Disclosed are: a visible-light-responsive titanium oxide microparticle dispersion comprising an aqueous dispersion medium and titanium oxide microparticles dispersed therein, and a peroxotitanium component, an iron component andor a copper component and a tin component, wherein the content of the peroxotitanium component is 0. Methods of using the optics collection and detection systems are also described. Embodiments separate an antenna signal into an in-band signal and out-of-band impedance, generate an error signal related to the out-of-band impedance, apply the error signal to a controller circuit configurable to generate an impedance error signal representing the change in antenna impedance, and apply the impedance error signal to the selectively adjustable impedance.