Soluble Cadmium Research Articles

An investigation on the structural and optical properties of mercaptosuccinic acid capped cadmium telluride quantum dots

In this work, a sonication induced modified wet chemical approach is adopted to synthesize highly luminescent and water soluble cadmium telluride (CdTe) quantum dots (QDs). The morphology, size, crystal structural, and optical properties of CdTe QDs are investigated for different refluxing time (1–4 h). The refluxing time-dependent optical constants viz. band gap energy and Urbach energy of the QDs are estimated from UV–Visible absorption spectra. The optical band gap energy decreased from ~ 2.12 to 1.92 eV and the Urbach energy increased from ~ 361 to 487 meV, with the increase in refluxing time. CdTe QDs are found to be uniform in size. The average size of the QDs estimated from the High Resolution Transmission Electron Microscope image analysis is about 5.8 and 8.2 nm for refluxing times 1 and 4 h, respectively. The growth mechanism of the QDs as a function of refluxing time has also been discussed. The fluorescence spectra of the QDs, revealed emission peaks having wavelength from ~ 534 to 585 nm, under the excitation wavelength of 320 nm. The fluorescence emission peaks showed a bathochromic shift with increasing refluxing time. CdTe QDs also exhibit excitation-dependent fluorescence behaviour. Two crystalline phases of the CdTe QDs, namely hexagonal and cubic are confirmed from the High Resolution Transmission Electron Microscope images and Selected Area Electron Diffraction patterns analysis. The phase transformation from hexagonal to cubic is successfully achieved by tuning the refluxing time from 1 to 4 h.

Binding of Water‐Soluble CdSe Quantum Dots with Human Serum Albumin: Further Studies into their Effects on Dietary Polyphenol Binding and Sensing of Antibiotic Lomefloxacin

AbstractSynthesis of surface modified quantum dots (QDs) having potential biological activities are great important in biomedicinal chemistry. Here, we have synthesized mercapto propanoic acid (MPA) and thiolactic acid (TLA) coated water soluble cadmium selenide (CdSe) QDs having biological activity. Dispersion of QDs into a biological fluid can form protein corona. Hence, the binding of CdSe QDs with the carrier protein, human serum albumin (HSA) have been executed using spectroscopic methods. The binding affinity order of CdSe QDs‐HSA complexes were found in the order of 105 M−1 at 298 K. CdSe QDs are also affects the binding affinities of dietary polyphenols (naringin: NG and naringenin: NRG) towards HSA. The synthesized CdSe QDs was employed to sensing of antibiotic lomefloxacin by fluorescence quenching mechanism. The detection limit was found 0.70‐1.83 μg mL−1. The CdSe QDs also demonstrate the detection of lomefloxacin under uv light based on color change of the solutions.

Comparative Study of the Photocatalytic Hydrogen Evolution over Cd1-xMnxS and CdS-β-Mn3O4-MnOOH Photocatalysts under Visible Light.

A series of solid solutions of cadmium and manganese sulfides, Cd1−xMnxS (x = 0–0.35), and composite photocatalysts, CdS-β-Mn3O4-MnOOH, were synthesized by precipitation with sodium sulfide from soluble cadmium and manganese salts with further hydrothermal treatment at 120 °C. The obtained photocatalysts were studied by the X-ray diffraction method (XRD), UV-vis diffuse reflectance spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N2 low temperature adsorption. The photocatalysts were tested in hydrogen production using a Na2S/Na2SO3 aqueous solution under visible light (λ = 450 nm). It was shown for the first time that both kinds of photocatalysts possess high activity in hydrogen evolution under visible light. The solid solution Cd0.65Mn0.35S has an enhanced photocatalytic activity due to its valence and conduction band position tuning, whereas the CdS-β-Mn3O4-MnOOH (40–60 at% Mn) samples were active due to ternary heterojunction formation. Further, the composite CdS-β-Mn3O4-MnOOH photocatalyst had much higher stability in comparison to the Cd0.65Mn0.35S solid solution. The highest activity was 600 mmol g−1 h−1, and apparent quantum efficiency of 2.9% (λ = 450 nm) was possessed by the sample of CdS-β-Mn3O4-MnOOH (40 at% Mn).

