Photo-Induced Microfluidic Production of Ultrasmall Glyco Gold Nanoparticles.

Ultra-small gold nanoparticles (UAuNPs) are extremely interesting for applications in nanomedicine thanks to their good stability, biocompatibility, long circulation time and efficient clearance pathways. UAuNPs engineered with glycans (Glyco-UAuNPs) emerged as excellent platforms for many applications since the multiple copies of glycans can mimic the multivalent effect of glycoside clusters. Herein, we unravel a straightforward photo-induced synthesis of Glyco-UAuNPs based on a reliable and robust microfluidic approach. The synthesis occurs at room temperature avoiding the use of any further chemical reductant, templating agents or co-solvents. Exploiting 1 H NMR spectroscopy, we showed that the amount of thiol-ligand exposed on the UAuNPs is linearly correlated to the ligand concentration in the initial mixture. The results pave the way towards the development of a programmable synthetic approach, enabling an accurate design of the engineered UAuNPs or smart hybrid nano-systems.

Bifunctional Europium(III) and Niobium(V)-Containing Saponite Clays for the Simultaneous Optical Detection and Catalytic Oxidative Abatement of Blister Chemical Warfare Agents.

For the first time, the co-presence in the saponite structure of luminescent EuIII and catalytic NbV metal sites was exploited for the simultaneous detection and catalytic abatement of sulfur-containing blister chemical warfare agents. Metal centers were introduced in structural positions of the saponite (in the interlayer space or inside the inorganic framework) following two different synthetic methodologies. The functionalized saponites were able to reveal the presence of a sulfur mustard simulant (2-chloroethyl)ethyl sulfide (CEES) after few seconds of contact time and more than 80 % of the substrate was catalytically decomposed after 24 h in the presence of aqueous hydrogen peroxide.

Gold nanoparticles morphology does not affect the multivalent presentation and antibody recognition of Group A Streptococcus synthetic oligorhamnans.

The development of novel delivery systems capable of enhancing the antibody binding affinity and immunoactivity of short length saccharide antigens is at the forefront of modern medicine. In this regard, gold nanoparticles (AuNPs) raised great interest as promising nano-vaccine platform, as they do not interfere with the desired immune response and their surface can be easily functionalized, enabling the antigen multivalent presentation. In addition, the nanoparticles morphology can have a great impact on their biological properties. Gram-positive Group A Streptococcus (GAS) is a bacterium responsible for many infections and represents a priority healthcare concern, but a universal vaccine is still unavailable. Since all the GAS strains have a cell wall characterized by a common polyrhamnose backbone, this can be employed as alternative antigen to develop an anti-GAS vaccine. Herein, we present the synthesis of two oligorhamnoside fragments and their corresponding oligorhamnoside-AuNPs, designed with two different morphologies. By competitive ELISA we assessed that both symmetric and anisotropic oligorhamnan nanoparticles inhibit the binding of specific polyclonal serum much better than the unconjugated oligosaccharides.

More Efficient Prussian Blue Nanoparticles for an Improved Caesium Decontamination from Aqueous Solutions and Biological Fluids.

Any release of radioactive cesium-137, due to unintentional accidents in nuclear plants, represents a dangerous threat for human health and the environment. Prussian blue has been widely studied and used as an antidote for humans exposed to acute internal contamination by Cs-137, due to its ability to act as a selective adsorption agent and to its negligible toxicity. In the present work, the synthesis protocol has been revisited avoiding the use of organic solvents to obtain Prussian blue nanoparticles with morphological and textural properties, which positively influence its Cs+ binding capacity compared to a commercially available Prussian blue sample. The reduction of the particle size and the increase in the specific surface area and pore volume values compared to the commercial Prussian blue reference led to a more rapid uptake of caesium in simulated enteric fluid solution (+35% after 1 h of contact). Then, after 24 h of contact, both solids were able to remove >98% of the initial Cs+ content. The Prussian blue nanoparticles showed a weak inhibition of the bacterial luminescence in the aqueous phase and no chronic detrimental toxic effects.

CNF-Functionalization as Versatile Tool for Tuning Activity in Cellulose-Derived Product Hydrogenation.

