Dense arrays of well-dispersed gold nanoparticles (AuNPs) on optical fibers are shown to bridge the gap in sensitivity and sensing performance between localized surface plasmon resonance (LSPR) and classical SPR sensing. A simple self-assembly method relying on a poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) block copolymer brush layer was used to immobilize AuNPs of different diameters from 10 to 92 nm on optical fibers. In comparison with standard AuNP deposition methods using (3-aminopropyl)trimethoxysilane (APTMS) and polyelectrolytes, the sensitivity with the PS-b-P4VP templating method was found to be 3-fold better, a consequence of the smaller gap between particles and the presence of fewer AuNP aggregates. Hence, the sensitivity of the LSPR sensor for IgG was comparable to a classical SPR, also on optical fibers, and about 68% of that for a prism-based wavelength-interrogation SPR instrument. The reproducibility and the detection limit of the LSPR sensor were about the same as the SPR sensor. The enhanced performance of the LSPR sensors using the PS-b-P4VP block copolymer fabrication method paves the way for use of these LSPR biosensors in a smaller and more cost-effective platform.

A surface-plasmon-resonance (SPR)-induced absorption band has been found for low-energy Ti+ implanted (subplanted) into single-crystalline SiO2 at specific substrate temperatures. The observed SPR absorption band is in the 650–850 nm wavelength range, i.e., in the visible (red) and near-infrared regions, indicating the formation of Ti nanoparticles in the subsurface layer of the SiO2 matrix. This was confirmed by calculations based on the Mie scattering theory. The SPR absorption band becomes distinguishable only at temperatures ⩾600 °C and reached its maximum at 800 °C (1/2Tm of elemental Ti). The intensity is significantly reduced at a temperature of 1000 °C (2/3Tm). The evolution of the SPR absorption with substrate temperature is discussed.

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