@article{prevo_hon_velev_2007, title={Assembly and characterization of colloid-based antireflective coatings on multicrystalline silicon solar cells}, volume={17}, ISSN={["0959-9428"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33847048603&partnerID=MN8TOARS}, DOI={10.1039/b612734g}, abstractNote={Evaporation from a moving meniscus was used for controlled convective assembly of colloidal silica nanoparticles into antireflective coatings (ARCs) onto the rough uneven surfaces of polycrystalline silicon solar cells. The nanocoatings reduced the reflectance of the solar cells by approximately 10% across the near UV to near IR spectral range, which provided a 17% increase in the output power of the devices (which translated to a 10% relative increase in the efficiency). Microstructural analysis via SEM showed that while the surface coverage was uniform over long ranges, the thickness of the particle coatings varied locally due to the rough, undulating substrate surface. The UV/vis reflectance data of the silica coated solar cells could be modelled with the Fresnel reflectance relation by assuming a distributed range of thicknesses for the coatings, in good agreement with the microstructural data. We show that particulate films deposited on rough surfaces can function as ARCs even though they do not attain 0% reflectance. These silica particle-based coatings can be further modified by attachment of monolayers of fluorosilanes, which may make them superhydrophobic and/or self-cleaning.}, number={8}, journal={JOURNAL OF MATERIALS CHEMISTRY}, author={Prevo, Brian G. and Hon, Emily W. and Velev, Orlin D.}, year={2007}, pages={791–799} }
 @article{prevo_kuncicky_velev_2007, title={Engineered deposition of coatings from nano- and micro-particles: A brief review of convective assembly at high volume fraction}, volume={311}, ISSN={["1873-4359"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35648966536&partnerID=MN8TOARS}, DOI={10.1016/j.colsurfa.2007.08.030}, abstractNote={In this paper, we review the state of the art of a simple, easily controlled convective assembly technique for rapid deposition of structured micro- and nano-particle coatings. The advantages afforded by this method are improved process efficiency and reduced material consumption relative to standard dipcoating techniques. Structured coatings larger than a few square centimeters are deposited in minutes from aqueous suspension volumes of approximately 10–20 μl. The governing mechanism of particle deposition is convective assembly at high volume fractions. Our research with monodisperse polystyrene latex showed that a volumetric flux balance incorporating the evaporating solvent and assembling particle fluxes can accurately relate the deposition process parameters to the coating structure and properties. Operational ’phase’ diagrams were constructed that demonstrate good correspondence between coating thickness and structure to the operational parameters of the coatings process predicted on the basis of the material balance model. These ’phase’ diagrams may be instrumental in turning the colloidal deposition into a usable and scaleable technology. This deposition technique can be applied to a variety of colloidal systems, including the fabrication of conductive and antireflective coatings, surface-enhancing Raman scattering (SERS) substrates, and lithographic masks.}, number={1-3}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Prevo, Brian G. and Kuncicky, Daniel M. and Velev, Orlin D.}, year={2007}, month={Dec}, pages={2–10} }
 @article{yuan_petsev_prevo_velev_atanassov_2007, title={Two-dimensional nanoparticle arrays derived from ferritin monolayers}, volume={23}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34249704060&partnerID=MN8TOARS}, DOI={10.1021/la062891f}, abstractNote={A scalable technique for making silica coatings with embedded two-dimensional arrays of iron oxide nanoparticles is presented. The iron oxide nanoparticle arrays were formed by depositing quasi-crystalline ferritin layers, an iron storage protein with an iron oxide mineral core, on solid substrates by a spread-coating technique based on evaporation-induced convective assembly. The layer of protein molecular arrays was then encapsulated in a silica matrix film deposited from a sol precursor. The organic protein shell of the ferritin molecules was then removed by controlled pyrolysis, leaving ordered iron oxide cores bound in the silica matrix. This article is the first report on combining convective self-assembly of proteins with sol-gel techniques of oxide film formation. The technique is technologically feasible and scalable to make coatings of encapsulated ordered magnetic clusters tens of cm(2) or larger in size.}, number={10}, journal={LANGMUIR}, author={Yuan, Zhen and Petsev, Dimiter N. and Prevo, Brian G. and Velev, Orlin D. and Atanassov, Plamen}, year={2007}, month={May}, pages={5498–5504} }
