Controlling gold nanoparticle assembly on electron beam-reduced nitrophenyl self-assembled monolayers via electron dose

Abstract

Electron Beam Lithography is a well-established tool suitable for the modification of substrate surface chemistry. It therefore follows that the deposition and self-assembly of nanoparticles on a surface can be directed using this method. This work explores the effect of electron dose on the electron beam lithographic patterning of selfassembled monolayers (SAMs) on gold surfaces. Electron beam irradiation of the sample induces conversion of the SAM terminal functional aromatic nitro (NO 2 ) moieties to aromatic amino (NH 2 ) moieties. The cationic NH 2 functionalised regions direct the site-specific assembly of anionic citrate-passivated gold nanoparticles in aqueous solution at pH 4.5. Control of nanoparticle attachment to the SAM is demonstrated over the exposure range 5,000-125,000 μC/cm 2 . Overexposure led to significant numbers of secondary electrons reaching the surface, causing conversion of functional aromatic moieties outside of the regions irradiated, which reduced feature quality and regional selectivity of adsorption.

Lamellar Orientation of a Block Copolymer via an Electron-Beam Induced Polarity Switch in a Nitrophenyl Self-Assembled Monolayer or Si Etching Treatments

“…In other words, after EB irradiation the SAMs underwent selective reduction. It has previously been reported that EB lithography and the irradiation of x-ray can induce the transition of the SAM terminal function aromatic nitro (NO 2 ) moieties to aromatic amino (NH 2 ) moieties [46][47][48][49][50][51][52][53]. Thus, EB irradiation results in a chemically striped patterned substrate consisting of alternating stripes of SAM with an aromatic NO 2 terminal functionality and SAM with aromatic NH 2 terminal functionality, as shown Figure 2.…”

“…The gold coated samples were then cleaned in piranha solution (mixture solution of 30% hydrogen peroxide and concentrated sulfuric acid) (Warning: Piranha solution is very reactive and corrosive) for 5 min at room temperature. 6-(4-nitrophenoxy) hexane-1-thiol (NPHT) was prepared as detailed elsewhere [46]. To deposit the SAMs, a 10 mmol solution of NPHT was created in ethanol solvent, and the gold samples submerged in the solution for 48 h. Deposition was terminated using a 15 s rinse in the solvent and the samples were then dried with nitrogen.…”

Lamellar orientation of block copolymer using polarity switch of nitrophenyl self-assembled monolayer induced by electron beam

“…6-(4-nitrophenoxy) hexane-1-thiol (NPHT) was prepared as detailed elsewhere. 46 To deposit the SAMs a 10mmol solution of NPHT was created in ethanol solvent, and the gold samples submerged in the solution for 48 h. Deposition was terminated using a 15 s rinse in the solvent and the samples were then dried with nitrogen. The rinse and dry was repeated twice to ensure maximum removal of physisorbed multilayers.…”

“…It has previously been reported that EB lithography and x-ray irradiation can induce conversion of the SAM terminal function aromatic nitro (NO 2 ) moieties to aromatic amino (NH 2 ) moieties. [46][47][48][49][50][51][52][53] pre-coated with SAM. It is known that the PMMA block preferentially wets on SAMs that contain polar groups.…”

Controllable Fabrication of Large-Size Defect-Free Domains of 2D Colloidal Crystal Masks Guided by Statistical Experimental Design

“…Many methods for patterning surfaces have been developed to prepare large-area monolayer colloidal crystals, such as photolithography [11,12], X-ray lithography [13], electron beam lithography [14,15] and nano-imprint lithography [16]. However, these methods either demand expensive equipment, require a relatively long time for the fabrication, or give a low throughput, which limits their application.…”