Surface-Initiated ARGET ATRP of Poly(Glycidyl Methacrylate) from Carbon Nanotubes via Bioinspired Catechol Chemistry for Efficient Adsorption of Uranium Ions

Surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) integrated with mussel-inspired polydopamine (PDA) chemistry was, for the first time, employed for controlled grafting of poly­(glycidyl methacrylate) (PGMA) brushes from carbon nanotubes (CNTs). The strategy initially involved deposition of a PDA layer by spontaneous self-polymerization, which is a benign and nonsurface specific way for anchoring 2-bromoisobutyryl bromide to form initiators on the CNTs. Dense and uniform PGMA brushes were then grown via ARGET ATRP using low concentration of Cu catalyst in different solvents. With abundant highly reactive epoxy groups, the PGMA-grafted CNTs could serve as a versatile platform for further modification or functionalization. Ethylenediamine ligands were facilely introduced, imparting the functionalized CNTs with record-high adsorption ability toward uranium ions among CNTs composites. The integrated strategy combining surface-initiated ARGET ATRP technique and PDA chemistry would provide new opportunities for surface engineering of nanomaterials for advanced applications

Effects of dual-labeling methods on chlorophyll a (Chl-a), chlorophyll b (Chl-b), total chlorophyll content (Chl a+b) and carotenoids (Cx-c) contents in tobacco seedling.

<p>*significant difference (α = 0.05, LSD) among treatments within the same variety. Error bars represent ±S.E.</p

The tobacco seeds of MSYY85 pelleted with T1 method were attracted by a small magnet.

<p><b>Ck</b>: the control seeds pelleted without magnetic powder and fluorescent materials did not be attracted by a magnet; <b>a</b>: the seeds pelleted with T1 (2 g seeds pelleted with 15 g bentonite and 84 g blend powder which consisted of 79.6 g talc, 0.2 g fluorescein and 4.2 g magnetic powder) were attracted by a magnet; the white arrow showed a small magnet.</p

Fluorescence in seedling of MSYY85 pelleted with T3 method under illumination of different lights.

<p><b>Ck</b>: the top row, seedlings from control seeds pelleted without rhodamine B and magnetic powder after 7 days germination (×7); two columns from left to right: under natural light and green light, respectively; <b>A</b> and <b>B</b>: seedlings from seeds pelleted with T3 (2 g seeds pelleted with 15 g bentonite and 84 g powder mixture which consisted of 79.8 g talc and 4.2 g magnetic powder. Meanwhile, a 2.0 mg/ml of rhodamine B solution was sprayed in place of water when the seed was coated with bentonite (RB and MP dual-labels)) germinated for 7 days (A, the second row) and 16 days (B, the third row), respectively (×7); <b>a</b>: the cotyledon of control seedling under green light excitation (546 nm) (×20); <b>b</b> and <b>c</b>: the cotyledon of T3 seedling under green light excitation (546 nm) after 7 and 16 days germination, respectively (×20).</p

Effects of dual-labeling methods on superoxidase dismutase (SOD) activity and malondialdehyde (MDA) content of tobacco seedling.

<p>*significant difference (α = 0.05, LSD) among treatments within the same variety. Error bars represent ±S.E.</p

Fluorescence in cracked seeds of MS YY85 pelleted with dual-labeling method under illumination of different lights.

<p>Ck: the top row, the control pellets treated without fluorescent materials and magnetic powder (×7); three columns from left to right: under natural light, blue light and green light, respectively; T: Seeds pelleted with fluorescent materials and magnetic powder under natural light; T1: 2 g seeds pelleted with 15 g bentonite and 84 g powder mixture which consisted of 79.6 g talc, 0.2 g fluorescein and 4.2 g magnetic powder (FR and MP dual-labels); T3: 2 g seeds pelleted with 15 g bentonite and 84 g powder mixture which consisted of 79.8 g talc and 4.2 g magnetic powder. Meanwhile, a 2.0 mg/ml of rhodamine B solution was sprayed in place of water when the seed was coated with bentonite (RB and MP dual-labels).</p

Fluorescence in seedling of MSYY85 pelleted with T1 method under illumination of different lights.

