Novel ultra-sensitive and highly selective cyanine sensors based on solvent-free microwave synthesis for the detection of trace hypochlorite ions in drinking water.

The adoption of chlorine in drinking water disinfection with the determination of residual chlorine in the form of hypochlorite ion (ClO-) is in widespread demand. Several sensors including colorimetric, fluorometric, and electrochemical methods are currently in use, but detection limits and ease of application remain a challenge. In this work, two new cyanine derivatives-based ClO- sensors, that were prepared by solvent-free microwave synthesis, are reported. The two sensors are highly sensitive and selective to ClO-, exhibiting a noticeable color change visible to the naked eye. Additionally, the sensors can detect ClO- without interference from other potential water pollutants, with low detection limits of 7.43 ppb and 0.917 ppb based on absorption performance. When using fluorometric methods, the sensors' detection limits are pushed down to 0.025 ppb and 0.598 ppb for sensors I and II, respectively. The sensors can be loaded with paper strips for field and domestic detection of ClO- in tap water treatment installations. Using the quartz crystal microbalance (QCM) technique, these sensors showed strong detection sensitivity to ClO-, with detection limits of 0.256 ppm and 0.09 ppm for sensors I and II, respectively. Quantum chemical studies using density functional theory (DFT) calculations, natural bond orbital (NBO) analysis, molecular electrostatic potential (MESP), and time-dependent density functional theory (TD-DFT) supported the findings. The sensing mechanism is rationalized in terms of radical cation formation upon ClO- oxidation of cyanine sensors I and II.

In situ anchoring of iron and zinc oxides nanoparticles onto rice husk cellulose for efficient wastewater remediation.

The development of effective and economical technologies for the treatment of contaminated wastewater has been of great significance to researchers. Therefore, an equal molar ratio of iron and zinc oxides nanoparticles was hydrothermally immobilized on the cellulose fibers of rice husk. Using XRD, SEM, FTIR, EDX, TEM, VSM, BET, and TGA/DTG, the structure, and characteristics of Cel/α-Fe2O3-ZnO, a ternary nanocomposite, were affirmed. The nanocomposite displayed a mesoporous structure with a substantial surface area. The efficiency of nanocomposite as a new adsorbent has been studied for the extraction of reactive black 5 (RB5), which is a diazo-anionic dye from simulated wastewater. The medium's pH was the dominant factor of RB5 adsorption, and the optimal removal effectiveness was acquired at pH 2. The adsorption values of RB5 correspond to second-order kinetics. They also matched Langmuir with a maximum capacity of 99.30 mg g-1. For real industrial wastewater, Cel/α-Fe2O3-ZnO has successfully reduced a number of major pollutants, including ammonia (92.73 %), color (92.88 %), COD (91.53 %), BOD5 (84.97 %), TSS (96.27 %), TP (52.17 %) and TN (47.23 %). These results illustrate the effective application of the ternary nanocomposite in wastewater treatment.

Hydrophilic gold nanospheres: influence of alendronate, memantine, and tobramycin on morphostructural features.

Turkevich gold nanospheres are the original nanospheres that have been modified over time. Its combination with targeting medications such as alendronate, memantine, and tobramycin will provide additional benefits in targeting specific areas in the bone, brain, and microorganisms, respectively. Hence, The reactivity and stability of nanospheres with various drug concentrations (milli-,micro-, and nano-levels) have been studied. With alendronate, the absorbance spectra of nanospheres at [Formula: see text] 520 nm were always stable and no redshifts occurred. In contrast, the spectra with memantine and tobramycin were stable at the nano-level and redshifts occurred at the milli- and micro-levels. HRTEM and DLS revealed that the core diameter was relatively stable in all cases, whereas the hydrodynamic diameter and zeta potential varied with varying drug concentrations. Increasing concentration increased hydrodynamic diameter slightly with memantine (from 64.99 to 98.41 nm), dramatically with tobramycin (from 135.3 to 332.16 nm), and almost negligibly with alendronate (from 52.08 to 58.94 nm ). Zeta Potential, conversely, is reduced as concentration increases. Memantine had the greatest reduction in negativity, followed by tobramycin, but alendronate had a slight increase in negativity. Benefits from this research would be in targeted drug delivery, where stability and reactivity of gold nanospheres are critical.

Plasmonic Surface of Metallic Gold and Silver Nanoparticles Induced Fluorescence Quenching of Meso-Terakis (4-Sulfonatophenyl) Porphyrin (TPPS) and Theoretical-Experimental Comparable.

