A new, facile, general one-phase synthesis for thiol-functionalized gold, palladium, and iridium nanoparticles, using tetrahydrofuran (THF) as the solvent and lithium triethylborohydride (Superhydride) as the reducing agent, is presented. For octadecanethiol-functionalized gold (Au/ODT) nanoparticles, HRTEM of drop-cast particle-films revealed the formation of spherical particles of d = 4 ± 0.3 nm average size. Electron diffraction shows fcc packing arrangement, similar to that of bulk gold. The crystalline gold cores are surrounded with closely packed n-alkyl chains mainly in an all-trans conformation, adopting orthorhombic packing as confirmed by FTIR spectroscopy. Particles are arranged in a discrete solidlike assembly with a correlation length of ∼5 nm, as the interparticle distance (center-to-center) and a constant edge-to-edge distance of 1 nm as shown by FFT analysis. Using the same synthetic procedure gold nanoparticles functionalized with 11-hydroxyundecane-1-thiol and with 4‘-bromo-4-mercaptobiphenyl were prepared. TEM images of drop-cast Pd/ODT and Ir/ODT nanoparticles show an average size of 2.25 nm for the former, while for the latter the distribution is broader with the majority of particles between 2.25 and 4.25 nm. Both nanoparticles are crystalline with fcc packing. FTIR spectroscopy reveals that octadecyl chains are close-packed in all-trans conformation, and that there is presumably one chain in unit cell.

We have functionalized amorphous Fe2O3 nanoparticles with alkanesulfonic and octadecanephosphonic acids. TEM reveals nanoparticles 5−10 nm in diameter. FTIR spectra suggest that while in all cases the alkyl chains are packed in a solid-like arrangement, packing disorder increased with decreasing chain length. TGA of the sulfonic acid-functionalized Fe2O3 nanoparticles shows that moieties started to decompose and desorb from the iron oxide surface at about 260 °C. In the case of the octadecanephosphonic acid (OPA)-functionalized Fe2O3, moieties started to decompose and desorb at 340 °C. It is suggested that free Fe−OH groups can serve as proton donors to assist in the sulfonic acid desorption process and that because of the diprotic nature of the phosphonic acid these free surface Fe−OH groups may no longer be available. Among all, the octadecanesulfonic acid coating displays the lowest magnetization, which may be explained by the high packing and ordering of the alkyl chains on the particle surface. The saturation curve of the OPA case gives the smallest value of magnetization we have ever measured for functionalized Fe2O3 nanoparticles. It is suggested that the spin state of surface Fe3+ ions is affected by the bonded surfactant, through a mechanism of pπ−dπ P−O, and dπ−dπ Fe−P interactions and that the phosphonate empty d orbitals increase magnetic interactions between neighboring Fe3+ spins.

We have studied the effects of relative mole ratios of the reactant precursors in the one-phase synthesis of alkaneselenoate- and alkanethiolate-functionalized gold nanoparticles. Specifically, we prepared a series of dodecaneselenoate (DDSe)- and dodecanethiolate (DDT)-functionalized gold nanoparticles using four different Se/Au and S/Au mole ratios in reactant mixtures at two different reaction temperatures employing three different solvents. In all cases, the synthesis relied on the reduction of H[AuCl4], in the presence of dodecanethiol (DDT) and didodecyl diselenide (DD2Se2) using lithium triethylborohydride (superhydride) as the reducing agent. Nanoparticle formation, structure, and bonding characteristics were investigated using a combination of transmission electron microscopy, UV absorption spectroscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Passivation by alkyl selenide was more efficient and was characterized by greater chain density and stronger Au−Se bond strength when high ligand/substrate ratios were employed. Particle size was surprisingly uniform in all cases, independent of mole ratio. By contrast, particle size (2−5 nm) was found to increase with increasing mole ratios when the passivating ligand was alkanethiolate, whose chain grafting density increased with increasing mole ratio, fully coincided with the literature. These results can be reconciled in terms of a simple mechanistic scenario wherein the nanoparticle formation using alkanethiolate ligands proceeds via the formation of a “polymer-like” intermediate between the Au ions and the alkanethiolate ligands prior to reduction whereas such an intermediate is not formed when selenoate is used as the binding ligand.

