Effects of crystallization temperature on the characteristics of sugar crystals in date fruit syrup as measured by differential scanning calorimetry (DSC), polarized microscopy (PLM), and X-ray diffraction (XRD).

Characteristics of sugar crystals are important for developing set-syrup due to their contribution to the desired mouth feel when consumed. Two types of set-syrup (i.e. seeds with and without) were developed by storing the syrup at -20, 4 and 15 °C. The melting temperatures (onset and peak), and enthalpy of set-syrup without seeds (SN) were 30.2 °C, 74.6 °C and 42.2 kJ/kg respectively. In the case of SN, enthalpy decreased with the decrease of crystallization temperature (P < 0.05), while there was insignificant change in the case of set-syrup with seeds (SW) (P > 0.05). Polarized Light Microscopy (PLM) images showed that finer crystals were formed in the cases of set-syrups (i.e. SN and SW) as the storage temperature was decreased. X-ray diffraction (XRD) analysis showed the formation of different polymorphic sugar crystals. Crystallization temperatures at 4 and -20 °C can be used to produce finer crystals with varied polymorphic characteristics.

Sn2+ Doping: A Strategy for Tuning of Fe3O4 Nanoparticles Magnetization Dipping Temperature/Amplitude, Irreversibility, and Curie Point.

Doped magnetite (SnxFe3-2/3xO4) nanoparticles (NPs) (12-50 nm) with different amount of Sn2+ ions (x) were synthesized using co-precipitation method. Sn2+ doping reduces the anticipated oxidation of Fe3O4 NPs to maghemite (γ-Fe2O3), making them attractive in several magnetic applications. Detailed characterizations during heating-cooling cycles revealed the possibility of tuning the unusual observed magnetization dipping temperature/amplitude, irreversibility, and Curie point of these NPs. We attribute this dip to the chemical reduction of γ-Fe2O3 at the NPs surfaces. Along with an increase in the dipping temperature, we found that doping with Sn2+ reduces the dipping amplitude, until it approximately disappears when x = 0.150. Based on the core-shell structure of these NPs, a phenomenological expression that combines both modified Bloch law (M = M0[1 - γ(T/TC)]ß) and a modified Curie-Weiss law (M = - α[1/(T - TC)δ]) is developed in order to explain the observed M-T behavior at different applied external magnetic fields and for different Sn2+ concentrations. By applying high enough magnetic field, the value of the parameters γ and δ ≈ 1 which are the same in modified Bloch and Curie-Weiss laws. They do not change with the magnetic field and depend only on the material structure and size. The power ß for high magnetic field was 2.6 which is as expected for this size of nanoparticles with the core dominated magnetization. However, the ß value fluctuates between 3 and 10 for small magnetic fields indicating an extra magnetic contribution from the shell structure presented by Curie-Weiss term. The parameter (α) has a very small value and it turns to negative values for high magnetic fields.

Removal of heavy metal ions by capacitive deionization: Effect of surface modification on ions adsorption.

Activated carbon cloth (ACC) coated with zinc oxide (ZnO) nanoparticles (NPs) have been used as electrodes in flow-by capacitive deionization (CDI) system. Aqueous solution of individual Pb2+ and Cd2+ ions and mixed Pb2+ and Cd2+ ions were used as test contaminant in CDI system to study the effect of surface modification upon ions removal efficiency. Due to the aggregated structure of ZnO NPs on ACC surface, the modified ACC electrodes develop the additional surface area as well as dielectric barrier therefore resulting in higher specific capacitance. In addition, coating with ZnO NPs effectively reduced physical adsorption whereby enhanced the ions adsorption rate and capacity during electrosorption process. Upon incorporating with ZnO NPs, the electrosorption efficiency was enhanced from 17% to 33% for Pb2+, from 21% to 29% for Cd2+ and from 21% to 35% for mixed Pb2+ and Cd2+ ions. The power consumption of individual ions and mixed ions removal process for ACC and ZnO NPs modified ACC were also discussed. Furthermore, used ACC electrodes surfaces were examined using photoelectron spectroscopy (XPS) and results were also conferred. The CDI ACC electrodes with ZnO NPs showed a promising and an effective way for heavy metal removal applications.

Free and partially encapsulated manganese ferrite nanoparticles in multiwall carbon nanotubes.

Free and partially encapsulated manganese ferrite (MnFe2O4) nanoparticles are synthesized and characterized regarding structure, surface, and electronic and magnetic properties. The preparation method of partially encapsulated manganese ferrite enables the formation of a hybrid nanoparticle/tube system, which exhibits properties of manganese ferrite nanoparticles inside and attached to the external surface of the tubes. The effect of having manganese ferrite nanoparticles inside the tubes is observed as a shift in the X-ray diffraction peaks and as an increase in stress, hyperfine field, and coercivity when compared to free manganese ferrite nanoparticles. On the other hand, a strong charge transfer from the multiwall carbon nanotubes is attributed to the attachment of manganese ferrite nanoparticles outside the tubes, which is detected by a significant decrease in the σ band emission of the ultraviolet photoemission spectroscopy signal. This is followed by an increase in the density of states at the Fermi level of the attached manganese ferrite nanoparticles in comparison to free manganese ferrite nanoparticles, which leads to an enhancement of the metallic properties.

