## 1 Introduction  
In the past decades, gold nanomaterials have attracted considerable interest because of their wide application in catalysis [1; 2; 3; 4; 5; 6], biomedicine [7; 8; 9], biology [10; 11; 12], optics [13; 14; 15], and electronics [16]. Particularly, colloidal gold nanoparticles have been employed as a highly efficient substrate for surface-enhanced Raman scattering (SERS) for almost 30 years--since 1979 [17]; this is due to their exceptional SERS enhancement factor, excellent stability, good biocompatibility, and wide commercial availability [18; 19]. Gold spherical nanoparticles have been generally prepared via a citrate method as reported by [PERSON] and [PERSON] [20; 21; 22], biphasic method [23], and thermolysis method [24]. The citrate method produces nearly monodispersed colloidal gold nanoparticles with an average size of 10 to 100 nm, and these nanoparticles have served extensively as excellent substrates for SERS detection of a large variety of water-soluble analytes, such as dyes, protein, DNA/RNA, and food additives [25; 26]. Small-sized gold nanoparticles (\(<\)10 nm) soluble in low-polar and non-polar organic solvents were obtained by a one-phase method using amine derivatives or hydrosilane as reductants [27; 28; 29; 30] or by the thermolysis method [24]. Recently, ultralong gold nanowires and ultrathin gold nanorods have been successfully synthesized using oleylamine or hydrosilane as a reducing agent [31; 32] in organic solvents. The fabrication of the nanowires into aligned arrays for potential use in microelectronic devices have been achieved [33; 34]. In addition, the application of these nanowires as a SERS substrate in organic solvents has also been demonstrated [35], even though the SERS enhancement factor of these nanomaterials was quite limited. Since many hydrophobic toxicants and carcinogens, such as 3,4-benzopyrene, aflatoxin, and benzidine, are practically insoluble in water, those hydrophilic colloidal gold nanoparticles are not applicable because of their immiscibility with hydrophobic analytes. Therefore, it is still of considerable interest for chemists to develop a synthetic approach for the synthesis of hydrophobic gold nanomaterials with controllable and designable sizes and morphologies. However, the intensive synthesis and use of gold nanomaterials may cause health risks due to potential nanoparticle exposure since the toxic effects of most commercial nanoparticles (e.g., Ag, Au, TiO\({}_{2}\), etc.) on the human body have not been fully evaluated [36; 37]. [PERSON] recently observed the release of nanostructured objects in submicron size and their aggregates containing titanium dioxide from weathered industrial paints [38] and investigated the emission of nanoparticles from functional materials for medical applications and their aerosol formation [39]. Cases of nanoparticle exposure at workplaces during the synthesis of metal nanoparticles have also been reported [40]. Nano-safety and occupational health become a core subject in particle science [41]. As many previously reported syntheses of gold nanoparticles required lengthy reaction times, complicated operations, high temperatures, or multi-step manipulations, these approaches resulted in a greater chance of exposure to nanoparticles. Therefore, a fast and simple preparation of gold nanomaterials at mild conditions is highly desirable. Herein, we report a versatile one-pot synthesis of hydrophobic gold nanomaterials including round nanodots, short nanobars, long nanorods, and silk-like ultralong and ultrathin nanowires by the reduction of chloroauric acid with hydrosilane in organic solvents at room temperature. The size and morphology of the gold nanomaterials are readily controlled by changing the feeding molar ratio of chloroauric acid to oleylamine (OAm), oleic acid (OA), and hydrosilane. The obtained gold nanoparticles are employed as efficient organic-soluble SERS substrates for the detection of hydrophobic toxicants, such as 3,4-benzopyrene, and carcinogens, such as benzidine.