Kinetic and equilibrium adsorption of methylene blue and remazol dyes onto steam-activated carbons developed from date pits

Steam-activated carbons DS2 and DS5 were prepared by gasifying 600 °C-date pits carbonization products with steam at 950 °C to burn-off = 20 and 50%, respectively. The textural properties of these carbons were determined from the nitrogen adsorption at ?196 °C. The chemistry of the carbon surface was determined from the surface pH and from neutralization of the surface carbon–oxygen groups of basic and acidic type. The kinetic and equilibrium adsorption of MB and RY on DS2 and DS5 was determined at 27 and 37 °C and at initial sorption solution pH 3–7.DS2 and DS5 have expanded surface area, large total pore volume and contain both micro and mesoporosity. They have on their surface basic and acidic groups of different strength and functionality. This enhanced the sorption of the cationic dye (MB) and of the anionic dye (RY). The adsorption of MB and RY on DS2 and DS5 involves intraparticle diffusion and followed pseudo-second order kinetics. The adsorption isotherms were applicable to the Langmuir isotherm and high monolayer capacities for MB and RY dyes were evaluated indicating the high efficiencies of the carbons for dye adsorption.     

A novel HMP-2 dye of high extinction coefficient designed for enhancing the performance of ZnO platelets

Newly designed cis-[Ru(H₂dcbpy) (L) (NCS)₂ (HMP-2), where L is 4-(4-(N,N-di-(p-hexyloxyphenyl)-amino)styryl)-4′-methyl-2,2′-bipyridine, sensitizing dye of high extinction coefficient than the routinely preferred ruthenium (II) cis-di(thiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylic acid) (N3) sensitizing dye is explored. Electrochemically synthesized ZnO (plates of 4–5 μm in height and 100–150 nm in width) electrodes are dipped intentionally in N3 and HMP-2 dyes for 20 h so as to observe large surface agglomeration effect for ZnO/N3 system. Due to the local inhomogeneity resulting from the Zn²⁺/dye complex layer formed between ZnO platelets and N3 dye, its solar-to-electrical conversion efficiency is inferior than aggregation-free ZnO/HMP-2.     

The effect of UV-A (352 nm) stress on chlorophyll fluorescence,chlorophyll a content,thickness of upper cortex and determinate DNA damage in Physcia semipinnata

In the present study, Physcia semipinnata samples were exposed to UV-A (352 nm) in 20 J m^?2 for 24 h, 48 h and 72 h to seek the alterations in the PSII photosynthetic quantum yield, thallus anatomy and DNA mutation rate in response to radiation. The Fv/Fm ratio decreased in P. semipinnata following exposure to UV-A for 24 h, 48 h and 72 h. The data of the present study reported that Chla degradation occurred by exposition of UV-A for 24 h, 48 h and 72 h. Photobiont size and thickness of upper cortex layer also showed a gradually decrease in P. semipinnata thallus sections during 24 h, 48 h and 72 h. The thickness of the upper cortex layer, exposed to UV-A for 72 h, of P. semipinnata thallus reduced 64%, compared with control. The random amplified polymorphic DNA (RAPD) technique was used to detect DNA damage. The main changes observed in the RAPD profiles resulted in both appearance and disappearance of different bands and variation of their intensity. According to RAPD assay, the genetic distance between the control group and 24 h, 48 h and 72 h UV-A exposed, groups was found 56%, 78% and 84%, respectively.     

Identification of pyrazosulfuron-ethyl binding affinity and binding site subdomain IIA in human serum albumin by spectroscopic methods

Pyrazosulfuron-ethyl (PY) is a sulfonylurea herbicide developed by DuPont which has been widely used for weed control in cereals. The determination of PY binding affinity and binding site in human serum albumin (HSA) by spectroscopic methods is the subject of this work. From the fluorescence emission, circular dichroism and three-dimensional fluorescence results, the interaction of PY with HSA caused secondary structure changes in the protein. Fluorescence data demonstrated that the quenching of HSA fluorescence by PY was the result of the formation of HSA–PY complex at 1:1 molar ratio, a static mechanism was confirmed to lead to the fluorescence quenching. Hydrophobic probe 8-anilino-1-naphthalenesulfonic acid (ANS) displacement results show that hydrophobic patches are the major sites for PY binding on HSA. The thermodynamic parameters ΔH° and ΔS° were calculated to be ?36.32 kJ mol^?1 and ?35.91 J mol^?1 K^?1, which illustrated van der Waals forces and hydrogen bonds interactions were the dominant intermolecular force in stabilizing the complex. Also, site marker competitive experiments showed that the binding of PY to HSA took place primarily in subdomain IIA (Sudlow's site I). What presented in this paper binding research enriches our knowledge of the interaction between sulfonylurea herbicides and the physiologically important protein HSA.     