Mitigations of Syzygium cummini Fruit Extract on CdCl2 Induced Histopathological Changes in Laboratory Mouse Epididymids

The aim of present project was to determine the harmful effects of CdCl2 on epididymis of adult mice (Mus musculus). Histopathological changes in epididymis of mice treated with 50ppm of CdCl2 were studied in this research work. Moreover, remedial effects of Jambul fruit extract were also studied. Study was conducted on 30 male albino mice divided into three groups (n=10) as follows; {(a) Control (C); (untreated); (b) CdCl2 {50ppm CdCl2 as drinking water (15 days) and for natural recovery CdCl2 free water (7days); (c) CdCl2+Jambul extract (CdCl2+J) 50ppm CdCl2 in drinking water for 15 days followed by 0.2mLJambul extract (7days)}. All animals were dissected on day 21st for surgical removal of epididymis. The results revealed that mean tubular cross-sectional area of caput, corpus and cauda epididymis was significantly increased in CdCl2 treated group compared to Control and Cd+J treated groups. A single peritoneal administration of soluble cadmium causes an acute hemorrhagic reaction in proximal end of caput epididymis. The lining epithelium of the proximal caput was atrophied, tubules were dilated and spermatozoa within the lumen were disintegrated.

Effect of Calcium Magnesium Phosphate on Remediation Paddy Soil Contaminated with Cadmium Using Lime and Sepiolite

The combined application of amendments, such as hydroxyhistidine and zeolite, can effectively reduce both the bioavailability of heavy metals in soil and the bioaccumulation of heavy metals by rice, thus improving the safety of agricultural products. In this work, the effect of calcium magnesium phosphorus fertilizer on the content of available Cd in paddy soil and Cd accumulation in various parts of rice by lime combined with sepiolite was studied using a plot experiment. The results show that calcium magnesium phosphorus fertilizer can significantly promote the remediation effect of lime combined with sepiolite. Compared with the treatment with lime combined with sepiolite, the application of calcium magnesium phosphorus fertilizer significantly decreases the available Cd content in the soil and the Cd accumulation in the brown rice. With calcium magnesium phosphorus fertilizer of 2250 kg·hm-2, Cd2+ in soil formed less soluble cadmium phosphate, the content of extractable, reducible and oxidizable Cd was reduced, and the percentage of available Cd content in the soil was significantly (P<0.05) reduced by 46.97%. Meanwhile, the Cd content in brown rice was decreased to 0.04 mg·kg-1, which is far lower than the level required by the National Standard for Food Safety (GB 2762-2017) (0.2 mg·kg-1). In addition, the production of brown rice was increased by 28.34%. Correlation analysis shows that the Cd content in rice roots, straw, and brown rice was positively correlated with the available Cd content in soil (P<0.01), and between the Cd content in brown rice and in roots and straw (P<0.01). In general, the results indicate that the available Cd content in soil was the key factor affecting the Cd content in brown rice. The application of calcium magnesium phosphorus fertilizer can improve the amendment of lime combined with sepiolite for available Cd in soil and reduce the Cd absorption of rice roots and straw so that the Cd content in brown rice is reduced. The results show that the application of calcium magnesium phosphorus fertilizer enhances the effect of reducing the Cd content in brown rice by lime combined with sepiolite. Finally, it can both meet the safety requirements of brown rice quality and increase the yield of brown rice in Cd-contaminated paddy soil.