Colloidal metallic nanoparticles have attracted a lot of interest in the last two decades owing to their simple synthesis and fascinating optical properties. In this manuscript, a study of the effect of both gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs) on the fluorescence emission (FE) of TPPS has been investigated utilizing steady-state fluorescence spectroscopy and UV-Vis spectrophotometry. From the observed electronic absorption spectra, there is no evidence of the ground state interaction between metallic Au NPs or Ag NPs with TPPS. On the other side, the FE spectra of TPPS have been quenched by both Ag and Au NPs. Via applying quenching calculations, Ag NPs showed only traditional static fluorescence quenching of TPPS with linear Stern-Volmer (SV) plots. On the contrary, quenching of TPPS emission by Au NPs shows composed models. One model is the sphere of action static quenching model that prevails at high quencher concentrations leading to non-linear SV plots with positive deviation. However, at low Au NPs concentrations, traditional dynamic quenching occurs with linear SV plots. The quantum calculations for TPPS structure have been obtained using Gaussian 09 software: in which the TPPS optimized molecular structure was achieved using DFT/B3LYP/6-311G (d) in a gaseous state. Also, the calculated electronic absorption spectra for the same molecule in water as a solvent are obtained using TD/M06/6-311G + + (2d, 2p). Furthermore, the theoretical and experimental results comparable to UV-Vis spectra have been investigated.

Novel aspartic-based bio-MOF adsorbent for effective anionic dye decontamination from polluted water.

In this study, a cost-effective powdered Zn l-aspartic acid bio-metal organic framework (Zn l-Asp bio-MOF) was reported as an efficient adsorbent for Direct Red 81 (DR-81) as an anionic organic dye. The prepared bio-MOF was characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission transmission electron microscopy (FETEM), surface area analysis (BET), and thermal gravimetrical analysis (TGA). The resulting bio-MOF has a large surface area (180.43 m2 g-1) and large mesopore volume (0.144 cm3 g-1), as well as good chemical inertness and mechanical stability. The optimum dosage from the Zn l-Asp bio-MOF was 1.0 g L-1 at pH = 7 for 95.3% adsorption of 10 ppm DR-81 after 45 min. Thermodynamic analysis results demonstrated that the decontamination processes were done with spontaneous, thermodynamically, and exothermic nature onto the fabricated bio-MOF. Kinetic parameters were well-fitted with pseudo-second-order kinetics, and the adsorption process was described by the Freundlich isotherm. The adsorption data proved that Zn l-Asp bio-MOF is an effective adsorbent for DR-81 from aqueous solutions with high stability and recycling ability for eight cycles, as well as the easy regeneration of the sorbent.

Spectroscopic Behavior and Photophysical Parameters of 2-(Acetoxymethyl)-6-(1,2,4-triazinylaminodihydroquinazolinyl)tetrahydropyran Derivative in Different Solid Hosts.

Optical and photophysical properties of 6-substituted-1,2,4-Triazine fluorescent derivative dye doped in silicate based sol-gel, homopolymer of methyl methacrylate (PMMA), and copolymer (MMA/diethylene glycol dimethacrylate) (DEGDMA) were investigated. The pores of different hosts and caging of the dye were found to effect on the parameters such as molar absorptivity, cross sections of singlet-singlet electronic absorption and emission spectra, excited state lifetime, quantum yield of fluorescence. The dipole moment of electronic transition, the length of attenuation and oscillator strength of electronic transition from So → S1 have been calculated. The dye was pumped with different powers using 3rd harmonic Nd: YAG laser of 355 nm and pulse duration 8 ns, with repetition rate 10 Hz. Good photo stability for dye was attained. After 55,000 pumping pulses of (10 mJ/pulse), the photo-stabilities were decreased to 53%, 48%, and 45% of the initial ASE of dye in sol gel, PMMA, and Co-polymer respectively. The dye in sol-gel matrix showed improvement of photo stability compared with those in organic polymeric matrices.

Laser performance and investigation of the optimal density functional and the dependence of the basis sets for (E, E)-2,5-bis (3,4-dimethoxystyryl) pyrazine (BDP) molecule.

