Analysis of artist’s palette on a 16th century wood panel painting by portable and laboratory Raman instruments

Non-destructive analysis of the artist’s palette of ancient wooden panel paintings is a difficult task and studies are rare. Here we compare different methods of analysis of a wooden panel painting, dated to the early sixteenth century, mainly by Raman and infrared spectroscopies. Raman spectra were recorded on collected/sampled micrometric fragments using portable Raman instruments with laser excitation lines at 532 and 785 nm and transportable Raman instruments at 532, 633 and 785 nm; a fixed 1064 nm Raman spectrometer was also used. Infrared analyses were performed in Attenuated Total Reflection (ATR-FTIR) mode. Using the portable instrument, the Raman spectra evidenced white lead, calcite and vermilion only. Raman spectra recorded by transportable and fixed instruments enabled the identification of most of the artist’s palette: (i) white lead, calcite, gypsum and cerussite for white colour; (ii) vermilion, red lead, litharge, haematite for red; (iii) azurite, indigo and lapis lazuli for blue. IR spectra gave information on the organic binding media. XRF analysis on a brown pigment suggested an heterogeneous mixture of a red pigment (such as haematite and/or minium) and a green one as malachite. GC-MS analysis allowed identifying terpenic resin in the composition of the outer protective layer.     

Identification of the chemical forms of uranium compounds in micrometer-size particles by means of micro-Raman spectrometry and scanning electron microscope

We used a micro-Raman spectrometer with two different laser excitation sources (514 and 785 nm) and variable laser powers to identify some uranium chemical species contained in airborne particulate matter. In the first part of this paper, we demonstrate that characteristic Raman bands mentioned in the literature for several uranium compounds relevant in the nuclear industry (UO₂, UO₄·(4H₂O), U₃O₈, UO₂F₂ and UF₄) can be identified in particles in the few μm to 30 μm size range. In the second part of the paper, we describe a method to carry out Raman analysis on airborne uranium particles sampled along with a majority of other kinds of particles simply by dabbing adhesive carbon disks on dusty surfaces. This methodology involves an SEM equipped with an energy dispersive X-ray analyser and software for automated detection of particles specifically to locate uranium particles on the substrate before the Raman analysis. Then the sample holder is transferred to the micro-Raman spectrometer and particles are relocated using landmarks and simple geometric calculations. Raman analyses are carried out with the laser that gives the best signal to noise ratio. With such a method particles as small as 5 μm can be efficiently analysed, although most of the smaller particles cannot be analysed due to limited precision of the relocation process. This methodology was successfully applied to 20 particles collected in a nuclear facility.     

Analysis of volatile organic compounds of ‘Fuji’ apples following electron beam irradiation and storage

The volatile organic compounds of non-irradiated and electron-beam irradiated ‘Fuji’ apples (Malus domestica Borkh.) at 0, 0.5, and 1 kGy were isolated through simultaneous distillation extractions and analyzed using gas chromatograph–mass spectrometry. A total of 53 volatile organic compounds were characterized in 0 and 1 kGy irradiated samples, whereas two more compounds related to ketone and terpenoid group were identified in 0.5 kGy irradiated samples. The contents of volatile compounds were 24.33, 36.49, and 35.28 mg/kg in 0, 0.5, and 1 kGy irradiated samples, respectively. The major compounds identified were butanol, hexanal, [E]-2-hexenal, and hexanol in all samples. The relative content of alcohol increased after 30 days of storage in all samples, whereas that of aldehyde decreased. Although the contents of some volatile compounds were changed by electron-beam irradiation, the total yield and major flavor compounds of irradiated ‘Fuji’ apples were similar to, or even greater than, those of the control. Therefore, the application of e-beam irradiation if required for microbial decontamination of ‘Fuji’ apples is an acceptable method as it does not bring about any major quantitative changes of volatile organic compounds.     

