Polymeric bidimensional self-assembling of [Hg(RC6H4NNNC6H4R)2Py] (R = m-acetyl) through metal-η,η-arene π-interactions and non classical C-H?O bonding: Synthesis and X-ray characterization of a bis diaryl symmetric-substituted triazenide complex of Hg(II)

Deprotonated 1,3-bis(3-acetylphenyl)triazene reacts with Hg(CH₃COO)₂ and pyridine to give light-yellow crystals of {[Hg^II(RC₆H₄NNNC₆H₄R)₂Py]}_n (R = acetyl). The tectons [Hg^II(RC₆H₄NNNC₆H₄R)₂Py] [R = CH₃C(O)] are linked to pairs as centrosymmetric dimers through reciprocal metal-η²-arene π-interactions. The dimeric units are operated by a screw axis 2₁ parallel to the crystallographic direction [0 1 0], also through a reflection-translation plane parallel to the c-axis, resulting a supramolecular bidimensional (2D) assembling of the dimeric tectons through non classical C-H?(O)CCH₃ bonding.     

Fabrication of phytic acid sensor based on mixed phytase-lipid Langmuir-Blodgett films

This paper reports the surface activity of phytase at the air-water interface, its interaction with lipid monolayers, and the construction of a new phytic acid biosensor on the basis of the Langmuir-Blodgett (LB) technique. Phytase was inserted in the subphase solution of dipalmitoylphosphatidylglycerol (DPPG) Langmuir monolayers, and its incorporation to the air-water interface was monitored with surface pressure measurements. Phytase was able to incorporate into DPPG monolayers even at high surface pressures, ca. 30 mN/m, under controlled ionic strength, pH, and temperature. Mixed Langmuir monolayers of phytase and DPPG were characterized by surface pressure-area and surface potential-area isotherms, and the presence of the enzyme provided an expansion in the monolayers (when compared to the pure lipid at the interface). The enzyme incorporation also led to significant changes in the equilibrium surface compressibility (in-plane elasticity), especially in liquid-expanded and liquid-condensed regions. The dynamic surface elasticity for phytase-containing interfaces was investigated using harmonic oscillation and axisymmetric drop shape analysis. The insertion of the enzyme at DPPG monolayers caused an increase in the dynamic surface elasticity at 30 mN m(-)(1), indicating a strong interaction between the enzyme and lipid molecules at a high-surface packing. Langmuir-Blodgett (LB) films containing 35 layers of mixed phytase-DPPG were characterized by ultraviolet-visible and fluorescence spectroscopy and crystal quartz microbalance nanogravimetry. The ability in detecting phytic acid was studied with voltammetric measurements.     

Thermal analysis of hair treated with oxidative hair dye under influence of conditioners agents

This research aimed the effect on Caucasian hair tresses treated with oxidative hair dye, either incorporated or not with conditioners agents, analyzed by Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TG). The formulations of hair dyes were emulsions oil-in-water with light blond color containing or not the conditioners agents: silanetriol and panthenol; PEG-12 dimethicone; hydrolyzed silk, hydrolyzed milk protein, and lactose. Each dye (1.5 g) was applied in the hair tress (2.0 g/20.0 cm of length of Caucasian light-brown), previously treated, more 1.5 g of hydrogen peroxide 20 vol during 40 min. Evaluation of mass loss of the different hair sample demonstrates that these chemical hair treatments impair the hair fibers, reduced their moisture content with respect to the untreated hair. The incorporation of conditioners agents (silanetriol and panthenol; PEG-12 dimethicone; hydrolyzed silk, hydrolyzed milk protein, and lactose) in oxidative hair dyes types did not decrease the damage caused on the tresses by the coloring process quantified by TG/DTG. However, the DSC curves demonstrated those conditioners agents (silanetriol and panthenol; PEG-12 dimethicone) dislocated the beginning of the third event in 20 °C and they inhibited the presence of the fourth event, having characterized thermal protection to the hair.     