This manuscript includes some photophysical parameters and some optical properties such as absorption and emission spectra of the (E, E)-2,5-bis (3,4-dimethoxystyryl) pyrazine (BDP) by applying sol-gel and copolymer matrices. The BDP molecular structure is incorporated in sol-gel matrix and copolymer of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA). In case of sol-gel matrix, the BDP molecular structure has higher quantum yield in addition to photostability maxima. The laser behavior of this molecular structure containing sol-gel matrix is good senior compared to copolymer one via using diode laser (450 nm) as pumping laser of power 160 mW. Also, the fluorescence profile of the BDP molecular structure is sensitized via using cadmium sulfide (CdS) quantum dots (QDs) by applying sol-gel host. The optimized structure of the BDP molecule is obtained via applying B3LYP/6-31G(d) level of theory. The electronic absorption and emission spectra of the BDP molecular structure in ethanol solvent were calculated using time-dependent density functional theory (TDDFT) at CAM-B3LYP/6-31G + + (d, p) level. The obtained theoretical results were compared to experimental ones.

Spectral Behavior and Photophysical Parameters of Dihydrophenanthro[9,10-e][1,2,4]Triazine Derivative Dyes in Sol-Gel and Methyl Methacrylate Polymer Matrices.

This paper deals with the optical and photophysical properties of dihydrophenanthro[9,10-e][1,2,4]triazine fluorescent dyes doped in Silicate based sol-gel and homo-poly methyl methacrylate (PMMA). Solid hosts were found to effect on the optical and photophysical parameters such as molar absorptivity, cross sections of singlet-singlet electronic absorption and emission spectra, excited state lifetime, quantum yield of fluorescence. The dipole moment of electronic transition, the length of attenuation and oscillator strength of electronic transition from So → S1 have been calculated. The dyes were pumped with different powers using 3rd harmonic Nd:YAG laser of 355 nm and pulse duration 8 ns, with a repetition rate at (10 Hz). Good photostability for compounds 1 and 2 were attained. It was decreased to 49% & 54% and 46% & 40% of the initial ASE of dyes in sol gel and PMMA, respectively, after 55,000 pumping pulses at (10 mJ/pulse). The dyes in sol-gel showed improved photostability compared with those in organic polymeric matrices.

Binary coagulation system (graphene oxide/chitosan) for polluted surface water treatment.

In this study, chitosan (CS) is used as a natural coagulant aid alongside graphene oxide (GO) to remove turbidity and numerous pollutants from raw and artificially contaminated surface water. The coagulation capability of the system (GO/CS) was assessed with respect to a water sample's turbidity, pH, coagulant dose, settling velocity, and temperature. The presence of CS enhanced the coagulation capacity of GO at varied pH levels and no GO residue was detected in the water after the treatment. The proposed system achieved high turbidity removal efficiency (≥98.3%) for all turbidity levels. A mixture of GO (8 mg/L) and CS (2 mg/L) was ideal to remove algae (99.5%) and bacteria (≥95.0%). Furthermore, it demonstrated a high coagulation capacity to remove dyes, direct brown-2 (DB-2), methylene blue (MB), and Pb(II) ions from artificially contaminated surface water. Interestingly, the sludge exhibited an extraordinary adsorption capacity for DB-2, MB, and Pb(II) ions. The adsorption process followed the pseudo-second-order kinetic model, and was consistent with the Langmuir model, with an adsorption capacity of up to 667.8, 400.7, and 459.1 mg/g for DB-2, MB, and Pb(II) ions, respectively. Therefore, the presented binary coagulation system is of great potential economic value for the treatment of raw surface water and wastewater.

Novel eco-friendly electrospun nanomagnetic zinc oxide hybridized PVA/alginate/chitosan nanofibers for enhanced phenol decontamination.

In the current study, poly(vinyl alcohol)/alginate/chitosan (PVA/Alg/CS) composite nanofiber was immobilized with six different ratios of nanomagnetic zinc oxide (M-ZnO) (0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, and 1 wt%) via the electrospinning technique. The various fabricated composite (M-6) nanofibers were characterized using Fourier transform infrared (FTIR), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), atomic force microscope (AFM), thermogravimetric analysis (TGA), mechanical testing machine, and optical contact angle measurement. The fabricated composite nanofibers were applied for the adsorption of phenol from aqueous solutions. The 1.0 wt% M-ZnO/PVA/Alg/CS composite nanofibers were selected as the best phenol adsorbent with removal percentage of 84.22%. The influence of different processing parameter such as contact time, composite nanofiber dosage, pH, initial pollutant concentration, and temperature were examined. Increasing nanofiber dosage and the solution temperature was found to enhance the phenol adsorption onto the prepared nanocomposites. The maximum percentage of phenol removal was achieved at 84.22% after 90 min. Meanwhile, the maximum monolayer adsorption capacity (at pH = 5.0) was estimated to be 10.03 mg g-1 at 25 °C. Kinetic, isotherm, and thermodynamic studies were designated to proof the endothermic, spontaneous, and thermodynamically nature of the phenol adsorption process. These outcomes indicate the effectiveness of the fabricated M-ZnO/PVA/Alg/CS nanofibers as adsorbent materials for phenol from aqueous solutions.

