Yongzhen Yang

Efficient adsorptive removal of dibenzothiophene by graphene oxide-based surface molecularly imprinted polymer

Molecularly imprinted polymers on GO nanosheets (MIPs/GO) for desulfurization are synthesized using dibenzothiophene (DBT) as template, methacrylic acid (MAA) as monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. The formation of this hybrid material is verified by Fourier transform infrared spectroscopy, thermal gravimetric and atomic force microscopy analysis. The adsorption results show that the prepared MIPs/GO exhibit excellent adsorption capacity (up to 181.9 mg g−1 at 298 K) and fast mass transfer and binding kinetics for DBT. The kinetics and isotherm data can be well described by the pseudo-first-order kinetic model and the Freundlich isotherm, respectively. Competitive adsorption experiments demonstrate that MIPs/GO show higher affinity toward target molecule DBT than toward structural analogue benzothiophene.

Temperature and magnetism bi-responsive molecularly imprinted polymers: Preparation, adsorption mechanism and properties as drug delivery system for sustained release of 5-fluorouracil.

Temperature and magnetism bi-responsive molecularly imprinted polymers (TMMIPs) based on Fe3O4-encapsulating carbon nanospheres were prepared by free radical polymerization, and applied to selective adsorption and controlled release of 5-fluorouracil (5-FU) from an aqueous solution. Characterization results show that the as-synthesized TMMIPs have an average diameter of about 150 nm with a typical core-shell structure, and the thickness of the coating layer is approximately 50 nm. TMMIPs also displayed obvious magnetic properties and thermo-sensitivity. The adsorption results show that the prepared TMMIPs exhibit good adsorption capacity (up to 96.53 mg/g at 25 °C) and recognition towards 5-FU. The studies on 5-FU loading and release in vitro suggest that the release rate increases with increasing temperature. Meanwhile, adsorption mechanisms were explored by using a computational analysis to simulate the imprinted site towards 5-FU. The interaction energy between the imprinted site and 5-FU is -112.24 kJ/mol, originating from a hydrogen bond, Van der Waals forces and a hydrophobic interaction between functional groups located on 5-FU and a NIPAM monomer. The electrostatic potential charges and population analysis results suggest that the imprinted site of 5-FU can be introduced on the surface of TMMIPs, confirming their selective adsorption behavior for 5-FU.

Magnetic thermosensitive core/shell microspheres: synthesis, characterization and performance in hyperthermia and drug delivery

In order to explore a stable and biocompatible material for encapsulating magnetic nanoparticles and supporting thermosensitive polymers, the present study describes a facile route for preparing monodisperse hybrid microspheres with superparamagnetic cores, in which Fe3O4 nanocrystals are encapsulated in carbon microsphere matrices (Fe3O4/carbon). Magnetic thermosensitive core/shell structure microspheres were prepared using Fe3O4/carbon microspheres as cores, N-isopropylacrylamide as a thermosensitive monomer, potassium persulfate as initiator and N,N-methylene bisacrylamide as crosslinker. A series of investigations using field emission scanning electron microscopy, transmission electron microscopy, Fourier transformation infrared spectroscopy, thermogravimetry and dynamic light scattering was carried out to characterize the hybrid microspheres. The as-synthesized microspheres have a hydrodynamic diameter of 280 nm with a lower critical solution temperature at around 45 °C. They are superparamagnetic with a saturation magnetization of 13.75 emu g−1 at 20 kOe. They generate heat when an inductive magnetic field is applied to them and have a specific absorption rate of 77.0 W g−1 at 230 kHz and 290 Oe, showing good potential for hyperthermia. The controlled release experiments demonstrate that the microspheres have excellent drug-loading and temperature-triggered drug-release ability for 5-fluorouracil.

