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The stability and removal of water-dispersed CdSe/CdS core-shell quantum dots from water
Chen, Xu,Ok, Yong Sik,Mohan, Dinesh,Pittman Jr., Charles U.,Dou Jr., Xiaomin Elsevier 2017 CHEMOSPHERE - Vol.185 No.-
<P><B>Abstract</B></P> <P>The increasingly wide use of semiconductor nanocrystals inevitably leads to their release into aquatic environment. The aggregation behaviors of 3-mercaptopropionic acid-capped CdSe/CdS core-shell quantum dots (MPA-QDs) under various water chemistry conditions were examined and their removal using Fe<SUP>3+</SUP> and Al<SUP>3+</SUP> coagulants was evaluated. Cationic species rather than concentrations affected the stability of MPA-QDs. Adding 2 mM Ca<SUP>2+</SUP> led to a much larger ζ-potential decrease and particle size increase than adding 150 mM K<SUP>+</SUP> at each tested solution pH. This indicated that complexation and depletion of surface-bound carboxyl groups by divalent Ca<SUP>2+</SUP> has a more pronounced effect than compression of the electrical double layer by high concentrations of monovalent K<SUP>+</SUP>. The presence of humic acid increased the stability of MPA-QDs, which might increase negative surface charging <I>via</I> overcoating or bind to the surface of MPA-QDs. The nanoparticles exhibited similar aggregation kinetics patterns in tap water and seawater, but varying patterns in the lake water because of the co-existence of 2.3 mM total of Ca<SUP>2+</SUP> and Mg<SUP>2+</SUP>. MPA-QDs (5 mg L<SUP>−1</SUP>) were readily coagulated by 2.4 mM Al<SUP>3+</SUP> or 1.2 mM Fe<SUP>3+</SUP> in tap water. Al<SUP>3+</SUP> and Fe<SUP>3+</SUP> can bind with carboxyl groups of the surface capping ligands, neutralize the negative charges on the surface of MPA-QDs and decrease the electrostatic repulsion forces to induce MPA-QDs aggregation. In addition, MPA-QDs could be bound with and wrapped into the flocs of hydrolysis products of coagulants. The results reported here could help broaden our understanding of the impacts and remediation of water-dispersed core-shell QD nanoparticles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The stability, aggregation and remediation of core/shell QDs were evaluated. </LI> <LI> Ca<SUP>2+</SUP> led to severe aggregation of soluble QDs than K<SUP>+</SUP> at much lower concentrations. </LI> <LI> Depletion of surface bound ligand has a more pronounced effect than compression EDL. </LI> <LI> QDs exhibited different aggregation patterns in tap water, seawater and lake water. </LI> <LI> Both Fe<SUP>3+</SUP> and Al<SUP>3+</SUP> were able to remediate QDs from water but the former was better. </LI> </UL> </P>
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Akanksha Grover,Tej Prakash Soni,Nidhi Patni,Dinesh Kumar Singh,Naresh Jakhotia,Anil Kumar Gupta,Lalit Mohan Sharma,Shantanu Sharma,Ravindra Singh Gothwal 대한방사선종양학회 2021 Radiation Oncology Journal Vol.39 No.1
Purpose: Intensity-modulated radiotherapy (IMRT) provides higher dose to target volumes and limits the dose to normal tissues. IMRT may be applied using either simultaneous integrated boost (SIB-IMRT) or sequential boost (SEQ-IMRT) technique. The objectives of this study were to compare acute toxicity and objective response rates between SIB-IMRT and SEQ-IMRT in patients with locally advanced head and neck cancer. Materials and Methods: Total 110 patients with locally advanced carcinoma of oropharynx, hypopharynx, and larynx were randomized equally into the two arms (SIB-IMRT vs. SEQ-IMRT). Patients in SIB-IMRT arm received dose of 66 Gy in 30 fractions, 5 days a week, over 6 weeks. SEQ-IMRT arm’s patients received 70 Gy in 35 fractions over 7 weeks. Weekly concurrent cisplatin chemotherapy was given in both arms. Patients were assessed for acute toxicities during the treatment and for objective response at 3 months after the radiotherapy. Results: Grade 3 dysphagia was significantly more with SIB-IMRT compared to SEQ-IMRT (72% vs. 41.2%; p = 0.006) but other toxicities including mucositis, dermatitis, xerostomia, weight-loss, incidence of nasogastric tube intubation and hospitalization for supportive management were similar in both the arms. Patients in SIB-IMRT arm showed better treatment-compliance and had significantly less treatment-interruption compared to SEQ-IMRT arm (p = 0.028). Objective response rates were similar in both the arms (p = 0.783). Conclusion: Concurrent chemoradiation with SIB-IMRT for locally advanced head and neck cancer is well-tolerated and results in better treatment-compliance, similar objective response rates, comparable incidence of mucositis and higher incidence of grade 3 dysphagia compared to SEQ-IMRT.
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Ahmad, Mahtab,Lee, Sang Soo,Oh, Sang-Eun,Mohan, Dinesh,Moon, Deok Hyun,Lee, Young Han,Ok, Yong Sik Ecomed 2013 Environmental science and pollution research inter Vol.20 No.12
<P>Trichloroethylene (TCE) is one of the most hazardous organic pollutants in groundwater. Biochar produced from agricultural waste materials could serve as a novel carbonaceous adsorbent for removing organic contaminants from aqueous media. Biochars derived from pyrolysis of soybean stover at 300 C and 700 C (S-300 and S-700, respectively), and peanut shells at 300 C and 700 C (P-300 and P-700, respectively) were utilized as carbonaceous adsorbents to study batch aqueous TCE remediation kinetics. Different rate-based and diffusion-based kinetic models were adopted to understand the TCE adsorption mechanism on biochars. With an equilibrium time of 8-10 h, up to 69 % TCE was removed from water. Biochars produced at 700 C were more effective than those produced at 300 C. The P-700 and S-700 had lower molar H/C and O/C versus P-300 and S-300 resulting in high aromaticity and low polarity accompanying with high surface area and high adsorption capacity. The pseudo-second order and intraparticle diffusion models were well fitted to the kinetic data, thereby, indicating that chemisorption and pore diffusion were the dominating mechanisms of TCE adsorption onto biochars.</P>
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