Spectral Database for Postage Stamps by Means of FT-IR Spectroscopy

A Fourier transform infrared (FT-IR) spectroscopy study on the entire Italian postage stamps production is presented in this work. Crossing 150 years of issues from the unification of Italy until today, a time line of the major components constituting the stamps has been defined, based on the wide spectral database built on the basis of the numerous analyzed exemplars. Even though it is easy to find reports about stamps’ issues history, information arising from these investigations contributes to throw light upon the substances incorporated in the stamps, which could be described as hybrid or composite materials (a sort of undisclosed or hidden story). As a result of the whole spectra acquired in attenuated total reflectance (ATR) mode, changes in paper composition showed the transition from the protein sizing glue to starch sizing; also the employment of kaolin varied through time. First it was used as the extender in the pigment–medium mixture, and finally it constituted the coating on the stamp surface. Also the chemical composition of the adhesive gum on the rear side of stamps has been subjected to modifications, as well as the front side. The earliest back glue was a protein-based adhesive; then it was replaced by gum arabic first and by poly­(vinyl acetate) (PVAC) later. FT-IR spectroscopy, supported by the detailed database developed, has been applied, for the first time, in the very useful detection of two counterfeit samples: a fake of the famous Gronchi Rosa, issued in 1961, and a regummed 2 cent red stamp, issued in 1865. The information held in the whole spectral data has been selected and employed in the principal component analysis (PCA) statistical analysis

Spectroscopic Investigation of the Selective Interaction of Mercuric and Cupric Ions with a Porphyrin Active Layer

The mechanisms of interaction between a tetrapyridyl-substituted porphyrin and Hg­(II) and Cu­(II) ions have been investigated by means of different spectroscopic techniques. Reflection spectroscopy investigations of the porphyrin Langmuir floating film and by polarization modulation infrared (IR) reflection adsorption spectroscopy at the air–water interface provided evidence of the active role played by the pyridyl substituents of the porphyrin in the interaction with the analyte. Such behavior seems to be very selective toward Cu²⁺ and Hg²⁺ ions, as demonstrated by the IR measurements in difference mode. UV–vis and IR characterizations suggest a deeply different interaction between the active molecules and the two analytes. In fact, the interaction of Hg²⁺ ions with the tetrapyrrolic derivative molecules involves both the pyridyl substituents and the central bite of the ring. On the other hand, in the case of Cu²⁺ ions, spectroscopic evidence suggests that the cupric ions interact with only the porphyrin peripheral substituents. A relevant fluorescence quenching of the Langmuir–Schaefer (LS) film is observed when even a 0.5 nM HgCl₂ or 0.5 nM CuCl₂ aqueous solution is fluxed on the LS film

Enhanced Solar-Driven Applications of ZnO@Ag Patchy Nanoparticles

ZnO@Ag patchy nanostructures were demonstrated to be efficient and stable photocatalysts for the photodegradation of organic contaminants in aqueous solutions. The photoinduced charge transfer from the conduction band of ZnO toward the Fermi level of the noble metal was favored and exploited to enhance the photocatalytic efficiency of ZnO, with a mechanism based on hole stabilization. Naked ZnO and ZnO@Ag patchy nanostructures were demonstrated to degrade methylene blue, a model compound, in aqueous solution under 370–800 nm light irradiation (100 mW cm^–2); in particular, the introduction of silver nanoparticles allowed one to increment twice the constant rate of the reaction when fitted as pseudo-first-order kinetics. Furthermore, the degradation of 2,4-dichlorophenol under direct sunlight irradiation was studied. The photo-oxidation catalyzed by patchy nanostructures was noticeably increased. In fact, the observed half time (<i>t</i>_1/2) was reduced by almost 4 times in comparison with the value observed for bare ZnO

