A Pencil-Drawn Electronic Tongue for Environmental Applications

We report on the development of a simple and cost-effective potentiometric sensor array that is based on manual “drawing” on the polymeric support with the pencils composed of graphite and different types of zeolites. The sensor array demonstrates distinct sensitivity towards a variety of inorganic ions in aqueous media. This multisensor system has been successfully applied to quantitative analysis of 100 real-life surface waters sampled in Mahananda and Hooghly rivers in the West Bengal state (India). Partial least squares regression has been utilized to relate responses of the sensors to the values of different water quality parameters. It has been found that the developed sensor array, or electronic tongue, is capable of quantifying total hardness, total alkalinity, and calcium content in the samples, with the mean relative errors below 18%.

In situ spectroscopic identification of the six types of asbestos

Exposure to asbestos fibres is related to a number of severe lung diseases, and therefore, rapid, accurate and reliable in situ or on-site asbestos detection in real-life samples is of considerable importance. This work presents a comprehensive investigation of all six types of asbestos by mid-infrared ATR-FTIR, NIR spectroscopy and Raman microspectroscopy. Our studies demonstrate that for practical applications, NIR spectroscopy is potentially the most powerful method for asbestos identification in materials utilised by the construction industry. By focusing on the narrow spectral region, 7300-7000 cm^-1 (~1370-1430 nm, overtones of O‒H vibrations), which is highly specific to these materials, and optimising the sensitivity and resolution of the instrumentation, we have been able to discriminate and identify each of the six types of asbestos with the level of detection significantly better than 1 wt%. Furthermore, straightforward computational analysis has allowed for automated objective evaluation of the spectroscopic data.

Correction: Synthesis of nanostructured catalysts by surfactant-templating of large-pore zeolites

[This corrects the article DOI: 10.1039/C9NA00004F.].

Synthesis of nanostructured catalysts by surfactant-templating of large-pore zeolites

Zeolites and related crystalline molecular sieves are utilised in a wide range of reactions and processes due to their regular microporous structure, strong acidity, shape selectivity and ion-exchange properties. However, their practical applications can be limited by the small size of the channels and cavities of the microporous structures, and therefore, a great deal of effort has been devoted to enhancing the transport of large-sized molecules in the host pores. Several commercially available zeolites, including faujasite (FAU), mordenite (MOR), beta (BEA), ZSM-5 (MFI) and zeolite L (LTL), have been exposed to a variety of acid and base treatments in the presence of a surfactant (cetyltrimethyl ammonium bromide, CTAB), which led to the controlled introduction of intracrystalline mesoporosity. The detailed characterisation of the obtained mesostructured zeolites has been carried out using FTIR spectroscopy, high resolution TEM, XRD, N₂ adsorption, ²⁹Si and ²⁷Al MAS NMR. This work demonstrates a successful application of the supramolecular templating approach for generating tuneable mesoporosity in a range of zeolites possessing 12-membered ring channels, which has been applied to zeolite L for the first time, thus producing hierarchical meso-microporous materials with improved accessibility of active sites and enhanced catalytic performance in dealkylation of tri-isopropylbenzene.

Correction: Synthesis of nanostructured catalysts by surfactant-templating of large-pore zeolites

[This corrects the article DOI: 10.1039/C9NA00004F.].

Formation of copper nanoparticles in LTL nanosized zeolite: spectroscopic characterization

The state of copper species stabilized in nanosized LTL zeolite subjected to various post-synthesis treatments was unveiled by a range of spectroscopic techniques. FTIR and UV-Vis studies demonstrated that the reduction process of copper in the LTL nanosized zeolite leads to the formation of different species including Cu²⁺, Cu⁺ and Cu nanoparticles (Cu NPs). The adsorption of probe molecules (NO and CO) was used to selectively monitor the copper species in the LTL nanosized zeolite upon oxidation and reduction post-synthesis treatments. Both the Cu²⁺ and Cu⁺ species were probed by NO and CO, respectively. The amount of Cu⁺ in the LTL zeolite nanocrystals was about 43% as determined by FTIR, while the amount of Cu NPs was about 55% determined by the UV-Vis spectroscopic characterization. These results were complemented by EPR, ²⁹Si and ⁶³Cu MAS NMR spectroscopic data. The EPR spectroscopy was further applied to monitor the effective reduction of the Cu²⁺ species and their re-oxidation, while the ⁶³Cu MAS NMR verified the presence of Cu NPs in the LTL nanosized zeolite crystals.

Effects of CaCl2 and MgCl2 on Fourier transform infrared spectra of lung cancer cells

The cations Ca2+ and Mg2+ are two important factors in the growth and maintenance of living cells. The addition of Ca2+ to living cells can cause a change in the three-dimensional (3D) structure of calcium binding proteins. Therefore, we decided to study whether the addition of CaCl2 and MgCl2 to three in vitro growing lung cancer cell lines could cause changes that could be measured by Fourier Transform Infrared Spectroscopy. The addition of CaCl2 or MgCl2 to lung cancer cells caused an increase in absorbance of the trough at 1410 cm(-1). This translated into an inversion of the 1410/1395 cm(-1) ratio following the addition of CaCl2 or MgCl2 for all three lung cancer cell lines. Also, the amide I peak shifted from around 1631 cm(-1) to lower wavenumbers when CaCl2 or MgCl2 was added to cancer cells. Furthermore, the addition of these two substances caused a shift of the peak between 3290 and 3395 cm(-1). Finally, while the addition of CaCl2 to lung cancer cells was associated with an increased cell death, this was not the case following the addition of MgCl2. This would confirm that the changes seen in the spectra of all three cell lines are due to metabolic and ionic shifts rather than cell death.