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Nanocomposite matrices of silver/poly(3-hexylthiophene) (P3HT) were prepared in ultrahigh vacuum through vapor-phase codeposition. Change in microstructure, chemical nature, and electronic properties with increasing filler (Ag) content were investigated using in situ XPS and UPS, and ambient AFM. At least two chemical binding states occur between Ag nanoparticles and sulfur in P3HT at the immediate contact layer, but no evidence of interaction between Ag and carbon (in P3HT) was found. AFM images reveal a change in Ag nanoparticles size with concentration which modifies the microstructure and the average roughness of the surface. Under codeposition, P3HT largely retains its conjugated structures, which is evidenced by the similar XPS and UPS spectra to those of P3HT films deposited on other substrates. We demonstrate here that the magnitude of the barrier height for hole injection (epsilon(v)(F)) and the position of the highest occupied band edge (HOB) with respect to the Fermi level of Ag may be controlled and changed by adjusting the metal (Ag) content in the composite. Furthermore, UPS reveals distinct features related to the C 2p (sigma states) in the 5-12 eV regions, indicating the presence of ordered P3HT, which is different from solution processed films.
ACS Appl Mater Interfaces 2009 Dec
PMID:Photoemission spectroscopy and atomic force microscopy investigation of vapor-phase codeposited silver/poly(3-hexylthiophene) composites. 2035 49

Silver-nanoparticle-embedded aminosilica colloids synthesized via aminosilane-induced spontaneous reduction reaction exhibit selective adhesion properties on hydrophobic surfaces and have been utilized as a simple and one-step procedure to create patterned nanocomposite film with silver to aminosilica mole ratio at 0.9:1. Substrates that enable self-assembly of the colloids include silicon wafer, polydimethylsiloxane, and microscope slide, where patterns of hydrophilic surface were either created using oxygen plasma treatment or stamped with chemical ink using microcontact printing. Upon substrates being immersed in a solution containing silver-aminosilica colloids, particles attach to hydrophobic surfaces and continuously self-assemble onto the deposited film, allowing us to fabricate nanocomposite patterns with controllable thickness (approximately 200 nm).
ACS Appl Mater Interfaces 2009 Dec
PMID:Self-assembly of silver-aminosilica nanocomposites through silver nanoparticle fusion on hydrophobic surfaces. 2035 56

In this work, we describe how to realize a new sensing platform for an easy and fast detection of analytes. In particular, we utilized enhanced fluorescence emission on silver island films (SIFs) coupled to the total internal reflection fluorescence mode (TIRF) to develop a new assay format for the detection of target analytes. Here, as an example, we report on the detection of the toxic peptides present in gliadin (Gli). Our assay was performed as follows: (1) gliadin was first captured on surfaces coated with anti-Gli antibodies; (2) the surfaces were then incubated with fluorophore-labeled anti-Gli antibodies; (3) the signal from the fluorophore-labeled anti-Gli antibody bound to the antigen was detected by TIRF. The system was examined on glass surfaces and on SIFs. We observed a relevant enhancement of the signal from SIFs compared to the signal from the glass substrate not modified with a SIF. In addition, the estimated detection limit (EDL) of our methodology was 60 ng/mL (or lower). This limit is therefore lower than the clinical cut-off for Gli presence in food for celiac patients. The advantage of our method is a reduced number of testing steps, which allows for easy detection of residual toxic peptides in food labeled as gluten free. The proposed technology can be easily expanded to the determination of different target analytes.
ACS Appl Mater Interfaces 2009 Dec
PMID:Nanostructured silver-based surfaces: new emergent methodologies for an easy detection of analytes. 2035 74

A sensitive and selective colorimetric detection method for mercury(II) has been well-established in this paper. It was based on the conformation change of mercury-specific oligonucleotides (MSO) from random coil structure to hairpin structure upon the addition of Hg(2+) and the phenomenon of salt-induced unmodified silver nanoparticles (AgNPs) aggregation. The calibration curve showed that the net absorption ratio value at 395 and 570 nm increased linearly over the Hg(2+) concentration range of 25-500 nM with a limit of detection of 17 nM. The other environmentally relevant metal ions did not interfere with the determination of Hg(2+).
ACS Appl Mater Interfaces 2010 Feb
PMID:Colorimetric detection of mercury(II) ion using unmodified silver nanoparticles and mercury-specific oligonucleotides. 2035 77

A novel hybrid material comprising silver aggregates supported on the porous structure of a free-standing carbon nanotube film was devised and fabricated. This material readily allows filtration of large volumes of fluids, while retaining the active analytes on silver aggregates so that their characteristic surface-enhanced resonance Raman scattering signals could be registered. The direct identification of multiple analytes at the attomolar regime was readily achieved through their single-molecule spectra.
ACS Appl Mater Interfaces 2010 Jan
PMID:Free-standing carbon nanotube films as optical accumulators for multiplex SERRS attomolar detection. 2035 15