Background Variation and Threshold Values for Cadmium Concentration in Terra Rossa Soil from Dalmatia, Croatia

The objectives of this study were to (i) establish the background variation and determine a threshold values for aqua regia soluble cadmium (Cd) in Terra Rossa soil at the local scale (Dalmatia, Croatia), (ii) check for possible soil Cd enrichment comparing its concentration at two different depths, and (iii) compare the threshold values for Cd calculated applying different statistical techniques with soil guideline values (SGV) as defined in Croatia and other national systems in Europe. The four statistical methods (the mean ± 2 standard deviations [mean ± 2SD], the median ± 2 median absolute deviations [median ± 2MAD], the (upper) Tukey inner fence (TIF), and the percentile-based approach) were used to establish the threshold values for Cd and identify samples with high Cd concentrations deviating from the background variation in a studied dataset. Overall, 74 samples from the A horizon of Terra Rossa soil were analyzed for aqua regia soluble Cd concentration (CdA); major soil properties—pH, CaCO3, soil organic carbon (SOC) content, P2O5, K2O, and particle-size distribution—were also determined in these samples. The underlying cambic B horizon was analyzed only for Cd concentration (CdB) The median CdA and CdB values of 1.84 and 1.70 mg kg–1, respectively as well as the maximum value of 8.53 mg kg–1 in the A horizon and 7.56 mg kg–1 in the B horizon obtained in this study attested to anomalously high Cd concentrations. The median CdA/CdB ratio was close to unity (1.07) indicating very low Cd enrichment in the A horizon. The [median ± 2MAD] method achieved the lowest threshold Cd value of 4.68 mg kg–1 and, consequently, a maximum number of outliers; it was followed by the classical [mean ± 2SD] method (5.01 mg kg–1), the Q95th percentile (5.29 mg kg–1), the Q98th percentile (5.64 mg kg–1), and the TIF method with the highest threshold value of 6.93 mg kg–1. All specified threshold values for Cd concentration repeatedly exceeded the maximum admissible concentrations (MACv) for agricultural land as defined in soil guideline values developed in Croatia and in several countries of the European Union. These findings indicate that more attention should be paid to the unusually high Cd concentrations in Terra Rossa soils originating from the natural sources; a more detailed geochemical survey of these soils should be performed in the future.

Water soluble cadmium selenide quantum dots for ultrasensitive detection of organic, inorganic and elemental mercury in biological fluids and live cells.

Mercury exists in organic, inorganic, and elemental forms; all of them are highly toxic. A sensor which could detect all forms of mercury below the permissible level in environmental and biological samples would be advantageous. A facile method to synthesize N-acetyl cysteine capped cadmium selenide quantum dots (CdSe QDs) with an emission at 554 nm was reported. CdSe QDs showed high sensitivity and selectivity toward Hg in aqueous media as well as biological fluids like simulated cerebrospinal fluid, saliva, and urine, and also in natural fluids like juices of tomato, sugarcane, and lime. The sensing mechanism is attributed to the interactions between Hg and CdSe QDs inducing fluorescence quenching. The limit of detection is 1.62, 0.75, and 1.27 ppb for organic, inorganic and elemental mercury, respectively, which is below WHO guidelines. The suitability of the sensor for estimating Hg in biological fluids was demonstrated by recovery experiments. Besides sensing, a two color cell imaging method was developed employing CdSe QDs and acridine orange. Using this method, the uptake of Hg in living cells was demonstrated.

Trace metal availability in soil horizons amended with various urban waste composts during 17 years – Monitoring and modelling

Recycling organic residues in agrosystems presents several benefits but faces the question of contaminants, among them a few trace metals which eventually accumulate in soils following regular applications of organic waste products (OWP) and represent an ecological risk. The increase of total trace metal contents in amended topsoils can be predicted by a mass balance approach, but the evolution of their available fractions is a more intricate issue. We aimed at modelling this evolution by using the dataset of a long-term field experiment of OWP applications (manure and three urban waste composts). Two operationally-defined fractions of 6 trace metals have been quantified in the OWP and amended topsoils between 2002 and 2015: the soluble and potentially available metals, extracted in 0.01 M CaCl2 and 0.05 M EDTA solutions, respectively.The potentially available metals have progressively increased in amended topsoils, at rates depending on elements and types of OWP. For Zn, these increases corresponded in average to inputs of potentially available Zn from OWP. But the soil stocks of potentially available Cu increased faster than from the inputs of EDTA-extractable Cu, showing linear regression slopes between 1.4 and 2.5, depending on OWP type. The influence of OWP has been provisionally interpreted in the light of their efficiency to increase soil organic matter and their inputs of reactive oxides.Soluble copper has increased with repeated amendments. But soluble cadmium, nickel and zinc have generally decreased, as they are influenced by changing soil variables such as pH and organic matter. Statistic models were used to unravel the relationships between soluble and EDTA-extractable metals and other soil variables. For Cu, the most satisfactory models just relate soluble and potentially available Cu. Developing such models could contribute to predict the long-term effects of a precise scenario of agricultural OWP recycling upon available trace metals in soils.