Recognition of DNA based on changes in the fluorescence intensity of CdSe/CD QDs–phenanthroline systems

The CdSe quantum dots (QDs) modified by mercapto-β-cyclodextrin (CD) were synthesized and characterized by transmission electron microscopy, powder X-ray diffraction, excitation and emission spectra, and fluorescence lifetime. When λ_ex = 370 nm, the fluorescence peak of CdSe/CD QDs is at 525 nm. Phenanthroline (Phen) is able to quench their fluorescence, which can be recovered by the addition of DNA. The quenching and restoration of fluorescence intensity were found to be linearly proportional to the amount of Phen and DNA, respectively. The variation of the fluorescence intensity of the CdSe/CD QDs–Phen system was studied, and it was demonstrated to result from a static mechanism due to the formation of a Phen inclusion complex with the CdSe QDs modified by mercapto-β-cyclodextrin. The fluorescence recovery was due to the binding of DNA with Phen in the inclusion complex, leading to the freeing of the CdSe/CD QDs. The binding constants and sizes of the binding sites of the Phen–DNA interaction were calculated to be 1.33 × 10⁷ mol^?1 L and 10.79 bp.     

Complexation thermodynamics between butyl rhodamine B and calix[n]arenesulfonates (n = 4, 6, 8)

The characteristics of host–guest complexation between water-soluble calix[n]arenesulfonates (CnS, n = 4, 6, 8) and butyl rhodamine B (BRB) were investigated by fluorescence spectrometry. Fluorescence spectroscopy experiments were performed in pH 8.0 Tris(3-aminomethane)–HCl buffer solution at different temperature to calculate the stability constants (K_S) for the stoichiometric 1:1 inclusion complexes of C4S, C6S, and C8S with BRB. The complex stability constant monotonically increased with the number of phenolic units in the calixarene ring. The thermodynamic parameters at T = 298 K for the inclusion complexes were calculated through Van’t Hoff analysis. The inclusion complexes of CnS with BRB were driven by the favorable enthalpic changes, accompanying negative entropy changes. The stability constants were affected by the acidity of the solution. When pH was 8.0, the stability constants reached the maximum. The complex interaction was mainly attributed to the weak forces including electrostatic interaction and hydrogen bonding.     

Synthesis and fluorescence characteristics of novel asymmetric cyanine dyes for DNA detection

Sixteen new asymmetric monomethine cyanine dyes have been synthesized and their spectral characteristics and interaction with double stranded DNA have been investigated. The dyes absorb in the region 453–519 nm and have molar absorptivities in the range 37.900–93.100 l M^?1 cm^?1. The dyes do not have intrinsic fluorescence, but in the presence of dsDNA they exhibited a significant enhancement in fluorescence. The most pronounced increase was found for D9, D10, D12 and D16 allowing the recommendation of these dyes as the most sensitive DNA markers. Thermodynamic analysis of cyanine–DNA complexation was carried out using the McGhee & von Hippel non-cooperative excluded site model, and binding parameters have been derived. A hypothesis describing the DNA–dye binding mode has been proposed.     