Promising Piezoelectric Properties of New ZnO@Octadecylamine Adduct

A supramolecular adduct formed by the interaction among octadecylamine (ODA) and zinc oxide nanostructures was promoted. A stable dispersion of the ZnO@ODA adduct was obtained and characterized by means of thermogravimetric analysis and infrared and Raman spectroscopy. Then, the supramolecular adduct was spread at the air/water interface of a Langmuir trough. The presence of octadecylamine gave amphiphilic features to the ZnO@ODA adduct that was transferred from the air/water interface to solid substrates by Langmuir–Schaefer (LS) method. The transferred film was characterized by tunnel electron microscopy that highlighted rectangular well-shaped structures assembled by nanostructure of ZnO arranged in an ODA matrix. Piezoelectric feature of large LS film (1 cm²) was tested and a very promising response was observed as a consequence of the application of a pressure of 1 kPa

Human Hepatocarcinoma Cell Targeting by Glypican‑3 Ligand Peptide Functionalized Silica Nanoparticles: Implications for Ultrasound Molecular Imaging

Silica nanoparticles (SiNPs) are widely studied nanomaterials for their potential employment in advanced biomedical applications, such as selective molecular imaging and targeted drug delivery. SiNPs are generally low cost and highly biocompatible, can be easily functionalized with a wide variety of functional ligands, and have been demonstrated to be effective in enhancing ultrasound contrast at clinical diagnostic frequencies. Therefore, SiNPs might be used as contrast agents in echographic imaging. In this work, we have developed a SiNPs-based system for the in vitro molecular imaging of hepatocellular carcinoma cells that express high levels of glypican-3 protein (GPC-3) on their surface. In this regard, a novel GPC-3 targeting peptide was designed and conjugated to fluorescent silica nanoparticles. The physicochemical properties, acoustic behavior, and biocompatibility profile of the functionalized SiNPs were characterized; then binding and uptake of both naked and functionalized SiNPs were analyzed by laser scanning confocal microscopy and transmission electron microscopy in GPC-3 positive HepG2 cells, a human hepatocarcinoma cell line. The results obtained showed that GPC-3-functionalized fluorescent SiNPs significantly enhanced the ultrasound contrast and were effectively bound and taken up by HepG2 cells without affecting their viability

Langmuir–Schaefer Films for Aligned Carbon Nanotubes Functionalized with a Conjugate Polymer and Photoelectrochemical Response Enhancement

Single-walled carbon nanotubes (SWCNTs) were suspended in 1,2-dichloroethane by noncovalent functionalization with a low-band-gap conjugated polymer <b>1</b> alternating dialkoxyphenylene–bisthiophene units with benzo­[<i>c</i>]­[2,1,3]­thiadiazole monomeric units. The suspended <b>1</b>/SWCNT blend was transferred onto different solid substrates by the Langmuir–Schaefer deposition method, resulting in films with a high percentage of aligned nanotubes. Photoelectrochemical characterization of <b>1</b>/SWCNT thin films on indium–tin oxide showed the benefits of SWCNT alignment for photoconversion efficiency

Ethane-Bridged Zn Porphyrins Dimers in Langmuir–Schäfer Thin Films: Spectroscopic, Morphologic, and Magneto-Optical Surface Plasmon Resonance Characterization

This work reports on the structural and spectroscopic properties, as well as the gas-sensing performance, of ethane-bridged Zn porphyrin dimers (ZnPP) in Langmuir–Schäfer (LS) thin films toward volatile organic compounds in a magneto-optical surface plasmon resonance (MOSPR) configuration. Structural and spectroscopic properties of ethane-bridged ZnPP thin films deposited onto proper Au/Co/Au magneto-optical substrates were inspected in dry air conditions and after exposure to amine vapors by means of IR spectroscopy, scanning probe microscopy, and MOSPR techniques. The molecular organization of the thin films deposited by the LS technique is investigated. The overall results suggest the presence in all cases of mainly the anti-conformer of the investigated porphyrin dimers. The strong interaction between <i>n</i>-butylamine vapors at high concentration and Zn porphyrin thin layers leads to a great conformational change in the porphyrin structure, which is linked to a change in the optical anisotropy of the realized LS layer

