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Electrospun carbon nanofibers were activated with melamine-polyacrylonitrile [melamine-blended carbon nanofibers (MACNFs)] for use as a fibrous adsorbent for indoor CO 2 removal. Although, melamine doping was intended solely to incorporate basic nitrogen functionalities on the nanofibers, it also shortened fabrication time, conserving time, and energy cost. The specific surface area and microporosity of the fibers were enhanced from 412 m 2 g −1 and 0.1646 cm 3 g −1 to 547 m 2 g −1 and 0.220 cm 3 g −1 , respectively, upon final CO 2 activation of the nanofibers. With the chemical properties, we observed significant tethering of pyridine functionality. The sample, MACNF-7 (10 mL of polymer solution doped with 0.7 g of melamine), provided the optimum melamine doping condition to achieve the highest CO 2 adsorption capacity of 3.15 mmol g −1 . The adsorption performance was based on simultaneous improvement in microporosity (physical) and surface basicity (chemical) properties of the adsorbent. However, in a binary mixture with nitrogen, the selective adsorption of CO 2 showed the predominance of the improved surface basicity over microporosity. The highest CO 2 selective capture (1.22 mmol g −1 ) was occurred for a CO 2 :N 2 ratio of 0.15:0.85, with a selectivity of 58.19 at 273 K. In a regeneration test, stable and robust performance was achieved more than five cycles.

The morphologies and surface conditions of ZnO microstructures have been controlled facilely via a microwave-assisted one-pot synthetic route by varying the ammonia concentration of the reaction mixture. Ammonia affects the nucleation, growth, and hydrolysis kinetics of a zinc glycerolate intermediate to induce shape variation from flower-like ZnO microstructures to various ZnO twin microstructures with a preferred exposure of ± (0001) polar planes. The as-prepared ZnO microstructures are mesoporous, as they have large specific surface areas and high specific pore volumes that have resulted from the microwave-assisted fast hydrolysis of the zinc glycerolate intermediate microstructures. Owing to the novel features of microwaves, the ZnO microstructures have numerous microcracks and wrinkles on their surfaces and show characteristic defect-driven orange emission, whose intensity increases with the specific surface area. The photocatalytic degradation rate constant of rhodamine B via our prepared ZnO microstructures has been found to increase linearly with the specific surface area, the specific pore volume, and the polar-surface exposure. Our simple and rapid microwave-assisted synthetic method is considered to be beneficial to the development of morphology-controlled metal oxides that are applicable for ecofriendly waste-water treatments.

Phosphonic acids bind strongly to quantum dots (QDs), improving stability. However, it is difficult to introduce desired ligands to QDs passivated with phosphonic acids via ligand exchange. Here, we have investigated the efficient addition of X-type ligands to wurtzite CdSe QDs passivated with phosphonic acids using Z-type ligands. Oleic acid (OA) and Cd­(OA)2 were used as examples of the desired X-type and Z-type ligands, respectively, and octadecylphosphonic acid (ODPA) was used as a passivating ligand for CdSe QDs. OA ligands were not introduced at all into the QDs when OA itself was used as the X-type ligand. However, after Z-type ligand addition, the added OA ligand accounted for 35% of the total ligands and only 20% of ODPA was dissociated from QDs. In addition, photoluminescence (PL) and its lifetime increased 6.1 and 2.8 times, respectively, indicating that Z-type ligands bound to trap sites to increase PL. Thus, we suggest that a sufficient amount of the desired ligand can be introduced, enhancing the quantum yields of CdSe QDs substantially. Our approach can be applied to various applications requiring energy input/output control and exciton lifetime extension in QDs.

Water-dispersive CdS quantum dots (QDs) have been rapidly synthesized in a polyol solvent of ethylene glycol at 160 °C without using nonpolar organic solvents, and their stepwise growth mechanisms have been investigated thoroughly. The growth rate of CdS QDs in the second step of ≥70 s is prominently slower than that in the first step of ≤70 s. The dominant growth mechanism of CdS QDs switches from the Ostwald ripening (OR) growth in the first step to the oriented attachment (OA) growth in the second step. The fast decay time of 40 ns and the slow decay time of 300 ns in photoluminescence decay profiles are due to the decay times of excitons in internal defects and OA-induced defects, respectively. In the first step, internal defects are eliminated by the OR growth to reduce photoluminescence, and the center of the photoluminescence of the slow decay component shifts from 550 to 600 nm. In the second step, the OA growth occurs to enhance the number of OA-induced defects, increasing photoluminescence at 600 nm.