Raman study on pentacene:C60 bulk heterojunction films

We measured 785 nm excited Raman and infrared spectra of pentacene-d₁₄. The observed spectra were assigned on the basis of the Raman and infrared spectra calculated by the density functional theory (DFT) method at the B3LYP/6⬜311 + G** level. We measured 785 nm excited Raman spectrum of a pentacne-d₁₄:C₆₀ bulk heterojunction film. The spectrum was assigned on the basis of the wavenumber shifts upon deuteration of pentacene. The assignments of the 1462 and 493 cm^↙1 A_g bands of C₆₀ were confirmed. The 511, 453, and 256 cm^↙1 bands, which were observed only in pentacene:C₆₀ bulk heterojunction films, did not show large deuteration shifts. This result indicates that the 511, 453, and 256 cm^↙1 bands are attributed to activation of the silent modes of C₆₀ due to symmetry lowering_.     

Uranium recovery from Uro area phosphate ore,Nuba Mountains,Sudan

This study was carried out in a laboratory scale to recover uranium from Uro area phosphate ore in the eastern part of Nuba Mountains in Sudan. Phosphate ore samples were collected, and analyzed for uranium abundance. The results showed that the samples contain a significant concentration of uranium with an average of 310.3 μg/g, which is 2.6 times higher than the world average of phosphate. The green phosphoric acid obtained from the samples was found to contain uranium in the range of 186–2049 μg/g, with an average of 603.3 μg/g, and about 98% of uranium content of the phosphate ore was rendered soluble in the phosphoric acid. An extraction process using 25% tributylphosphate, followed by stripping process using 0.5 M sodium carbonate reported that more than 98% of uranium in the green phosphoric acid exists as uranyl tricarbonate complex, moreover, sodic decomposition using 50% sodium hydroxide showed that about 98% of the uranium was precipitated as sodium diuranate concentrate that is known as the yellow cake (Na₂U₂O₇). Further purification and calcinations of the yellow cake led to the formation of the orange powder of uranium trioxide (UO₃). The chemical analysis of the obtained uranium concentrates; yellow cake and uranium trioxide proved their nuclear purity and that they meet the standard commercial specification. The obtained results proved that uranium from Uro phosphate ore was successfully recovered as uranium trioxide with an overall recovery percentage of 93%.     

Characterization of a capillary spray cell for easy analysis of extracts of biological samples

We present a very simple electrospray unit, a capillary spray cell, for easy analysis of small (10–50 μL) sample aliquots. The sample, e.g., an unfiltered extract, is injected to a small sample cell, made of alumina and containing a short fused silica capillary mounted in its side. By the application of a 5 kV potential between the sample cell and the entrance orifice of a mass spectrometer with an atmospheric pressure interface, the sample is dragged out of the cell at a rate of a few μL/min and an electrospray is generated at the tip of the silica capillary. The capillary spray cell benefits from a high internal diameter (up to 250 μm) and very easy and inexpensive replacement of the capillary, which makes the sprayer well suited for analysis of unfiltered extracts. We demonstrate the direct analysis of extracts from plants and insects. In quantitative measurements using internal standards, a relatively high sensitivity (low ng/mL) is obtained together with good linearity (R² = 0.998) in the range of 10–1000 ng/mL. The capillary spray cell is also suited for use with field portable mass spectrometers, since no syringe pump or nebulizer gas is needed. Furthermore, the capillary spray cell is easily manufactured by most mechanical workshops.     

Characterisation of rotary kiln residues from the pyrolysis of shredder residues: Issues with lead

Stringent legislation is being to be implemented across Europe relating to heavy metal contamination into the environment. This study thus focuses on developing a method for reliably determining the lead content of automotive shredder residue (ASR). The material is first pyrolysed to remove organic fractions. Different analytical methods were then used to investigate the concentrations of heavy metals in the burned char, which varies from chunks of metals in larger sized fractions to fine powders of mostly non-metals. By considering results from ICP-MS, EDXRF, WDXRF and a portable EDXRF, it was found that varying values were obtained but that consistent ‘consensus values’ could be determined. Such ‘consensus’ values of lead, copper, iron and zinc are thus reported, and show that properly depolluted ELVs have significantly lower lead levels than normal shredder residue (SR) feed −8000 ppm versus 16,000 ppm. The finest fraction, <850 μm, makes up around half of the mass of the SR and has only 2700 ppm and 5400 ppm lead concentration values for depolluted ELVs and normal SR, respectively, making it of interest for further work to develop uses as a feed in other industries.     