Functional Enzymes in Nonaqueous Environment: The Case of Photosynthetic Reaction Centers in Deep Eutectic Solvents

Deep eutectic solvents (DESs) are emerging as a new class of green solvents with the potential to replace organic solvents in several fundamental and applied processes. In this work, we offer an unprecedented characterization of the behavior of the bacterial photosynthetic reaction center (RC) from <i>Rhodobacter sphaeroides</i> in a series of choline chloride based DESs. RC is a membrane-spanning three-subunit pigment–protein complex that, upon illumination, is capable of producing a stable charge-separated state. Thus, it represents the ideal model for carrying out basic studies of protein–solvent interactions. Herein, we first report that, in many DES mixtures investigated, RC (a) is stable, (b) is capable of generating the charge-separated state, and (c) is even able to perform its natural photocycle. It proved, indeed, to be effective in reducing quinone molecules to quinol by withdrawing electrons from cytochrome <i>c</i>. As an example of biotechnological application, a photoelectrochemical cell based on DES-dissolved RC has also been designed and successfully employed to generate photocurrents arising from the reduction of the electron-donor ferrocenemethanol

Stimulatory Effects of Methyl-β-cyclodextrin on Spiramycin Production and Physical–Chemical Characterization of Nonhost@Guest Complexes

Spiramycin is a macrolide antibiotic and antiparasitic that is used to treat toxoplasmosis and various other infections of soft tissues. In the current study, we evaluated the effects of α-cyclodextrin, β-cyclodextrin, or methyl-β-cyclodextrin supplementation to a synthetic culture medium on biomass and spiramycin production by Streptomyces ambofaciens ATCC 23877. We found a high stimulatory effect on spiramycin production when the culture medium was supplemented with 0.5% (w/v) methyl-β-cyclodextrin, whereas α-cyclodextrin or β-cyclodextrin weakly enhanced antibiotic yields. As the stimulation of antibiotic production could be because of spiramycin complexation with cyclodextrins with effects on antibiotic stability and/or efflux, we analyzed the possible formation of complexes by physical–chemical methods. The results of Job plot experiment highlighted the formation of a nonhost@guest complex methyl-β-cyclodextrin@spiramycin I in the stoichiometric ratio of 3:1 while they excluded the formation of complex between spiramycin I and α- or β-cyclodextrin. Fourier-transform infrared spectroscopy measurements were then carried out to characterize the methyl-β-cyclodextrin@spiramycin I complex and individuate the chemical groups involved in the binding mechanism. These findings may help to improve the spiramycin fermentation process, providing at the same time a new device for better delivery of the antibiotic at the site of infection by methyl-β-cyclodextrin complexation, as it has been well-documented for other bioactive molecules

Data_Sheet_1_Selective Targeting of Proteins by Hybrid Polyoxometalates: Interaction Between a Bis-Biotinylated Hybrid Conjugate and Avidin.docx

<p>The Keggin-type polyoxometalate [γ-SiW₁₀O₃₆]⁸⁻ was covalently modified to obtain a bis-biotinylated conjugate able to bind avidin. Spectroscopic studies such as UV-vis, fluorimetry, circular dichroism, coupled to surface plasmon resonance technique were used to highlight the unique interplay of supramolecular interactions between the homotetrameric protein and the bis-functionalized polyanion. In particular, the dual recognition mechanism of the avidin encompasses (i) a complementary electrostatic association between the anionic surface of the polyoxotungstate and each positively charged avidin subunit and (ii) specific host-guest interactions between each biotinylated arm and a corresponding pocket on the tetramer subunits. The assembly exhibits peroxidase-like reactivity and it was used in aqueous solution for L-methionine methyl ester oxidation by H₂O₂. The recognition phenomenon was then exploited for the preparation of layer-by-layer films, whose structural evolution was monitored in situ by ATR-FTIR spectroscopy. Finally, cell tracking studies were performed by exploiting the specific interactions with a labeled streptavidin.</p