Fast profiling of cocaine seizures by FTIR spectroscopy and GC-MS analysis of minor alkaloids and residual solvents.

In this study, samples coming from large seizures of cocaine which took place in Italian Customs areas during 2011 and 2012 were examined. Minor alkaloids and residual solvents, analyzed by gas chromatography-mass spectrometry (GC-MS) and head space (HS)-GC-MS, respectively, were processed by principal component analysis (PCA), highlighting groupings of samples according to their chemical similarity. A hypothesis about the geographical origin of samples was also provided: most of them were compatible with Colombia as country of origin.

NLO response of photoswitchable azobenzene-based materials.

The nonlinear optical (NLO) response of three π-conjugated azobenzene (AB) derivatives was investigated under picosecond laser excitation by means of the Z-scan technique to evaluate the effect of an ethynyl-based conjugated spacer on the NLO properties of ABs. All modules possessed large third-order nonlinearity, but unexpectedly it was the less extended AB derivative that exhibited the largest NLO response. This finding has been confirmed by means of DFT calculations and was attributed to a higher cis/trans ratio of the particular AB derivative in its investigated photoequilibrated state.

Molecular and electronic properties transferred to Silicon via wet-chemistry surface nanofunctionalization: ethynylferrocene on Si(100).

In the frame of our research activity on covalent anchoring of functional molecules on Si oriented surfaces, we report here on the hybrid species resulting from the reaction of ethynylferrocene with H-Si(100) either in a single, direct step, or after production of a self-assembled alpha,omega-bifunctional alkyl monolayer. In the former approach, a short Si-C covalent bond is established through visible-light activation of the unsaturated side arm of ethynylferrocene via an extra-mild approach. In the latter case, an azide-alkyne Huisgen cycloaddition reaction ("click" chemistry) is induced between the C[triple bond]C group of the molecule and the -N3 terminations of undecyl hydrocarbon chains pre-assembled onto H-Si(100).

Cathodic electrografting of versatile ligands on Si(100) as a low-impact approach for establishing a Si--C bond: a surface-coordination study of substituted 2,2'-bipyridines with CuI ions.

Three distinct wet chemistry recipes were applied to hydrogen-terminated n- and p-Si(100) surfaces in a comparative study of the covalent grafting of two differently substituted 2,2'-bipyridines. The applied reactions require the use of heat, or visible light under a controlled atmosphere, or a suitable potential in an electrochemical cell. In this last case, hydrogen-terminated silicon is the working electrode in a cathodic electrografting (CEG) reaction, in which it is kept under reduction conditions.

Electrochemical reversibility of vinylferrocene monolayers covalently attached on H-terminated p-Si(100).

A reversible electrochemical behavior is demonstrated on a specially prepared redox-functionalized H-Si(100) surface, obtained via an extra-mild grafting procedure from vinylferrocene. The results of a detailed XPS and electrochemical characterization of the resulting hybrid are reported and discussed to propose it as a reference system for high-quality electroactive monolayers on Si. The investigated ferrocene derivative bears a functional group suitable for a mild route to covalent anchoring on Si, which is based on a photoinduced reaction with visible light under an inert atmosphere.

Controlled loading of oligodeoxyribonucleotide monolayers onto unoxidized crystalline silicon; fluorescence-based determination of the surface coverage and of the hybridization efficiency; parallel imaging of the process by Atomic Force Microscopy.

Unoxidized crystalline silicon, characterized by high purity, high homogeneity, sturdiness and an atomically flat surface, offers many advantages for the construction of electronic miniaturized biosensor arrays upon attachment of biomolecules (DNA, proteins or small organic compounds). This allows to study the incidence of molecular interactions through the simultaneous analysis, within a single experiment, of a number of samples containing small quantities of potential targets, in the presence of thousands of variables. A simple, accurate and robust methodology was established and is here presented, for the assembling of DNA sensors on the unoxidized, crystalline Si(100) surface, by loading controlled amounts of a monolayer DNA-probe through a two-step procedure.