Visualization 2.mp4

3D RI tomograms rendering of Pandorina morum algae

Molecular Ordering and Dipole Alignment of Vanadyl Phthalocyanine Monolayer on Metals: The Effects of Interfacial Interactions

We present an <i>in situ</i> low-temperature scanning tunneling microscopy (LT-STM) study to elucidate the effects of interfacial interactions on the molecular ordering and dipole alignment of dipolar vanadyl phthalocyanine (VOPc) monolayer on metal surfaces, including Cu(111), Ag(111), Au(111), and graphite. The adsorption of VOPc on the relatively inert graphite surface leads to the formation of well-ordered molecular dipole monolayer with unidirectionally aligned O-up configuration. In contrast, VOPc on Cu(111), Ag(111), and Au(111) adopts both O-up and O-down configurations. The VOPc strongly chemisorbs on Cu(111), leading to the formation of one-dimensional molecular chains, and two-dimensional molecular islands comprising pure O-down adsorbed VOPc molecules at low and high coverage, respectively. In contrast, VOPc physisorbs on Au(111) and results in an orientation transition from flat-lying to inclined molecular islands. Regarding the interfacial interaction strength, the Ag(111) represents an intermediate case (weak chemisorption), which enables the formation of disordered phase and ordered islands, as well as the orientation transition within the disordered phase

Visualization 3.mp4

3D RI tomograms rendering of HeLa cell

Visualization 1.mp4

Tomographic reconstruction of two enlarged regions of human buccal epithelial cell

Dipole Orientation Dependent Symmetry Reduction of Chloroaluminum Phthalocyanine on Cu(111)

We demonstrate a dipole orientation dependent symmetry reduction of 4-fold symmetric chloroaluminum phthalocyanine (ClAlPc) molecules on a Cu(111) surface by combined low temperature scanning tunneling microscopy (LT-STM) and density functional theory (DFT) calculations. Unexpected symmetry reduction from 4-fold (C4) to 2-fold (C2) was observed for Cl-down (dipole up) adsorbed ClAlPc, while molecules adopted Cl-up (dipole down) configuration reserved the C4 symmetry. DFT calculations indicated strong charge accumulation at the interface region between Cu surface and the Cl atom in Cl-down adsorbed ClAlPc due to the electron transfer from the bonded Cu atoms. This can result in charge redistribution within the phthalocyanine (Pc) macrocycle, and the formation of anionic Pc with an uptake of 1.3 e, which can be subjected to Jahn–Teller distortion. The inequivalent charge distribution onto the four lobes would be further enlarged due to the conformational distortion. The two down-bended lobes with more electrons interact stronger with the substrate and are much closer to the surface, leading to the C2 symmetry with one pair of up-bended lobes brighter and longer than their perpendicular counterparts for Cl-down adsorbed ClAlPc

Visualization 1. Large SBP phase video of unstained HeLa cells in vitro recovered by using SFPM .

Visualization 1 shows Large SBP phase video recovered by using SFPM with single-shot acquisition speed (50 Hz) for tracking dynamic subcellular features of unstained HeLa cells in vitro

Media 2: Lensless phase microscopy and diffraction tomography with multi-angle and multi-wavelength illuminations using a LED matrix

Originally published in Optics Express on 01 June 2015 (oe-23-11-14314

Media 1: Lensless phase microscopy and diffraction tomography with multi-angle and multi-wavelength illuminations using a LED matrix

Originally published in Optics Express on 01 June 2015 (oe-23-11-14314

Growth Intermediates for CVD Graphene on Cu(111): Carbon Clusters and Defective Graphene

Graphene growth on metal films via chemical vapor deposition (CVD) represents one of the most promising methods for graphene production. The realization of the wafer scale production of single crystalline graphene films requires an atomic scale understanding of the growth mechanism and the growth intermediates of CVD graphene on metal films. Here, we use <i>in situ</i> low-temperature scanning tunneling microscopy (LT-STM) to reveal the graphene growth intermediates at different stages via thermal decomposition of methane on Cu(111). We clearly demonstrate that various carbon clusters, including carbon dimers, carbon rectangles, and ‘zigzag’ and ‘armchair’-like carbon chains, are the actual growth intermediates prior to the graphene formation. Upon the saturation of these carbon clusters, they can transform into defective graphene possessing pseudoperiodic corrugations and vacancies. These vacancy-defects can only be effectively healed in the presence of methane via high temperature annealing at 800 °C and result in the formation of vacancy-free monolayer graphene on Cu(111)

Preparation of High-Temperature Resistant Polyimide Fibers by Introducing the <i>p</i>‑Phenylenediamine into Kapton-Type Polyimide

To improve the heat resistance of polyimide (PI) fibers for application in harsh environments and establish a correlation among the chemical structure, fabrication performance, and material properties, a simple and rigid diamine, p-phenylenediamine (p-PDA) was incorporated into the Kapton-type PI synthesized from pyromellitic dianhydride and 4,4-diaminodiphenylmethane (ODA). The comprehensive properties of these co-PI fibers were systematically investigated to assess the impact of p-PDA addition. Two-dimensional wide-angle X-ray diffraction (WAXD) was used to investigate the evolution of the aggregation structure of the co-PI fibers during the processing. The thermogravimetric analyzer (TGA) test shows that the incorporation of p-PDA improves the heat resistance of polyimide fibers, with the 10 wt % weight loss temperature (T10%) ranging from 582 to 605 °C and the maximum decomposition temperature (Tmax) of 611–635 °C for the co-PI fibers with different p-PDA contents. Additionally, the potential degradation mechanism of the PI fibers was examined by utilizing pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and other thermal analyses. By introducing p-PDA, the content of O element (ether bond in ODA) in the system decreases, leading to a reduction in oxygen free radicals from ODA during the decomposition process of polyimides. The decrease in active species can cause a decrease in the decomposition rate and improve the heat resistance of the polyimide fibers. The study of the thermal decomposition mechanism of polyimides provides a valuable foundation for the preparation of high-performance polymer fibers with enhanced thermal resistance and excellent overall performance