Total pressure and excess Gibbs energy for the ternary mixture di-isopropyl ether + 1-propanol + benzene and its corresponding binary systems at 313.15 K

Total pressure measurements are reported for the ternary system ‘di-isopropyl ether + 1-propanol + benzene’ and two of the binary systems involved ‘di-isopropyl ether + 1-propanol’ and ‘1-propanol + benzene’ at 313.15 K. Data reduction by Barker's method provides correlations for G^E using the Margules equation for the binary systems and the Wohl expansion for the ternary system. Wilson, NRTL and UNIQUAC models have been applied successfully to both the binary and the ternary systems.     

Recent advances in understanding blue copper proteins

The type 1 (T1) or blue Cu (BC) proteins are a highly studied group of electron transfer (ET) active sites in bioinorganic chemistry. In this review, we cover several more recent results which extend the understanding of the geometric and electronic structure of these interesting Cu ET sites. Spectroscopic methods in tandem with density functional theory (DFT) and time dependent-DFT (TD-DFT) calculations have been used in studies of S → Se variants as well as a series of metal-varied model complexes (M = Mn²⁺ → Zn²⁺). The ligand and metal perturbations further defined the origins of the unique spectral features of BC proteins. These unique spectral features show different temperature dependencies in different T1 sites, and contrasts drawn between their behaviors define the role of the protein in tuning the geometric and electronic structure of the BC site for function. This has been termed the ‘entatic’ or ‘rack-induced’ state in bioinorganic chemistry.     

Electrodeposition of Ag nanoparticles onto carbon coated TEM grids: A direct approach to study early stages of nucleation

An innovative experimental approach to study the electrodeposition of small nanoparticles and the early stages of electrochemical nucleation and growth is presented. Carbon coated gold TEM grids are used as substrates for the electrodeposition of silver nanoparticles so that electrochemical data, FESEM, HAADF–STEM and HRTEM data can be acquired from the same sample without the need to remove the particles from the substrate. It is shown that the real distribution of nanoparticles cannot be resolved by FESEM whereas HAADF–STEM analysis confirms that a distribution of ‘small’ nanoparticles (d ≈ 1–2 nm) coexist with ‘large’ nanoparticles corresponding to a bimodal size distribution. Besides, particles grown under the same conditions have been found to present different structures such as monocrystals, polycrystals or aggregates of smaller particles.     

Asymmetric biocatalytic reduction of ketones using hydroxy-functionalised water-miscible ionic liquids as solvents

Bi- and monophasic ionic liquid (IL)/buffer systems were successfully employed for the biocatalytic reduction of ketones catalysed by the alcohol dehydrogenase ADH-‘A’ from Rhodococcus ruber via hydrogen transfer. Two different catalyst preparations were employed, namely recombinant ADH-‘A’ ‘immobilised’ in Escherichia coli and partially purified ADH-‘A’. For biphasic systems conversions were acceptable until 20% v v⁻¹ of IL. In contrast, hydroxy-functionalised ‘Tris-like’-ILs were successfully employed in monophasic systems up to 90% v v⁻¹ IL. The use of these solvents allowed highly stereoselective enzymatic carbonyl reductions at substrate concentrations from 1.2 to 1.5 M.     

Controlling cellular activity by manipulating silicone surface roughness

Silicone elastomers exhibit a broad range of beneficial properties that are exploited in biomaterials. In some cases, however, problems can arise at silicone elastomer interfaces. With breast implants, for example, the fibrous capsule that forms at the silicone interface can undergo contracture, which can lead to the need for revision surgery. The relationship between surface topography and wound healing – which could impact on the degree of contracture – has not been examined in detail. To address this, we prepared silicone elastomer samples with rms surface roughnesses varying from 88 to 650 nm and examined the growth of 3T3 fibroblasts on these surfaces. The PicoGreen^® assay demonstrated that fibroblast growth decreased with increases in surface roughness. Relatively smooth (∼88 nm) PDMS samples had ca. twice as much fibroblast DNA per unit area than the ‘bumpy’ (∼378 nm) and very rough (∼604 and ∼650 nm) PDMS samples. While the PDMS sample with roughness of ∼650 nm had significantly fewer fibroblasts at 24 h than the TCP control, fibroblasts on the smooth silicone surprisingly reached confluence much more rapidly than on TCP, the gold standard for cell culture. Thus, increasing the surface roughness at the sub-micron scale could be a strategy worthy of consideration to help mitigate fibroblast growth and control fibrous capsule formation on silicone elastomer implants.     