Optimization of flocculation conditions for soluble cadmium removal using the composite flocculant of green anion polyacrylamide and PAC by response surface methodology

In this work, we describe a flocculation performance evaluation of a novel anionic polyacrylamide (APAM) synthesized using low dose γ-ray initiation. The APAM structure and morphology were characterized using Fourier transform-infrared spectroscopy (FTIR), High performance liquid chromatography (HPLC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) techniques. In comparison to commercially purchased APAM (Mw = 1.0 × 107), γ-ray initiation was demonstrated to be a more effective method to increase molecular weight, decrease the residual acrylamide monomer, and improve thermal stability. Flocculant performance was evaluated by assessing their ability to remove Cd(II) from water. We utilized the Plackett-Burman (PB), steepest ascent, and response surface methodology (RSM) experimental design to identify the optimal flocculating conditions for the removal of soluble Cd(II). Under optimal conditions [26.84 mg L−1 CaO, 71.28 mg L−1 polyaluminium chloride (PAC) and 2.87 mg L−1 APAM], the maximum percent removal of Cd(II) was observed to reach 93.65%. A potential flocculation mechanism for the Cd(II) removal from water was further studied by evaluating the colloid Zeta potential. Results from these studies demonstrated that PAC had a greater capability to change the Zeta potential of collide under alkaline conditions, while APAM played a critical role in the bridging, enmeshment, and sweeping effect. The composite of two types of predominance makes considerable sense in regards to enhancing flocculating efficiency, decreasing secondary pollution, and reducing flocculant cost.

Effects of Pseudomonas chenduensis and biochar on cadmium availability and microbial community in the paddy soil

The cadmium contamination in the paddy soil results in serious environmental pollutions. In situ soil remediation based on the applications of additives such as functional microorganisms and biochars has gradually attained more attentions. However, how these exogenous additives affect the local microbial communities is less discussed. In this study, a heavy metal resistant bacterium (Pseudomonas chenduensis, strain MBR) and biochar derived from oil palm fibers were separately added into the simulated Cd-contaminated paddy soil to investigate the roles of these additives in the soil remediation and regulating local microbial community. The results showed that compared with control, the addition of the strain MBR and biochar reduced the exchangeable/acid soluble cadmium fraction by 30% and 18%, respectively. Moreover, higher microbial diversity, more deterministic effects and less variation in microbial community were observed in the treatments supplemented with the strain MBR and biochar, and the increase of the deterministic effects on microbial interactions was demonstrated by network analysis further. Additionally, the abundance of the strain MBR in the paddy soil decreased as time passed, which maximally decreased the disturbance for the local micro-ecological niche and ensured ecological security. These results showed that two additives supplementation, in particular Pseudomonas chenduensis, can significantly decrease cadmium availability, contributing to the reduction of the disturbance on soil microbial community and maintaining microbial stability under cadmium pressure. It highlights a new criterion referred to micro-ecology for the evaluation of the roles of additives in local soil remediation.

Phytase-mediated mineral solubilization from cereals under in vitro gastric conditions.