Carbon nanofibers (CNFs) have been functionalized by introducing O, N, and P containing groups in order to investigate the effect of support functionalization in Ru catalysed hydroxymethyl furfural (HMF) and levulinic acid (LA) hydrogenation. In the case of HMF, despite the fact that no effect on selectivity was observed (all the catalysts produced selectively gamma-valerolactone (GVL)), the functionalization strongly affected the activity of the reaction. O-containing and N-containing supports presented a higher activity compared to the bare support. On the contrary, in HMF hydrogenation, functionalization of the support did not have a beneficial effect on the activity of a Ru-catalysed reaction with respect to bare support and only CNFs-O behaved similarly to bare CNFs. In fact, when CNFs-N or CNFs-P were used as the supports, a lower activity was observed, as well as a change in selectivity in which the production of ethers (from the reaction with the solvent) greatly increased.

Ruthenium on Carbonaceous Materials for the Selective Hydrogenation of HMF.

We report the use of Ru catalysts supported in the activated carbon (AC) and carbon nanofibers (CNFs) for the selective production of liquid fuel dimethylfuran (DMF) and fuel additives alkoxymethyl furfurals (AMF). Parameters such as the reaction temperature and hydrogen pressure were firstly investigated in order to optimise the synthesis of the desired products. Simply by using a different support, the selectivity of the reaction drastically changed. DMF was produced with AC as support, while a high amount of AMF was produced when CNFs were employed. Moreover, the reusability of the catalysts was tested and deactivation phenomena were identified and properly addressed. Further studies need to be performed in order to optimise the stability of the catalysts.

Fluidic Manufacture of Star-Shaped Gold Nanoparticles.

Star-shaped gold nanoparticles (StarAuNPs) are extremely attractive nanomaterials, characterized by localized surface plasmon resonance which could be potentially employed in a large number of applications. However, the lack of a reliable and reproducible synthetic protocols for the production of StarAuNPs is the major limitation to their spreading. For the first time, here we present a robust protocol to manufacture reproducible StarAuNPs by exploiting a fluidic approach. Star-shaped AuNPs have been synthesized by means of a seed-less protocol, employing ascorbic acid as reducing agent at room temperature. Moreover, the versatility of the bench-top microfluidic protocol has been exploited to afford hydrophilic, hydrophobic and solid-supported engineered StarAuNPs, by avoiding intermediate NP purifications.

Characterization of a Poly-4-Vinylpyridine-Supported CuPd Bimetallic Catalyst for Sonogashira Coupling Reactions.

CuPd bimetallic solvated metal atoms (SMA) synthesized by metal vapor synthesis (MVS) technique and supported on poly-4-vinylpyridine (PVPy) resin, showed significantly higher catalytic activity in Sonogashira-type carbon-carbon coupling reactions than the corresponding monometallic Cu and Pd systems as well as their physical mixture. The analysis of the bimetallic catalyst combining transmission electron microscopy techniques and X-ray absorption fine structure (XAFS) spectroscopy revealed the presence of small Pd nanoparticles (dm =2.5 nm) while the analysis of the X-ray absorption data, at the Cu K-edge suggests the formation of thin and incomplete Cu oxide layers around the Pd-rich cores.

Synthesis of Nanocrystalline TiOF2 Embedded in a Carbonaceous Matrix from TiF4 and D-Fructose.

Nanostructured titanium oxide difluoride embedded in a matrix of amorphous carbon was synthesized by pyrolysis of D-fructose in the presence of titanium tetrafluoride (optimal Ti/fructose molar ratio = 5.5), both in the solid state at ca. 150 °C and in suspension of 1,2-dichloroethane at reflux temperature. The resulting solid materials were characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and elemental analysis. In every case, PXRD and TEM data indicated the presence of an unique crystalline phase (TiOF2) embedded in a light matrix (amorphous carbon). The average crystal size of the powder can be regulated by varying the reaction time.

Photoelectrochemical Behavior of Electrophoretically Deposited Hematite Thin Films Modified with Ti(IV).