Adsorption studies of Cd(II) onto Al2O3/Nb2O5 mixed oxide dispersed on silica matrix and its on-line preconcentration and determination by flame atomic absorption spectrometry

The present study describes the adsorption characteristic of Cd(II) onto Nb₂O₅/Al₂O₃ mixed oxide dispersed on silica matrix. The characterization of the adsorbent has been carried out by infrared spectroscopy (IR), scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), energy dispersive X-ray fluorescence analysis (EDXRF) and specific surface area (S_BET). From batch experiments, adsorption kinetic of Cd(II) was described by a pseudo-second-order kinetic model. The Langmuir linear isotherm fitted to the experimental adsorption isotherm very well, and the maximum adsorption capacity was found to be 17.88 mg g⁻¹. Using the effective material, a method for Cd(II) preconcentration at trace level was developed. The method was based on on-line adsorption of Cd(II) onto SiO₂/Al₂O₃/Nb₂O₅ at pH 8.64, in which the quantitative desorption occurs with 1.0 mol L⁻¹ hydrochloric acid towards FAAS detector. The experimental parameters related to the system were studied by means of multivariate analysis, using 2⁴ full factorial design and Doehlert matrix. The effect of SO₄²⁻, Cu²⁺, Zn²⁺ and Ni²⁺ foreign ions showed no interference at 1:100 analyte:interferent proportion. Under the most favorable experimental conditions, the preconcentration system provided a preconcentration factor of 18.4 times, consumption index of 1.08 mL, sample throughput of 14 h⁻¹, concentration efficiency of 4.35 min⁻¹, linear range from 5.0 up to 35.0 μg L⁻¹ and limits of detection and quantification of 0.19 and 0.65 μg L⁻¹ respectively. The feasibility of the proposed method for Cd(II) determination was assessed by analysis of water samples, cigarette sample and certified reference materials TORT-2 (Lobster hepatopancreas) and DOLT-4 (Dogfish liver).     

Different salinities water characterization by DSC-cooling

Water is a fundamental element of life. Its multiple uses are indispensable for a wide spectrum of human activities. This study aims to characterize water from different salinities obtained in the Cariri region of Paraíba, Brazil. The samples were analyzed using the DSC-coupled to the Peltier system (DSC-Cooling) and physical–chemical water tests performed employing reactive kits, using the Spectroquant Merck^? specific for each test. The calorimetric curves showed crystallization phase transitions with different characteristics in peak format and crystallization temperatures between the samples of different salinities. The calorimetric data obtained in the process of crystallization of water is directly correlated to the physico-chemical parameters of conductivity and total dissolved solids, showing that the analytical technology DSC-cooling/heating is suitable for characterization of different salinities water.     

Information visualization techniques for sensing and biosensing

The development of new methods and concepts to visualize massive amounts of data holds the promise to revolutionize the way scientific results are analyzed, especially when tasks such as classification and clustering are involved, as in the case of sensing and biosensing. In this paper we employ a suite of software tools, referred to as PEx-Sensors, through which projection techniques are used to analyze electrical impedance spectroscopy data in electronic tongues and related sensors. The possibility of treating high dimension datasets with PEx-Sensors is advantageous because the whole impedance vs. frequency curves obtained with various sensing units and for a variety of samples can be analyzed at once. It will be shown that non-linear projection techniques such as Sammon's Mapping or IDMAP provide higher distinction ability than linear methods for sensor arrays containing units capable of molecular recognition, apparently because these techniques are able to capture the cooperative response owing to specific interactions between the sensing unit material and the analyte. In addition to allowing for a higher sensitivity and selectivity, the use of PEx-Sensors permits the identification of the major contributors for the distinguishing ability of sensing units and of the optimized frequency range. The latter will be illustrated with sensing units made with layer-by-layer (LbL) films to detect phytic acid, whose capacitance data were visualized with Parallel Coordinates. Significantly, the implementation of PEx-Sensors was conceived so as to handle any type of sensor based on any type of principle of detection, representing therefore a generic platform for treating large amounts of data for sensors and biosensors.     

Leaf volatiles and secretory cells of Alpinia zerumbet (Pers.) Burtt et Smith (Zingiberaceae)

Plant leaves are commonly used in folk medicine and food industry. Their volatile composition is an important determinant in such applications. However, to properly assess the quality of volatiles, proper analytic tools must be utilised. Accordingly, the static headspace technique was used to evaluate the main volatiles emitted from in vitro-grown Alpinia zerumbet plants cultured with indole-3-acetic acid, thidiazuron, benzyladenine or kinetin, under standard physical conditions, as compared to those of field-grown donor plants. Although the leaf aroma of the donor plants was found to be a complex mixture, mainly consisting of sabinene, α and γ-terpinene, 1,8-cineole and caryophyllene, volatile analyses from most of the in vitro samples only revealed the presence of sabinene and caryophyllene. Many alkanes were found in the aromas after treating plantlets with cytokinins. Histochemical analysis of leaf sections was also carried out. Secretory cells found in the epidermis and mesophyll showed a strong positive reaction to lipophilic compounds using Oil red and Nile blue reagents. These findings demonstrated how in vitro conditions may alter the quality of volatiles in micropropagation systems, while leaf anatomy analysis revealed a large quantity of oil cells in the mesophyll as a constant feature responsible for the production of volatile compounds in both donor and in vitro-grown plants.     

