NOVELTY - A nanoparticle (N1) comprises anatase titanium oxide, and at least one element selected from dopant metal and a dopant nonmetal. The nanoparticle is not a nanosphere.    USE - As a nanoparticle (e.g. nanorod, nanofiber, nanowire, nanobelt, nanosheet, nanoprism and nanonetwork), which is useful in nanofiber and catalytic composition (claimed); in catalysis, water and air purification, gas sensing, hydrogen production, solar energy production, fiber lasers, additives for composites and fabrics, and cancer therapy; in cleaning composition and disinfecting personal care product; in anti-microbial surface coating, self-cleaning coatings, dye-sensitized solar cells; in production of hydrogen and oxygen from water; and as bioactive agents.    ADVANTAGE - The nanoparticle containing titanium oxide over titanium oxide does not in a nanoparticulate form, and thus increases the photocatalytic activity of the nanoparticles. When an organic substance is in contact with the catalytic composition containing the nanoparticle and is irradiated with visible light, the concentration of the organic substance is reduced by 40% within 4 hours. When bacteria are in contact with the catalytic composition containing the nanoparticle and are irradiated with visible light, the concentration of living bacteria is reduced by 20% within 20 hours. The production of nanoparticle is carried out at lower temperature and avoids the calcining step. The production of nanoparticle is performed on a large scale, and is less expensive to carry out than conventional high temperature processes.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a nanofiber (N2) comprising anatase titanium oxide. The nanofiber has a longest dimension of greater than 200 nanometers, and an aspect ratio of greater than 20:1;    (2) a catalytic composition comprising the nanoparticles (N1). When an organic substance is in contact with the catalytic composition and is irradiated with visible light, the concentration of the organic substance is reduced by 40% within 4 hours. When bacteria are in contact with the catalytic composition and are irradiated with visible light, the concentration of living bacteria is reduced by 20% within 20 hours;    (3) making nanoparticles (N1) involving heating the reaction mixture of titanium source, polar organic solvent, and optionally dopant nonmetal source and dopant metal salt, in an autoclave at 170-300degreesC for at least 5 hours.