Colloidal crystals by electrospraying polystyrene nanofluids

Abstract

This work introduces the electrospray technique as a suitable option to fabricate large-scale colloidal nanostructures, including colloidal crystals, in just a few minutes. It is shown that by changing the deposition conditions, different metamaterials can be fabricated: from scattered monolayers of polystyrene nanospheres to self-assembled three-dimensional ordered nanolayers having colloidal crystal properties. The electrospray technique overcomes the main problems encountered by top-down fabrication approaches, largely simplifying the experimental setup. Polystyrene nanospheres, with 360-nm diameter, were typically electrosprayed using off-the-shelf nanofluids. Several parameters of the setup and deposition conditions were explored, namely the distance between electrodes, nanofluid conductivity, applied voltage, and deposition rate. Layers thicker than 20 μm and area of 1 cm2 were typically produced, showing several domains of tens of microns wide with dislocations in between, but no cracks. The applied voltage was in the range of 10 kV, and the conductivity of the colloidal solution was in the range of 3 to 4 mS. Besides the morphology of the layers, the quality was also assessed by means of optical reflectance measurements showing an 80% reflectivity peak in the vicinity of 950-nm wavelength.

Mechanical properties of Al2O3 inverse opals by means of nanoindentation

“…Colloidal crystal electrospraying [9] was used to produce the layers used in this work. The silicon substrate was contacted to a high voltage power supply (Ultravolt highvoltage bipolar source, −15 kV to +15 kV, Ronkonkoma, NY,USA.)…”

“…Recently a new technique has been developed enabling to simultaneously produce large area colloidal crystals while keeping good optical quality. This technology, named Electrospray Colloidal Crystal (ECC) deposition [9,10,11], produces centimeter size samples with up to 50 layers of polystyrene or silicon dioxide nanospheres with diameter in the range from 200 nm to 1 µm. The nanoparticle colloidal solution of distilled water is pumped through a small needle of 150 µm in diameter.…”

Quantifying disorder in colloidal films spin-coated onto patterned substrates

“…Numerous techniques have been used to obtain well-ordered dried colloidal deposits [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. However, it is challenging to obtain defect-free colloidal crystals over large areas.…”

Laser contact through electrosprayed alumina inverse opals on silicon

“…The present research focuses on the compatibility problems associated with the fabrication and integration of the photonic structure while keeping the electrical and mechanical properties of the original solar cell. In particular, we study the use of laser firing to create contacts through Al 2 O 3 inverse opals.. For the inverse opal formation, we use colloidal crystals defined by electrospray deposition technique as scaffolds [11][12][13]. This technique is able to create colloidal crystals in the cm 2 range becoming a good choice if the photonic structure has to be applied to commercially relevant devices.…”