Doping hematite with different elements is a common strategy to improve the electrocatalytic activity towards the water oxidation reaction, although the exact effect of these external agents is not yet clearly understood. Using a feasible electrophoretic procedure, we prepared modified hematite films by introducing in the deposition solution Ti(IV) butoxide. Photoelectrochemical performances of all the modified electrodes were superior to the unmodified one, with a 4-fold increase in the photocurrent at 0.65 V vs. SCE in 0.1 M NaOH (pH 13.3) for the 5% Ti-modified electrode, which was the best performing electrode. Subsequent functionalization with an iron-based catalyst led, at the same potential, to a photocurrent of ca. 1.5 mA·cm(-2), one of the highest achieved with materials based on solution processing in the absence of precious elements. AFM, XPS, TEM and XANES analyses revealed the formation of different Ti(IV) oxide phases on the hematite surface, that can reduce surface state recombination and enhance hole injection through local surface field effects, as confirmed by electrochemical impedance analysis.

Photo-induced microfluidic production of ultrasmall platinum nanoparticles.

We describe here the synthesis of ultrasmall Pt nanoparticles (NPs) obtained by a robust and reliable protocol using UV-Vis photoreduction of a platinum salt precursor, under continuous flow conditions. These ligand-free Pt NPs were rapidly dispersed onto a solid support or stabilized towards aggregation as a colloidal solution by the addition of an appropriate ligand in the reaction mixture. The proposed protocol exploits a microfluidic platform where the Pt4+ precursor is photo-reduced to small Pt0 NPs (1.3 nm) at room temperature in the presence of ethanol, without any additional reducing agent. We apply the protocol to prepare Pt NPs highly dispersed on carbon support (Pt/C) proven to be a very efficient heterogeneous catalyst for both the hydrosilylation of terminal alkynes and hydrogenation of nitroaromatic compounds, selected as model reactions. Furthermore, we exploit the versatility of this microfluidic approach to produce stabilized aqueous/ethanol colloidal solutions of Pt NPs, employing a ligand of choice (e.g., PVP or a thiol-ligand). These colloids offer long-term storage and further ligand modification. We showcase the synthesis of biocompatible glycol-stabilized Pt nanoparticles as an exemplary application.

Multifunctional interfaces for multiple uses: Tin(II)-hydroxyapatite for reductive adsorption of Cr(VI) and its upcycling into catalyst for air protection reactions.

Evidence collected to date by our group has demonstrated that tin(II)-functionalized hydroxyapatites (Sn/HAP) are a newly discovered class of ecofriendly reductive adsorbents for Cr(VI) removal from wastewaters. In this work an upgraded series of Sn/HAP materials assured a maximum removal capacity of ≈ 20 mgCr/g, doubling the previously reported value for Sn/HAP materials, thanks to higher Sn-dispersion as proved by X-ray photoelectron spectroscopy and electron microscopy. Insights on kinetics and thermodynamics of the reductive adsorption process are provided and the influence of pH, dosage, and nature of Cr(VI) precursors on chromium removal performances have been investigated. Pseudo-second-order kinetics described the interfacial reductive adsorption process on Sn/HAP, characterized by low activation energy (21 kJ mol-1), when measured in the 278-318 K range. Tests performed in the 2-6 pH interval showed similar efficiency in terms of Cr(VI) removal. Conventional procedures of recycling and regeneration resulted ineffective in restoring the pristine performances of the samples due to surface presence of both Sn(IV) and Cr(III). To overcome these weaknesses, the used samples (Sn + Cr/HAP) were upcycled into catalysts in a circular economy perspective. Used samples were tested as catalysts in gas-phase catalytic processes for air pollution remediation: selective catalytic reduction of NOx (NH3-SCR), NH3 selective catalytic Oxidation (NH3-SCO), and selective catalytic oxidation of methane to CO2. Catalytic tests enlightened the interesting activity of the upcycled Sn + Cr/HAP samples in catalytic oxidation processes, being able to selectively oxidize methane to CO2 at relatively low temperature.

Glucose-coated superparamagnetic iron oxide nanoparticles prepared by metal vapor synthesis can target GLUT1 overexpressing tumors: In vitro tests and in vivo preliminary assessment.