Optical, photo physical parameters and photo stability of 6-Substituted-1, 2, 4-Triazine mono glucosyl derivative to act as a laser dye in various solvents.

The optical properties of a visible absorption range6-Substituted-1, 2, 4-Triazine mono glucosyl fluorescent derivative dye, such as absorption spectra, emission spectra in different solvents, were experimentally investigated. As well, some important photo physical parameters such as extinction coefficient (ε), cross-sections of the absorption (σa) and the emission (σe), quantum yield (фf), fluorescence lifetime, oscillator strength (f), the dipole moment (µ), decay rate radiative constant (kr), energy yield of fluorescence (Ef) and the length of attenuation Λ (λ) were assessed. The ground-state (µg) and excited-state (µe) dipole moments by solvatochromic correlations method were reported. The dye amplified spontaneous emission (ASE) of 2 × 10-4M with different input pumping energies of a continuous wave blue diode laser (λ = 450 nm) was studied. Photostability of dye was observed that was decreased to 53% of its initial energy by pumping with 100 mW of diode laser after exposure to 120 min.

Synthesis of Hollow Co-Fe Prussian Blue Analogue Cubes by using Silica Spheres as a Sacrificial Template.

Herein, we report a novel method for the formation of hollow Prussian blue analogue (CoFe-PBA) nanocubes, using spherical silica particles as sacrificial templates. In the first step, silica cores are coated by a CoFe-PBA shell and then removed by etching with hydrofluoric acid (HF). The cubic shape of CoFe-PBA is well-retained even after the removal of the silica cores, resulting in the formation of hollow CoFe-PBA cubes. The specific capacity of the hollow CoFe-PBA nanocubes electrodes is about two times higher than that of solid CoFe-PBA nanocubes as storage materials for sodium ions. Such an improvement in the electrochemical properties can be attributed to their hollow internal nanostructure. The hollow architecture can offer a larger interfacial area between the electrolyte and the electrode, leading to an improvement in the electrochemical activity. This strategy can be applied to develop PBAs with hollow interiors for a wide range of applications.

Loading of doxorubicin and thymoquinone with F2 gel nanofibers improves the antitumor activity and ameliorates doxorubicin-associated nephrotoxicity.

AIMS: This study aimed to elucidate the benefits of nanoformulation of doxorubicin (DOX) and thymoquinone (TQ) loaded with nanofibers of poly-N-acetyl glucosamine (pGlcNAc), which is known as F2 gel, over their conventional free forms. Moreover, evaluate the role of TQ in improving chemotherapeutic effect and ameliorating nephrotoxicity of DOX. MAIN METHODS: The drugs were loaded into F2 gel followed by measurement of physicochemical characterization. Next, MCF-7 and HEPG2 cells were treated with the prepared formulations and assessed for apoptosis alongside with cellular proliferation. Furthermore, we experimentally induced Heps liver carcinoma in mice and at the end of the treatment, mice were sacrificed and serum samples were used to assess nephrotoxicity markers; blood urea nitrogen (BUN) and creatinine. Additionally, renal tissue was used for determination of oxidative markers and antioxidant enzymes; whereas, tumor tissue was utilized to measure nuclear factor kappa B (NF-κB) and caspase 3. KEY FINDINGS: Nanoformulation showed dramatic increase in apoptosis, caspase 3, and antioxidant enzymes; in contrast to, dramatic fall in cell viability, tumor volume, oxidative and nephrotoxicity markers, and NF-κB compared to corresponding free therapies. Combined therapy was superior in conserving the measured parameters compared to other treated groups. SIGNIFICANCE: F2 gel loaded with DOX and TQ revealed enhanced antitumor activity with minimal toxicity. Moreover, using TQ as an adjuvant with DOX could augment its cytotoxicity and ameliorate nephrotoxicity.

