-ethylenedioxythiophene)
(PEDOT)), electrodiffractive and electrochromic properties were investigated
from a novel two-component composite nanostructured electrodeposited
grating that incorporated both ZnO and either WO3 or PEDOT.
The sequential electrodeposition of these two materials through a
photopatterned photoresist layer onto a fluorine-doped tin oxide (FTO)-coated
glass substrate created a grating structure that exhibited optical
diffraction that could be modulated electrochemically. SEM images
of the electrochromic gratings revealed that the ZnO electrodeposition
created a high surface area nanostructured thin film. The nanostructured
ZnO is nonabsorbing, but its high refractive index and large surface
area redirect light into the electrochromic grating and create a 4-fold
enhancement in the grating’s electrodiffractive response.
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