Acid ascorbic influence in gold nanorods growth with longitudinal plasmon band in near infrared – NIR

ABSTRACT The present work reports the ascorbic acid effect (0,60-0,98 µM) on the aspect ratio (AR) of gold nanorods with bands of longitudinal plasmon (LP) in the near infrared (958 -1085 nm), grown by seed-mediated chemical route. Cloroauric acid-1mM as precursor agent was used, obtained from a stock solution prepared by dissolving metallic gold (99,99%) in aqua regia. Benzyldimethylhexadecylammonium chloride (BDAC) and cetyltrimethylammonium bromide (CTAB) at molar ratio 0,75 (BDAC/CTAB) as surfactants were used. Scanning electron microscopy images implemented with a transmitted electron detector and absorption spectra revealed that the AR reaches a maximum of 7,3 and a band of PL of 1085 nm for a critical concentration of ascorbic acid of 0,68 µM, equivalent to a molar AA/Au3+ of 1,5. As ascorbic acid increase to 0,98 µM, the AR decreases up to 6 and consequently, its PL band decreases up to 958 nm.