 @article{kuncicky_prevo_velev_2006, title={Controlled assembly of SERS substrates templated by colloidal crystal films}, volume={16}, ISSN={["1364-5501"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33645067906&partnerID=MN8TOARS}, DOI={10.1039/b512734c}, abstractNote={Convective assembly at high volume fractions was used to assemble gold nanoparticles into structured porous films templated by colloidal crystals. These gold nanofilms have hierarchical porosity and were proven to be stable and efficient substrates for surface-enhanced Raman spectroscopy (SERS). The control over the film structure allowed optimization of their performance for potential sensor applications.}, number={13}, journal={JOURNAL OF MATERIALS CHEMISTRY}, author={Kuncicky, DM and Prevo, BG and Velev, OD}, year={2006}, pages={1207–1211} }
 @article{millman_bhatt_prevo_velev_2005, title={Anisotropic particle synthesis in dielectrophoretically controlled microdroplet reactors}, volume={4}, ISSN={["1476-4660"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-11144319950&partnerID=MN8TOARS}, DOI={10.1038/nmat1270}, abstractNote={The miniaturization of chemical and biological processes in microfluidic devices and bioarrays is a major technological achievement. Microchips performing multiphase material synthesis operations could be a future step in this trend of miniaturizing technology. Here we show how electrically controlled chips can be used for the synthesis and manipulation of new types of particles with advanced structure. The method is based on a technique that allows freely suspended droplets and particles to be entrapped and transported using electric fields. The fields that hold and guide the droplets and particles are applied through arrays of electrodes submerged in the oil. Each of the microdroplets suspended on the surface of fluorinated liquid serves as a microscopic reactor, where the particles are formed by solidification of the carrier droplets. Controlled on-chip assembly, drying, encapsulation and polymerization were used to make anisotropic 'eyeball' and striped particles, polymer capsules and semiconducting microbeads.}, number={1}, journal={NATURE MATERIALS}, author={Millman, JR and Bhatt, KH and Prevo, BG and Velev, OD}, year={2005}, month={Jan}, pages={98–102} }
 @article{prevo_hwang_velev_2005, title={Convective assembly of antireflective silica coatings with controlled thickness and refractive index}, volume={17}, ISSN={["1520-5002"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-22944488858&partnerID=MN8TOARS}, DOI={10.1021/cm050416h}, abstractNote={Convective assembly at high volume fraction was used to deposit silica nanoparticle coatings onto glass and silicon substrates. By allowing control of the film structure and thickness, this technique provides a means for making large-scale coatings with antireflective properties. The reflectance was reduced by 50% for silicon (at 600 nm) and by 70% for single glass/air surface. Microstructural investigations using SEM, AFM, profilometry, and ellipsometry provided good correlation to the observed macroscopic optical properties. By virtue of the coatings' uniformity, the reflectance and transmission spectra from both substrates could be modeled well by classical reflection relations, using a volume-averaged refractive index. Data analysis showed that the relatively high packing fraction in nanocoatings made from monodisperse spheres is responsible for the limit on antireflective capabilities. To overcome this restriction, low-density silica coatings were made from binary colloidal mixtures of different diam...}, number={14}, journal={CHEMISTRY OF MATERIALS}, author={Prevo, BG and Hwang, Y and Velev, OD}, year={2005}, month={Jul}, pages={3642–3651} }
 @article{finkel_prevo_velev_he_2005, title={Ordered silicon nanocavity arrays in surface-assisted desorption/ionization mass spectrometry}, volume={77}, ISSN={["1520-6882"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-13844320727&partnerID=MN8TOARS}, DOI={10.1021/ac048645v}, abstractNote={We report here a simple method to generate ordered nanocavity arrays on a Si wafer and use it in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). A close-packed SiO2 nanosphere array was first deposited on a low-resistivity Si wafer using a convective self-assembly method. The nanoparticle array was then used as a mask in a reactive ion etching (RIE) process to selectively remove portions of the Si surface. Subsequent sonication removed those