Sulfhydryl Functionalized Magnetic Chitosan as an Efficient Adsorbent for High-Performance Removal of Cd(II) from Water: Adsorption Isotherms, Kinetic, and Reusability Studies

In this study, dimercaptosuccinic acid-functionalized magnetic chitosan (Fe3O4@CS@DMSA) was synthesized via in situ coprecipitation process and amidation reaction, aiming to eliminate cadmium (Cd(II)) ions from an aqueous environment. The structure, morphology, and particle size of the Fe3O4@CS@DMSA adsorbent were investigated using FTIR, TEM, EDX, TGA, zeta potential, and XRD techniques, and the obtained results approved the successful synthesis of the Fe3O4@CS@DMSA nanocomposite. The influence of external adsorption conditions such as pH solution, adsorbent mass, initial Cd(II) concentration, temperature, and contact time on the adsorption process was successfully achieved. Accordingly, pH: 7.6, contact time: 210 min, and adsorbent mass:10 mg were found to be the optimal conditions for best removal. The adsorption was analyzed using nonlinear isotherm and kinetic models. The outcomes revealed that the adsorption process obeyed the Langmuir and the pseudo-first-order models. The maximum adsorption capacity of Fe3O4@CS@DMSA toward Cd(II) ion was 314.12 mg/g. The adsorption mechanism of Cd(II) on Fe3O4@CS@DMSA nanocomposite is the electrostatic interaction. The reusability test of Fe3O4@CS@DMSA nanocomposite exhibited that the adsorption efficiency was 72% after the 5th cycle. Finally, this research indicates that the Fe3O4@CS@DMSA exhibited excellent characteristics such as high adsorption capacity, effective adsorption-desorption results, and easy magnetic separation and thus could be an effective adsorbent for removing Cd(II) ions from aqueous solutions.

Synthesis, structural characterization, computational studies and stability evaluations of metal ions and ZnONPs complexes with dimercaptosuccinic acid

Meso-2,3-dimercaptosuccinic acid (DMSA) is one of the efficient chelating reagents for treating the toxicity of several heavy metals. Currently, nanomaterial have been applied to various parts including zinc Oxide nanoparticles (ZnONPs). ZnONPs have several properties and are used as many applications. An increasing the amount of ZnONPs in commercial products causes risks related to free radicals or reactive oxygen species (ROS) in the body, leading to oxidative stress and eventually to the cancer process. In the present work, we mainly focused on the study of DMSA complexes in term of metal ions and nanoparticles. The synthesis of DMSA-ZnONPs by the co-precipitation method were determined, followed by Scanning Electron Microscope, Fourier Transform Infrared Spectroscopy and UV-Vis spectrophotometry confirming successful synthesis process. The stability study of the DMSA complexes with metal ions and ZnONPs were determined and evaluated the stability constant (K), with the Benesi- Hildebrand equation. All complexes with DMSA were formed at a 1:2 ratio by the dithiol group and the carboxyl group with different stability constants. Therefore, these results can help of an understanding of the interaction and its behavior between DMSA with heavy metal ion and ZnONPs. In addition, the stable structure of DMSA and metal ion complexes were predicted using the B3LYP and the 6-31G (d,p) basis set which the most stable structure of meso-DMSA was 2R,3S conformation and the metal ions and DMSA complexes was complex 2a with the binding energy of -1553.46 kcal mol^-1.

One-pot synthesis of the stable CdZnTeS quantum dots for the rapid and sensitive detection of copper-activated enzyme

Galactose oxidase is a copper-activated enzyme and have a vital role in metabolism of galactose. Much of the work is focused on determining the amount of galactose in the blood rather than measuring the amount of galactose oxidase to urge the galactosemia patients to restrict milk intake. Here, a simple and effective method was developed for Cu²⁺ and copper-activated enzyme detection based on homogenous alloyed CdZnTeS quantum dots (QDs). Meso- 2,3-dimercaptosuccinic acid (DMSA) was used as the reducing agent for preparing QDs and the highest quantum yield of CdZnTeS QDs was 69.4%. In addition, the as-prepared CdZnTeS QDs show superior fluorescence properties, such as good photo-/chemical stability. The DMSA was the surface ligand of the QDs, containing abundant -SH and -COOH, thus the surface ligands have a high affinity with Cu²⁺. Therefore, this developed probe can be applied for Cu²⁺ and galactose oxidase detection and shows a good sensitivity in the buffer. Then, this probe was successfully used for Cu²⁺ and galactose oxidase detection in real samples with the satisfactory results. The proposed fluorescence quenching strategy gives a new and simple insight for enzyme assay without the enzyme-catalyzed reaction.