<p><b>Ck</b>: the top row, seedlings from control seeds pelleted without fluorescein and magnetic powder after 7 days germination (×7); two columns from left to right: under natural light and blue light, respectively; <b>A</b> and <b>B</b>: seedlings from seeds pelleted with T1 (2 g seeds pelleted with 15 g bentonite and 84 g powder mixture which consisted of 79.6 g talc, 0.2 g fluorescein and 4.2 g magnetic powder (FR and MP dual-labels)) germinated for 7 days (A, the second row) and 16 days (B, the third row), respectively (×7); <b>a</b>: the cotyledon of control seedling under blue light excitation (495 nm) after 7 days germination (×20); <b>b</b> and <b>c</b>: the cotyledon of T1 seedling under blue light excitation (495 nm) after 7 and 16 days germination, respectively (×20).</p

Bioinspired Polydopamine (PDA) Chemistry Meets Ordered Mesoporous Carbons (OMCs): A Benign Surface Modification Strategy for Versatile Functionalization

Mussel-inspired polydopamine (PDA) chemistry was employed for the surface modification of ordered mesoporous carbons (OMCs), improving the hydrophilicity, binding ability toward uranium ions, as well as enriching chemical reactivity for diverse postfunctionalization by either surface grafting or surface-initiated polymerization. Uniform PDA coating was deposited on the surface of CMK-3 type OMCs via self-polymerization of dopamine under mild conditions. Surface properties and morphology of the PDA-coated CMK-3 can be tailored by adjusting the dopamine concentration and coating time, without compromising the meso-structural regularity and the accessibility of the mesopores. Due to high density of −NH groups (4.7 μmol/m² or 2.8 group/nm²) and −OH groups (9.3 μmol/m² or 5.6 group/nm²) of the PDA coating, the modified CMK-3 showed improved hydrophilicity and superior adsorption ability toward uranyl ions (93.6 mg/g) in aqueous solution. Moreover, with the introduction of α-bromoisobutyryl bromide (BiBB) initiator to the PDA-coated CMK-3, we demonstrated for the first time that activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) can be conducted for controlled growth of polymer brushes from the surface of OMCs. Thus, PDA chemistry paves a new way for surface modification of OMCs to create a versatile, multifunctional nanoplatform, capable of further modifications toward various applications, such as environmental decontamination, catalysis, and other areas

Copolymer-Templated Synthesis of Nitrogen-Doped Mesoporous Carbons for Enhanced Adsorption of Hexavalent Chromium and Uranium

Polyacrylonitrile (PAN) homopolymer and polyacrylonitrile-<i>block</i>-poly­(<i>n</i>-butyl acrylate) (PAN-<i>b</i>-PBA) block copolymer were synthesized via supplemental activator reducing agent atom transfer radical polymerization and used as precursors to nitrogen-doped nanocarbons. Carbonization was performed at two different temperatures (500 and 800 °C) to fabricate nanocarbons with different structural properties and nitrogen contents. Copolymer-templated nitrogen-doped carbons (CTNCs) had larger surface area and higher mesoporosity than PAN homopolymer-templated nanocarbons (PANCs), due to the presence of PBA block acting as a sacrificial porogen. Adsorption performances of PANCs and CTNCs for Cr­(VI) and U­(VI) species were systematically studied. Due to the well-defined structure and larger surface area, CTNCs showed stronger adsorption ability than PANCs. The nitrogen atoms incorporated into the carbon framework led to higher electrostatic attraction for Cr­(VI) anions at low pH and complexation with U­(VI) cations at high pH. Theoretical maximum adsorption capacities of CTNC-500 on Cr­(VI) and U­(VI) were 333.3 mg/g (pH = 2) and 17.2 mg/g (pH= 5), respectively. CTNCs also showed preferential adsorption for U­(VI) compared to other ions, which might be explained by the hard and soft acids and bases theory. Thus, the copolymer-templated nitrogen-doped mesoporous carbons developed in this study represent a new class of nanocarbon sorbents with potential for removing heavy metal contaminants in either cationic or anionic form from aqueous media and thus mitigating environmental pollution