Visible Absorption Band Research Articles

Synthesis, structure, and characterization of RbNdGe2O6 as a novel visible-light-driven catalyst for photodegradation methylene blue

A novel lanthanide germanate, namely RbNdGe2O6, has been successfully synthesized by high-temperature solid-state reaction in open air atmosphere for the first time. Single crystal X-ray diffraction indicates a 3D framework composed of 1D neodymium oxygen chains connected with cyclogermanate Ge3O9 units with Rb+ located in the internal space. X-ray powder diffraction coupled with Rietveld refinement reveals the sample’s phase purity we have prepared. Thermal behavior analysis shows RbNdGe2O6 is very stable, it doesn’t decomposition until heated up to 998 ​°C. UV–visible absorption and diffuse reflection spectrum feature characteristic absorption bands of f-electron transition and an optical bandgap value of 4.65 ​eV. Magnetic susceptibilities measurement gives significant antiferromagnetic interactions between magnetic centers. The photodegradation experiments were performed to evaluate photocatalytic activities of RbNdGe2O6. By using P25 as a reference, RbNdGe2O6 features to be an effective visible-light-driven catalyst in photodegrading methylene blue. Although the BET value of RbNdGe2O6 is only 3% that of P25, the photocatalytic activity reaches 0.55 times that of P25. Furthermore, the proposed photocatalytic mechanism which dominated by holes was further verified by adding ammonium oxalate as a quencher.

Preparation and properties of polyimides having porphyrin moieties for heavy metals removal

A tetramine monomer containing porphyrin moiety is prepared in high purity by the propionic acid-mediated condensation of pyrrole with 4-cyanobenzaldehyde and then reduction in the tetracyano intermediate. The thermally stable porphyrin-based polyimides (PI)s are prepared using tetramine and four aromatic tetracarboxylic dianhydrides via a two-step method in quantitative yields with inherent viscosities of 0.34–0.63 dL/g. The PIs are soluble in some organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide. The resultant PIs had high glass transition temperatures and displayed outstanding thermal stability up to 500 °C. The resulting polymers revealed strong UV–Vis absorption band around 422 nm in DMF. Wide-angle XRD measurements exhibited that the PIs were amorphous. The polymer films had tensile strengths 101–128 MPa, elongates at break of 7–11% and tensile moduli of 2.0–2.2 GPa. One of the PIs was applied to examine the adsorption properties of two heavy metal ions (Cd2+ and Hg2+) at pH 7. The results revealed that the applied PI was an outstanding sorbent for heavy metal ions. The goal of this study is the preparation of hydrophobic PIs for ion-selective membranes and chemical sensors to adsorb of toxic heavy metals.

A new phenothiazine-based selective visual and fluorescent sensor for cyanide

A new donor-π-acceptor derived from phenothiazine, namely 2-(2-((10-hexyl-10H-phenothiazin-3-yl)methylene)-3-oxo-2,3-dihydroinden-1-ylidene) malononitrile (PTZON) was synthesized and fully characterized, and its potential as a fluorescent sensor for cyanide anion was investigated. The PTZON showed a visible absorption band at 564 nm corresponds to an intramolecular charge transfer (ICT) and an emission band at 589 nm in CH3CN/H2O. The results of cyanide anion titration revealed ratiometric changes in both absorption and fluorescence spectra as a result of the nucleophilic addition of cyanide anion via Michael addition. The optical studies, FT-IR spectra, NMR, high-resolution mass, and DFT calculations confirmed the sensing mechanism. The selectivity of PTZON as a cyanide anion fluorescent sensor was proved in mixed solvent solutions, and the sensitivity was as low as 0.011 µM, which is far lower than the value allowed by the United States Environmental Protection Agency for drinking water (1.9 µM). Also, the detection limit of PTZON was assessed to be 3.39 μM by the spectrophotometric method. The binding stoichiometry between PTZON and cyanide anion was found to be 1:1 as evidenced by mass spectra. TLC silica-coated plates test strips demonstrated the fluorescent detection of cyanide anion.

