## 1 Introduction  
Titanium dioxide (TiO\({}_{2}\)) is regarded as one of the most fascinating materials for environmental applications [1; 2]. It has been intensively investigated as a photocatalyst due to its high photocatalytic activity. Despite numerous advantages, such as low fabrication cost, environmental friendliness, and high chemical stability, TiO\({}_{2}\) still cannot be widely applied due to its inherent drawbacks. TiO\({}_{2}\) has a rapid electron-hole recombination [3] and a high bandgap energy [4]. These drawbacks can be overcome by coupling the semiconductor with plasmonic metal nanoparticles [5]. The plasmonic metal nanoparticles are expected to not only improve the visible light absorption, but also to minimize the electron-hole recombination reaction in TiO\({}_{2}\). It has been demonstrated that surfacial plasmonic resonance improved the light absorption, increased the charge separation, and enhanced the suppression of electrons and holes, and thus significantly improved hydrogen generation [6]. There are many methods to support the adhesion of Au nanoparticles on the titania surface, such as photodeposition [7], deposition-precipitation [8], as well as the sol-gel method [9; 10]. However,the improvement of the photocatalyst activity (PCA) in Au loaded titania is just several times higher than that of the original one. This may be due to the week connection between the Au nanoparticles and the TiO\({}_{2}\) surface. It is noted that PCA shows significantly more improvement in the one spot synthesis method than in the multistep one [9]. In order to improve the adhesion of gold nanoparticles on its surface, TiO\({}_{2}\) normally follows a lengthy complicated procedure of surface activation to attach the oxygenic or nitrogenous functional groups or even both on its surface and subsequently undergoes a surface functionalization by adding the appropriate ligands (e.g., MPTMS-3-mercapto-propyl-tri-metoxy-silane). For example, [PERSON] et al. [11] used a solution of NH\({}_{4}\)OH:H\({}_{2}\)O\({}_{2}\):H\({}_{2}\)O (5:1:1 in volume) to treat TiO\({}_{2}\) for 20 h at room temperature or under the UV radiation for 1 h and then illuminated with deep ultraviolet (DUV) for 10 min to improve its wettability. [PERSON] et al. [12], however, incubated TiO\({}_{2}\) at 80 \({}^{\circ}\)C in a NaOH solution for 1 h to add the OH groups and then in a urea solution for 4 h to add the nitrogenous groups. Plasma technology has been efficiently used in the fabrication of nanomaterials [13] especially the plasma-liquid interaction method [14]. For gold nanoparticle synthesis, Au\({}^{3+}\) can be reduced either by solvated electrons or by reactive species generated in the solution [15]. The two most dominant reactions are:  
\[\left[AuCl_{4}\right]^{+}+3e_{aq}^{-}\to Au^{0}+4 Cl^{-}\]  
and  
\[nH_{2}O_{2}+nOH+Au^{3+}\rightarrow\left[AuCl_{4}\right]^{+}+nHO_{2}^{-}+nH_{ 2}O\]  
where \(e_{aq}^{-}\) stands for solvated electron. Recently, the electrochemical reduction of HAuCl\({}_{4}\) acid in dense hydrosols of high-index diamond sub-micrometer sized particles was tested as a promising \"green\" fabrication route for \"metallic nanoparticle-dielectric\" clusters in their colloidal solutions. The plasma-liquid interaction approach requires only water-based solutions with the metal precursor and is completely free of any additional reducing and/or capping agents [16]. It showed successful decoration of gold nanoparticles (AuNPs) onto the diamond surface. In the presence of the diamond particles, substantial \"red\" spectral shifts of the plasmonic resonance were observed for the AuNPs, being more pronounced for the decorated diamond particles (\(\approx\)536 nm), than for those adsorbed AuNPs on their surfaces from the mechanical mixture of their colloids (\(\approx\)530 nm). These shifts of the plasmonic resonance peak could be unambiguously related to the high-index dielectric environment of the AuNPs, provided by their attachment to the diamonds [17].