Hongmei Qin

Solution-processed bulk heterojunction solar cells based on a porphyrin small molecule with 7% power conversion efficiency

A porphyrin small molecule with less bulky substituents at the porphyrin periphery has been synthesized as a donor material, which exhibits a power conversion efficiency of up to 7.23% under AM 1.5 G irradiation (100 mW cm−2) for the solution-processed bulk heterojunction solar cells with PC61BM as the acceptor material.

High-Efficiency Small Molecule-Based Bulk-Heterojunction Solar Cells Enhanced by Additive Annealing

Solvent additive processing is important in optimizing an active layers morphology and thus improving the performance of organic solar cells (OSCs). In this study, we find that how 1,8-diiodooctane (DIO) additive is removed plays a critical role in determining the film morphology of the bulk heterojunction OSCs in inverted structure based on a porphyrin small molecule. Different from the cases reported for polymer-based OSCs in conventional structures, the inverted OSCs upon the quick removal of the additive either by quick vacuuming or methanol washing exhibit poorer performance. In contrast, the devices after keeping the active layers in ambient pressure with additive dwelling for about 1 h (namely, additive annealing) show an enhanced power conversion efficiency up to 7.78% with a large short circuit current of 19.25 mA/cm(2), which are among the best in small molecule-based solar cells. The detailed morphology analyses using UV-vis absorption spectroscopy, grazing incidence X-ray diffraction, resonant soft X-ray scattering, and atomic force microscopy demonstrate that the active layer shows smaller-sized phase separation but improved structure order upon additive annealing. On the contrary, the quick removal of the additive either by quick vacuuming or methanol washing keeps the active layers in an earlier stage of large scaled phase separation.

Polyglycerol-functionalized nanodiamond as a platform for gene delivery: Derivatization, characterization, and hybridization with DNA.

Summary A gene vector consisting of nanodiamond, polyglycerol, and basic polypeptide (ND-PG-BPP) has been designed, synthesized, and characterized. The ND-PG-BPP was synthesized by PG functionalization of ND through ring-opening polymerization of glycidol on the ND surface, multistep organic transformations (–OH → –OTs (tosylate) → –N3) in the PG layer, and click conjugation of the basic polypeptides (Arg8, Lys8 or His8) terminated with propargyl glycine. The ND-PG-BPP exhibited good dispersibility in water (>1.0 mg/mL) and positive zeta potential ranging from +14.2 mV to +44.1 mV at neutral pH in Milli-Q water. It was confirmed by gel retardation assay that ND-PG-Arg8 and ND-PG-Lys8 with higher zeta potential hybridized with plasmid DNA (pDNA) through electrostatic attraction, making them promising as nonviral vectors for gene delivery.

Direct Fabrication of the Graphene-Based Composite for Cancer Phototherapy through Graphite Exfoliation with a Photosensitizer.

We report on the application of pristine graphene as a drug carrier for phototherapy (PT). The loading of a photosensitizer, chlorin e6 (Ce6), was achieved simply by sonication of Ce6 and graphite in an aqueous solution. During the loading process, graphite was gradually exfoliated to graphene to give its composite with Ce6 (G-Ce6). This one-step approach is considered to be superior to the graphene oxide (GO)-based composites, which required pretreatment of graphite by strong oxidation. Additionally, the directly exfoliated graphene ensured a high drug loading capacity, 160 wt %, which is about 10 times larger than that of the functionalized GO. Furthermore, the Ce6 concentration for killing cells by G-Ce6 is 6-75 times less than that of the other Ce6 composites including GO-Ce6.

Efficient delivery of chlorin e6 into ovarian cancer cells with octalysine conjugated superparamagnetic iron oxide nanoparticles for effective photodynamic therapy

In cancer treatment, efficient delivery of active anticancer drugs into cancer cells is highly desirable for maximizing therapeutic effects and alleviating side effects. In this work, a nanocarrier consisting of an Fe3O4 core, a polyglycerol coating, and an octalysine functionality (SPION-PG-Lys8) has been designed, synthesized and used to deliver a photosensitizer, chlorin e6 (Ce6), into cancer cells for photodynamic therapy (PDT) of cancer cells. SPION-PG-Lys8 is colloidally stable in various aqueous solutions, showing a high positive zeta potential of 47.2 ± 6.9 mV in pure water. In vitro characterization reveals that SPION-PG-Lys8 is efficiently taken up by SKOV3 ovarian cancer cells, exhibiting low cytotoxicity, and suppressed autophagy compared to bare SPIONs. Negatively charged Ce6 is thus loaded on the SPION-PG-Lys8 through electrostatic attraction to yield a SPION-PG-Lys8/Ce6 nanocomplex with a positive zeta potential of 22.4 ± 4.3 mV. SPION-PG-Lys8/Ce6 is more easily taken up by the cells than free Ce6, and surprisingly, the internalized SPION-PG-Lys8/Ce6 is found to be enriched in the mitochondria. SPION-PG-Lys8/Ce6 exhibits almost no cytotoxicity under dark conditions, but strong photocytotoxicity due to the light-triggered production of reactive oxygen species (ROS) destroying the mitochondria. Taken together, our results highlight the great potential of SPION-PG-Lys8 as an efficient carrier of Ce6 for photodynamic cancer therapy.

Water redissoluble chiral porphyrin–carbon nanotube composites

The redissoluble functional compound/carbon nanotube (CNT) composites are important for post processing because CNT dispersions usually easy aggregate and therefore make additional processing very difficult. Due to the outstanding electronic, photophysical and photochemical properties of porphyrin and CNT composites, the chiral nanocomposites of chiral porphyrins and single-walled carbon nanotubes (SWNTs) are quite promising for applications in chiral catalysis and bio-sensing. The porphyrins used for the solubilization of CNTs are usually tetra-phenyl porphyrin (TPP) analogues. However, TPP analogues do not favor the formation of π–π interactions because the aryl groups prevent the porphyrin moiety from approaching the CNT surface due to the perpendicular conformation of the porphyrin moiety and its aryl group substituents. In this paper, non-TPP type porphyrins with chiral and hydrophilic substituents, that make the porphyrins soluble in water, were synthesized. SWNTs were effectively dissolved into water by the non-TPP type chiral porphyrins, and the dissolved chiral porphyrin/SWNTs composites could be easily redissolved. Both the dissolved and redissolved SWNT solutions are very stable and did not form apparent aggregates even after being kept for six months. Spectroscopic studies show that the binding properties of the chiral porphyrins to SWNTs are different in basic and neutral solution, which should contribute to the development and understanding in the study of sensors, biosensors, and catalysts made from chiral molecule/CNT composites.

Hyperbranched polyglycerol-grafted titanium oxide nanoparticles: synthesis, derivatization, characterization, size separation, and toxicology

We have been developing surface functionalization of various nanoparticles including nanodiamond and iron oxide nanoparticles in view of biomedical applications. In this context, TiO2 nanoparticles (TiO2 NP) are functionalized with polyglycerol (PG) to provide water-dispersible TiO2–PG, which is further derivatized through multi-step organic transformations. The resulting TiO2–PG and its derivatives are fully characterized by various analyses including solution-phase 1H and 13C NMR. TiO2–PG was size-tuned with centrifugation by changing the acceleration and duration. At last, no cytotoxicity of TiO2 NP, TiO2–PG, and TiO2–PG functionalized with RGD peptide was observed under dark conditions.