Influence of Atomic Hydrogen, Band Bending, and Defects in the Top Few Nanometers of Hydrothermally Prepared Zinc Oxide Nanorods.

We report on the surface, sub-surface (top few nanometers) and bulk properties of hydrothermally grown zinc oxide (ZnO) nanorods (NRs) prior to and after hydrogen treatment. Upon treating with atomic hydrogen (H*), upward and downward band bending is observed depending on the availability of molecular H2O within the structure of the NRs. In the absence of H2O, the H* treatment demonstrated a cleaning effect of the nanorods, leading to a 0.51 eV upward band bending. In addition, enhancement in the intensity of room temperature photoluminescence (PL) signals due to the creation of new surface defects could be observed. The defects enhanced the visible light activity of the ZnO NRs which were subsequently used to photocatalytically degrade aqueous phenol under simulated sunlight. On the contrary, in the presence of H2O, H* treatment created an electronic accumulation layer inducing downward band bending of 0.45 eV (~1/7th of the bulk ZnO band gap) along with the weakening of the defect signals as observed from room temperature photoluminescence spectra. The results suggest a plausible way of tailoring the band bending and defects of the ZnO NRs through control of H2O/H* species.

Evidence for enhanced optical properties through plasmon resonance energy transfer in silver silica nanocomposites.

Silver nanoparticles were dispersed in the pores of monolithic mesoporous silica prepared by a modified sol-gel method. Structural and microstructural analyses were carried out by Fourier transform infrared spectroscopy and transmission electron microscopy. X-ray photoelectron spectroscopy was employed to determine the chemical states of silver in the silica matrix. Optical absorption studies show the evolution absorption band around 300 nm for silver (Ag) in a silica matrix and it was found to be redshifted to 422 nm on annealing. Photoluminescence studies indicate the presence of various luminescent emitting centers corresponding to silver ions and silver dimers in the SiO2 matrix. The enhancement of absorption and photoluminescence properties is attributed to plasmon resonance energy transfer from Ag nanoparticles to luminescent species in the matrix.

Composition, Electronic and Magnetic Investigation of the Encapsulated ZnFe2O 4 Nanoparticles in Multiwall Carbon Nanotubes Containing Ni Residuals.

We report investigation on properties of multiwall carbon nanotubes (mCNTs) containing Ni residuals before and after encapsulation of zinc ferrite nanoparticles. The pristine tubes exhibit metallic character with a 0.3 eV reduction in the work function along with ferromagnetic behavior which is attributed to the Ni residuals incorporated during the preparation of tubes. Upon encapsulation of zinc ferrite nanoparticles, 0.5 eV shift in Fermi level position and a reduction in both the π band density of state along with a change in the hybridized sp(2)/sp(3) ratio of the tubes from 2.04 to 1.39 are observed. As a result of the encapsulation, enhancement in the σ bands density of state and coating of the zinc ferrite nanoparticles by the internal layers of the CNTs in the direction along the tube axis is observed. Furthermore, Ni impurities inside the tubes are attracted to the encapsulated zinc ferrite nanoparticles, suggesting the possibility of using these particles as purifying agents for CNTs upon being synthesized using magnetic catalyst particles. Charge transfer from Ni/mCNTs to the ZnFe2O4 nanoparticles is evident via reduction of the density of states near the Fermi level and a 0.3 eV shift in the binding energy of C 1 s core level ionization. Furthermore, it is demonstrated that encapsulated zinc ferrite nanoparticles in mCNTs resulted in two interacting sub-systems featured by distinct blocking temperatures and enhanced magnetic properties; i.e., large coercivity of 501 Oe and saturation magnetization of 2.5 emu/g at 4 K.

Self-organization of gold nanoparticles on silanated surfaces.

The self-organization of monolayer gold nanoparticles (AuNPs) on 3-aminopropyltriethoxysilane (APTES)-functionalized glass substrate is reported. The orientation of APTES molecules on glass substrates plays an important role in the interaction between AuNPs and APTES molecules on the glass substrates. Different orientations of APTES affect the self-organization of AuNps on APTES-functionalized glass substrates. The as grown monolayers and films annealed in ultrahigh vacuum and air (600 °C) were studied by water contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, UV-visible spectroscopy and ultraviolet photoelectron spectroscopy. Results of this study are fundamentally important and also can be applied for designing and modelling of surface plasmon resonance based sensor applications.

Role of central metal ions in hematoporphyrin-functionalized titania in solar energy conversion dynamics.