Colorimetric detection toward halide ions by a silver nanocluster hydrogel

We reported a novel colorimetric method for highly selective halide ions (Cl−, Br−and I−) recognition by Ag nanoclusters hydrogel (Ag–NCs hydrogel). The Ag–NCs hydrogel could discriminate Cl−, Br−and I− ions from a wide range of environmentally important anions, identified by the distinct UV–vis absorption band changes or the change in the color of Ag–NCs hydrogel. On the basis of this strategy, 20 μM and 200 μM of Cl−, 5 μM and 100 μM of Br−, 5 μM and 100 μM of I− could be recognized within 5 min by UV–vis spectrum and naked eye observation, respectively. The surface color of hydrogel changed from yellow to dark green for Cl−, to brown for Br−, and to deep brown for I−. In addition, this sensing method had been applied successfully to detect chloride anion in real water samples such as tap water, pond water and pure water. Therefore, this rapid, facile, and cost-effective colorimetric assay based on Ag–NCs hydrogel was attractive and promising.

Humidity Sensing through Reversible Isomerization of a Covalent Organic Framework.

Here we report that a covalent organic framework (COF), which contains 2,5-di(imine)-substituted 1,4-dihydroxybenzene (diiminol) moieties, undergoes color changes in the presence of solvents or solvent vapor that are rapid, passive, reversible, and easily detectable by the naked eye. A new visible absorption band appears in the presence of polar solvents, especially water, suggesting reversible conversion to another species. This reversibility is attributed to the ability of the diiminol to rapidly tautomerize to an iminol/cis-ketoenamine and its inability to doubly tautomerize to a diketoenamine. Density functional theory (DFT) calculations suggest similar energies for the two tautomers in the presence of water, but the diiminol is much more stable in its absence. Time-dependent DFT calculations confirm that the iminol/cis-ketoenamine absorbs at longer wavelength than the diiminol and indicate that this absorption has significant charge-transfer character. A colorimetric humidity sensing device constructed from an oriented thin film of the COF responded quickly to water vapor and was stable for months. These results suggest that tautomerization-induced electronic structure changes can be exploited in COF platforms to give rapid, reversible sensing in systems that exhibit long-term stability.

Structural, optical and impedance spectroscopy study of thin film of polyaniline (PANI/ZnO) nanocomposite

Modern organic electronic and power electronic devices gained attention due their superior performance and efficiency with reduced cost. While nanocomposites of these organic semiconductors have high potential to further enhance these properties. In this work, thin films of zinc oxide-polyaniline (ZnO-PANI) nanocomposite with different compositions of ZnO (50, 60 and 70 wt%) are deposited by spin coater onto the surface of p-Si. The phase identification of the samples is identified through x-ray diffraction analysis. Pure ZnO showed wurtzite crystalline while PANI and nanocomposites of ZnO-PANI showed amorphous structure. The optical absorption band gap was evaluated from Ultraviolet–visible spectroscopy absorption studies and band gaps were calculated from Tauc’s plots. The Ultraviolet–visible spectroscopy showed that by increasing ZnO content in the nanocomposite, the band gap increases from 3.25 eV to 3.3 eV and 3.4 eV for 50–50, 60–40 and 70–30 wt% respectively. The AC electrical properties of the nanocomposites were studied by using impedance spectroscopy. The parameters extracted from the impedance plots and conductivity values showed that 50–50 wt% is more conductive while that of 70%–30% wt is more resistive.

