The nanoparticles are monodisperse with a narrow distribution of size and error of ±1.8 nm with similar results reported previously. , The nanoparticles are stabilized by citrate molecules and therefore have a negative zeta potential as mentioned in Figure . Next, a thin layer of PAH (1.5 ± 0.3 nm) is coated on the Au nanoparticle surface. Since PAH is a cationic polyelectrolyte, consequently, the zeta potential of the colloidal suspension containing Au@PAH core-shell nanoparticles changes from negative to positive at pH 6. The isoelectric point of PAH is at pH 10. The solutions of Au nanoparticles, PAH and TALH have a pH of 5.5, 5.2 and 6.2, respectively. Therefore, the pH of the suspension was not changed so as to have a net positive surface charge. Subsequently, TALH of varying concentrations was added to the prepared Au@PAH suspension. TALH has a negative zeta potential arising from the lactate and hydroxyl groups. By increasing the amount of TALH injected into the Au@PAH colloid, this ultimately enabled to obtain structures of a) closely arranged small SPs (Au@CloseSmall), b) closely arranged large SPs (Au@CloseLarge), and c) distantly arranged small SPs (Au@DistantSmall) of Au@PAH@TALH. For full clarity, the notation 'small/large' is with respect to the overall supraparticle size, and not the size of the constituting Au nanoparticles, which is fixed at 15 nm. After SP formation, the hybrid structures were subjected to a calcination step at 450°C for 30 mins to convert the TALH precursor into a photocatalytically active crystalline TiO2 phase.