Synthesis of Photoluminescent 2D Self-Assembled Silver Thiolate Nanoclusters for Sensors and Biomolecule Support.

Silver thiolate nanoclusters (Ag NCs) show distinctive optical properties resulting from their hybrid nature, metallic and molecular, exhibiting size-, structure-, and surface-dependent photoluminescence, thus enabling the exploitation of Ag NCs for potential applications in nanobiotechnology, catalysis, and biomedicine. However, tailoring Ag NCs for specific applications requires achieving long-term stability and may involve modifying surface chemistry, fine-tuning ligand composition, or adding functional groups. In this study, we report the synthesis of novel Ag NCs using 2-ethanephenylthiolate (SR) as a ligand, highlight critical points addressing stability, and characterize their optical and structural properties. A preliminary electrical characterization revealed high anisotropy, well suited for potential use in electronics/sensing applications. We also present the synthesis and characterization of Ag NCs using 10-carboxylic 2-ol thiolate (SR'COOH) having a terminal carboxylic group for conjugation with amine-containing molecules. We present a preliminary assessment of its bioconjugation capability using bovine serum albumin as a model protein indicating its prospective application as a biomolecule support.

Silver thiolate nanoclusters as support for chiral ligands: application in heterogeneous phase asymmetric catalysis.

Silver thiolate nanoclusters have been functionalized with a chiral amino alcohol ligand that has previously shown high catalytic efficiency in different asymmetric reactions. The as-developed nanostructured catalyst, which can be easily recovered by simple centrifugation, has been tested in the addition of nitromethane to aromatic aldehydes, showing the same catalytic activity as the homogeneous ligand. Moreover, it was reused for two further recycling cycles without loss of efficiency. To the best of our knowledge, this is the first example of silver nanoclusters employed as a support for chiral ligands for heterogeneous phase asymmetric catalysis.

On Tailoring Co-Precipitation Synthesis to Maximize Production Yield of Nanocrystalline Wurtzite ZnS.

Pyroelectric materials can harvest energy from naturally occurring ambient temperature changes, as well as from artificial temperature changes, notably from industrial activity. Wurtzite- based materials have the advantage of being cheap, non-toxic, and offering excellent opto-electrical properties. Due to their non-centrosymmetric nature, all wurtzite crystals have both piezoelectric and pyroelectric properties. Nanocrystalline wurtzite ZnS, being a room temperature stable material, by contrast to its bulk counterpart, is interesting due to its still not well-explored potential in piezoelectric and pyroelectric energy harvesting. An easy synthesis method-a co-precipitation technique-was selected and successfully tailored for nanocrystalline wurtzite ZnS production. ZnS nanopowder with nanoparticles of 3 to 5 nm in size was synthesized in ethyl glycol under medium temperature conditions using ZnCl2 and thiourea as the sources of Zn and S, respectively. The purified and dried ZnS nanopowder was characterized by conventional methods (XRD, SEM, TEM, TG and FTIR). Finally, a constructed in-house pilot plant that is able to produce substantial amounts of wurtzite ZnS nanopowder in an environmentally friendly and cost-effective way is introduced and described.

Fine-Tuning Synthesis of Fluorescent Silver Thiolate Nanoclusters.

Noble metal thiolate nanoclusters are a new class of nanomaterials with molecular-like properties such as high dispersibility and fluorescence in the visible and infrared spectral region, properties highly requested in biomedicine for imaging, sensing and drug delivery applications. We report on three new silver phenylethane thiolate nanoclusters, differing for slight modifications of the preparation, i.e., the reaction solvent and the thiolate quantity, producing changes in the nanocluster composition as well as in the fluorescence behavior. All samples, excited in the range 250-500 nm, emit around 400 and 700 nm differing in the emission maxima and behavior. The silver thiolate nanoclusters have been characterized by way of C, H, S elemental analyses and Thermal Gravimetric Analysis (TGA) to determine the nanocluster composition, Scanning Transmission Electron Microscopy (STEM) to investigate the nanocluster morphology and UV-Vis and fluorescence spectroscopy to study their optical properties.

