Resorcinol-formaldehyde based carbon nanospheres by electrospraying

Abstract

Carbon nanospheres were synthesized using sol-gel processing of organic and aqueous resorcinol formaldehyde (RF) sols combined with electrospraying technique. RF sol was electrosprayed to form nanodroplets which were collected on a Si wafer. After oven drying at 60°C for 12 h, RF nano-droplets were pyrolyzed at 900°C in an inert atmosphere to yield the carbon nanospheres. This study reports the optimization of various process parameters including needle diameter, applied electric potential and liquid flow rate in order to get spherical, mono-disperse particles. For the organic RF sol, the optimized parameters, needle diameter 0⋅241 mm, electric potential, 1⋅5 kV/cm and a flow rate of 0⋅8 ml/h, enabled the synthesis of nearly monodispersed carbon nano-spheres with diameter of 30⋅2 ± 7⋅1 nm. With the same conditions, aqueous RF sol produced irregularly shaped nanoparticles with a smaller mean diameter and much higher variance (17⋅4 ± 8⋅0 nm). The surface properties were significantly influenced by the surface morphologies as demonstrated by the water contact angle (WCA) studies. The surface covered with the RF derived carbon nano-spheres was extremely hydrophilic (WCA 10⋅1°) as compared to a much weaker hydrophilicity of the RF derived carbon films (WCA 83⋅3°). The hydrophilic carbon nanospheres reported here may have potential applications as adsorbents and in controlled drug delivery, biosensors and carbon-based microelectromechanical systems (C-MEMS) including bio-MEMS.

Synthesis of carbon xerogel nanoparticles by inverse emulsion polymerization of resorcinol–formaldehyde and their use as anode materials for lithium-ion battery

“…However there are a few studies on generating the porosity in carbon xerogels either by activation or by tailoring the process conditions. [20][21][22][23] Some of these techniques either lack in bulk production of carbon nanoparticles or are too complex and need very careful control. 10,11,19 In this work, we report a facile way to synthesize interconnected carbon xerogel nanoparticles by repetitive inverse emulsion polymerization of RF gel followed by subcritical drying followed by pyrolysis in the nitrogen atmosphere.…”

Fabrication of Resorcinol-Formaldehyde Xerogel Based High Aspect Ratio 3-D Hierarchical C-MEMS Structures

“…The high voltage allows for the elongation of the liquid meniscus at the nozzle opening to form a jet which finally disrupts into fine droplets (in electro spraying) or fibers (in electro spinning). In previous work, we optimized the various process parameters involved in the electrospraying of SU-8 and RF sols to form roughly monodisperse carbon sub-micron and nano-spheres (31,32).…”

“…During electrospraying a polymer spray is ejected towards a collector screen from a spraying syringe filled with polymer solution by applying a high voltage between syringe and substrate. The electrospraying set up was homebuilt and details of this set-up were reported in previous papers (31,32). SU-8 photoresist (SU-8 2002; viscosity 7 cSt at 25°C) (MicroChem Corp. USA) was electrosprayed to deposit sub-micron beads while RF sol was electrosprayed in the form of nano-sized droplets.…”

Low temperature catalyst-assisted pyrolysis of polymer precursors to carbon

“…Among the different polymers, PAN and resorcinol-formaldehyde (RF) organic gel were well studied because of their high carbon yield. Apart from carbon yield, RF organic gel is also identified as a widely used precursor to produce carbon xerogel, aerogel and cryogels with wide range of surface area and morphologies [16][17][18][19][20] for their applications as electrodes in energy storage devices.…”