Browsing by Subject "Cadmium"

Now showing 1 - 7 of 7

Open Access
Artifcial intelligence–based approaches to evaluate and optimize phytoremediation potential of in vitro regenerated aquatic macrophyte Ceratophyllum demersum L.
(2023-01-06) Aasim, M.; Ali, Seyid Amjad; Aydin, S.; Bakhsh, A.; Sogukpinar, C.; Karatas, M.; Khawar, K.M.; Aydin, M.E.
Water bodies or aquatic ecosystem are susceptible to heavy metal accumulation and can adversely afect the environment and human health especially in underdeveloped nations. Phytoremediation techniques of water bodies using aquatic plants or macrophytes are well established and are recognized as eco-friendly world over. Phytoremediation of heavy metals and other pollutants in aquatic environments can be achieved by using Ceratophyllum demersum L. — a well-known foating macrophyte. In vitro regenerated plants of C. demersum (7.5 g/L) were exposed to 24, 72, and 120 h to 0, 0.5, 1.0, 2.0, and 4.0 mg/L of cadmium (CdSO4·8H2O) in water. Results revealed signifcantly diferent relationship in terms of Cd in water, Cd uptake by plants, bioconcentration factor (BCF), and Cd removal (%) from water. The study showed that Cd uptake by plants and BCF values increased signifcantly with exposure time. The highest BCF value (3776.50) was recorded for plant samples exposed to 2 mg/L Cd for 72 h. Application of all Cd concentrations and various exposure duration yielded Cd removal (%) between the ranges of 93.8 and 98.7%. These results were predicted through artifcial intelligence–based models, namely, random forest (RF), extreme gradient boosting (XGBoost), and multilayer perceptron (MLP). The tested models predicted the results accurately, and the attained results were further validated via three diferent performance metrics. The optimal regression coefcient (R2) for the models was recorded as 0.7970 (Cd water, mg/L), 0.9661 (Cd plants, mg/kg), 0.9797 bioconcentration factor (BCF), and 0.9996 (Cd removal, %), respectively. These achieved results suggest that in vitro regenerated C. demersum can be efcaciously used for phytoremediation of Cd-contaminated aquatic environments. Likewise, the proposed modeling of phytoremediation studies can further be employed more comprehensively in future studies aimed at data prediction and optimization.
Open Access
A bright cadmium-free, hybrid organic/quantum dot white light-emitting diode
(American Institute of Physics, 2012-12-06) Yang, X.; Divayana, Y.; Zhao, D.; Swee Leck, K.; Lu, F.; Tiam Tan, S.; Putu Abiyasa, A.; Zhao Y.; Demir, Hilmi Volkan; Wei Sun, X.
We report a bright cadmium-free, InP-based quantum dot light-emitting diode (QD-LED) with efficient green emission. A maximum brightness close to 700 cd/m2 together with a relatively low turn-on voltage of 4.5 V has been achieved. With the design of a loosely packed QD layer resulting in the direct contact of poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl) benzidine] (poly-TPD) and 2,2′,2″-(1,3,5-benzinetriyl)-tris(1- phenyl-1-H-benzimidazole) (TPBi) in the device, a ternary complementary white QD-LED consisting of blue component (poly-TPD), green component (QDs), and red component (exciplex formed at the interface between poly-TPD and TPBi) has been demonstrated. The resulting white QD-LED shows an excellent color rendering index of 95.
Open Access
Chemically specific dynamic characterization of photovoltaic and photoconductivity effects of surface nanostructures
(American Chemical Society, 2010) Ekiz, O. Ö.; Mizrak, K.; Dâna, A.
We report characterization of photovoltaic and photoconductivity effects on nanostructured surfaces through light induced changes in the X-ray photoelectron spectra (XPS). The technique combines the chemical specificity of XPS and the power of surface photovoltage spectroscopy (SPV), with the addition of the ability to characterize photoconductivity under both static and dynamic optical excitation. A theoretical model that quantitatively describes the features of the observed spectra is presented. We demonstrate the applicability of the model on a multitude of sample systems, including homo- and heterojunction solar cells, CdS nanoparticles on metallic or semiconducting substrates, and carbon nanotube films on silicon substrates.
Open Access
Electronic properties of graphene nanoribbons doped with zinc, cadmium, mercury atoms
(Elsevier B.V., 2018) Ömeroğlu, O.; Kutlu, E.; Narin, P.; Lisesivdin, S. B.; Özbay, Ekmel
The effect of substitutional impurities as Zinc (Zn), Cadmium (Cd) and Mercury (Hg) on electronic properties of graphene nanoribbons (GNRs) was investigated by using Density Functional Theory (DFT). A substantial change in the electronic properties of GNR structures was observed while changing the position of dopant atom from the edge to the center of armchair graphene nanoribbons (AGNRs) and zigzag graphene nanoribbons (ZGNRs). The calculations are shown that the electronic band gap of GNRs can be controlled depending on the position of dopant atoms. The calculated electronic band structures for both AGNRs and ZGNRs show spin-dependent metallic or semiconductor behavior according to the position of dopant atoms. From the Density of States (DOS) information, quasi-zero-dimensional (Q0D) and quasi-one-dimensional (Q1D) type behaviors are observed. It is shown that because the doped ZGNRs had the lowest total energies, ZGNRs are energetically more stable than AGNRs.