Synthesis of nonplanar bipyridyls bridged by disilane and disiloxane and their phosphorescent copper complexes

Disilane‐ and disiloxane‐bridged bipyridyls (DSBPy and DSOBPy) were prepared and their optical properties were investigated in comparison with those of previously reported monosilane‐ and monogermane‐bridged counterparts. The UV–visible absorption and photoluminescence bands of DSBPy and DSOBPy were blue‐shifted as a result of elongation of the bridging units from monosilane and monogermane to disilane and disiloxane, likely due to the enhanced twisting of the bipyridyl units. Phosphorescent complexes DSBPy–Cu and DSOBPy–Cu were prepared by the interaction of DSBPy and DSOBPy with Cu2I2(PPh3)2. X‐ray diffraction studies of their single‐crystal structures revealed polymeric structures composed of repeat units of DSBPy or DSOBPy and [CuII(PPh3)]2. Organic light‐emitting diodes with the ITO/PEDOT:PSS/DSBPy–Cu or DSOBPy–Cu:PCTSQ/TAZ/Al structure were fabricated to examine the applications of the complexes as electroluminescent materials. The devices emitted yellow light with emission maxima at approximately 600 nm, and maximal luminance reached 120 and 190 cd m−2 for devices based on DSBPy–Cu and DSOBPy–Cu, respectively. The performance of the DSOBPy–Cu‐based device was improved by using TAZ as the dopant of the emissive layer, and luminance was increased to 390 cd m−2.

Step-scheme porous g-C3N4/Zn0.2Cd0.8S-DETA composites for efficient and stable photocatalytic H2 production

In recent years, environmental pollution and energy crisis have become increasingly serious issues owing to the burning of fossil fuels. Among the many technologies, decomposition of water to produce hydrogen has attracted much attention because of its sustainability and non-polluting characteristic. However, highly efficient decomposition of water that is driven by visible light is still a challenge. Herein, we report the large-scale preparation of step-scheme porous graphite carbon nitride/Zn0.2Cd0.8S-diethylenetriamine (Pg-C3N4/Zn0.2Cd0.8S-DETA) composite by a facile solvothermal method. It was found by UV-vis spectroscopy that 15%Pg-C3N4/Zn0.2Cd0.8S-DETA exhibited suitable visible absorption edge and band gap for water decomposition. The hydrogen production rate of 15%Pg-C3N4/Zn0.2Cd0.8S-DETA composite was 6.69 mmol g−1 h−1, which was 16.73, 1.61, and 1.44 times greater than those of Pg-C3N4, CdS-DETA, and Zn0.2Cd0.8S-DETA, respectively. In addition, 15%Pg-C3N4/Zn0.2Cd0.8S-DETA composite displayed excellent photocatalytic stability, which was maintained for seven cycles of photocatalytic water splitting test. We believe that 15%Pg-C3N4/Zn0.2Cd0.8S-DETA composite can be a valuable guide for the development of solar hydrogen production applications in the near future.

Selective oxidation of benzyl alcohol catalyzed by ruthenium (III) complexes derived from tridentate mer-ligands having phenolato donor

In this work, four ruthenium complexes [Ru(L1−4)(PPh3)Cl2](1–4) containing phenolate-imine ligands [L1−4H = condensed product of 2-(1-phenylhydrazinyl)-pyridine with different substituted salicylaldehyde, H = phenolic dissociable proton] were synthesized and characterized by different spectroscopic methods like IR and UV–Visible spectral studies. Solid-state structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction and tridentate coordination of the ligand having NNO donors was observed in a meridional fashion. Structure optimization was performed by density functional theory (DFT) calculations. Time-dependent DFT (TD-DFT) method was utilized to explain and assign UV–Visible absorption bands found for complexes. These complexes were utilized for the oxidation of benzyl alcohol to benzaldehyde. The plausible mechanism for benzyl alcohol oxidation was proposed on the basis of literature. In situ generated RuIVO intermediate obtained in solution in presence of various oxidants viz. H2O2,m-CPBA, TBHP was supposed to be key intermediate for such oxidation.