A Simple Ball Milling and Thermal Oxidation Method for Synthesis of ZnO Nanowires Decorated with Cubic ZnO2 Nanoparticles.

In this work, we propose the synthesis of ZnO nanostructures through the thermal oxidation of ball-milled powders with the introduction of Mg and Sn doping species at the preliminary step of milling. We investigate the advantages and challenges of this two steps process for the production and fabrication of highly crystalline ZnO nanowires. This simple method allows us to fabricate ZnO nanowires with a higher quality core crystal at a much lower temperature and for a shorter processing time than the state-of-the-art, and decorated with by ZnO2 nanoparticles as determined via TEM analysis. The main findings will show that the crystalline core of the nanowires is of hexagonal ZnO while the nanoparticles on the surface are ZnO2 cubic type. Generally, the method proves to be suitable for applications that require a high surface-to-volume ratio, for example, catalysis phenomena, in which the presence of zinc oxides species can play an important role.

Design of a fluorescent and clickable Ag38(SRN3)24 nanocluster platform: synthesis, modeling and self-assembling.

Fluorescent atomically precise Ag38(11-azido-2-ol-undecane-thiolate)24 nanoclusters are easily prepared using sodium ascorbate as a "green" reducer and are extensively characterized by way of elemental analyses, ATR-FTIR, XRD, SAXS, UV-vis, fluorescence spectroscopies, and theoretical modeling. The fluorescence and the atomically determined stoichiometry and structure, the facile and environmentally green synthesis, together with the novel presence of terminal azido groups in the ligands which opens the way to "click"-binding a wide set of molecular species, make Ag38(11-azido-2-ol-undecane-thiolate)24 nanoclusters uniquely appealing systems for biosensing, recognition and functionalization in biomedicine applications and in catalysis.

High yield synthesis of pure alkanethiolate-capped silver nanoparticles.

One-phase, one-pot synthesis of Ag(0) nanoparticles capped with alkanethiolate molecules has been optimized to easily achieve a pure product in quantitative yield. We report the synthesis of dodecanethiolate-capped silver particles and the chemophysical, structural, and morphologic characterization performed by way of UV-vis, (1)H NMR, and X-ray photoelectron (XPS) spectroscopies, X-ray powder diffraction (XRD) and X-ray absorption fine structure analysis (XFAS), electron diffraction and high-resolution transmission electron microscopy (HR-TEM), and scanning and transmission electron microscopy (SEM and TEM). Depending on the molar ratio of the reagents (dodecylthiosulphate/Ag(+)), the mean Ag(0) particle size D(XRD) is tuned from 4 to 3 nm with a narrow size distribution. The particles are highly soluble, very stable in organic solvents (hexane, toluene, dichloromethane, etc.), and resistant to oxidation; the hexane solution after one year at room temperature does not show any precipitation or formation of oxidation byproducts.

Linear ß-amino alcohol catalyst anchored on functionalized magnetite nanoparticles for enantioselective addition of dialkylzinc to aromatic aldehydes.

A linear ß-amino alcohol ligand, previously found to be a very efficient catalyst for enantioselective addition of dialkylzinc to aromatic aldehydes, has been anchored on differently functionalized superparamagnetic core-shell magnetite-silica nanoparticles (1a and 1b). Its catalytic activity in the addition of dialkylzinc to aldehydes has been evaluated, leading to promising results, especially in the case of 1b for which the recovery by simple magnetic decantation and reuse was successfully verified.

Layered silver nanoparticles embedded in a BaF(2) matrix: optical characterization.