Enzymatic dephosphorylation of phytic acid (inositol hexakisphosphate) in cereals may improve mineral bioavailability in humans. This study quantified enzymatic dephosphorylation of phytic acid by measuring inositol tri- to hexakisphosphate (InsP3-6) degradation and iron and zinc release during microbial phytase action on wheat bran, rice bran and sorghum under simulated gastric conditions. InsP3-6 was depleted within 15-30 min of incubation using an Aspergillus niger phytase or Escherichia coli phytase under simulated gastric conditions, with the two enzymes dephosphorylating cereal phytic acid at similar rates and to similar extents. Microbial phytase-catalyzed phytate dephosphorylation was accompanied by increased iron and zinc release from the cereal substrates. However, for wheat bran at pH 5, the endogenous wheat phytase activity produced mineral release equal to or better than that of the microbial phytases. No increases in soluble cadmium, lead or arsenic were observed with microbial phytase-catalyzed phytate dephosphorylation. Microbial phytase treatment abated phytate chelation hence enhanced the release of iron and zinc from phytate-rich cereals under simulated gastric conditions. The data infer that acid-stable microbial phytases can help improve iron bioavailability from phytate-rich cereal substrates via post-ingestion activity. © 2015 Society of Chemical Industry.

An impedimetric aptasensor based on water soluble cadmium telluride (CdTe) quantum dots (QDs) for detection of ibuprofen

An impedimetric aptasensor is reported here for the ultrasensitive detection of ibuprofen (IBP) using water soluble cadmium telluride (CdTe) quantum dots (QDs) as the efficient electrochemical platform. The CdTe QD layer was used as a quite suitable interface for the subsequent conjugation of the aptamer (Apt). CdTe QDs owing to their large surface area, caused the increase in the amount of Apt absorbed on the modified electrode which resulted in enhanced signal response. Also, their ion centers may have had a major role on amplifying the signal. In this method, the IBP specific Apt is immobilized onto the glassy carbon electrode (GCE) and through the specific binding of the IBP and its Apt, the IBP/Apt complex is formed. More importantly, the developed strategy shows highly sensitive responses to IBP, responses more sensitive than those of previously reported methods. Under optimal conditions, IBP was detected by electrochemical impedance spectroscopy (EIS) quantitatively. Calibration curve for IBP concentration was linear up to 20μM and the detection limit was as low as 16pM. The developed aptasensor was successfully used to detect IBP in real samples such as spiked human serum and pharmaceutical formulations. The use of CdTe QDs as a unique platform and the elimination of antibodies or enzymes for the amplified detection of the IBP, are the advantages of the developed aptasensor. Our work will shed light on new diagnostic applications of aptasensors and is quite promising as an alternative approach for various target assays.

Cadmium sulfide quantum dots modified with the human transferrin protein siderophiline for targeted imaging of breast cancer cells

We describe the fairly easy preparation of thiol stabilized water soluble cadmium sulfide quantum dots and the modification of their surface with the human transferrin protein siderophiline. The particles are shown to enable targeted imaging of human breast adenocarcinoma cell (type MCF7). The fluorescence quantum yield of the modified QDs is ~0.74. The particles have an average diameter of 8.1 ± 0.1 nm as determined in solution by dynamic light scattering. The cancer cells were imaged by fluorescence microscopy of the QDs which display strong green fluorescenece under 350 nm excitation. A cytotoxicity assay showed 66 and 78 % cell viabilities, respectively, after 24 h of incubation with the QDs and modified QDs.

Cadmium removal from aqueous solution by brown seaweed, Sargassum angustifolium

Four kinds of indigenous seaweed were employed for assessing their soluble cadmium biosorption performance. Sargassum angustifolium revealed the greatest capacity in the range of equilibrium cadmium concentration lower than 0.5mmol l−1. It was further examined by optimization, equilibrium, kinetic and thermodynamic studies. It was found that1 g l−1 biosorbent at initial pH of 6 and 38 °C revealed the highest Cd2+ uptake. Kinetic studies revealed that the Cd2+ biosorption included a two-stage mechanism with an initial rapid stage during the first 30 min where ion exchange was the dominant mechanism. The process gradually reached equilibrium after 40-50 min of contact where the metal adsorption occurred too low due to the intraparticle diffusion. However, it was not the sole rate-limiting step. The pseudo-second order kinetic model, unlike the pseudo-first order, excellently described the experimental data in the whole range of contact time. The Langmuir isotherm model was more successful in describing the equilibrium data than the Freundlich and D-R models. Using this isotherm model, a relationship was proposed to predict the dose of biosorbent needed for removing specific initial cadmium concentration from aqueous solution or to meet a desire equilibrium cadmium concentration. The spontaneity and endothermicity as well as increasing randomness at the solid/solution interface during the biosorption were revealed by means of the thermodynamic studies.