Synthesis of Some Unusual (1,2,4‐Oxadiazole)‐Linked Hexenopyranosides and Mannopyranosides

A copper‐catalyzed reaction of propargyl 4,6‐di‐O‐acetyl‐2,3‐dideoxy‐α‐D‐erythro‐hex‐2‐enopyranoside with 3‐(4‐azidophenyl)‐1,2,4‐oxadiazoles gave the corresponding hexenopyranosides bearing an 1,2,4‐oxadiazole subunit in the aglyconic part of the molecule. The same reaction between ethyl 4‐azido‐2,3,4‐trideoxy‐α‐D‐erythro‐hex‐2‐enopyranoside and acetylenic 1,2,4‐oxadiazoles afforded the corresponding hexenopyranosides carrying a triazole and a 1,2,4‐oxadiazole ring at C‐4 of the carbohydrate. Combination of the two sequences gave hexenopyranosides displaying two 1,2,4‐oxadiazole subunits, each one being embedded in the C‐1 and C‐4 frameworks, of the carbohydrate moiety. A simple dihydroxylation reaction of these unsaturated carbohydrates yielded a series of mannopyranosides bearing one or two 1,2,4‐oxadiazole subunits at C‐1 or C‐4. These new compounds were evaluated for their cytotoxic activities against two cell strains: NCI‐H₂₉₂ (lung carcinoma) and Hep‐2 (larynx carcinoma), some of them presenting impressive cell growth inhibitions.     

Internal standardization for the determination of cadmium,cobalt, chromium and manganese in saline produced water from petroleum industry by inductively coupled plasma optical emission spectrometry after cloud point extraction

In the present paper a procedure is proposed for the determination of traces of Cd, Co, Mn and Cr in petroleum industry produced water by inductively coupled plasma optical emission spectrometry. The procedure is based on cloud point extraction of these metals, as their dithizonate complexes, into the surfactant-rich phase of octylphenoxypolyethoxyethanol surfactant (Triton X-114). Extractions were carried out in solutions with salinities between 10‰ and 70‰. Since residual salinity in the surfactant-rich phase caused differences in its transport to the plasma, yttrium was used as an internal standard to correct for this effect. The simultaneous metal extraction procedure was optimized by response surface methodology using a Doehlert design and desirability function. Enhancement factors of 21, 21, 9 and 19, along with limits of quantification of 0.093, 0.20, 0.73 and 1.2 μg L^− 1, and precision expressed as relative standard deviation (n = 8, 20.0 μg L^− 1) of 5.8, 1.2, 1.7 and 5.7% were obtained for Cd, Co, Mn and Cr, respectively. The accuracy was evaluated by spike recovery tests on the high salinity water samples with salinity of 40 and 63‰.     

Controlled Radical Polymerization of 2,3‐Epithiopropyl Methacrylate

We report first results on the controlled radical polymerization of 2,3‐epithiopropyl methacrylate (ETMA) also known as thiiran‐2‐ylmethyl methacrylate. Reversible addition‐fragmentation chain transfer (RAFT) of ETMA was carried out in bulk and in solution, using AIBN as initiator and the chain transfer agents: cyanopropyl dithiobenzoate (CPDB) and cumyl dithiobenzoate (CDB). A linear increase of the number‐average molecular weight and decrease of the polydispersity with monomer conversion were observed using CPDB as transfer agent, indicating a controlled process. Atom transfer radical polymerization (ATRP) of ETMA was performed under different reaction conditions using copper bromide complexed by tertiary amine ligands and ethyl 2‐bromoisobutyrate (EBiB) or 2‐bromopropionitrile (BPN) as initiator. All experiments lead to a crosslinked polymer. Preliminary studies in the absence of initiator showed that the CuBr/ligand complex alone initiates the ring‐opening polymerization of thiirane leading to a poly(propylene sulfide) with pendant methacrylate groups.