Halogen bond triggered aggregation induced emission in an iodinated cyanine dye for ultra sensitive detection of Ag nanoparticles in tap water and agricultural wastewater.

Aggregation induced emission (AIE) has emerged as a powerful method for sensing applications. Based on AIE triggered by halogen bond (XB) formation, an ultrasensitive and selective sensor for picomolar detection of Ag nanoparticles (Ag NPs) is reported. The dye (CyI) has an iodine atom in its skeleton which functions as a halogen bond acceptor, and aggregates on the Ag NP plasmonic surfaces as a halogen bond donor or forms halogen bonds with the vacant π orbitals of silver ions (Ag+). Formation of XB leads to fluorescence enhancement, which forms the basis of the Ag NPs or Ag+ sensor. The sensor response is linearly dependent on the Ag NP concentration over the range 1.0-8.2 pM with an LOD of 6.21 pM (σ = 3), while for Ag+ it was linear over the 1.0-10 µM range (LOD = 2.36 µM). The sensor shows a remarkable sensitivity for Ag NPs (pM), compared to that for Ag+ (µM). The sensor did not show any interference from different metal ions with 10-fold higher concentrations. This result indicates that the proposed sensor is inexpensive, simple, sensitive, and selective for the detection of Ag NPs in both tap and wastewater samples.

Enhanced anticancer effect and reduced toxicity of doxorubicin in combination with thymoquinone released from poly-N-acetyl glucosamine nanomatrix in mice bearing solid Ehrlish carcinoma.

The incidence of breast cancer remarkably increases all over the world. Therefore, there is a great demand to introduce new approaches into cancer treatment field. The current study was designated to evaluate the role of doxorubicin (DOX) and/or thymoquinone (TQ) nanomatrix in potentiating the cytotoxicity of either drug, and to investigate the ability of TQ to reduce cardiotoxicity of DOX in solid Ehrlich carcinoma (SEC)-bearing mice. DOX and TQ were loaded into F2 gel, which is a fully-acetylated poly-N-acetyl glucosamine nanofiber. SEC was induced in female albino mice as a model for experimentally induced breast cancer. Mice were randomly divided into eight groups (n=10): normal control, tumor control, F2 gel, free DOX, DOX+F2 gel, free TQ, TQ+F2 gel, and DOX+TQ+F2 gel. On day 28th from tumor inoculation, mice were sacrificed and blood samples were collected for measurement of the cardiac markers; lactate dehydrogenase (LDH) and creatine kinase (CK-MB). In addition, cardiac tissue was utilized for determination of lipid peroxide, and tumor tissue was used for measurement of anti-apoptotic protein Bcl-2 as well as gene expression of the tumor suppressor gene P53. DOX and/or TQ showed a significant reduction in tumor volume, cardiac markers, tumor Bcl-2, and P53 upregulation compared to free conventional therapies. Co-treatment with DOX+TQ+F2 gel was superior to all other groups in exerting beneficial effects. Use of TQ as an adjuvant therapy with DOX could improve its cytotoxic effects and limit its cardiac toxicity. Furthermore, loading of DOX and/or TQ into F2 gel showed a remarkable anti-cancer activity.

Coagulation effectiveness of graphene oxide for the removal of turbidity from raw surface water.

This study presents the performance of graphene oxide (GO) as a coagulant in turbidity removal from naturally and artificially turbid raw surface water. GO is considered an excellent alternative to alum, the more common coagulant used in water treatment processes, to reduce the environmental release of aluminum. Effects of GO dosage, pH, and temperature on its coagulation ability were studied to determine the ideal turbidity removal conditions. The turbidity removal was ≥95% for all levels of turbid raw surface water (20, 100, and 200 NTU) at optimum conditions. The role of alkalinity in inducing turbidity removal by GO coagulation was much more pronounced upon using raw surface water samples compared with that using artificially turbid deionized water samples. Moreover, GO demonstrated high-performance removal of biological contaminants such as algae, heterotrophic bacteria, and fecal coliform bacteria by 99.0%, 98.8% and 96.0%, respectively, at a dosage of 40 mg/L. Concerning the possible environmental release of GO into the treated water following filtration process, there was no residual GO in a wide range of pH values. The outcomes of the study highlight the excellent coagulation performance of GO for the removal of turbidity and biological contaminants from raw surface water.

Laser Performance of Some Oxazole Laser Dyes in Restricted Matrices.