Multilayer stacks of silver and BaF(2) alternate layers have been deposited by thermal evaporation on a silica substrate with the aim to obtain Ag clusters dispersed in a BaF(2) insulator matrix. The Ag layer thickness was approximately 1.2 nm; the thickness of the BaF(2) layer was approximately 25 nm. The samples were thermally treated for a 1 h thermal annealing process at 500 degrees C. These kinds of multilayer device also have several applications in the field of optics for the realization of antireflection coatings. However, optical characterization of dielectric matrices that contain layered metallic nanoparticles still remains an unsolved problem in the field of nanostructured optical coatings. Therefore, the surface plasmon resonance peak that appears in the optical absorption spectra because of the formation of Ag nanoclusters inside the BaF(2) insulator matrix has been monitored and fitted by numerical codes. In particular, a previously published theoretical model, based on the Maxwell-Garnett effective medium theory, modified to take into account the effects that are due to the particle shapes and the spatial arrangement of the clusters, has been employed to fit the optical absorption spectra.

Functionalized Magnetic Nanoparticles as Catalysts for Enantioselective Henry Reaction.

With the aim to easily recover and reuse the catalyst, an efficient amino alcohol catalyst previously tested in the asymmetric addition of diethylzinc to several aromatic aldehydes has been immobilized on proper functionalized superparamagnetic core-shell magnetite-silica nanoparticles and employed in the Henry reaction in the semi-homogeneous phase. The nanocatalyst exhibits a promising catalytic activity that remains unchanged in the three catalytic cycles performed. The results prove that highly efficient catalysts, by being immobilized on suitable magnetic nanosupports, can be easily recovered and reused, maintaining their catalytic behavior.

Early failure of a locked titanium plate in a proximal humeral fracture: Case report and metallurgic analysis.

Angular stability locking plates are commonly used in proximal humeral fractures, especially in old patients with osteoporotic bones. These implants show good results in short and midterm follow-up, but complications are not uncommon. Here we present a case report to describe a case of early failure of a proximal angular stability plate implanted in a 72 years old female with a highly unstable two part proximal humeral fracture. An optical and metallurgic analysis was also conducted to study the modalities of failure. We concluded that anatomic reduction and restoration of the medial cortical support are crucial in order to minimize the mechanical load on the bone-metal interface and to prevent mechanical failure, in particular when the fracture rim drop in the weak point of the plate that was found in the proximal two symmetric holes (Holes E).

Nanocluster superstructures or nanoparticles? The self-consuming scaffold decides.

We show that using the same reaction procedure, by hindering or allowing the formation of a reaction intermediate, the Ag+dodecanethiolate polymeric complex, it is possible to selectively obtain Ag dodecanethiolate nanoparticles or Ag dodecanethiolate nanoclusters in the size range 4-2 nm. Moreover, the Ag dodecanethiolate nanoclusters display a lamellar superstructure templated from the precursor Ag+dodecanethiolate polymeric complex. A plausible formation mechanism is illustrated where, starting from the precursor and scaffold lamellar Ag+ thiolate polymeric complex, first the nanocluster Agn0 core is formed by reduction of isoplanar Ag+ ions, followed by Ag+ thiolate units that build protection, the nanocluster shell, around the core. The nanoclusters are characterized by elemental analyses, XRD, ATR-FTIR, XPS, XAS, MALDI, ESI, UV-Vis and fluorescence measurements. The luminescent Ag15(dodecanethiolate)11·2H2O nanocluster is achieved in good yield after 4 hours of reaction whereas after 2 hours, the luminescent Ag35(dodecanethiolate)16 is isolated. Both Ag nanoclusters present emission bands in the range 330-450 nm, the shifting depending on the excitation wavelength. This phenomenon is attributed to a possible dipolar state causing distribution in energies due to variability of dipole-dipole interactions. Moreover, both nanoclusters further present a NIR emission at about 700 nm independent from the excitation wavelength. Thanks to their optical and structural properties, the synthesized nanoclusters, perfect molecular/nanoparticle hybrids, have great potentiality for new applications in nanotechnologies.