Using a combination of fluorescence correlation and infrared absorption spectroscopies, we characterize lipid lateral diffusion and membrane phase structure as a function of protein binding to the membrane surface. In a supported membrane configuration, cholera toxin binding to the pentasaccharaide headgroup of membrane-incorporated GM1 lipid alters the long-range lateral diffusion of fluorescently labeled probe lipids, which are not involved in the binding interaction. This effect is prominently amplified near the gel-fluid transition temperature, Tm, of the majority lipid component. At temperatures near Tm, large changes in probe lipid diffusion are measured at average protein coverage densities as low as 0.02 area fraction. Spectral shifts of the methylene symmetric and asymmetric stretching modes in the lipid acyl chain confirm that protein binding alters the fraction of lipid in the gel phase.

A new one-phase synthesis of thiol-functionalized platinum nanoparticles is presented. Using tetrahydrofuran as the solvent and lithium triethylborohydride (“superhydride”) as the reducing agent, platinum nanoparticles functionalized by octadecanethiol were prepared. Fourier transform infrared spectroscopy (FTIR), tunneling electron microscopy (TEM), and powder X-ray diffraction were used to analyze the nanoparticles. The results show that the nanoparticles are single crystals with fcc structure, that their average size is ∼3 nm, and that the octadecyl chains are close packed in a solid-like assembly.

The formation enthalpies by in situ direct synthesis calorimetry for a series of silver alkanethiolates, AgS(CH 2 ) n CH 3 , with various long chain-length substituents (n ) 9, 11, 15, and 17) are reported. The calorimetric results support a mechanism of stepwise hierarchical assembly involving primary directional interactions between Ag and S forming the inorganic core and secondary stacking facilitating the formation of the three-dimensional structure. The formation enthalpy data are chain-length dependent, indicating an energy of -4 ( 0.5 kJ/mol per methyl group due to alkyl chain interactions. The chain independent component of the enthalpy associated with bonding between Ag and S is -137 ( 6 kJ/mol, which is consistent with previous experimental data and ab initio calculations for these and related materials. A new recrystallization method offers significantly improved structural consistency across the chain-length series. Larger purified crystals, prepared by this method, were used to probe the structure, thermodynamics of phase transitions, and thermal stability, using a combination of differential scanning and solution calorimetry, thermogravimetric analysis, evolved gas Fourier transform infrared spectroscopy, and temperature-dependent X-ray diffraction. The DSC data show that the temperature of the main phase transition at 131°C is essentially independent of the length of the alkyl chain substituents for recrystallized samples. This chain-length independence does not reflect constant enthalpy of transition but rather a complex interplay between enthalpic and entropic contributions. In agreement with previous studies, this phase transition is assigned to a fully reversible transformation from the layered crystalline structure to a columnar mesophase, characterized by structural rearrangements of the inorganic framework and partial conformational disordering of the chain substituents. In situ scanning calorimetry in toluene upon slow heating from room temperature to 110°C, where the sample appeared to dissolve in the toluene near 100°C, gives insight into chain assembly and crystal growth. The second reaction seen in DSC at 210°C is an irreversible transformation to an amorphous derivative, ultimately leading to the formation of silver and silver sulfide crystals resulting from the chemical decomposition of alkyl chains.