Superparamagnetic iron oxide nanoparticles (SPIONs) coated with glucose (Glc-SPIONs) were prepared by a new approach called Metal Vapor Synthesis (MVS) and their morphological/structural features were investigated by transmission electron microscopy (TEM) and dynamic light scattering. TEM analysis revealed the presence of small roundish crystalline iron oxide nanoparticles in the organic amorphous phase of glucose, The particles were distributed in a narrow range (1.5 nm-3.5 nm) with a mean diameter of 2.7 nm. The hydrodynamic mean diameter of the Glc-SPIONs, was 15.5 nm. From 4 mg/mL onwards, there was a constant level of positive contrast in a T1-weighted sequence. In vitro experiments were performed in three cell lines: pancreatic cancer (PSN-1), human thyroid cancer (BCPAP), and human embryonic kidney non-tumor cells. We evaluated GLUT1 expression in each cell line and demonstrated that the exposure time and concentration of the Glc-SPIONs we used did not affect cell viability. PSN-1 cells were the most effective at internalizing Glc-SPIONs. Although significantly higher than the control cells, a lower Fe content was detected BCPAP cells treated with Glc-SPIONs. To confirm the involvement of GLUT1 in Glc-SPIONs internalization, cellular uptake experiments were also conducted by pre-treating cancer cells with specific GLUT1 inhibitors, All the inhibitors reduced the cancer cell uptake of Glc-SPIONs In vivo tests were performed on mice inoculated with Lewis lung carcinoma. Mice were treated with a single i.v. injection of Glc-SPION and our results showed a great bioavailability to the malignant tissue by the i.v. administration of Glc-SPIONs. Glc-SPIONs were efficiently eliminated by the kidney. To the best of our knowledge, our study demonstrates for the first time that Glc-SPIONs prepared with MVS can be electively internalized by tumor cells both in vitro and in vivo by exploiting one of the most universal metabolic anomalies of cancer.

A way to decylamine-stabilized gold nanoparticles of tailored sizes tuning their growth in solution.

Acetone solvated Au nanoparticles (Au NPs) were prepared by Metal Vapour Synthesis (MVS) co-condensing Au and acetone vapours. Nanoparticles growth was quenched at different times by using decylamine (DA) as stabilizer and DA-stabilized Au NPs were characterized by UV-Vis, NMR DOSY and HRTEM techniques. The dependence of metal clustering processes on gold concentration was investigated.

Effect of Carbon Support, Capping Agent Amount, and Pd NPs Size for Bio-Adipic Acid Production from Muconic Acid and Sodium Muconate.

The effect of support, stabilizing agent, and Pd nanoparticles (NPs) size was studied for sodium muconate and t,t-muconic acid hydrogenation to bio-adipic acid. Three different activated carbons (AC) were used (Norit, KB, and G60) and carbon morphology did not affect the substrate conversion, but it greatly influenced the adipic acid yield. 1% Pd/KB Darco catalyst, which has the highest surface area and Pd surface exposure, and the smallest NPs size displayed the highest activity. Furthermore, the effect of the amount of the protective agent was studied varying metal/protective agent weight ratios in the range of 1/0.00-1/1.20, using KB as the chosen support. For sodium muconate reduction 1% Pd/KB_1.2 catalyst gave the best results in terms of activity (0.73 s-1), conversion, and adipic acid yield (94.8%), while for t,t-muconic acid hydrogenation the best activity result (0.85 s-1) was obtained with 1% Pd/KB_0.0 catalyst. Correlating the results obtained from XPS and TEM analyses with catalytic results, we found that the amount of PVA (polyvinyl alcohol) influences mean Pd NPs size, Pd(0)/Pd(II) ratio, and Pd surface exposure. Pd(0)/Pd(II) ratio and Pd NPs size affected adipic acid yield and activity during sodium muconate hydrogenation, respectively, while adipic acid yield was related by exposed Pd amount during t,t-muconic acid hydrogenation. The synthesized catalysts showed higher activity than commercial 5% Pd/AC.

Size-controlled synthesis and NMR characterization of mesitylene-vinylsiloxanes stabilized Pt nanoparticles in solution.