This article reports the optical properties such as absorption profile, molar absorptivity, fluorescence profile and photo-physical parameters such as dipole moment, oscillator strength, fluorescence quantum yields, fluorescence lifetimes, laser performance and finally photostability of 2,5-Bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBOT),1,4-Bis(5-phenyl-2-oxazolyl)benzene (POPOB), 5-diphenyel-oxazole (PPO) laser dyes in different restricted hosts. (BBOT), (POPOB) and (PPO) are embedded in transparent silica-based nanoporous sol-gel glass and copolymer matrix of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA). The absorption and fluorescence properties of these laser dyes in sol-gel glass matrices are compared with their respective properties in copolymer host. In case of sol-gel matrix, all dyes had higher quantum yields as well as lasing wavelength maxima. The laser performances as well as the photostability of these laser dyes in sol-gel glass displayed senior behavior compared with (MMA/ HEMA) copolymer samples upon using nitrogen laser (337.1 nm) as pumping energy.

Photo-induced interaction of thioglycolic acid (TGA)-capped CdTe quantum dots with cyanine dyes.

The photo-induced interaction of three different sizes of thioglycolic acid (TGA)-capped CdTe quantum dots (CdTe QDs) with two monomethine cyanine dyes belonging to the thiazole orange (TO) family has been studied. Positively charged cyanines interact with QDs surface which is negatively charged due to capping agent carboxylate ions. The energy transfer parameters including Stern-Volmer constant, Ksv, number of binding sites, n, quenching sphere radius, r, the critical energy transfer distance, R0, and energy transfer efficiencies, E have been calculated. The effect of structure and the number of aggregating molecules have been studied as a function of CdTe QDs particle size. Combining organic and inorganic semiconductors leads to increase of the effective absorption cross section of the QDs which can be utilized in novel nanoscale designs for light-emitting, photovoltaic and sensor applications. A synthesized triplet emission of the studied dyes was observed using CdTe QDs as donors and this is expected to play a potential role in molecular oxygen sensitization and in photodynamic therapy (PDT) applications.

A highly efficient and selective turn-on fluorescent sensor for Hg2+, Ag+ and Ag nanoparticles based on a coumarin dithioate derivative.

Based on chelation-enhanced fluorescence, a new fluorescent coumarin derivative probe 3(1-(7-hydroxy-4-methylcoumarin)ethylidene)hydrazinecarbodithioate for Hg(2+), Ag(+) and Ag nanoparticles is reported. Fluorescent probe acts as a rapid and highly selective "off-on" fluorescent probe and fluorescence enhancement by factors 5 to 12 times was observed upon selective complexation with Hg(2+), Ag(+) and Ag nanoparticles. The molar ratio plots indicated the formation of 1:1 complexes between Hg(2+) and Ag(+) with the probe. The linear response range covers a concentration range 0.1 × 10(-5) -1.9 × 10(-5) mol/L, 0.1 × 10(-5) -2.3 × 10(-5) mol/L and 0.146 × 10(-12) -2.63 × 10(-12) mol/L for Hg(2+), Ag(+) and Ag nanoparticles, respectively. The interference effect of some anions and cations was also tested.

Structural and fluorescence quenching characterization of hematite nanoparticles.

Nanoparticles of the dominant hematite form (α-Fe(2)O(3)) of iron oxide have been prepared by a simple route of dropping FeCl(3) solution into boiling water. The nanoparticles have been characterized by transmission electron microscopy (TEM), UV-visible electronic absorption spectroscopy, chemical stoichiometry, thermal analysis methods (TGA, DSC and DTA), XRD, FTIR and magnetic susceptibility measurements. Kinetic analysis of the DSC calorigram of thermal dehydration of the nanoparticles reveals one stage of the dehydration process of energy of activation of 29.0 kJ mol(-1). The role of iron oxide nanoparticles in fluorescence quenching of coumarin thiourea derivatives (I-IV) was investigated at room temperature (296 K) by means of steady-state fluorescence spectroscopy. The quenching process was characterized by Stern-Volmer (S-V) plots which display a positive deviation from linearity. This could be explained by static and dynamic quenching models. The positive deviation in the S-V plot is interpreted in terms of ground-state complex formation model and sphere of action static quenching model. Various rate parameters for the fluorescence quenching process were determined by using the modified Stern-Volmer equation. The sphere of action static quenching model agrees very well with experimental results. Quenching constants for iron oxide nanoparticles are about four orders of magnitudes higher than quenching by Fe(3+) ions.