Recent advances in molecular imprinting technology for the deep desulfurization of fuel oils

As a novel adsorptive desulfurization method for the preparation of adsorbents, molecular imprinting technology is used to create specific molecular recognition sites in polymers to identify sulfur-bearing template molecules. It is a green process with potential applications because of its characteristics of mild conditions, simple operation, low investment, low pollution, high selectivity, no effect on octane value, and the possible reuse of the as-obtained benzothiophene-like compounds as fine chemicals. Recently, inorganic materials including silica gel, TiO2, K2Ti4O9, and carbon microspheres have been used as supports to prepare surface molecularly imprinted polymers for adsorbing dibenzothiophene and benzothiophene. Recent advances in molecular imprinting technology for deep desulfurization are summarized with carbon microsphere surface molecular imprinting technology highlighted. The review provides experimental references and theoretical guidance for designing and preparing green desulfurization materials. [New Carbon Materials 2013, 29(1): 1–14]

Fe-encapsulating carbon nano onionlike fullerenes from heavy oil residue

Fe-encapsulating carbon nano onionlike fullerenes (NOLFs) were obtained by chemical vapor deposition (CVD) using heavy oil residue as carbon source and ferrocene as catalyst precursor in an argon flow of 150 mL/min at 900 °C for 30 min. Field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy (EDS), x-ray diffraction (XRD), and Raman spectroscopy were used to characterize morphology and microstructure of the products. The results show that Fe-encapsulating NOLFs collected at the outlet zone of quartz tube had core/shell structures with sizes ranging from 3 to 6 nm and outer shells composed of poorly crystallized graphitic layers. Their growth followed particle self-assembling growth mechanism, and all atoms in the graphite sheets primarily arose from Fe-carbide nanoparticles.

Water-compatible surface molecularly imprinted polymers with synergy of bi-functional monomers for enhanced selective adsorption of bisphenol A from aqueous solution

Water-compatible molecularly imprinted polymers (MIPs) with dual monomer–template interactions were synthesized via the synergy of bi-functional monomers of water-soluble 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and styrene (St) for the selective adsorption of bisphenol A (BPA) from aqueous media using porous graphene oxide as a support. Both hydrogen bonds and π–π interactions are responsible for the adsorption of BPA on the synthesized MIPs. The formation and structure of the MIPs are verified by Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy and dispersion analysis in water. The adsorption results show that the adsorption capacity of MIPs is greatly enhanced by virtue of the synergy of AMPS and St. The MIPs prepared with a molar ratio (AMPS:St) of 2.5:2.5 exhibit the highest adsorption capacity (up to 85.7 mg g−1 at 293 K) toward BPA in aqueous media. The kinetics and isotherm data can be well fitted with the pseudo-second-order kinetic model and the Freundlich isotherm, respectively. Competitive adsorption experiments demonstrate that the synthesized MIPs display excellent selectivity toward BPA against analogue molecules. The MIPs show good recoverability and exhibit excellent adsorption affinity toward BPA even in complex river water. This work provides a versatile approach for the fabrication of high performance MIPs for application in aqueous environments.

Microwave-assisted hydrothermal synthesis of solid-state carbon dots with intensive emission for white light-emitting devices

A one-pot microwave-assisted hydrothermal approach was developed to quickly synthesize organosilane-functionalized carbon dots (Si-CDs) within 5 minutes. With the assistance of N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (KH-792) as distance barrier chains, aggregation-caused quenching is suppressed successfully, which contributes to the emission of bright blue fluorescence by solid-state Si-CDs (λem ∼ 454 nm). The photoluminescence quantum yield of the as-prepared Si-CDs in the solid state reaches 65.8% with an optimized molar ratio of the reactant citric acid to KH-792 of 1 : 5 and a reaction temperature of 180 °C, which is 2.5-fold that of their solution. Together with their good film-forming ability and thermal stability, Si-CDs were applied to fabricate a white-light-emitting device with color coordinates of (0.32, 0.36) and a correlated color temperature of 6071 K. Our results indicate that the as-prepared Si-CDs are promising materials with efficient solid-state emission to be used in lighting, backlight displays and other optoelectronic devices.