Open Access
Highly fluorescent pyrene-functional polystyrene copolymer nanofibers for enhanced sensing performance of TNT
(American Chemical Society, 2015) Senthamizhan, A.; Celebioglu A.; Bayir, S.; Gorur, M.; Doganci, E.; Yilmaz, F.; Uyar, Tamer
A pyrene-functional polystyrene copolymer was prepared via 1,3-dipolar cycloaddition reaction (Sharpless-type click recation) between azide-functional styrene copolymer and 1-ethynylpyrene. Subsequently, nanofibers of pyrene-functional polystyrene copolymer were obtained by using electrospinning technique. The nanofibers thus obtained, found to preserve their parent fluorescence nature, confirmed the avoidance of aggregation during fiber formation. The trace detection of trinitrotoluene (TNT) in water with a detection limit of 5 nM was demonstrated, which is much lower than the maximum allowable limit set by the U.S. Environmental Protection Agency. Interestingly, the sensing performance was found to be selective toward TNT in water, even in the presence of higher concentrations of toxic metal pollutants such as Cd2+, Co2+, Cu2+, and Hg2+. The enhanced sensing performance was found to be due to the enlarged contact area and intrinsic nanoporous fiber morphology. Effortlessly, the visual colorimetric sensing performance can be seen by naked eye with a color change in a response time of few seconds. Furthermore, vapor-phase detection of TNT was studied, and the results are discussed herein. In terms of practical application, electrospun nanofibrous web of pyrene-functional polystyrene copolymer has various salient features including flexibility, reproducibility, and ease of use, and visual outputs increase their value and add to their advantage.
Open Access
Synthesis of stable mesostructured coupled semiconductor thin films: meso-CdS-TiO2 and meso-CdSe-TiO2
(2010) Okur, H. İ.; Türker, Y.; Dag, Ö.
Cd(II) ions can be incorporated into the channels of mesostructured titania films, using the evaporation-induced self-assembly (EISA) approach, up to a record high Cd/Ti mole ratio of 25%. The film samples were obtained by spin or dip coating from a mixture of 1-butanol, [Cd(H20)4] (N03)2, HNO3, and Ti(OC4H 9)4 and then aging the samples under 50% humidity at 30 0C (denoted as meso-xCd(II)-y TiO2). The nitrate ions, from nitric acid and cadmium nitrate, play important roles in the assembly process by coordinating as bidentate and bridged ligands to Cd(II) and Ti(IV) sites, respectively, in the mesostructured titania films. The film samples can be reacted under a H 2S (or H2Se) gas atmosphere to produce CdS (or CdSe) on the channel surface and/or pore walls. However, the presence of such a large number of nitrate ions in the film samples also yields an extensive amount of nitric acid upon H2S (or H2Se) reaction, where the nanoparticles are not stable (they undergo decomposition back to metal ion and H2S or H2Se gas). However, this problem can be overcome by further aging the samples at 130 °C for a few hours before H2S (or H2Se) reaction. This step removes about 90% of the nitrate ions, eliminates the nitric acid production step, and stabilizes the CdS nanoparticles on the surface and/or walls of the pores of the coupled semiconductor films, denoted as meso-xCdS-yTiO2. However, the H2Se reaction, additionally, needs to be carried at lower H2Se pressures in an N2 atmosphere to produce stable CdSe nanoparticles on the surface and/or walls of the pores of the films, denoted as meso-xCdSe-.yTiO2. Otherwise, an excessive number of Se8 particles form in the film samples.
Open Access
Temperature-dependent optoelectronic properties of quasi-2D colloidal cadmium selenide nanoplatelets
(Royal Society of Chemistry, 2017) Bose, S.; Shendre, S.; Song, Z.; Sharma, V. K.; Zhang, D. H.; Dang C.; Fan, W.; Demir, Hilmi Volkan
Colloidal cadmium selenide (CdSe) nanoplatelets (NPLs) are a recently developed class of efficient luminescent nanomaterials suitable for optoelectronic device applications. A change in temperature greatly affects their electronic bandstructure and luminescence properties. It is important to understand how and why the characteristics of NPLs are influenced, particularly at elevated temperatures, where both reversible and irreversible quenching processes come into the picture. Here we present a study of the effect of elevated temperatures on the characteristics of colloidal CdSe NPLs. We used an effective-mass envelope function theory based 8-band k·p model and density-matrix theory considering exciton-phonon interaction. We observed the photoluminescence (PL) spectra at various temperatures for their photon emission energy, PL linewidth and intensity by considering the exciton-phonon interaction with both acoustic and optical phonons using Bose-Einstein statistical factors. With a rise in temperature we observed a fall in the transition energy (emission redshift), matrix element, Fermi factor and quasi Fermi separation, with a reduction in intraband state gaps and increased interband coupling. Also, there was a fall in the PL intensity, along with spectral broadening due to an intraband scattering effect. The predicted transition energy values and simulated PL spectra at varying temperatures exhibit appreciable consistency with the experimental results. Our findings have important implications for the application of NPLs in optoelectronic devices, such as NPL lasers and LEDs, operating much above room temperature.