Background: The bulk production of Gold Nanoparticles (AuNPs) and their concentrated
ink, with desirable properties such as morphology, purity, stability and final Au concentration, remains
Objective: (i) Synthesis of AuNPs through Ultrasonic Spray Pyrolysis (USP) from different precursors.
(ii) Preparation of their concentrated ink and (iii) Test their feasibility for ink jet printing onto a
glossy paper substrate.
Method: Initially, two different start materials were used - precursor: Gold Chloride with its nanoparticles
as C-AuNPs, and Gold Acetate with its nanoparticles as A-AuNPs stabilised with PVP40 in deionised
water. The concentrated ink was prepared from both AuNPs, and filtered up to the [Au] of
1000 ppm. Ink-jet printing was performed, and the obtained patterns were analysed through SEM.
Results: The [Au] in the obtained solutions, determined through ICP-OES analysis, was, for CAuNPs,
about 100 ppm, and 150 ppm for A-AuNPs. In the case of C-AuNPs the solution was rose,
and for A-AuNPs violet. TEM investigation revealed that C-AuNPs dominated in a circular shape
with size about 18 nm; contrary to this, A-AuNPs were mostly in ellipsoid shape, with size in the longitudinal
direction of about 36 nm. EDX analyses detected 99.9 wt. % of Au in both AuNPs, which is
evidence that these were of high purity. Due to different AuNPs` sizes and [Au], the colloidal solutions
showed maximum absorbance wavelength of 532 nm for C-AuNPs and 528 nm for A-AuNPs.
SEM results showed that A-AuNPs were significantly better for printing on the paper substrate than
C-AuNPs, due to their ellipsoidal shape, as the flow behaviour had been much smoother through the
nozzle as compared to the circular shape. The printed area with A-AuNPs reflected in better incorporation
of nanoparticles on the paper surface and high-density connectivity among AuNPs.
Conclusions: C-AuNPs and A-AuNPs were synthesised successfully under optimum parameters of
evaporation temperature, reaction temperature and gas flow rates. The spherical shape of C-AuNPs as
compared to the ellipsoidal nature of A-AuNPs was due to the rapid sintering of Gold Chloride at a
higher temperature of 300ºC as compared to Gold Acetate.