Effects of gamma irradiation on the grape vine moth,Lobesia botrana,eggs

Eggs of the grape vine moth, Lobesia botrana (Denis and Schiffermuller), ranging in age from 1–24 to 73–96 h, were exposed, at 24 h intervals, to gamma radiation ranging from 25–600 Gy. The effects of gamma radiation on egg hatch, pupation, adult emergence, sex ratio and rate of development were examined. Results showed that the radiosensitivity of the grape vine moth eggs decreased with increasing age and increased with increasing radiation dose. Egg hatch in 1–24 h old eggs was significantly affected at 25 Gy and completely prevented at 100 Gy. At the age of 25–48 h, radiation sensitivity was only a little lower; egg hatch at 100 Gy was <1% and at 125 Gy no egg hatch was observed. Egg sensitivity to gamma irradiation decreased significantly in the 49–72 h age group; egg hatch was 66% at 100 Gy, and 500 Gy did not completely stop egg hatch (<1%). Eggs irradiated a few hours before egg hatch (73–96 h old) were the most resistant; 150 Gy had no significant effect on egg hatch and at 600 Gy over 33% of the eggs hatched. When pupation or adult emergence was used as a criterion for measuring effectiveness, however, the effects of gamma radiation were very severe. In the most resistant age group (73–96 h old), 150 Gy completely prevented pupation and adult emergence and all larvae resulting from eggs irradiated <49 h old died before pupation. In addition, the rate of development of immature stages resulting from irradiated eggs was negatively affected and sex ratio was skewed in favor of males.     

Ultrasensitive determination of gold in geogas by laser excited atomic fluorescence spectrometry

Ultratrace gold (Au) in geogas samples has been determined by means of laser excited atomic fluorescence spectrometry combined with graphite electrothermal atomization and time-gate technique. Gold atoms were excited from the ground state to the 6p²P_3/2 state by a pulsed laser beam with a wavelength of 242.8 nm. Fluorescence photons with a wavelength of 312.3 nm were measured by a photon-counting unit. The time-gate technique was used to reduce the background radiation caused by the furnace. This method has proved to be highly sensitive with minimal background interference. Eighty-two geogas samples were analysed and the Au contents obtained were in the range of 0.002–0.182 ng l⁻¹. The study of Au concentration of geogas in soil is of great interest in prospecting gold deposits.     

In vitro photodynamic activity of chloro(5,10,15,20-tetraphenylporphyrinato)indium(III) loaded-poly(lactide-co-glycolide) nanoparticles in LNCaP prostate tumour cells

In(III)-meso-tetraphenylporphyrin (InTPP) was encapsulated into nanoparticles (smaller than 200 nm) of poly(d,l-lactide-co-glycolide) (PLGA) using the emulsification–evaporation technique. The photodynamic efficacy of InTPP-loaded nanoparticles and its cellular uptake was investigated with LNCaP prostate tumour cells, in comparison with the free InTPP. The effects of incubation time (1–3 h), drug concentration (1.8–7.7 μmol/L) and incident light dose (15–45 J/cm²) with both encapsulated and free InTPP were studied. The type of cell death induced by the photochemical process using both encapsulated and free InTPP was also investigated. Cell viability was reduced more significantly with increasing values of these effects for InTPP-loaded nanoparticles than with the free drug. The cellular death induced by both encapsulated and free InTPP was preponderantly apoptotic. Confocal laser scanning microscopy data showed that the InTPP-loaded nanoparticles, as well free InTPP, were localized in the cells, and always in the perinuclear region. Encapsulated InTPP was measured by the intensity of fluorescence intensity of cell extracts and was three times more internalized into the cells than was the free InTPP. Electron paramagnetic resonance experiments corroborated the participation of singlet oxygen in the photocytotoxic effect of nanoparticles loaded with InTPP.     

Efficient passivation of SnO2 nano crystallites by Indoline D-149 via dual chelation

For the first time in SnO₂ based dye solar cells, here we report, efficiency exceeding 3% of the cells consisting with Indoline D-149 dye with unmodified SnO₂ nano-crystallites. The cells sensitized with metal free D-149 dye together with liquid electrolyte comprising with 0.5 M tetrapropyl ammonium iodide and 0.05 M iodine in a mixture of acetonitrile and ethylene carbonate (1:4 by volume) delivered a short circuit current density of 10.4 mA cm^?2 with an open circuit voltage of 530 mV under the illumination of 100 mW cm^?2 (AM1.5) having an efficiency of 3.1%. As evident from the FTIR measurement, strong surface passivation of recombination centers of SnO₂ crystallites due to the dual mode of attachment of dye molecules to the surface of SnO₂ via both COOH and S–O direct bond might be the possible reason for this enhancement in these SnO₂ based cells.     

