The localized electrodeposition of Ag on Au coated with self-assembled monolayers (SAMs) by scanning electrochem. microscopy (SECM) is reported. The SAMs were ω-functionalized alkanethiols X-(CH2)2SH, X = OH, NH2, CO2H, SO3H, as well as 4-mercaptobenzoic acid. The SAMs were characterized by XPS and cycling voltammetry (CV). The anodic dissoln. of a Ag microelectrode, which was held within a few microns from the Au surface, formed a well-controlled flux of Ag+. Deposition of Ag nanostructures was driven by the electrochem. redn. of the Ag+ on the Au surface. The effect of the functional group on the Ag local deposition was studied and compared with bulk deposition on the same SAMs. For bulk deposition, the interaction between Ag+ ions and the functional group of the alkanethiols slowed the kinetics of Ag deposition, shifting the deposition to potential that is more neg. and caused the formation of large, well-faceted Ag crystals. A clear correlation between the potential shift value and the morphol. of deposited Ag was obsd. The local deposition of Ag showed distinct difference compared to bulk deposition. A continuous and homogeneous Ag film was formed locally below the Ag microelectrode in the presence of a 3-mercaptopropionic acid monolayer. This was obsd. when a 120 s delay between the electrogeneration of the Ag ions and the application of a neg. potential to the Au surface was applied. Also, the potential applied to the Au surface also affected deposition. The deposited Ag was recollected by the Ag microelectrode by stripping the Ag from the Au surface while holding the microelectrode in the same position. This enabled calcg. the thickness of the Ag film deposited on the Au coated with 3-mercaptopropionic acid. Addnl. expts. clearly indicated that the mechanism of deposition involved complexation of Ag ions by the SAM and their local redn., which commenced prior to applying a neg. potential to the Au surface. [on SciFinder(R)]

A flow-through electrode made of a C nanotubes (CNT) film deposited on a polytetrafluoroethylene (PTFE) membrane was assembled and employed for the detn. of low concn. of Cu as a model system by linear sweep anodic stripping voltammetry (LSASV). CNT films with areal mass ranging from 0.12 to 0.72 mg cm-2 were characterized by measurement of sheet resistance, H2O permeation flux and capacitance. Also, CNT with two different sizes and PTFE membrane with two different pore diams. (0.45 and 5.0 μm) were evaluated during the optimization of the electrode. Thick layers made of small CNT exhibited the lowest sheet resistance and the greatest anal. response, whereas thin layers of large CNT had the lowest capacitance and the highest permeation flux. Electrodes made of 0.12 mg cm-2 of large CNT deposited on 5.0 μm PTFE enabled sufficiently high mass transfer and collection efficiency for detecting 64 ppt of Cu(II) within 5 min of deposition and 4.0 mL min-1 flow rate. The anal. response was linear over 4 orders of magnitude (10-9 to 10-5 M) of Cu(II). The excellent performance of the flow-through CNT membrane integrated in a flow cell makes it an appealing approach not only for electroanal., but also for the electrochem. treatment of waters, such as the removal of low concns. of heavy metals and orgs. [on SciFinder(R)]

Calcium phosphate (CaP) ceramics are used in orthopedics and dentistry due to their excellent osseointegration and biocompatibility. The electrodeposition of CaP on titanium alloy covered with self-assembled monolayers (SAMs) was studied with respect to the influence of chain length, end-group charge, and anchoring group. SAMs with end-groups similar to the functional groups on the side chains of collagen were selected. This study is divided to three parts: (1) studying the effects of SAMs on the titanium substrate, (2) studying the process of nucleation and growth of the CaP on specific SAMs, and (3) characterizing the CaP coatings using various surface anal. techniques. It was concluded that the nucleation and growth behavior of CaP changed in the presence of the SAMs. Different surface energies and crystallog. phases were assocd. with this change. Although the nucleation remained progressive, the growth changed from three-dimensional on bare surfaces to two-dimensional on SAMs-covered surfaces. Moreover, the deposition kinetics was slower on SAMs-covered surfaces, with phases contg. a higher Ca/P ratio. Examn. of the coating revealed that different SAMs lead to different surface morphologies of the coating while maintaining its degree of crystallinity. Yet, the phase content changes from hydroxyapatite and octacalcium phosphate (HAp + OCP) on the bare electrode to OCP only on the SAMs-covered electrode. These changes may have a substantial effect on the in vivo behavior by changing the coating's soly. and surface morphol., thus affecting cell adhesion, proliferation, and differentiation processes. [on SciFinder(R)]