Hybrid metal-dual sulfide core–shell nanostructures with enhanced photocatalytic properties

In this study, we report a facile cation-exchange method to synthesize three different metal@dual sulfide hybrid nanostructures with enhanced photocatalytic properties. Starting from clusters of Au@Ag2S with a poorly crystalline shell, excess amounts of Cd2+, Zn2+ and Pb2+ are used to promote the thermodynamically unfavored cation-exchange under elevated temperature. The change of shell compositions accompanies the disassembly of Au@Ag2S clusters into monodisperse ternary core–shell nanostructures with modulated optical properties. Interestingly, it is found that Au@Ag2S–CdS outperforms Au@Ag2S–ZnS and Au@Ag2S–PbS in the visible-light-driven photodegradation of methylene blue, which can be largely attributed to the improved shell crystallinity, enhanced visible light absorption and appropriate band alignment for charge transfer.

Observations and numerical modelling of a convective disturbance in a large-scale cyclone in Jupiter’s South Temperate Belt

Moist convective storms in Jupiter develop frequently and can trigger atmospheric activity of different scales, from localized storms to planetary-scale disturbances including convective activity confined inside a larger meteorological system. In February 2018 a series of convective storms erupted in Jupiter’s South Temperate Belt (STB) (planetocentric latitudes from −23° to −29.5°). This occurred inside an elongated cyclonic region known popularly as the STB Ghost, close to the large anticyclone Oval BA, resulting in the clouds from the storms being confined to the cyclone. The initial storms lasted only a few days but they generated abundant enduring turbulence. They also produced dark features, possibly partially devoid of clouds, that circulated around the cyclone over the first week. The subsequent activity developed over months and resulted in two main structures, one of them closely interacting with Oval BA and the other one being expelled to the west. Here we present a study of this meteorological activity based on daily observations provided by the amateur community, complemented by observations obtained from PlanetCam UPV/EHU at Calar Alto Observatory, the Hubble Space Telescope and by JunoCam on the Juno spacecraft. We also perform numerical simulations with the EPIC General Circulation Model to reproduce the phenomenology observed. The successful simulations require a complex interplay between the Ghost, the convective eruptions and Oval, and they demonstrate that water moist convection was the source of the initial storms. A simple scale comparison with other moist convective storms that can be observed in the planet in visible and methane absorption band images strongly suggests that most of these storms are powered by water condensation instead of ammonia.

Enhanced photocatalytic performance of Cu2O nano-photocatalyst powder modified by ball milling and ZnO

In this paper, a ball milled Cu2O-ZnO nano-photocatalyst with good photocatalytic performance in visible light range was prepared. Effect of ZnO presence and ball milling of Cu2O on the structure, microstructure, optical properties and photocatalytic performance were studied. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), high resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) analysis and UV–Vis spectrophotometer were used as characterization techniques. FESEM results indicated that ball milling of Cu2O changed the morphology of Cu2O-ZnO composite. The uniform formation of ZnO particles with average size of 30 nm over the Cu2O surface was observed. The formation of p-n heterostructure with good contact between Cu2O and ZnO nanoparticles was found by HRTEM image. Ball milling of Cu2O promotes visible light absorption and reduction band gap to 1.9 eV in Cu2O-ZnO photocatalyst. Intensity of PL spectra for the ball milled Cu2O-ZnO photocatalyst was obviously lower. Ball milled Cu2O-ZnO photocatalyst shows the highest photocatalytic activity and degradation efficiency of 98% was obtained for 2 mg/L methylene blue (MB) solution after 240 min. The kinetics of the photodegradation was followed the Langmuir-Hinshelwood (L-H) model and degradation rates were decreased by increase of MB concentration. In the case of ball milled Cu2O and presence of ZnO, the MB degradation kinetics was two times faster.