The rapid self-assembly of microwire patterns of 52-nm aluminum and 19-nm silver nanoparticles was demonstrated under microwave heating using novel surfactant-solvent systems. Colloid solutions of 0.03% (w/v) nanoaluminum in 10% (v/v) poly(dimethylsiloxane)-acetone were used to self-assemble the microwire patterns of Al on glass substrates, which were dipped into the solution and held against the wall. Also, colloids of 0.001% (w/v) nanosilver prepared in an acetone solution of 33.3% (v/v) chloroform, 16.6% (v/v) poly(dimethylsiloxane), and 0.3% (v/v) Tween-20 were utilized for the deposition of microwire patterns under microwave heating at 51-55 degrees C. The evaporation-induced self-assembly of microwire patterns at the contact line was due to stick-slip dynamics. The rapid self-assembly of micropatterns of nanoaluminum and nanosilver was also demonstrated under microwave radiation within 2 min, and the width of the microwires was about 1-20 mum depending on the concentration of nanoparticles.
ACS Appl Mater Interfaces 2010 Jan
PMID:Rapid microwave-assisted deposition of microwire patterns of nanoaluminum and nanosilver from colloids. 2035 17

DC-magnetron sputtering with an Ag target on textile surfaces produced Ag particles with sizes approximately 4.7 nm (+/-15%). Sputtering for 15 s led to Ag layers of 15-20 nm. The threshold sputtering time precluding airborne bacterial growth was about 60 s. In this case, the coating was approximately 40-50 nm thick and the cotton Ag loading was 0.0026 wt %. The Ag particle size did not vary significantly with sputtering time between 15 and 600 s. Only coatings above this thickness lead to bacterial inactivation. Ag/Pt targets with sputtering times<60 s did not increase the bactericide performance of the Ag cotton samples with respect to sputtering from an Ag target alone, as expected from the position of Pt respect to Ag in the electrochemical series (Galvanic effect). The Ag cotton deposition led to very thin metallic semitransparent gray color coatings. X-ray of the Ag cotton suggested the presence of amorphous and crystalline Ag species. By X-ray photoelectron spectroscopy (XPS), it was found that the amount of oxidized silver species on the cotton was similar for sputtering times of 60 and 600 s, but the total amount of Ag deposited was almost two times higher after 600 s sputtering. This suggests that the positive silver-ions were located mainly at the silver interface. The type of silver ions produced using the Ag/Pt sputtering was determined to be very similar at 15, 60, and 600 s with the silver ions produced with the Ag target. This explains the lack of an increased inhibitory effect of Pt during the inactivation of airborne bacteria when present in the Pt/Ag target with respect to the Ag target, because in both cases similar silver ionic species were found.
ACS Appl Mater Interfaces 2010 Jan
PMID:Magnetron-sputtered Ag surfaces. New evidence for the nature of the ag ions intervening in bacterial inactivation. 2035 39

Bifunctionalized silver nanoparticles (triazole-carboxyl Ag NPs) were synthesized through a click reaction and have a cooperative effect on recognition of Co(2+), resulting in appreciable changes in color and absorption properties over other metal ions tested, including Fe(2+), Mn(2+), Hg(2+), Ni(2+), Cd(2+), Cu(2+), Zn(2+), Pb(2+), Li(+), Na(+), K(+), Cs(+). The functionalized silver nanoparticles became aggregated in solution in the present of Co(2+) through cooperative metal-ligand interaction. The colorimetric sensor allows a rapidly quantitive assay of Co(2+) down to the concentration of 7.0 x 10(-6) M. Moreover, the triazole-carboxyl AgNPs can be capable of evaluating the exceeding standard of Co(2+) in drinking water.
ACS Appl Mater Interfaces 2010 Mar
PMID:Cooperative binding of bifunctionalized and click-synthesized silver nanoparticles for colorimetric co(2+) sensing. 2035 69

A new approach to achieve coalescence and sintering of metallic nanoparticles at room temperature is presented. It was discovered that silver nanoparticles behave as soft particles when they come into contact with oppositely charged polyelectrolytes and undergo a spontaneous coalescence process, even without heating. Utilizing this finding in printing conductive patterns, which are composed of silver nanoparticles, enables achieving high conductivities even at room temperature. Due to the sintering of nanoparticles at room temperature, the formation of conductive patterns on plastic substrates and even on paper is made possible. The resulting high conductivity, 20% of that for bulk silver, enabled fabrication of various devices as demonstrated by inkjet printing of a plastic electroluminescent device.
ACS Nano 2010 Apr 27
PMID:Triggering the sintering of silver nanoparticles at room temperature. 2037 43

On the basis of the protection reaction between ethanethiol and aldehyde, we designed and synthesized two new ratiometric fluorescent chemosensors, 3 and 4, by using intramolecular charge transfer (ICT) as a signaling mechanism. Upon the addition of Hg(2+) ion, both probes displayed apparent luminescence color changes, which could be observed by naked eyes under a UV lamp. Unexpectedly, both chemosensors also gave response to the addition of trace silver ions, making this kind of chemosensors as the first example of ratiometric fluorescent probe that showed dual channel fluorescence for both Hg(2+) and Ag(+). The test strips experiments suggested that 3 and 4 could serve as practical fluorescent probes for rapid detection of Hg(2+) ion.
ACS Appl Mater Interfaces 2010 Apr
PMID:A new approach to design ratiometric fluorescent probe for mercury(II) based on the Hg(2+)-promoted deprotection of thioacetals. 2042 27


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