Ca phosphate (CaP) ceramics were used in orthopedics and dentistry due to their excellent biocompatibility and osseointegration. Here, the electro-assisted deposition of CaP on two different self-assembled monolayers (SAMs), 2-mercaptoacetic acid (MAA) and 2-mercaptoethanol (ME), was studied both at short (up to 3 min) and long (2 h) deposition periods on well-defined evapd. Au surfaces. The end group of the monolayer has a major effect on the growth of the CaP coating. The deposition was slower and less elec. efficient on MAA SAM, but surface cracking was essentially eliminated due to redn. of the crystallog. mismatch. The carboxylic acid may facilitate CaP growth by attracting Ca2+ ions to the surface, which could explain the higher amt. of side reactions occurring at the beginning of the deposition. [on SciFinder(R)]

Calcium phosphates are of great interest for biomedical applications such as bone tissue engineering, bone fillers, drug and gene delivery, and orthopedic and dental implant coating. Here, the first electrochem. driven coating of medical implants using hydroxyapatite (HAp) nanoparticles (NPs) as building blocks is reported. This uncommon combination offers a simple, straightforward, and economic process with well controllable, pure, single-phase HAp. Cryst., pure HAp NPs are formed by pptn. reaction. The HAp NPs are dispersed by either citrate or poly(acrylic acid) to form pH sensitive dispersion. Controllable and homogeneous coating of medical implants is accomplished by altering the pH on the surface upon applying either a const. potential or current. The process involves protonation of the carboxylic acid moieties, which causes the irreversible aggregation of the HAp NPs due to diminishing the repulsive forces between the particles. Deposition is further demonstrated on a com. dental implant. Moreover, the adhesion of the coating satisfies FDA and international std. requirements. A porous interconnected network of bone-like HAp layer is formed during soaking in a simulated body fluid for 30 d and is similar to bone generation, and it therefore holds promise for further in vivo testing. [on SciFinder(R)]

An aq. suspension of WO3/poly(4-(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl-methoxy)-1-butanesulfonic acid) (PEDTS) hybrid nanoparticles (NPs) is prepd. by air-assisted oxidative polymn. and simultaneous attachment of PEDTS on WO3-NPs, and used for electrochromic (EC) film fabrication via air-brush spraying. The hybrid EC device exhibits enhanced EC properties compared to the ones based on WO3-NP or PEDTS alone. [on SciFinder(R)]

A major component of solar thermal systems is the solar absorber, which converts light into heat. We report on achieving high absorptance, excellent adhesion, and high thermal stability of carbon nanotube-based black coatings by applying a layer of Boehmite (AlOOH) on top of the carbon nanotube (CNT) film by soln.-processed spray deposition. The CNT layer made-up by spraying, functions as an absorbing layer and the AlOOH serves as an anti-reflecting and protecting film. The anti-reflecting property of AlOOH layer effectively increases the absorptance of CNT coating by decreasing the reflectance. The effect of the thickness of AlOOH layer on the absorptance, adhesion, and thermal stability of the resulting CNT/AlOOH coating was investigated. The CNT/AlOOH coating with optimized thickness of AlOOH layer shows very high absorptance (α) of 0.975. The adhesion of the coating is in the range of 95-100% with significant increase of thermal stability. This new approach is expected to open new possibilities for fabricating low-cost, highly efficient and thermally stable solar-thermal devices which are based on simple coating processes. [on SciFinder(R)]

Molecularly imprinted polymer (MIP) particles offer many advantages as recognition objects. Therefore, we examd. thoroughly the effect of various exptl. parameters including cross-linker concn., nature of solvent, type of template and its concn., reaction vol. and temp. on the formation of particulate MIPs using pptn. polymn. The particles were characterized by various methods, such as XHR-SEM, HR-TEM and BET. Statistical calcns. were carried out using ImageJ software over population of at least 200 particles in each expt. The reproducibility of MIP synthesis was examd. and the SD was better than 10%. MIP particles were imprinted with different Sudan dye derivs. (Sudan II, III, IV and Sudan orange G). Raman and FTIR spectroscopies were used to prove the successful imprinting. Reuptake measurements were carefully compared between non-imprinted molecularly polymer (NIP) and MIP particles employing the same quantity and similar diam. and polydispersity of NIP and MIP, as never reported before. The results showed that MIP particles imprinted by Sudan IV showed higher selectivity toward this specific dye as compared with MIPs imprinted by other Sudan dyes and NIPs. [on SciFinder(R)]