Dispersion of chromia films (eskolaite) in UV-VIS

Abstract Atomic layer deposited polycrystalline Cr2O3 films grown from chromyl chloride and methanol were analysed using spectrophotometry, spectral ellipsometry and atomic force microscopy. The films possessed polycrystalline eskolaite structure with rough sublayer in contact with air. Using the positions and peak widths of the two visible absorption bands as fixed from absorption measurements, we could determine the optical dispersion of the film material in 1.3 – 6 eV energy region. A direct band gap of chromia film grown in these conditions was 3.2 eV, the other also direct absorption band with a gap of 5.15 eV was found situated in UV.

Two Emissive Long-Lived Excited States of an Imidazole-Functionalized Ruthenium Dipyridophenazine Complex

A ruthenium(II) polypyridine-type complex based on the dipyridophenazine ligand with a directly fused imidazole unit (L1, dipyrido[3,2-a:2',3'-c]phenazine-10,11-imidazole) has been synthesized, and its electrochemical and photophysical properties have been studied. The cyclic voltammogram of [Ru(tbbpy)2(L1)]2+ (C1) (tbbpy is 4,4'-tert-butyl-2,2'-bipyridine) shows a cathodic shift of the phenazine-based reduction process compared to similar molecules, while the first detected reduction wave (-1.34 V vs Fc/Fc+) is assigned to the imidazole unit within the molecule. On the basis of the TD-DFT calculations, the strong visible absorption band exhibited by C1 is assigned to a metal-to-ligand charge transfer (MLCT) transition with a concurrent ligand-centered (LC) transition. At room-temperature, C1 features emission (Φ = 0.04) from its lowest excited states with time constants of 1.2 and 18.3 μs. These lifetimes are assigned to emission processes from the 3MLCT and 3LC state, respectively. This is the first time that a long-lived dual emission has been observed for a ruthenium(II) complex bearing a directly fused extended π-system. Furthermore, the emission of C1 is quenched upon water addition. In contrast to related compounds based on a dipyridophenazine ligand, the excited state energy is not shifted, and the lifetime is drastically decreased to 169 ns.

The adsorption of small size Pd clusters on a g-C3N4 quantum dot: DFT and TD-DFT study

In this study, the adsorption of Pdn cluster with different size (n = 2–8) on graphitized carbon nitride (g-C3N4) quantum dot has been studied using the density functional theory (DFT). The Pd2, Pd4 and Pd6 clusters showed tendency for landing at a corner of the six-fold cavity of g-C3N4 while the Pd8 cluster was landed on the top of the cavity of g-C3N4 for efficient interaction with all pyridine like nitrogen atoms of the cavity, simultaneously. The charge of Pdn cluster in Pdn/g-C3N4 (n = 2–6) complexes was positive showing the charge transfer from the metal cluster to g-C3N4 while the net charge of Pd8 in Pd8/g-C3N4 became negative showing an opposite direction of charge transfer in this complex. Moreover, it was found that by increasing the size of Pdn cluster, the energy band gap of Pdn/g-C3N4 complex becomes smaller compared with the bare g-C3N4. The time-dependent density functional theory (TD-DFT) was employed to calculate the absorption spectra of the bare g-C3N4 and Pdn/g-C3N4 complexes. It was observed that the presence of Pdn clusters on the g-C3N4 shifted the absorption peaks of g-C3N4 to the lower wavelengths. Also, it increased the intensity of the absorption bands in the range of 400 to 800 nm depending on the Pdn cluster size which could lead to the increase in the photo-catalytic activity of Pdn/g-C3N4 complexes compared to bare g-C3N4 in visible region. Most of the UV–vis absorption bands of the Pdn/g-C3N4 complexes in region of the 400–800 nm were related to the excitation of electron from the Pdn cluster to the g-C3N4 which decreases the recombination of electron-hole in the complexes compared to the bare g-C3N4. Mixing of the states of g-C3N4 with the states of Pdn clusters causes the decrease in the intensity of absorption bands of the g-C3N4 in the region of 200–300 nm.

