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The presence of anionic functional groups on the surface of microbial cells makes the bacterial biomass very attractive as metal cation removal tool for environmental bioremediation. To go insight to the heavy metal sorption abilities of Gram-negative bacteria, we characterized the extracellular uptake of Ni2+ ions by the phototrophic bacterium Rhodobacter sphaeroides, whose ability to sequester toxic metal ions has been widely documented. The sorption process proved to be well described by the Langmuir model, suggesting that the cell envelope behaves as an ideal adsorbent surface, showing a layer of chemically equivalent binding sites with high affinity for Ni2+. X-ray photoelectron spectroscopic data reveal that, at binding site saturation, Ni2+ ions fully displace alkali metal ions from the bacterial surface, while they are unable to displace Ca2+ and Mg2+ from their tight binding sites. The analysis of carbon, nitrogen and oxygen speciation, as arisen from high resolution spectra fitting, highlights that the Ni2+/K+ cation exchange affects the surface distribution of main chemical components, with increased contribution by peptides and phosphatidylcholines. A role of Ni2+ ions in favoring the stacking and/or packing of lipopolysaccharide sugar chains by interaction with carboxylate groups is proposed and discussed.

In this work, a novel composite sorbent material for water remediation from oily contaminants, based on a cellulose three-dimensional fibrous scaffold treated with stearic acid and expanded graphite flakes, is presented.The pristine cellulose foams are inherently omniphilic, absorbing indiscriminately both water and oils. However, after being modified with stearic acid and graphite via drop casting, they become superhydrophobic (still preserving their superoleophilic characteristics). As a result, the foams start exhibiting a highly selective behaviour which permits to absorb different kinds of oils and organic solvents, while repelling water completely.Thermal and chemical characterizations reveal that the modification treatment is successfully performed, while the performed mechanical tests demonstrate a good recovery of elasticity after repeated deformations and confirm that the elasticity of the foam is preserved after the treatment. Although based on natural materials, the fabricated foams exhibit oil absorption rate, saturation time and capacity values comparable to those of some synthetic materials with the same aim, exhibiting a very important added value, as it is based on low cost, green and biodegradable materials, requiring, at the same time, low processing costs and providing excellent reusability properties. Keywords: Biocomposite, Superhydrophobic, Superhydrophilic, Multifunctional material, Environment

This work reports on the spectroscopic properties and gas sensing performances of cobalt bis-porphyrin derivative ((Co-H)Por2) in a thin films form obtained by Langmuir–Schafer (LS) method towards Volatile Organic Compounds (VOCs) and an oxidizing gas in a Magneto-Optical Surface Plasmon Resonance (MO-SPR) configuration. In particular the optical and spectroscopic properties of (Co-H)Por2 multilayers deposited onto proper Au/Co/Au magneto-plasmonic (MP) transducers were inspected in dry air conditions and after exposure to different analyte gas concentrations. The molecular organization of these thin films deposited by Langmuir–Schafer technique has been investigated and a comparison between the MOSPR experimental data and simulation has been also reported. In order to validate our experimental results and obtain further insight into the physical mechanism of interaction between the organometallic molecules and magneto plasmonic nanostructured systems, numerical simulations based on Finite Element Method (FEM) techniques, have been performed. The optical and magneto-optical properties of these hybrid systems have been theoretically analyzed to confirm the experimental outcomes. Finally, a peculiar sensitivity of the MOSPR sensing probe in respect to investigated analytes has been recorded.

In the present manuscript it is reported a study carried out by means of micro-Raman and infrared spectroscopy on banknotes used in Italy during more than 50 years, since 1947 until 2001. For each specimen, three different features of the banknote (serial number, watermark and security mark) were considered and the measurements were repeated on three different banknotes of the same type. Differences were revealed in the paper banknote composition, red color used for the security mark and serial number black printing ink. Then, two certified fakes were analyzed and significant shifts on the main peak of red color pigment were revealed.

Porphyrins are tetrapyrrolic macrocycles with a fascinating and multifarious variegation of properties of essential significance in up-to-date and leading technologies. From a different point of view, the Langmuir–Blodgett technique allows the immobilisation of films with an accurate regulation of molecular organisation and thickness. As a logical upshot, this manuscript concerns a substantial object of consideration in contemporary research, the utilisation of Langmuir–Blodgett multilayers of porphyrins in sensing elements for the detection of analytes in different matrices. Investigations on the morphological, optical, structural and surface characteristics of these films are remarkably related to the significant properties of sensors with the ultimate goal of rationalising the innermost intercourses between the sensing behaviour and the peculiarities and molecular organisation brought about by the deposition method. The integration of the typical electrical and optical characteristics of porphyrins with the potentialities of the Langmuir–Blodgett multilayer has originated not only encouraging projects but has afforded also certainties on the accomplishment of operative chemical sensors.

