An approach is presented that permits wide and reversible control of the optical bandwidth of spherical gold nanoparticles assembled on thermoreversible hydrogel colloids for various plasmonic-based thermochromisms. Temperature-dependent swelling and shrinking behaviors of the hydrogel colloids in aqueous systems manipulated assembly structures and optical signals of gold nanoparticles in the hybrid colloids. The optical bandwidths of the hybrid colloids increased with temperature, and thermoreversible bandwidth variations of the hybrid colloids were increased with the diameter of gold nanoparticles (from 15 to 51 nm). These hybrid colloids exhibited multiple colors switching during temperature changes (maximum four colors: wine ↔ violet ↔ dark blue ↔ faint blue). For the hybrid colloids showing a small bandwidth variation, another method was introduced to display different color switching.

A super‐boosted hybrid plasmonic upconversion (UC) architecture comprising a hierarchical plasmonic upconversion (HPU) film and a polymeric microlens array (MLA) film is proposed for efficient photodetection at a wavelength of 1550 nm. Plasmonic metasurfaces and Au core–satellite nanoassembly (CSNA) films can strongly induce a more effective plasmonic effect by providing numerous hot spots in an intense local electromagnetic field up to wavelengths exceeding 1550 nm. Hence, significant UC emission enhancement is realized via the amplified plasmonic coupling of an HPU film comprising an Au CSNA and UC nanoparticles. Furthermore, an MLA polymer film is synergistically coupled with the HPU film, thereby focusing the incident near‐infrared light in the micrometer region, including the plasmonic nanostructure area. Consequently, the plasmonic effect super‐boosted by microfocusing the incident light, significantly lowers the detectable power limit of a device, resulting in superior sensitivity and responsivity at weak excitation powers. Finally, a triple‐cation perovskite‐based photodetector coupled with the hybrid plasmonic UC film exhibits the excellent values of responsivity and detectivity of 9.80 A W−1 and 8.22 × 1012 Jones at a weak power density of ≈0.03 mW cm−2, respectively, demonstrating that the device performance is enhanced by more than 104 magnitudes over a reference sample.

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It is necessary to understand the surface structural effects of electrodes on the bioalcohol productivity of Shewanella oneidensis MR-1, but this research area has not been deeply explored. Here, we report that the electricity-assisted isobutanol productivity of Shewanella oneidensis MR-1::pJL23 can be enhanced by sequentially modifying a graphite felt (GF) surface with Au nanoislands (Au), cysteamine (NH), and Au nanoparticles (Au NPs). After bacteria were incubated for 50 h with the unmodified GF under various electrode potentials (vs Ag/AgCl), the bacterial isobutanol concentrations increased from 2.9 ± 1 mg/L under no electricity supply to a maximum of 5.9 ± 1 mg/L at -0.6 V. At this optimum electrode potential, the concentrations continued increasing to 9.1 ± 1, 14 ± 2, and 27 ± 2 mg/L when the GF electrodes were modified with Au, NH-Au, and Au NP-NH-Au, respectively. We further studied how each surface structure affected the bacterial adsorptions, current profiles, and biofilms' electrochemical performances. In particular, these modifications induced the adsorption of elongated bacteria, with the amount dependent on the electrode structure. In the presence of electric supply, the amount of elongated bacteria further increased. We also found that the NH-Au-GF and Au NP-NH-Au-GF electrodes themselves could increase the concentrations to 11 ± 0.3 and 12 ± 2 mg/L, respectively, upon the bacterial incubation without electricity. Among the electrodes tested, the contribution of electricity to the bacterial isobutanol production was the greatest with the Au NP-NH-Au-GF electrode. After 96 h of incubation, the concentration increased to 72 ± 2 mg/L, which was 4.7 and 3.7 times the previously reported values obtained without and with electricity, respectively.

We present a route that estimates the scattering/absorption characteristics of plasmonic nanoparticles by using fluorescence and UV-visible spectroscopy. Because elastic scattering of nanoparticles caused by a monochromatic incident light is reflected in fluorescence emission spectra when recording at the excitation wavelength, the scattering intensities at the excitation wavelength during fluorescence emission scans are used to compare the scattering characteristics of various plasmonic nanoparticles under conditions where the extinction values of all of the nanoparticles are kept constant at this wavelength. For the two excitation wavelengths (519 and 560 nm) we investigated, the scattering intensities of spherical gold nanoparticles increase with increasing size (15, 33, 51, 73, and 103 nm in diameter). These results are correlated with the nanoparticles' scattering efficiencies (the ratios of scattering to the extinction cross-sections), which are theoretically calculated in the literature using Mie theory. Then, linear calibration equations at each wavelength are derived to estimate the scattering efficiencies of two Au nanorods, Au nanocages, and spherical Ag nanoparticles (15, 25, 37, and 62 nm). The values are very comparable with literature values. For various purposes such as biomedicine and optoelectronics, the present method could be beneficial to those who wish to easily compare and determine the scattering characteristics of various plasmonic nanoparticles at a certain wavelength by using commercially-available spectroscopic techniques.

We report a method for controlling the detection sensitivity to or the degree of etching of Ag nanocubes by radicals by modifying their surfaces with poly(acrylic acid) or poly(allylamine hydrochloride) for wide-range quantification of radical compounds. The degree of Ag nanocube etching is influenced by the concentrations of the polyelectrolytes used for modification. These polyelectrolytes protect the Ag nanocubes, probably by either retarding (forming diffusion barriers) or preventing (blocking/entrapping/scavenging) the arrival of radicals to Ag nanocubes, or both. The weights of the two roles are different depending on the polyelectrolyte type; therefore, the sensitivities of Ag nanocubes are also influenced by this factor. The roles of the polyelectrolytes were demonstrated by using radical compounds produced from tetrahydrofuran and H2O2 and further confirmed with Ag nanospheres. Using the results, the radical sensitivities and detection ranges of polyelectrolyte-modified Ag nanoparticles could be manipulated. Moreover, we produced calibration curves for the wide-range quantification of radical compounds.

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