Study on the enhanced fluorescent spectrum of ciprofloxacin + Al(III) + La(III) + cetyltrimethylammonium bromide system and its application

The fluorescence of ciprofloxacin (CIP) in HAc–NaAc buffer solution and the presence of cetyltrimethylammonium bromide (CTMAB) enhanced visibly with adding Al(III) and La(III). This enhanced fluorescence spectra were studied, and a new co-luminescence system of CIP + Al(III) + La(III) + CTMAB was discovered. There was a linear relationship between the enhanced fluorescence intensity and the concentration of CIP in the range of 0.50–80.2 μg l^?1 under the optimized condition. A novel enhanced fluorescence method for the determination of trace CIP was established by using this co-luminescence system. The detection limit of the proposed method was 0.17 μg l^?1 for CIP. This method is simple, rapid and sensitive. The CIP in milk samples were analyzed by the proposed method with satisfactory results. The relative standard deviation and the recovery were in ranges of 3.21–4.34% and 97.1–100.1%, respectively. The mechanism of the co-luminescence reaction and the reasons for fluorescence enhancement has been discussed.     

Study on β-cyclodextrin inclusion of Zn(II) aromatic complex and its analytical application

A new β-cyclodextrin (β-CD) inclusion compound Zn(2H1NA)₂·2β-CD (2H1NA = 2-hydroxy-1-naphthoic acid) was prepared. The structure was characterized by ¹H NMR, IR, the fluorescence spectra, thermogravimetric analysis (TG–DTA) and elementary analysis. Meanwhile, the mechanism of the formation of the supramolecular system (2H1NA:Zn(II):β-CD) was studied and discussed by spectrofluorimetry. The results showed that the naphthalene rings of the Zn(II) aromatic complex Zn(2H1NA)₂ were encapsulated within the β-CD's cavity to form a 2:1 stoichiometry host–guest compound. The inclusion constant calculated was 1.27 × 10⁴ (L/mol)². A spectrofluorimetric method for the determination of 2H1NA in bulk aqueous solution in the presence of β-CD was developed based on the great enhancement of the fluorescence intensity of 2H1NA. The linear relationship was obtained in the range of 9.00 × 10^?7 to 2.50 × 10^?5 mol/L and the detection limit was 8.00 × 10^?7 mol/L. The proposed method was successfully applied to determine 2H1NA in waste water with recoveries of 97–104%.     

Determination of gallium at trace levels using a spectrofluorimetric method in synthetic U–Ga and Ga–As solutions

A simple, easy to use and selective spectrofluorimetric method for the determination of trace levels of gallium has been developed. A new Schiff base, N-o-vanillidine-2-amino-p-cresol (OVAC) was synthesized and its fluorescence activity with gallium investigated. Based on this chelation reaction, a spectrofluorimetric method has been developed for the determination of gallium in synthetically prepared Ga–U and Ga–As samples buffered at pH 4.0 using acetic acid–sodium acetate. The chelation reaction between Ga(III) and N-o-vanillidine-2-amino-p-cresol was very fast, requiring only 30 min at room temperature to complex completely. The limit of detection (LOD) (3σ) for Ga(III) was 7.17 nM (0.50 μg L^?1), determined from the analysis of 11 different solutions of 20 μg L^?1 Ga(III).     

A ruthenium(II) complex with the propionate ion: Synthesis,characterization and cytotoxic activity

The complex [Ru(η²-O₂CCH₂CH₃)(dppe)₂]PF₆ (dppe = 1,2-bis(diphenylphosphino)ethane) was prepared and characterized by elemental analysis, spectroscopic techniques, X-ray crystallography, HRESIMS and HRESIMS/MS. The characterization data are consistent with a cis arrangement for the dppe ligands and a bidentate coordination of the propionate ligand through carboxylate oxygens. Cytotoxicity assays were carried out on human and murine cancer and normal cell lines. In general, the [Ru(η²-O₂CCH₂CH₃)(dppe)₂]PF₆ complex was more cytotoxic than both its precursor cis–[RuCl₂(dppe)₂] and the reference metallodrug cisplatin. The best results against the HepG2 human tumour cell line and S180 murine tumour cell line were found with IC₅₀ values of 6.5 ± 0.2 and 0.18 ± 0.03 μM, respectively.     