One-Step Synthesis of Rox-DNA Functionalized CdZnTeS Quantum Dots for the Visual Detection of Hydrogen Peroxide and Blood Glucose

As the blood glucose concentration is an important clinical parameter of diabetes, the rapid and effective detection of blood glucose is very significant for monitoring and managing diabetes. Here, a facile method to prepare Rox-DNA functionalized CdZnTeS quantum dots (QDs) was developed. The Rox-DNA functionalized CdZnTeS QDs were prepared by a one-pot hydrothermal method through phosphorothioate DNA bound to QDs, which were employed as a ratiometric fluorescent probe for the rapid and sensitive detection of H₂O₂ and glucose. Compared with the traditional multistep construction of ratiometric fluorescent probes, this presented approach is simpler and more effective without chemical modification and complicated separation. The CdZnTeS QDs with green fluorescence is specifically sensitive to H₂O₂, while the red fluorescence of Rox is invariable. H₂O₂ is the product from the oxidation of glucose catalyzed by glucose oxidase (GOx). Therefore, a facile method to detect H₂O₂ and glucose with a detection limit of 0.075 μM for H₂O₂ and 0.042 μM for glucose was developed. In addition, this proposed probe has been employed for the detection of glucose in human serum with a satisfactory result. Moreover, this probe has been used for visual detection, and the health and diabetics can be distinguished by the naked eye. Meanwhile, this nanoprobe is also generalizable and can be extended to the detection of many other H₂O₂-mediated analytes.

Superparamagnetic iron oxide nanoparticles functionalized by peptide nucleic acids

Hydrophilic SPION were decorated with PNA decamers by SH/maleimide clickreaction as potential MRI and hyperthermia agents, and PNA carriers.

The important role of surface ligand on CdSe/CdS core/shell nanocrystals in affecting the efficiency of H₂ photogeneration from water

The use of colloidal semiconductor nanocrystals (NCs), especially those with a core/shell structure, for photocatalytic hydrogen (H₂) production from water is currently one of the hottest research fields. Although the ligand on the semiconductor NC surface is crucial to the optical and optoelectronic properties of the NC, the study of the ligand effect on the photocatalytic activity of H₂ generation is rarely reported. Herein, we employ nearly monodispersed CdSe/CdS core/shell NCs as a model photocatalytic system, and three kinds of ligands with different numbers of functional thiol groups (i.e., poly(acrylic acid), 3-mercaptopropionic acid and 2,3-dimercaptosuccinic acid) are selected as the ligands to investigate the effect of ligand on the efficiency of H₂ photogeneration. The results show that the H₂ photogeneration efficiency is highly dependent on the surface ligand of the NCs, and it increases with the increase of the number of the functional thiol groups in the ligand, and correspondingly, the photoluminescence intensity and average fluorescence lifetime, which are measured by steady state and time-resolved fluorescence measurements, are decreased. The surface trap-related charge separation efficiency, which is mediated by surface coating with different ligands, is supposed to cause the distinct ligand-dependent performance in the H₂ evolution.

Emission tunable, cyto/hemocompatible, near-IR-emitting Ag2S quantum dots by aqueous decomposition of DMSA

Size tunable aqueous Ag2S quantum dots emitting in the near-infrared region were synthesized through decomposition of meso-2,3-dimercaptosuccinic acid (DMSA) in water. The resulting NIR QDs are highly cyto- and hemocompatible, have quantum yields as high as 6.5% and are effective optical imaging agents based on in vitro evaluation.

One-pot noninjection route to CdS quantum dots via hydrothermal synthesis

Water-dispersible CdS quantum dots (QDs) emitting from 510 to 650 nm were synthesized in a simple one-pot noninjection hydrothermal route using cadmium chloride, thiourea, and 3-mercaptopropionic acid (MPA) as starting materials. All these chemicals were loaded at room temperature in a Teflon sealed tube and the reaction mixture heated at 100 °C. The effects of CdCl(2)/thiourea/MPA feed molar ratios, pH, and concentrations of precursors affecting the growth of the CdS QDs, was monitored via the temporal evolution of the optical properties of the CdS nanocrystals. High concentration of precursors and high MPA/Cd feed molar ratios were found to lead to an increase in the diameter of the resulting CdS nanocrystals and of the trap state emission of the dots. The combination of moderate pH value, low concentration of precursors and slow growth rate plays the crucial role in the good optical properties of the obtained CdS nanocrystals. The highest photoluminescence achieved for CdS@MPA QDs of average size 3.5 nm was 20%. As prepared colloids show rather narrow particle size distribution, although all reactants were mixed at room temperature. CdS@MPA QDs were characterized by UV-vis and photoluminescence spectroscopy, powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectrometry and MALDI TOF mass spectrometry. This noninjection one-pot approach features easy handling and large-scale production with excellent synthetic reproducibility. Surface passivation of CdS@MPA cores by a wider bandgap material, ZnS, led to enhanced luminescence intensity. CdS@MPA and CdS/ZnS@MPA QDs exhibit high photochemical stability and hold a good potential to be applied in optoelectronic devices and biological applications.