physically adsorbed SiO2 nanoparticles and exposed an ordered nanocavity array underneath. The importance of this approach is its capability of systematically varying surface geometries to achieve desired features, which makes detailed studies of the impacts of surface features on the desorption/ionization mechanism feasible. We demonstrated that the in-plane width and out-of-plane depth of the cavities were adjustable by varying etching times, and the intercavity spacing was controllable by varying the number of particle layers deposited. MS detection of small peptides on these substrates showed comparable sensitivity to conventional porous Si substrates (DIOS, desorption/ ionization on porous silicon). The desorption and ionization efficiency of these roughened surfaces exhibited a nonmonotonic relationship to the increased total surface area. Several possible factors contributing to the observed phenomenon are speculated upon. The application of this arrayed surface in metabolite detection of Arabidopsis thaliana root extracts is also demonstrated.}, number={4}, journal={ANALYTICAL CHEMISTRY}, author={Finkel, NH and Prevo, BG and Velev, OD and He, L}, year={2005}, month={Feb}, pages={1088–1095} }
 @article{prevo_fuller_velev_2005, title={Rapid deposition of gold nanoparticle films with controlled thickness and structure by convective assembly}, volume={17}, ISSN={["1520-5002"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-11844299566&partnerID=MN8TOARS}, DOI={10.1021/cm0486621}, abstractNote={We report how convective assembly at high volume fraction combined with thermal treatment allows robust fabrication of gold nanocoatings whose structure can be varied and correlated to their optical properties and conductance. Uniform films of gold nanoparticles were deposited directly from aqueous suspensions, where neither the nanoparticles, nor the substrates, were covered with ligands or pretreated in any way. The number of layers, optical absorbance, and electrical conductance of these nanocoatings could be controlled by the speed of deposition. The electronic, optical, and structural properties of the nanoparticle multilayers could be further tuned by post-deposition heat treatment. Scanning electron microscopy observations and electrical conductance measurements showed that heating leads to a transition from a near-percolated nanoparticle structure (conductivity approaching 2000 Ω-1cm-1) to a discontinuous insular structure (conductivity <10-5 Ω-1cm-1). These structural transitions change the coati...}, number={1}, journal={CHEMISTRY OF MATERIALS}, author={Prevo, BG and Fuller, JC and Velev, OD}, year={2005}, month={Jan}, pages={28–35} }
 @article{prevo_velev_2004, title={Controlled, rapid deposition of structured coatings from micro- and nanoparticle suspensions}, volume={20}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-1842582720&partnerID=MN8TOARS}, DOI={10.1021/la035295j}, abstractNote={The objective of the study was to develop the operational basis for rapid and controlled deposition of crystal coatings from particles of a wide size range. We deposited such structured coatings by dragging with constant velocity a small volume of liquid confined in a meniscus between two plates. Two types of structured coatings were characterized: latex colloidal crystals and thin layers from metallic nanoparticles. The crystal deposition was sped up by use of preconcentrated suspensions. Crystal coatings larger than a few square centimeters were deposited in minutes from aqueous suspension volumes of approximately 10 microL. The governing mechanism of crystal deposition is convective assembly at high volume fractions. The two major process parameters that allow control over the coating thickness and structure were the deposition speed and particle volume fraction. The evaporation rate was not found to affect the process to a large extent. A volumetric flux balance was used to relate the deposition parameters to coating structure and properties. Operational "phase" diagrams were constructed, relating the crystal layer thickness and packing symmetry to the process parameters. These diagrams could be instrumental in transforming the convective colloidal deposition into a robust scaleable technology.}, number={6}, journal={LANGMUIR}, author={Prevo, BG and Velev, OD}, year={2004}, month={Mar}, pages={2099–2107} }
 @article{velev_prevo_bhatt_2003, title={On-chip manipulation of free droplets}, volume={426}, ISSN={["0028-0836"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0346874344&partnerID=MN8TOARS}, DOI={10.1038/426515a}, number={6966}, journal={NATURE}, author={Velev, OD and Prevo, BG and Bhatt, KH}, year={2003}, month={Dec}, pages={515–516} }