Restricted meniscus convective self-assembly

Chen, Kai; Stoianov, Stefan V.; Bangerter, Justin; Robinson, Hans D.

doi:10.1016/j.jcis.2010.01.010

Cited by 54 publications

(45 citation statements)

References 42 publications

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“…Full-scale and bench-scale studies have shown that silver was removed by about 90% in WWTPs, with a small but significant fraction, partially in the form of AgNPs, remaining in the WWTP effluent while the majority partitioned into the sludge. 31,33,34 Although most of the silver was removed, WWTP effluent still had silver concentrations several orders of magnitude higher than typical river water, and it is expected that AgNPs will be relatively concentrated in WWTP effluents. 29,30,34 The results from these studies also suggest that areas where sludge is land applied will have higher than average concentrations of AgNPs in the soil.…”

Section: Release Of Agnps To the Environmentmentioning

confidence: 99%

Controlled Evaluation of Silver Nanoparticle Dissolution Using Atomic Force Microscopy

Kent

Vikesland

2012

Environ. Sci. Technol.

127

129

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Incorporation of silver nanoparticles (AgNPs) into an increasing number of consumer products has led to concern over the potential ecological impacts of their unintended release to the environment. Dissolution is an important environmental transformation that affects the form and concentration of AgNPs in natural waters; however, studies on AgNP dissolution kinetics are complicated by nanoparticle aggregation. Herein, nanosphere lithography (NSL) was used to fabricate uniform arrays of AgNPs immobilized on glass substrates. Nanoparticle immobilization enabled controlled evaluation of AgNP dissolution in an air-saturated phosphate buffer (pH 7, 25 °C) under variable NaCl concentrations in the absence of aggregation. Atomic force microscopy (AFM) was used to monitor changes in particle morphology and dissolution. Over the first day of exposure to ≥10 mM NaCl, the in-plane AgNP shape changed from triangular to circular, the sidewalls steepened, and the height increased by 6-12 nm. Subsequently, particle height and inplane radius decreased at a constant rate over a 2-week period. Dissolution rates varied linearly from 0.4 to 2.2 nm/d over the 10-550 mM NaCl concentration range tested. NaCl-catalyzed dissolution of AgNPs may play an important role in AgNP fate in saline waters and biological media. This study demonstrates the utility of NSL and AFM for the direct investigation of unaggregated AgNP dissolution.iii Acknowledgements I thank my advisor, Dr. Peter Vikesland, for his insight, guidance, and innovative ideas throughout my time at Virginia Tech, and for giving me the opportunity to work on this research project. He was ready and available to help whenever I needed his input. I also thank the other members of my committee,

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Section: Release Of Agnps To the Environmentmentioning

confidence: 99%

Controlled Evaluation of Silver Nanoparticle Dissolution Using Atomic Force Microscopy

Kent

Vikesland

2012

Environ. Sci. Technol.

127

129

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“…Park and coworkers proposed a modified convective assembly technique that uses a dip-coating apparatus to modulate the meniscus thinning rate, allowing for the formation of well-ordered, multilayered single-component and binary colloidal crystals [15]. Robinson et al later presented another variation that more rapidly deposits crystalline films than conventional convective assembly by altering the fluid evaporation rate through restricted movement of the meniscus along the top plate [16]. However, while these variations offer greater control over the assembly process, the utility of convective particle or cell assembly in thin films on an industrial scale is restricted because the total coating surface area is limited by the amount of suspended particles delivered by the continuously depleted (batch) coating meniscus volume.…”

Section: Figurementioning

confidence: 99%

“…Reactive microorganisms behave as charged particles in aqueous deposition systems and we have found that net charge leading to repulsion between particles or between particles and cells is an important factor in coating assembly [12]. These findings have resulted in emerging methods to generate colloidal arrays with varying thicknesses, particle sizes, and types ranging from charged latex particles [8,[11][12][13][14][15][16]] to live cells [9] to composite charged particle plus live cell mixtures [9,12,17]. Such convectively assembled arrays are well suited for applications that would benefit from an ordered microstructure, but do not require a completely defect-free, perfect colloidal crystal, such as assembly of microbial photo-reactive coatings [10], antireflective coatings [18,19], electrical circuits [17], chemical sensors [20,21], and porous membranes [3,[22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Continuous Convective-Sedimentation Assembly of Colloidal Microsphere Coatings for Biotechnology Applications

2013

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Continuous convective-sedimentation assembly (CCSA) is a deposition method that constantly supplies the coating suspension to the meniscus behind the coating knife by inline injection, allowing for steady-state deposition of ordered colloids (which may include particles or cells or live cell-particle blends) by water evaporation. The constant inflow of suspended particles available for transport to the drying front yields colloidal arrays with significantly larger surface areas than previously described and thus expands the ability of convective assembly to deposit monolayers or very thin films of multiple sizes of particles on large surfaces. Using sulfated polystyrene microspheres as a model system, this study shows how tunable process parameters, namely particle concentration, fluid sonication, and fluid density, influence coating homogeneity when the meniscus is continuously supplied. Fluid density and fluid flow-path sonication affect particle sedimentation and distribution. Coating microstructure, analyzed in terms of void space, does not vary significantly with relative humidity or suspended particle concentration. This study evaluated two configurations of the continuous convective assembly method in terms of ability to control coating microstructure by varying the number of suspended polymer particles available for transport to the coating drying front through variations in the meniscus volume.

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“…Typically, the monolayer is formed by drop coating, but many other variations have been investigated to increase control and uniformity 20 . One method is through convective self-assembly NSL (CSANSL) 19,21,22 , in which a drop of microsphere solution is trapped between a spreader and a substrate. The substrate is mechanically moved and the monolayer grows from the three phase contact line of the meniscus as it is dragged across the substrate surface.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of large-area metal nanoparticle arrays by nanosphere lithography for localized surface plasmon resonance biosensors

et al. 2011

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The localized surface plasmon resonance (LSPR) phenomenon that is characteristic of gold and silver nanoparticles has applications in areas such as portable and remote chemical and biological sensing. However, fabrication of metal nanoparticle arrays with high uniformity and repeatability, at a reasonable cost, is difficult. Nanosphere lithography (NSL) has been used to produce inexpensive nanoparticle arrays, through the use of monolayers of self-assembled microspheres as a deposition mask. However, lack of control over the location and size of the arrays, as well as poor uniformity over large areas, limits its use to research purposes. Here, we present large-area fabrication of nanoparticle arrays through both convective self-assembly NSL (CSANSL) and our new method, geometrically confined NSL (GCNSL). In GCNSL, microsphere assembly is confined to geometric patterns defined in photoresist. We show that 400nm polystyrene microspheres can be assembled inside of large arrays of photoresist trenches from 4-20µm in width and 500µm in length, with high uniformity, repeatability, and quality. Compared to CSANSL, GCNSL allows precise patterning of nanoparticle arrays for use in practical LSPR sensing devices, while still remaining inexpensive.

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Restricted meniscus convective self-assembly

Cited by 54 publications

References 42 publications

Controlled Evaluation of Silver Nanoparticle Dissolution Using Atomic Force Microscopy

Controlled Evaluation of Silver Nanoparticle Dissolution Using Atomic Force Microscopy

Continuous Convective-Sedimentation Assembly of Colloidal Microsphere Coatings for Biotechnology Applications

Fabrication of large-area metal nanoparticle arrays by nanosphere lithography for localized surface plasmon resonance biosensors

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