In this study, we have investigated the efficacy of electron transfer processes in hematoporphyrin (HP) and iron hematoporphyrin ((Fe)HP) sensitized titania as potential materials for capturing and storing solar energy. Steady-state and picosecond-resolved fluorescence studies show the efficient photoinduced electron transfer processes in hematoporphyrin-TiO2 (HP-TiO2) and Fe(III)-hematoporphyrin-TiO2 (Fe(III)HP-TiO2) nanohybrids, which reveal the role of central metal ions in electron transfer processes. The bidentate covalent attachment of HP onto TiO2 particulates is confirmed by FTIR, Raman scattering and X-ray photoelectron spectroscopy (XPS) studies. The iron oxidation states and the attachment of iron to porphyrin through pyrrole nitrogen atoms were investigated by cyclic voltammetry and FTIR studies, respectively. We also investigated the potential application of HP-TiO2 and Fe(III)HP-TiO2 nanohybrids for the photodegradation of a model organic pollutant methylene blue (MB) in aqueous solution under wavelength dependent light irradiation. To further investigate the role of iron oxidation states in electron transfer processes, photocurrent measurements were done by using Fe(III) and Fe(II) ions in porphyrin. This work demonstrates the role of central metal ions in fundamental electron transfer processes in porphyrin sensitized titania and their implications for dye-sensitized device performance.

Diagnostic utility of coeliac disease: a descriptive study in a tertiary care hospital, oman.

OBJECTIVES: The prevalence of coeliac disease in Oman is unknown. We aim to estimate the prevalence of coeliac disease in at-risk subjects, describe the clinical characteristics and laboratory findings associated with coeliac disease and the validity of serological testing for coeliac disease at the Royal Hospital, Oman over a period of three years. METHODS: This is a retrospective case finding study. The medical and laboratory records were reviewed for patients for whom serum antiendomysium IgA antibodies were requested at the Royal Hospital during a 3-year period (1(st) Jan 2006-31(st) Dec 2008). The data were extracted in order to assess the following: a) Prevalence rate of coeliac disease among at-risk subjects; b) Clinical characteristics in patients with coeliac disease and clinical manifestations for which the requesting clinicians considered coeliac disease as a possible diagnosis, including their specialties; c) Laboratory tests results in patients with coeliac disease; and d) Validity of antiendomysium antibodies testing in comparison with histopathology of jejunal biopsies for diagnosing coeliac disease. RESULTS: The study included 431 patients (250 females, 181 males) who were suspected of having (or screened for) coeliac disease. The median of age was 15 years (range: 9 months-74 years) with mean ± SD 18.95 ± 14.1 years. Of these, 15 (3.5%) patients (10 females, 5 males) with a median age of 19 years and mean 21.4 ± 13.0 years (range: 2.5-38 years), had positive antiendomysium antibodies results with median (range) of 160 (40-320) IU/L and mean± SD 204.5 ± 160 IU/L. Of these 15 patients, 13 had positive jejunal histopathological changes indicative of coeliac disease; the remaining 2 patients had no biopsy examination. Of the 44 patients with negative antiendomysium antibodies <10 IU/L who had jejunal biopsy, 41 were negative and 3 had histopathological changes suggestive of mild coeliac disease. All the 3 patients had serum total IgA levels within the reference range. The calculated validity indicators for antiendomysium antibodies were: sensitivity 81.3%, specificity 100%, positive predictive value 100%, negative predictive value 93.2% and efficiency 94.7%. The most common mode of presentation in patients with coeliac disease was gastrointestinal features, type 1 diabetes mellitus, anemia, short stature and hypothyroidism. The seropositivity in tye 1 diabetics was 4.9%. Investigations for coeliac disease were most frequently made by endocrinologists (pediatric and adult) who accounted for 53.8% followed by gastroenterologists (pediatric and adult) with 40.6% with less consideration by the other clinicians (5.6%). CONCLUSION: The availability of highly specific and sensitive serological test and increased awareness for coeliac disease among some medical specialties has increased the number of diagnosed cases of coeliac disease. The requesting for serological test is being made mainly by endocrinologists and gastroenterologists.

Unusual surface and edge morphologies, sp2 to sp3 hybridized transformation and electronic damage after Ar+ ion irradiation of few-layer graphene surfaces.

Roughness and defects induced on few-layer graphene (FLG) irradiated by Ar+ ions at different energies were investigated using X-ray photoemission spectroscopy (XPS) and atomic force microscopy techniques. The results provide direct experimental evidence of ripple formation, sp2 to sp3 hybridized carbon transformation, electronic damage, Ar+ implantation, unusual defects and edge reconstructions in FLG, which depend on the irradiation energy. In addition, shadowing effects similar to those found in oblique-angle growth of thin films were seen. Reliable quantification of the transition from the sp2-bonding to sp3-hybridized state as a result of Ar+ ion irradiation is achieved from the deconvolution of the XPS C (1s) peak. Although the ion irradiation effect is demonstrated through the shape of the derivative of the Auger transition C KVV spectra, we show that the D parameter values obtained from these spectra which are normally used in the literature fail to account for the sp2 to sp3 hybridization transition. In contrast to what is known, it is revealed that using ion irradiation at large FLG sample tilt angles can lead to edge reconstructions. Furthermore, FLG irradiation by low energy of 0.25 keV can be a plausible way of peeling graphene layers without the need of Joule heating reported previously.