Pt nanoclusters have been generated by reaction of Pt vapour and mesitylene vapour and the role of the mesitylene/platinum ratio and the Pt particle size has been evaluated, quenching the resulting mesitylene solvated Pt atoms with 1,3-divinyltetramethyldisiloxane (DVS) as additional ligand. The Pt particle sizes have been estimated on the basis of DOSY (Diffusion-Ordered SpectroscopY) analysis and information on their structure features have been obtained by combined use of 2D NMR techniques.

Selective catalytic amination of halogenated aldehydes with calcined palladium catalysts.

This work focuses on understanding the influence of the conditions used in the calcination step of palladium catalysts on the performance of this catalyst in the reductive amination of halogen-containing substrates. The results show that increasing the calcination temperatures (from 100 °C to 400 °C) has a detrimental effect on catalytic activity but a strong positive effect on the selectivity (from 45 to 96%), avoiding the undesired dehalogenation reaction. TEM investigation showed that the reason for the different selectivity can be addressed to different Pd mean particles size and particle size distribution. In particular, larger Pd particles obtained at the highest calcination temperature (400 °C) showed the best selectivity to halogenated benzylamines (96%), with a good stability in terms of both activity and selectivity as confirmed by performing recycling tests.

Metal vapor synthesis of ultrasmall Pd nanoparticles functionalized with N-heterocyclic carbenes.

The synthesis of N-heterocyclic carbene (NHC)-stabilized palladium nanoparticles (PdNPs) by an entirely new strategy comprising the NHC functionalization of ligand-free PdNPs obtained by metal vapor synthesis is described. Detailed characterization confirms the formation of very small monodisperse PdNPs (2.3 nm) and the presence of the NHC ligand on the Pd surface. The stable NHC-functionalized PdNPs dispersed onto a carbon support showed high activity in the hydrogenation of limonene with enhanced regioselectivity in comparison to bare PdNPs on carbon.

Synthesis of a highly reactive form of WO2Cl2, its conversion into nanocrystalline mono-hydrated WO3 and coordination compounds with tetramethylurea.

A new form of WO2Cl2 was obtained by modification of a literature procedure. Both the newly prepared WO2Cl2 and the commercial yellow WO2Cl2 exhibited an orthorhombic structure (powder X-ray diffraction, P-XRD), and their air exposure at room temperature afforded light green and lemon yellow WO3·H2O (orthorhombic phase), respectively. These materials were characterized by P-XRD, high-resolution transmission electron microscopy (HR-TEM) and scanning transmission electron microscopy (S-TEM). The analyses revealed the nanocrystalline nature of light green WO3·H2O, and the prevalent amorphism of lemon yellow WO3·H2O. The reactions of grey WO2Cl2 with one and two equivalents of tetramethylurea (tmu), in CH2Cl2 at room temperature, led to the isolation of the trinuclear complex [WO2Cl2(tmu)]3, 1 (45% yield), and the mononuclear one WO2Cl2(tmu)2, 2 (64%), respectively. Compounds 1 and 2 were fully characterized by analytical and spectroscopic methods, single crystal X-ray diffraction (SC-XRD) and DFT calculations.

TiO2 Nanotubes Arrays Loaded with Ligand-Free Au Nanoparticles: Enhancement in Photocatalytic Activity.

A new protocol to synthesize size-controlled Au nanoparticles (NPs) loaded onto vertically aligned anatase TiO2 nanotubes arrays (TNTAs) prepared by electrochemical anodization is reported. Ligand-free Au NPs (<10 nm) were deposited onto anatase TNTAs supports, finely tuning the Au loading by controlling the immersion time of the support into metal vapor synthesis (MVS)-derived Au-acetone solutions. The Au/TNTAs composites were characterized by electron microscopies (SEM, (S)TEM), X-ray diffraction, X-ray photoelectron spectroscopy, and UV-vis spectroscopy. Their photocatalytic efficiency was evaluated in toluene degradation in air under ambient conditions without thermal or chemical postsynthetic treatments. The role of Au loadings was pointed out, obtaining a three times enhancement of the pristine anatase TNTAs activity with the best sample containing 3.3 µg Au cm-2.