Morphology, UV–visible and ellipsometric studies of sodium lithium orthovanadate

Sodium lithium orthovanadates were prepared by the classic ceramic method technique. Structure, phase purity, composition, and morphology were characterized by X-ray powder diffraction, infrared spectroscopy, energy dispersive spectroscopy, scanning-electron microscopy and atomic force microscopy. The optical properties of NaxLi1−xCdVO4 (x = 0.5, 1) compounds prepared were recorded at room temperature using ultra-visible and ellipsometric spectroscopies in the spectral range (200–800) nm. The average reflectance of the pellets showed high reflectivity (over 80%) in the visible spectrum. The UV–Vis absorption bands are assigned to the charge transfer from the oxygen ligands to the central vanadium atom inside the [VO4]3− groups in the orthovanadate compounds. The optical band gaps Eg of both samples are evaluated using Kubelka–Munk function. The analysis of the data revealed the existence of optical allowed direct transition for NaxLi1−xCdVO4 (x = 0.5, 1). Spectroscopic ellipsometry measurements have been performed on NaxLi1−xCdVO4 (x = 0.5, 1) specimens and their optical properties were analyzed using the Cauchy model.

Effect of gemini surfactants on binding interactions of Coumarin 485 with calf thymus deoxyribonucleic acid in presence of nanotubes of β-cyclodextrin

Present study is focused on the binding of a dye, Coumarin 485 (C-485) with Calf thymus deoxyribonucleic acid (ctDNA), explored using the spectroscopic tools such as UV–visible absorption, steady-state fluorescence and fluorescence anisotropy, and time-resolved fluorescence spectroscopy and dynamic light scattering measurements. The hyperchromic shifts in UV–visible absorption and fluorescence bands depict that the C-485 binds with the ctDNA. Absorption spectrum of C-485 in presence of ctDNA, ethidium bromide displacement assay and iodide ion quenching experiment confirm that C-485 binds with ctDNA through the groove binding mode. β-Cyclodextrin (β-CD) molecules (host) in presence of C-485 (guest) form the nanotubes and secondary aggregates of nanotubes which has been explored as the carriers of C-485 for ctDNA. The binding efficiency of C-485 with β-CD is reduced in presence of ctDNA. Gemini surfactants, m-4-m (m = 12, 14 and 16) induce the release of C-485 from the cavities of nanotubes of β-CD. After getting released from the cavities, C-485 molecules bind with ctDNA in the form of inclusion complexes with β-CD/un-complexed state at a low concentration range of a gemini surfactant. A gemini surfactant with comparatively longer hydrocarbon tails pushes the guest molecules (C-485) out of the nanotubular cavities of β-CD more efficiently due to greater extent of hydrophobic interactions between the cavities and tails.

Europium ions and silver nanoparticles co-doped magnesium-zinc-sulfophosphate glasses: Evaluation of ligand field and Judd-Ofelt parameters

This paper reports the ligand field and Judd-Ofelt analyses of europium ions (Eu3+) and silver nanoparticles (AgNPs) activated magnesium-zinc-sulfophosphate glasses. Such glasses of composition 63.5P2O5–20MgO–15ZnSO4–1.5Eu2O3–yAgNPs (y = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.1 g in excess) were prepared via melt quenching method and characterized by different analytical tools. The feasibility of achieving a novel glass based efficient red laser and light emitting diodes (LEDs) was explored. XRD analyses of as-quenched samples verified their glassy character. UV–Vis–NIR absorption spectra of the studied glasses displayed eight peaks at 360, 380, 394, 414, 465, 531, 2091 and 2205 nm allocated to the 7F0→5L6,7F0→5G4,7F1→5L6,7F1→5D3, 7F0→5D2,7F1→5D17F6→7F0 and 7F1→7F6 transitions in the Eu3+. Observed improvement in the photoluminescence intensity associated to 5D0→7F2 transition was majorly attributed to the energy transfer among Eu3+ and AgNPs enabled localised surface plasmon resonance induced local field effects. TEM analysis confirmed the uniform dispersion and nucleation of AgNPs (average diameter ≈27.65 nm) in the glass matrix. Judd-Ofelt analyses were performed to calculate the intensity parameters (Ω2, Ω4 and Ω6) and radiative properties wherein the experimental optical data were utilized. For the studied glasses, the disclosed trend of Ω2˃Ω4 validated their ionic character and high symmetry environment around Eu3+. Proposed glass composition revealed excellent values of optical gain 2.82×10−25cm2S−1 to 20.81×10−25cm2S−1 and branching ratio (4.33–75.8%). Optimum values of critical laser parameters for 5D0→7F2 transition in MZSPEAg1.1 g glass was 20.8 × 10−25 cm2 s−1 for the optical gain and 21.1×10−22cm2 for gain bandwidth. Furthermore, the Racah parameters calculated from the first three significant visible absorption bands were reduced from 82.85×cm−1 to 72.33×cm−1 with the increase in AgNPs contents (from 0.1 to 1.1 g), signifying the weakening in f-f electrons repulsion. It was asserted that the proposed glass composition may contribute towards the development of solid-state laser and LEDs.