Accelerated formation and improved performance of CH3NH3PbI3-based perovskite solar cells via solvent coordination and anti-solvent extraction

The two-step sequential deposition method is widely used in the preparation of high-performance mesoscopic perovskite solar cells. However, when the conventional sequential deposition method is applied to fabricate bilayered mesostructured and planar-structured devices, inefficient conversion of PbI2 to perovskite has been a big challenge. In this work, we report a new solvent coordination and anti-solvent extraction (SCAE) strategy for preparing porous PbI2 films to rapidly convert all PbI2 into perovskite active layers in bilayered mesostructured perovskite solar cells. It is demonstrated that PbI2·DMSO (dimethyl sulfoxide, coordinated solvent) intermediate complexes are not only capable of restricting the fast growth of PbI2 grains, but also capable of facilitating the formation and regulation of porous PbI2 structures during the process of anti-solvent (chlorobenzene) extraction. With the porous PbI2 template, its complete conversion time into CH3NH3PbI3 is greatly shortened to less than ten minutes from one hour for the conventional method. The best device fabricated through the SCAE process exhibits a power conversion efficiency of above 15% under AM 1.5G solar illumination of 100 mW cm−2, appreciably outperforming the device without SCAE treatment, which can be ascribed to its uniform surface morphology and more efficient carrier transfer at the interfaces. The results highlight the tunability of the PbI2 morphology via the SCAE process and its importance to highly efficient perovskite conversion, the final perovskite morphology and device performance in a sequential deposition process.

Surface molecularly imprinted polymers grafted on ordered mesoporous carbon nanospheres for fuel desulfurization

Surface molecular imprinting is an effective measure to get adsorbent materials for definite substances. In this work, ordered mesoporous carbon nanospheres (OMCNS) were prepared as carriers by a hydrothermal method with phenolic resol as the carbon source and triblock copolymer Pluronic PF127 as the soft template. A surface molecularly imprinted polymer (SMIP/OMCNS) was then obtained through a series of functionalization, grafting and elution processes with dibenzothiophene (DBT) as a template, which was designed for the deep desulfurization of fuel products by removing DBT and its derivatives. By adopting OMCNS as a carrier, SMIP/OMCNS shows excellent adsorption capacity towards DBT (218.29 mg g−1), owing to the ordered mesoporous structure and high surface area of OMCNS. The better fitted pseudo-first-order model indicates that the adsorption involves mainly physical interactions, which are promoted by the mesoporous structure of OMCNS. The Langmuir and Freundlich models fitted better than the Dubinin–Radushkevich and Scatchard isothermal models did, which suggests the occurrence of both monolayer and multilayer interactions. The thermodynamics, selectivity and regenerability of SMIP/OMCNS were also investigated. The adsorption of DBT on SMIP/OMCNS proves to be an endothermic process. And the relative selectivity coefficients against benzothiophene, biphenyl and fluorine interferents reached 2.19, 2.29 and 2.37, respectively. As a result, SMIP/OMCNS can be a potential adsorbent material for deep desulfurization of fuel products and recovering DBT and its derivatives as valuable reagents for other value-added applications.

Optimal nitrogen and phosphorus codoping carbon dots towards white light-emitting device

Through a one-step fast microwave-assisted approach, nitrogen and phosphorus co-doped carbon dots (N,P-CDs) were synthesized using ammonium citrate (AC) as a carbon source and phosphates as additive reagent. Under the condition of an optimal reaction time of 140 s, the influence of additive with different N and P content on fluorescent performance of N,P-CDs was further explored. It was concluded that high nitrogen content and moderate phosphorus content are necessary for obtaining high quantum yield (QY) N,P-CDs, among which the TAP-CDs (CDs synthesized using ammonium phosphate as additive reagent) show high quantum yield (QY) of 62% and red-green-blue (RGB) spectral composition of 51.67%. Besides, the TAP-CDs exhibit satisfying thermal stability within 180 °C. By virtue of good optical and thermal properties of TAP-CDs, a white light-emitting device (LED) was fabricated by combining ultraviolet chip with TAP-CDs as phosphor. The white LED emits bright warm-white light with the CIE chromaticity coordinat...