Synthesis of ZnS nanoparticles from pyridine adducts of zinc(II) dithiocarbamates

Zn(thqdtc)₂, Zn(thqdtc)₂(py) and Zn(thiqdtc)₂(py) (where thqdtc = 1,2,3,4-tetrahydroquinolinecarbodithioate, thiqdtc = 1,2,3,4-tetrahydroisoquinolinecarbodithioate and py = pyridine) have been used as single source precursors for the synthesis of ZnS nanoparticles. The formation of ZnS nanoparticles was achieved by thermal decomposition of the complex under heating in presence of triethylenetetraamine. Transmission electron microscopy, energy dispersive X-ray analysis (EDAX) and powder X-ray diffraction studies were carried out to study the structure and morphology of the nanoparticles. The optical properties of the ZnS nanoparticles were studied by UV–visible and fluorescence emission spectral studies. UV–visible absorption spectral studies indicate a blue shift in the absorption maxima due to the quantum size effect. A single crystal X-ray analysis was carried out for a precursor [Zn(thqdtc)₂].     

Studies on the interaction between imidacloprid and human serum albumin: Spectroscopic approach

The interaction between imidacloprid (IMI) and human serum albumin (HSA) was investigated using fluorescence and UV/vis absorption spectroscopy. The experimental results showed that the fluorescence quenching of HSA by IMI was a result of the formation of IMI–HSA complex; static quenching was confirmed to result in the fluorescence quenching. The apparent binding constant K_A between IMI and HSA at three differences were obtained to be 1.51 × 10⁴, 1.58 × 10⁴, and 2.19 × 10⁴ L mol^?1, respectively. The thermodynamic parameters, ΔH° and ΔS° were estimated to be 28.44 kJ mol^?1, 174.76 J mol^?1 K^?1 according to the van’t Hoff equation. Hydrophobic interactions played a major role in stabilizing the complex. The distance r between donor (HSA) and acceptor (IMI) was obtained according to fluorescence resonance energy transfer. The effect of IMI on the conformation of HSA was analyzed using synchronous fluorescence spectroscopy CD and three-dimensional fluorescence spectra, the environment around Trp and Tyr residues were altered.     

Synthesis and laser application of the dithiolene nickel complex compounds

A series of dithiolene nickel complex compounds with a general formula (RCSCSR′)₂Ni that have an intense absorption band in near-IR region were successfully synthesized and the maximum IR absorption wavelengths of these dyes vary from 875 to 1495 nm in different solvents. Their characteristics of Q-switching and mode-locking for different lasers were investigated. Q-switched 1064 and 1079 nm laser with a polymer film or organic solution work satisfactorily and the pulse widths are 4–10 ns. The dyes in a variety of solutions show excellent properties in mode-locking the 1079 nm laser, particularly in mode-locking the 1340 nm laser. The pulse widths are 90–120 ps. The experimental results show that the choice of different ring substitutes and solvents will greatly influence the corresponding dye laser properties. It is also implied that BDN16 and BDN17 as the mode-locking dyes for the 1500 nm laser are satisfactory.     

Computational modeling of acrylodan-labeled cAMP dependent protein kinase catalytic subunit unfolding

Structure of the cAMP-dependent protein kinase catalytic subunit, where the asparagine residue 326 was replaced with acrylodan-cystein conjugate to implement this fluorescence reporter group into the enzyme, was modeled by molecular dynamics (MD) method and the positioning of the dye molecule in protein structure was characterized at temperatures 300 K, 500 K and 700 K. It was found that the acrylodan moiety, which fluorescence is very sensitive to solvating properties of its microenvironment, was located on the surface of the native protein at 300 K that enabled its partial solvation with water. At high temperatures the protein structure significantly changed, as the secondary and tertiary structure elements were unfolded and these changes were sensitively reflected in positioning of the dye molecule. At 700 K complete unfolding of the protein occurred and the reporter group was entirely expelled into water. However, at 500 K an intermediate of the protein unfolding process was formed, where the fluorescence reporter group was directed towards the protein interior and buried in the core of the formed molten globule state. This different positioning of the reporter group was in agreement with the two different shifts of emission spectrum of the covalently bound acrylodan, observed in the unfolding process of the protein.