Fabrication of metallic nanoparticles by electrochemical discharges

A method for the fabrication of metallic nanoparticles in large quantities by electrochemical discharges is presented. In an aqueous electrolyte, large current density (∼1 A/mm² at ∼20 V) leads to the formation of a ‘gas film’ around the electrode through which discharges occur. When metal ions are additionally present in the electrolyte and when the applied potential is cathodic, metal nanoparticles (typically 10–150 nm) are produced. The nanoparticles are formed in the solution and the gas film prevents them from depositing on the electrode. To control the size of the particles a method based on ‘rotating electrode’ is developed. Rotating the cathode rotates the fluid around it, which provides centrifugal force to the particles to move away from the electrode where they cannot grow. This method has been successfully used for fabrication of nanoparticles from several metal salts.     

Traditional Vinegars Identification by Colorimetric Sensor

An expanded colorimetric array detector that was capable of the highly sensitive and highly selective discrimination of vinegars was developed. The system of olfaction visualization and operational approach were discussed. Thirty dyes were selected from natural dyes, chemoresponsive dyes and pH dyes. A 5 × 6 colorimetric sensor array was created by printing the dyes on reverse phase silica gel plates. Four traditional vinegars were measured by the colorimetric sensor array. With cluster analysis, all samples were assembled ‘Zhenjiang Vinegar’, ‘Shanxi Vinegar’, ‘Sichuan Vinegar’, ‘Jiangzhe Vinegar’ when the similarity was 12. This work showed the potential applications of the olfaction visualization technology for visual analyzing and fingerprint identifying the aroma of food.     

Lattice potential energies and thermochemical properties of triethylammonium halides (Et3NHX) (X = Cl,Br, and I)

A series of triethylammonium halides (Et₃NHCl, Et₃NHBr, and Et₃NHI) was synthesized. The crystal structures of the three compounds were characterized by X-ray crystallography. The lattice potential energies and ionic radius of the common cation of the three compounds were obtained from crystallographic data. Molar enthalpies of dissolution of the compounds at various values of molality were measured in the double-distilled water at T = 298.150 K by means of an isoperibol solution-reaction calorimeter. According to Pitzer’s theory, the values of molar enthalpies of dissolution at infinite dilution and Pitzer’s parameters of the compounds were obtained. The values of apparent relative molar enthalpies, relative partial molar enthalpies of the solvent and the compounds at different molalities were derived from the experimental values of molar enthalpies of dissolution of the compounds. Finally, hydration enthalpy of the common cation Et₃NH⁺ was calculated to be ΔH₊ = ?(150.386 ± 4.071) kJ · mol^?1 by designing a thermochemical cycle.     

A thienoquinoxaline and a styryl-quinoxaline as new fluorescent probes for amyloid-β fibrils

Simple and easy to prepare quinoxaline derivatives proved able to stain amyloid fibers such as aggregated lysozyme and Aβ(1-40)-peptide by a fluorescence “turn on” mechanism. Thienoquinoxaline 1 allowed the detection of lysozyme and Aβ(1-40) fibers at λ = 555 and 532 nm, respectively, with excitation at λ = 450 nm. Styryl-quinoxaline 2 stained lysozyme and Aβ(1-40) fibers with fluorescence at λ = 579 and 567 nm, respectively, upon excitation at λ = 453 nm. The apparent K_d values for Aβ(1-40) fibers were 77 and 294 nM for 1 and 2, respectively. The sensitivity of the aggregates detection assay with these new dyes was higher than that of thioflavin T. Considering their unique fluorescence properties compared to other dyes reported in the field, they can be considered as additional staining tools for the detection and studies of peptide/protein aggregation.     