This study extends the concept of nanoparticle imprinted matrixes (NAIMs) to systems, in which template nanoparticles (NPs) are immobilized on a conducting surface and a polymer matrix is built around them before the release of the template NPs. Specifically, citrate-stabilized AuNPs, 40 nm in diam., were bound to a 3-aminopropyltriethoxysilane (APTES)-modified indium tin oxide (ITO) electrode at pH 5. Subsequently, a polymer matrix was generated by electropolymn. of self-inhibiting poly(phenol) (PPh) layer. The template AuNPs were removed either by electrooxidn. of the Au core during linear sweep voltammetry (LSV) in Cl--contg. aq. soln. or by chem. oxidn. in aq. KCN soln. After template removal, nanocavities were left behind, which showed size-selective in the competitive reuptake of analyte NPs demonstrated by the preference for citrate-stabilized silver nanoparticles (AgNPs) with 20 nm diam. over AuNPs with 50 nm diam. The remaining nanocavities and their size-recognition ability were examd. by SEM and LSV. Complementing studies by X ray photoelectron spectroscopy and scanning force microscopy corroborated the template embedding, template release and analyte NP uptake. [on SciFinder(R)]

VO2 has garnered much attention in recent years as a promising candidate for thermochromic window applications due to rising awareness about energy conservation. However, the trade-off between improving the luminous transmittance (Tlum) and solar modulation ability (ΔTsol) limits the commercialization of VO2-based smart windows. Four major nanostructuring approaches were implemented to enhance both Tlum and ΔTsol, namely nanocomposites, nanoporous films, biomimetic moth-eye structures and anti-reflection coating (ARC) multilayers. This work demonstrates a novel approach that fabricates periodic, micro-patterned structures of VO2 using a facile screen printing method. The micro-patterned structure is able to favorably transmit visible light without sacrificing high near-IR modulation, and the patterned film shows improved Tlum (67% vs. 60%) and ΔTsol (8.8% vs. 6.9%) compared with continuous films. By varying the thickness, periodicity and solid concn., this approach can give a ΔTsol of 14.9% combined with a Tlum of 43.3%, which is comparable, if not superior to, some of the best reported results found using other approaches. [on SciFinder(R)]

The toxicity of nanoparticles is not only a function of the constituting material but depends largely on their size, shape and stabilizing shell. Hence, the speciation of nanoscale objects, namely, their detection and sepn. based on the different species, similarly to heavy metals, is of outmost importance. Here we demonstrate the speciation of gold nanoparticles (AuNPs) and their electrochem. detection using the concept of "nanoparticles imprinted matrixes" (NAIM). Neg. charged AuNPs are adsorbed as templates on a conducting surface previously modified with polyethylenimine (PEI). The selective matrix is formed by the adsorption of either oleic acid (OA) or poly(acrylic acid) (PAA) on the non-occupied areas. The AuNPs are removed by electrooxidn. to form complementary voids. These voids are able to recognize the AuNPs selectively based on their size. Furthermore, the selectivity could be improved by adsorbing an addnl. layer of 1-hexadecylamine, which deepened the voids. Interestingly, silver nanoparticles (AgNPs) were also recognized if their size matched those of the template AuNPs. The steps in assembling the NAIMs and the reuptake of the nanoparticles were characterized carefully. The prospects for the anal. use of NAIMs, which are simple, of small dimension, cost-efficient and portable, are in the sensing and sepn. of nanoobjects. [on SciFinder(R)]

Bone implants must be biocompatible and are usually built to promote osseointegration, e.g. by application of plasma spray calcium phosphate (CaP) coating. The risk of infection and biofilm formation on implant surfaces is a well-known problem. The combination of electrochem. deposited CaP coating with antibiotics may offer significant benefits. Here, we demonstrate an innovative in situ electrodeposition of gentamicin encapsulated in chitosan nanoparticles along with CaP. The deposition of the coating was obsd. and studied at several temps. A high drug loading into the coating and a controlled release of the drug over two days were demonstrated. [on SciFinder(R)]