Simple flow system with in-line gas-diffusion unit for determination of ethanol employing hypsochromic shift of visible absorbance band of methyl orange

The effect of solvent composition on the uv–visible spectrum of methyl orange was investigated for application to the quantitative determination of ethanol. At fixed pH, there was a hypsochromic shift of the absorbance band of methyl orange with increasing ethanol concentration. Using acetate buffer at pH 3.40 the change of absorbance at 530 nm of a solution of methyl orange containing known concentrations of standard ethanol was measured to provide a calibration curve. In order to apply this method to the analysis of alcoholic samples, such as distilled spirits, blended spirits and liquid herbal medicines, a simple gas-diffusion unit coupled with flow system was employed to separate the ethanol from sample matrices. Using the gas diffusion-flow system and employing an evaporation time of 2 min, a linear calibration range of 5–45% (v/v) ethanol was achieved ((ΔA = (0.0078 ± 0.0002)x(ethanol, %(v/v)) + (0.040 ± 0.005)), r2 = 0.998). The limit of detection (3σ blank/slope) was 2.23% (v/v). The developed gas diffusion-flow system was applied to the analysis of colorless distilled spirits, yellow blended spirits and dark brown herbal medicines that are available in the local markets of Bangkok, Thailand. Validation of the method was carried out by comparing the results with analysis using gas chromatography. There was no statistically significant difference at the 95% confidence level for all alcoholic samples analyzed.

One-step electrosynthesis of CdS quantum dots stabilized by babassu oil and luminescent films deposited by DoD technology

The electrochemical synthesis of CdS quantum-dots was carried out in a one-step electrochemical procedure using babassu oil (BO) as stabilizer. The electrochemical reduction of elemental sulfur in DMSO was investigated by cyclic voltammetry, showing the formation of polysulfides and S2−, such results are in agreement to literature. Thus, the CdS-BO electrosynthesis was realized in DMSO solvent and 30 mA constant current in cavity cell. The cadmium and sulfide ions were locally generated by simultaneous oxidation of a cadmium bar (sacrificial anode), and reduction of elemental sulfur in a graphite powder macroelectrode. The CdS-BO quantum-dots showed a UV–Vis absorption band at λmax = 387 nm with symmetrical emission band at λem = 547 nm, with a full width at half maximum (FWHM) of 124 nm. Lauric (C12H24O2, 48.9%) and myristic (C14H28O2, 20.4%) acids were identified as major components of the BO, in addition, 2.4% of free fatty acids were identified in the BO composition by titration, which explains the good stabilization of CdS QDs synthesized. The CdS-BO colloidal system was used as photonic ink and deposited on silica sheets by inkjet printing by drop on demand technology, without waste generation at all stages. The nanoparticles preserved luminescence after printing and drying, showing that the BO promotes an effective stabilization of the quantum dots.