Synthesis of Functional Nanomaterials via Colloidal Mask Templating and Glancing Angle Deposition (GLAD)

Abstract

Currently there is strong focus on the fabrication of porous thin films with a nanoscale morphology, e.g., for the realization of new optical devices, [1][2][3][4][5][6] novel superior biocompatible materials, [7][8][9][10] 2-D surfaces for stem cell culture/ tissue engineering, [11,12] and high surface area supports for catalysts. [13] In particular porous low refractive index thin films have proven promising as antireflection coatings [5] and noble metal nanoparticles/nanostructured thin films (Pt, Au, Ag) are known to support localized surface plasmon resonances (LSPRs) due to the collective excitation of conduction electrons inside the delicate nanofeatures by electromagnetic radiation, [4] an ability which in principle could enhance the performance of biosensors and optical devices. [4,6] Nanoscale surface topographies have also been reported to significantly affect both protein adsorption and cellular responses to biomaterial surfaces [7][8][9][10][13][14][15][16][17][18] making it a key parameter in the basic research and optimization of artificial biomaterials. [19] Thin films with a well-controlled surface morphology can be grown using the simple and efficient self assembly technique known as glancing angle deposition (GLAD) in which a vaporized particle flux arrives at the substrate from an oblique angle of incidence. [20][21] This causes increased shadowing compared to a particle flux perpendicular to the substrate (u ¼ 908) and, in turn, an enhanced roughening of the thin film when surface diffusion contributes little to the film growth. [22] With the GLAD technique it is possible to fabricate porousWe present a simple method for the fabrication of separated brush-like networks with both improved optical and biological properties. The brush networks were fabricated by combing the glancing angle deposition (GLAD) technique with colloidal mask templating. By changing the deposition angle during GLAD on the template layers as the amount of platinum deposited per area [surface mass density (g cm À2 )] it is possible to create a wide range of reproducible and localized brush-like networks consisting of high aspect ratio whiskers with different sizes and morphologies. The results presented here indicate that localized surface plasmons are present on the GLAD templated surfaces while cell assays with monocyte cells showed an impaired attachment to the brush structures. Consequently, deposition by means of a colloidal mask templating is indeed a very tunable and suited technique for the fabrication of multifunctional nanomaterials which could have potential impact on devices where both controlled optical properties and cell surface interactions are needed (for instance controlled cell adhesion on optical biosensor materials).

Perspectives on oblique angle deposition of thin films: From fundamentals to devices

“…For different in-vivo applications it is also critical that certain cells grow preferentially over others, a possibility that has been explored in-vitro by these same authors using OAD Pt films. In particular, they demonstrated that fibrinogen, an important blood protein, preferentially adheres to whisker-like nano-rough Pt substrates when compared to flat Pt surfaces, and that the proliferation of human fibroblasts is significantly reduced on these nanostructured surfaces [116]. Over the course of these studies, the growth of the film nanocolumns could be described by a power law relationship (see Sections 3.6 and 4.2) between the increments in their length and width [110].…”

“…For example, mass-produced metal wire grid polarizers are being fabricated via the OAD deposition of antireflection FeSi and SiO 2 layers on previously deposited aluminum columnar arrays [87,114,115]. Other emerging applications in biomedical areas [107,116,110,117], or for controlling the wetting properties of substrates [102,118], also rely on the use of patterned surfaces rather than the direct OAD of thin films (see Section 5.5).…”

“…In a series of works on the OAD of platinum films, either directly onto flat substrates or onto polymer-packed nanospheres to provide a second nanostructuring pattern to the layers (see Section 2.5), Dolatshahi-Pirouz et al [110,116,117] showed that the particular surface topography of these latter layers promotes the growth and proliferation of osteoblast cells. For different in-vivo applications it is also critical that certain cells grow preferentially over others, a possibility that has been explored in-vitro by these same authors using OAD Pt films.…”

A new highly automated sputter equipment for in situ investigation of deposition processes with synchrotron radiation

“…Concurrently, the vacuum system should be able to handle high pressure sputtering conditions (larger than 10 −1 mbar) which might be required during sputter deposition. Different sputter geometries such as glancing angle deposition (GLAD) 25,26 and co-sputter experiments 27 should be feasible as well as heating and cooling of the sample substrate. Since the apparatus has been implemented in the P03 beamline to use GIXS methods, the sputter direction is downwards.…”

Synthesis of Nano‐ and Micro‐Scale Topographies by Combining Colloidal Lithography and Glancing Angle Deposition (GLAD)

“…Here, we present a method by means of which we can synthesize unique platinum surfaces with controlled micro‐ and nano‐scale topographies through a combination of (GLAD) and colloidal surface patterning . Platinum was used since it offers a good biocompatibility and constitutes an integral part in various implantable electrodes.…”