10 research outputs found
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 stampsâ 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 pigmentâmedium
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 polyÂ(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 HgÂ(II) and CuÂ(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 airâwater
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 Cu<sup>2+</sup> and
Hg<sup>2+</sup> ions, as demonstrated by the IR measurements in difference
mode. UVâvis and IR characterizations suggest a deeply different
interaction between the active molecules and the two analytes. In
fact, the interaction of Hg<sup>2+</sup> 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 Cu<sup>2+</sup> ions, spectroscopic evidence suggests that the cupric ions
interact with only the porphyrin peripheral substituents. A relevant
fluorescence quenching of the LangmuirâSchaefer (LS) film is
observed when even a 0.5 nM HgCl<sub>2</sub> or 0.5 nM CuCl<sub>2</sub> 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 370â800 nm light irradiation
(100 mW cm<sup>â2</sup>); 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><sub>1/2</sub>) 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 LangmuirâSchaefer (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 cm<sup>2</sup>) 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 Glypicanâ3 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
LangmuirâSchaefer 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
dialkoxyphenyleneâbisthiophene units with benzoÂ[<i>c</i>]Â[2,1,3]Âthiadiazole monomeric units. The suspended <b>1</b>/SWCNT blend was transferred onto different solid substrates by the
LangmuirâSchaefer deposition method, resulting in films with
a high percentage of aligned nanotubes. Photoelectrochemical characterization
of <b>1</b>/SWCNT thin films on indiumâtin oxide showed
the benefits of SWCNT alignment for photoconversion efficiency
Ethane-Bridged Zn Porphyrins Dimers in LangmuirâSchaĚfer 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 LangmuirâSchaĚfer (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
pigmentâprotein 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 proteinâsolvent
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 PhysicalâChemical 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 Îą-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 ι-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 physicalâchemical 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 ι- 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 [Îł-SiW<sub>10</sub>O<sub>36</sub>]<sup>8â</sup> 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 H<sub>2</sub>O<sub>2</sub>. 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