Synthesis of Self-Supporting Gold Microstructures with Three-Dimensional Morphologies by Direct Replication of Diatom Templates

Abstract

Diatoms (unicellular algae) form porous silica walls (frustule) with intricate, hierarchically organized three-dimensional (3D) structures with micro- to nanoscale dimensions. This paper presents the fabrication of self-supporting gold microstructures with complex 3D morphologies by using electroless gold deposition onto a diatom silica substrate, followed by the substrate removal by acid dissolution. It was demonstrated that gold diatom replicas with distinct micro- to nanoscale structures can be created by a simple and scalable process based on electroless gold deposition. Excellent catalytic properties (catalytic rate constant k = 23.5 +/- 1 x 10(-2) min(-1)) of prepared gold replica catalysts were confirmed for the reduction process of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) in the presence of NaBH(4) as the reductant. This synthetic approach is general and flexible, and it is envisaged that it can be applied for the preparation of a wide range of different metals (Pt, Pd, Ag, Ni, etc.) offering more efficient catalytic, optical, or magnetic properties.

Diatoms: a biotemplating approach to fabricating drug delivery reservoirs

“…expensive lithographic procedures yet with the capability to create complex 3D metallic structures [42][43][44]. Similarly, other diatom replicas have been produced by Sandhage et al via oxidation-reduction gas/solid displacement reactions to form various structural replicas composed of magnesium oxide, zirconium dioxide, titanium dioxide and silicon [45][46][47][48][49].…”

Surface silylation of mesoporous/macroporous diatomite (diatomaceous earth) and its function in Cu(II) adsorption: The effects of heating pretreatment

“…Diatomite is easily available at a low cost because diatomaceous silica is the most abundant form of silica on earth. Diatomite also has many unique physical and chemical characteristics [3][4][5][6], such as highly developed mesoporosity and/or macroporosity, strong acid resistance, high mechanical strength and low thermal conductivity, enabling their wide uses in a variety of applications for high-performance technologies (e.g., microelectronics, chemo-and bio-sensors, and transducers) or as fillers, filters or supports, catalysts, adsorbents, and mild abrasives [4,7,8]. In particular, diatomite has been predominantly used as a filtration medium (e.g., filter aid) [9] for purifying various beverages and for gasification applications in fluidized bed reactors [4].…”

“…c-Aminopropyltriethoxysilane (APTES, H 2 NCH 2 CH 2 CH 2 Si 4 (OCH 2-CH 3 ) 3 ) was used to the silylate the diatomite. The raw diatomite sample was carefully purified to reduce the influences of the impurities.…”

Properties and potential application of modern adsorbents in formulation of solid drug delivery systems

“…Dobijaju se prečišćavanjem dijatomejske zemlje. U literaturi se navodi veći broj postupaka za dobijanje dijatomita (12)(13)(14). Jedan od najčešće korišćenih podrazumeva prečišćavanje sirovog materijala sledećim procesima: usitnjavanje, uklanjanje velikih agregata dijatomita, uklanjanje oksidiranih nečistoća tretiranjem uzorka kiselinom, razdvajanje čestica po veličini pomoću filtracione ili sedimentacione metode (14).…”