Carbon nanotubes are recent materials with an extremely appealing multiplicity of peculiar characteristics of paramount interest in contemporary advanced (nano)technologies. At the same time, the Langmuir–Blodgett technique allows to fabricate films with a substantial control and chance of modulation over thickness and molecular organisation. As a spontaneous outcome, this review deals with an actual subject of attention in up-to-date scientific investigations, i.e. the preparation, characterisation and applications of Langmuir–Blodgett films of pristine or functionalised single- or multi-walled carbon nanotubes in modern research.

This paper reports the use of optical trasduction techniques to characterise solid state chemo-optical sensors prepared by Langmuir–Schafer technique (LS) in thin film form based onto Cu(II) tris-(2,4-di- t -amylphenoxy)-(12-hydroxy-1,4,7,10-tetraoxadodecyl)-phthalocyanine macromolecules CuPcOH as active layers. The study consists in the UV–vis optical absorption monitoring of the active LS layers in the presence of specific five volatile organic compounds (VOCs) mixed in dry air in controlled atmosphere; in particular tert -butylamine, methanol, ethanol, hexane and ethyl acetate, all analytes of interests in the food quality control. The UV–vis spectra have been monitored by recording the dynamic variation in the integral of the absorbance curves in well defined spectral regions: 300–400 nm, 550–600 nm, 600–640 nm, 640–700 nm, covering the whole spectrum and centred around the typical absorption bands of phthalocyanine thin films. This simultaneous UV–vis four channel monitoring allowed to use only one active layer as sensing element where each selected spectral region generates independent sensors. The dependency of the above mentioned outputs towards the analytes has been discussed. A base optical characterisation of the investigated LS thin films has been performed.

A new approach to the preparation of TiO2 nanoparticles embedded in organic films is described. This room-temperature method is based on a Langmuir–Blodgett standard procedure using an aqueous subphase in which TiO(C2O4)22− is dissolved. Spectroscopic investigations on the subphase show that TiO2 nanoparticles are dispersed in the solution. Careful X-ray photoelectron spectroscopy characterisation of Langmuir–Blodgett films reveals that those particles are transferred into the interior of the films during growth of the n-octadecylamine layers.

Films of a dialkoxy poly( p -phenylenevinylene) (PPV) derivative bearing a bridged chain dialkoxy substituent on the aromatic rings (Bridged Dialkoxy PPV: BDA-PPV) were prepared via solvent casting and Langmuir–Blodgett (LB) techniques for applications in gas sensing devices. A description of the LB deposition of the sensing layers starting from an equimolar mixture of the polymer and arachidic acid is reported. Silicon substrates equipped with gold interdigitated electrodes have been used for both deposition procedures. In particular, the samples deposited by solvent casting evidence variation of the electrical conductivity when exposed to NO 2 oxidising agent at a working temperature of about 75 °C. They also exhibit selectivity towards NO 2 with respect to other different gases like carbon monoxide, nitrogen monoxide, ammonia and sulphur dioxide. On the contrary, LB multilayers, containing arachidic acid, have not shown any sensitivity towards all analysed gases.

The sensitivity of gadolinium bis-phthalocyanine assemblies to different concentrations of NO2 has been studied. Gold (on chrome) interdigitated electrodes on glass were passed through a floating Langmuir monolayer at 1000 mm min−1 for 20 excursions. This ultra-fast technique has greatly reduced the time needed to manufacture samples and has led to a defect structure in the deposited layers with an enhanced surface area to volume ratio. The resulting films were tested as chemiresistors in low concentrations of NO2 (0.25–4 ppm). A highly linear calibration plot (fractional current vs. concentration plot) was obtained over the concentration range 0.25–1.0 ppm, with a gradient of ∼210% ppm−1.

Thin films of meso-octaethylporphyrinogen were deposited on suitable surface by Langmuir–Blodgett technique in order to obtain optical sensors using Surface Plasmon Resonance (SPR)technique. In particular such coatings were tested in the molecular recognition of alcohol vapours such as ethanol and methanol. This resulted in a reversible shift in the resonance depth and position of the SPR curves. Different sensitivity and rate of response for different alcohol molecules were found.

Nitroso compounds and their complexes with metals have been used before only twice as suitable substances for the deposition of Langmuir–Blodgett (LB) films. To this purpose, two novel nitroso compound platinum complexes have been prepared and deposited. X-ray diffraction measurements evidence the existence of two peaks indicating two different structures in the films with different tilting. The films do not exhibit the modulation of the electrical conductivity in the presence of dopant gases in the atmosphere unlike films of similar nitroso complexes.

Langmuir-Blodgett films containing a mixture of fullerene (C 60 ) and arachidic acid (C 20 H 40 O 2 ) were deposited on three different substrates (glass, quartz and silicon). The details of the dipping procedure are explained for three different values of the monolayer pressure. Optical studies in air at room temperature on films of various thicknesses deposited on quartz substrates were performed. From transmittivity and reflectivity measurements the refractive index n and extinction coefficient k have been evaluated in the UV-visible spectral range. Finally, a preliminary structural analysis carried out by means of scanning electron microscopy has shown that the films are homogeneous with some isolated cracks.