Cadmium Mobility with Persulfate Chemical Oxidation: Effects of Soil Properties and Activation Methods

The potential effects of persulfate in situ chemical oxidation (ISCO) on metals and on long-term groundwater quality is an important issue because of the potential risks to public health and to the environment. Application of persulfate and its activation amendments to soil and groundwater can lead to complex interactions, altering geochemical conditions and processes, thereby affecting metals mobility. The mobility of cadmium sorbed on three soils varying in physical–chemical properties was investigated after chemical oxidation by unactivated and activated persulfate using mixed batch reactors. Each of the three soils was treated with two different concentrations of persulfate, 2.1 mM and 42 mM, and different activation amendments that included Fe(II), Fe(II)-EDTA, and high pH. Resulting solutions were analyzed for soluble cadmium after 48 h and 6 months. Results show that cadmium mobilization varied with the persulfate activation method and the soil type. The maximum amount of cadmium was mobilized with Fe(II)-EDTA activation and the least amount of cadmium was mobilized with high pH activation. In addition to Fe(II)-EDTA activation, cadmium was more mobile in soil with low soil organic carbon and low mineral content. Enhanced cadmium desorption at low pH and formation of soluble cadmium-EDTA complexes are the main mechanisms of cadmium mobilization from soils with persulfate ISCO.

Synergetic effects and flocculation behavior of anionic polyacrylamide and extracellular polymeric substrates extracted from Klebsiella sp. J1 on improving soluble cadmium removal

The performance and flocs properties in removing soluble cadmium of the dual flocculant APAM–MFX (anionic polyacrylamide APAM used in combination with extracellular polymeric substrates extracted from Klebsiella sp. J1 MFX) were studied compared with the performance of using bioflocculant alone. In addition, adsorption isotherms and kinetic process for Cd(II) adsorption onto APAM–MFX were investigated. APAM–MFX synergistically improved the Cd(II) removal percentage by 82.68%. Characteristic flocs formed by APAM–MFX indicated the synergetic effects resulted from additional bridging bonds between APAM and MFX. Adsorption process was best described by the Freundlich isotherm and pseudo-second order kinetic model. The mean free energy E (8.39–8.57kJmol−1) and activation energy Ea (45.09kJmol−1) were determined. Based on the results, the main mechanism of Cd(II) removal by APAM–MFX could be chemical ion exchange, and the liquid-film diffusion step was the rate-limiting step.

Investigation of trypsin–CdSe quantum dot interactions via spectroscopic methods and effects on enzymatic activity

The paper presents the interactions between trypsin and water soluble cadmium selenide (CdSe) quantum dots investigated by spectrophotometric methods. CdSe quantum dots have strong ability to quench the intrinsic fluorescence of trypsin by a static quenching mechanism. The quenching has been studied at three different temperatures where the results revealed that electrostatic interactions exist between CdSe quantum dots and trypsin and are responsible to stabilize the complex. The Scatchard plot from quenching revealed 1 binding site for quantum dots by trypsin, the same has been confirmed by making isothermal titrations of quantum dots against trypsin. The distance between donor and acceptor for trypsin–CdSe quantum dot complexes is calculated to be 2.8nm by energy transfer mechanisms. The intrinsic fluorescence of CdSe quantum dots has also been enhanced by the trypsin, and is linear for concentration of trypsin ranging 1–80μl. All the observations evidence the formation of trypsin–CdSe quantum dot conjugates, where trypsin retains the enzymatic activity which in turn is temperature and pH dependent.

