Formation of cotton-like nanogold assembly and their fluorescence property

A simple approach for the large-scale synthesis of cotton-like nanogold by a liquid-based process at room temperature is described. The gold fibres have diameters in the range of 15-40 nm and lengths longer than 50 μm, entwined into a complex mass. The first step of the preparation procedure involves the formation of gold seeds by reducing HAuCl4 with NaBH4 in a solution containing the desired quantity of cetyltrimetylammonium bromide (CTAB). In the subsequent step, the gold seeds continuously grow to form cotton-like nanogold in a solution containing HAuCl4, CTAB and L-ascorbic acid (AA) under an ultrasonic radiation field. The cotton-like nanogold has observable fluorescence, which might have great significance in biological and medical applications. HRTEM images showed that many defects and twin crystals exist in the turning junctions of as-prepared cotton fibres, which might be the reason the turning junctions in the fibres became stable