A wet photolithographic route for micropatterning fluid phospholipid bilayers is demonstrated in which spatially directed illumination by short-wavelength ultraviolet radiation results in highly localized photochemical degradation of the exposed lipids. Using this method, we can directly engineer patterns of hydrophilic voids within a fluid membrane as well as isolated membrane corrals over large substrate areas. We show that the lipid-free regions can be refilled by the same or other lipids and lipid mixtures which establish contiguity with the existing membrane, thereby providing a synthetic means for manipulating membrane compositions, engineering metastable membrane microdomains, probing 2D lipid-lipid mixing, and designing membrane-embedded arrays of soluble proteins. Following this route, new constructs can be envisaged for high-throughput membrane proteomic, biosensor array, and spatially directed, aqueous-phase material synthesis.

Al molar ratio of 2:1 was titrated with 0.1 M NaOH solution to approximately pH 9.5 under an N 2 atmosphere and aged for 24 h with vigorous stirring. The resulting white precipitate was collected by centrifugation and washed thoroughly with decarbonated water. The DNA±LDH hybrid was then prepared by intercalating doublestranded DNA into the interlayer space of the pristine LDH by an anion-exchange route. The DNA solution (2.6 mg mL ±1 ) was added to the LDH suspension (1 mg mL ±1 ) and mixed together in a shaking incubator for 7 days at 65 C. The resulting DNA±LDH hybrid was collected by centrifugation and washed with decarbonated water. For the preparation of PEO-coated DNA±LDH hybrid, 0.05 g of the DNA±LDH hybrid was dispersed in 50 mL of EtOH, and 50 mL of 0.5 % PEO±EtOH solution was added. After 30 min the PEO-coated DNA±LDH hybrid was washed with EtOH and then dried.Preparation of PPY-MAG Hybrid: The MAG (maghemite) nanoparticles were prepared by the method of Massart et al. [15,16] 3+ ratio of 0.5 were dissolved in deionized water, and heated to 50 C. Then, 150 mL of 8.6 M NH 4 OH solution was quickly added to the solution with vigorous mechanical stirring. The precipitated magnetite (Fe 3 O 4 ) was washed with deionized water and acetone, and magnetically decanted to remove the chloride ions and other non-magnetic impurities. The obtained magnetite was easily oxidized to maghemite as follows [13,17]. The magnetite (18 g) was treated with 2 M nitric acid solution for 15 min and 300 mL of aqueous 0.33 M iron(III) nitrate solution was then added. The resulting mixture was then boiled for another 15 min. The resulting maghemite particles were washed and dried in vacuo for subsequent polypyrrole coating. 1.7 g of maghemite was dispersed in liquid pyrrole for 30 min, and excess pyrrole was removed by magnetic decantation. This maghemite/pyrrole mixture was added to 200 mL of 0.15 M FeCl 3 /EtOH solution with stirring for 30 min to polymerize the surface pyrrole. Finally, the PPY/cFe 2 O 3 nanohybrids were washed with ethanol, separated by magnetic decantation, and dried in vacuo.DNA Stability Test under Enzyme Conditions: 96 units of DNase I (purchased from Sigma) was added to the DNA±LDH hybrid (15 lg) mixed with Ca 2+ /Mg 2+ ions and incubated at 37 C. After 2 h, the activation of DNase I was stopped by heating to 75 C for 30 min. The hybrid was then washed with decarbonated water. For the recovery of DNA from the hybrid, both the as-prepared DNA±LDH hybrid and the DNase I treated sample were acidified to a pH of about 2 with 0.01 M HCl solution for 30 min. The extracted DNA strands were amplified by PCR. Typical PCR was performed in 25 lL PCR buffer containing 200 lM of dNTPs (deoxynucleoside triphosphates), 0.2 lM of forward primer (AGGGT CGAAG TACGG AATAC), 0.2 lM of reverse primer (GTCCG GAGCA CTCCG CTCCG) and 1 U of Taq polymerase (Nova-taq, Genenmed). Thermocycling was at 95 C for 10 min followed by 35 cycles of 95 C for 30 s, 60 C for 30 s, 72 C for 30 s, and then 72 C for 10 min.