Synthesis and physical properties of various organic dyes derived from a single core skeleton, 1,2-dihydroindol-3-one

Various organic dyes were synthesized from 1,2-dihydroindol-3-one analogue via Robinson ring annulation, which proceeded efficiently using DBU as a base to give the π-expanded compounds. These compounds exhibited longer Stokes shifts (over 100 nm) than the 1,2-dihydroindol-3-ones (50–80 nm). Emission peaks of the obtained materials covered the 440–640 nm range.     

Role of laser pre-pulse wavelength and inter-pulse delay on signal enhancement in collinear double-pulse laser-induced breakdown spectroscopy

Dual-pulse (DP) laser-induced breakdown spectroscopy (LIBS) provides significant improvement in signal intensity as compared to conventional single-pulse LIBS. We investigated collinear DPLIBS experimental performance using various laser wavelength combinations employing 1064 nm, 532 nm, and 266 nm Nd:YAG lasers. In particular, the role of the pre-pulse laser wavelength, inter-pulse delay times, and energies of the reheating pulses on LIBS sensitivity improvements is studied. Wavelengths of 1064 nm, 532 nm, and 266 nm pulses were used for generating pre-pulse plasma while 1064 nm pulse was used for reheating the pre-formed plasma generated by the pre-pulse. Significant emission intensity enhancement is noticed for all reheated plasma regardless of the pre-pulse excitation beam wavelength compared to single pulse LIBS. A dual peak in signal enhancement was observed for different inter-pulse delays, especially for 1064:1064 nm combinations, which is explained based on temperature measurement and shockwave expansion phenomenon. Our results also show that 266 nm:1064 nm combination provided maximum absolute signal intensity as compared to 1064 nm:1064 nm or 532 nm:1064 nm.     

Novel core–shell SDC/amorphous Na2CO3 nanocomposite electrolyte for low-temperature SOFCs

Novel core–shell SDC (Ce_0.8Sm_0.2O_1.9)/amorphous Na₂CO₃ nanocomposite was prepared for the first time. The core–shell nanocomposite particles are smaller than 100 nm with amorphous Na₂CO₃ shell of 4–6 nm in thickness. The nanocomposite electrolyte shows superionic conductivity above 300 °C, where the conductivity reaches over 0.1 S cm⁻¹. Such high conductive nanocomposite has been applied in low-temperature solid oxide fuel cells (LTSOFCs) with an excellent performance of 0.8 W cm⁻² at 550 °C. A new potential approach of designing and developing superionic conductors for LTSOFCs was presented to develop interface as ‘superionic highway’ in two-phase materials based on coated SDC.     

HPLC-PDA analysis of ACE-inhibitors,hydrochlorothiazide and indapamide utilizing design of experiments

A simple, rapid, precise, accurate and sensitive high performance liquid chromatographic method has been developed for simultaneous determination of ACE inhibitors with hydrochlorothiazide and indapamide in pharmaceutical formulations. ‘Design of Experiments’ (DoE) using ‘central composite design’ (CCD) was applied to facilitate method development and optimization. Mobile phase was optimized utilizing response surface methodology using Design Expert software. Chromatographic separation was achieved on Hypersil®-Gold C₁₈ (100 × 4.6 mm, 3 μm, Thermo Fisher Scientific, USA), column at 25 °C. The mobile phase was 58% buffer (5 mM KH₂PO₄, containing triethylamine 0.25 ml/L), 25% acetonitrile and 17% methanol (pH adjusted to 2.8 ± 0.1). The analysis was performed at 215 nm. The mobile phase flow rate was 1.0 ml/min and injection volume 10 μl. The method was validated for linearity, limits of quantitation and detection, accuracy, precision, ruggedness and robustness as per the International Conference on Harmonization (ICH) guidelines. Calibration curves (for lisinopril, hydrochlorothiazide, captopril, imidapril, perindopril, indapamide and trandolapril) were linear in the concentration range of 5–35 μg/ml. The limit of detection and limit of quantitation for experimental drugs ranged from 0.03 to 0.61 and 0.08–1.84 μg/ml respectively.