Dynamics of rhizosphere properties and antioxidative responses in wheat (Triticum aestivum L.) under cadmium stress

In this study, we performed a rhizobox experiment to examine the dynamic changes in the rhizosphere properties and antioxidant enzyme responses of Triticum aestivum L. under three levels of cadmium stress. A set of micro-techniques (i.e., Rhizobox and Rhizon SMS) were applied for the dynamically non-destructive collection of the rhizosphere soil solution to enable the observation at a high temporal resolution. The dynamics of soluble cadmium and dissolved organic carbon (DOC) in the rhizosphere soil solutions of the Triticum aestivum L. were characterised by the sequence week 0 after sowing (WAS0)<3 weeks after sowing (WAS3)<10 weeks after sowing (WAS10), whereas the soil solution pH was found to follow an opposite distribution pattern. Systematically, both superoxide dismutase (SOD) and catalase (CAT) activities in the leaves of the Triticum aestivum L. increased concomitantly with increasing cadmium levels (p>0.05) and growth duration (p<0.05), whilst ascorbate peroxidase (APX) activity was induced to an elevated level at moderate cadmium stress with a decrease at high cadmium stress (p>0.05). These results suggested the enhancement of DOC production and the greater antioxidant enzyme activities were two important protective mechanisms of Triticum aestivum L. under cadmium stress, whereas rhizosphere acidification might be an important mechanism for the mobilisation of soil cadmium. The results also revealed that plant–soil interactions strongly influence the soil solution chemistry in the rhizosphere of Triticum aestivum L., that, in turn, can stimulate chemical and biochemical responses in the plants. In most cases, these responses to cadmium stress were sensitive and might allow us to develop strategies for reducing the risks of the cadmium contamination to crop production.

Solution-processed CdS transistors with high electron mobility

Solution-processed CdS field effect transistors (FETs) and solar cells are demonstrated via spin-coating and thermal annealing of soluble cadmium thiolate compounds. The synthesis is carried out in one simple step using cadmium oxide and tertiary alkane thiols. The cadmium thiolates are soluble in organic solvents such as chloroform and may be spin-coated, like organic semiconductors, to form thin films. The cadmium thiolate films decompose rapidly at 300 °C to yield semiconducting cadmium sulfide films. FETs are easily fabricated using these films and exhibit electron mobilities of up to 61 cm2 V−1 s−1, which compare favourably to FETs prepared from other solution-processed materials such as organic semiconductors, inorganic nanoparticles or chalcogenide films. Initial attempts to prepare hybrid bilayer solar cells were successfully realized by spin-coating a p-type semiconducting polymer layer on top of the n-type CdS film. These devices show significant photocurrent response from both the CdS and polymer layers, indicating that the CdS films are able to participate in photo-induced electron transfer from the polymer to the CdS layer as well as photo-induced hole transfer from CdS to the polymer layer.

In situ growth of well-dispersed CdS nanocrystals in semiconducting polymers

A straight synthetic route to fabricate hybrid nanocomposite films of well-dispersed CdS nanocrystals (NCs) in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) is reported. A soluble cadmium complex [Cd(SBz)2]2·MI, obtained by incorporating a Lewis base (1-methylimidazole, MI) on the cadmium bis(benzyl)thiol, is used as starting reagent in an in situ thermolytic process. CdS NCs with spherical shape nucleate and grow well below 200°C in a relatively short time (30 min). Photoluminescence spectroscopy measurements performed on CdS/MEH-PPV nanocomposites show that CdS photoluminescence peaks are totally quenched inside MEH-PPV, if compared to CdS/PMMA nanocomposites, as expected due to overlapping of the polymer absorption and CdS emission spectra. The CdS NCs are well-dispersed in size and homogeneously distributed within MEH-PPV matrix as proved by transmission electron microscopy. Nanocomposites with different precursor/polymer weight ratios were prepared in the range from 1:4 to 4:1. Highly dense materials, without NCs clustering, were obtained for a weight/weight ratio of 2:3 between precursor and polymer, making these nanocomposites particularly suitable for optoelectronic and solar energy conversion applications.