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Pang, Yi

Publications and source records attributed to Pang, Yi.

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Conformational change due to intramolecular hydrophobic interaction leads to large blue-shifted emission from single molecular cage solutions

In this communication, we demonstrate a unique negative solvatochromic emission (NSE) process from a conformational change of a coordination cage in response to solvent composition. The cationic cage contains two tetra-(4-pyridylphenyl)ethylene (TPPE) luminogens on two opposite faces, linked by Pt(PEt 3 ) 2 and isophthalate. When the solvent changes from acetone/acetonitrile/methanol to water, the emission of single cages gradually shifts to short wavelength (NSE) with a drastic value of ~60 nm. Small angle X-ray scattering (SAXS) measurements indicate a molecular conformational change during the process and intramolecular $\pi–\pi$ stacking and hydrophobic interaction between the TPPE planes could be the driving forces. As a comparison, a cage with a longer inter-fluorophore distance does not have such strong intramolecular interactions and only shows regular positive solvatochromic emission (PSE) under the same conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Effect of Cation–π Interaction on Macroionic Self‐Assembly

Abstract A series of rod‐shaped polyoxometalates (POMs) [Bu 4 N] 7 [Mo 6 O 18 NC(CH 2 O) 3 MnMo 6 O 18 (OCH 2 ) 3 CNMo 6 O 18 ] and [Bu 4 N] 7 [ArNMo 6 O 17 NC(CH 2 O) 3 MnMo 6 O 18 (OCH 2 ) 3 CNMo 6 O 17 NAr] (Ar=2,6‐dimethylphenyl, naphthyl and 1‐methylnaphthyl) were chosen to study the effects of cation–π interaction on macroionic self‐assembly. Diffusion ordered spectroscopy (DOSY) and isothermal titration calorimetry (ITC) techniques show that the binding affinity between the POMs and Zn 2+ ions is enhanced significantly after grafting aromatic groups onto the clusters, leading to the effective replacement of tetrabutylammonium counterions (TBAs) upon the addition of ZnCl 2 . The incorporation of aromatic groups results in the significant contribution of cation–π interaction to the self‐assembly, as confirmed by the opposite trend of assembly size vs. ionic strength when compared with those without aromatic groups. The small difference between two aromatic groups toward the Zn 2+ ions is amplified after combining with the clusters, which consequently triggers the self‐recognition behavior between two highly similar macroanions.

Luo, Jiancheng↗
DOE OSTI2018

Effect of Cation-π Interaction on Macroionic Self-Assembly

Here, a series of rod–shaped polyoxometalates (POMs) [Bu 4 N] 7 [Mo 6 O 18 NC(CH 2 O) 3 MnMo 6 O 18 (OCH 2 ) 3 CNMo 6 O 18 ] and [Bu 4 N] 7 [ArNMo 6 O 17 NC(CH 2 O) 3 MnMo 6 O 18 (OCH 2 ) 3 CNMo 6 O 17 NAr] (Ar=2,6–dimethylphenyl, naphthyl and 1–methylnaphthyl) were chosen to study the effects of cation–π interaction on macroionic self–assembly. Diffusion ordered spectroscopy (DOSY) and isothermal titration calorimetry (ITC) techniques show that the binding affinity between the POMs and Zn 2+ ions is enhanced significantly after grafting aromatic groups onto the clusters, leading to the effective replacement of tetrabutylammonium counterions (TBAs) upon the addition of ZnCl 2 . The incorporation of aromatic groups results in the significant contribution of cation–π interaction to the self–assembly, as confirmed by the opposite trend of assembly size vs. ionic strength when compared with those without aromatic groups. The small difference between two aromatic groups toward the Zn 2+ ions is amplified after combining with the clusters, which consequently triggers the self–recognition behavior between two highly similar macroanions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

ALG2 regulates glioblastoma cell proliferation, migration and tumorigenicity

Apoptosis-linked gene-2 (ALG-2), also known as programmed cell death 6 (PDCD6), has recently been reported to be aberrantly expressed in various tumors and required for tumor cell viability. The aim of the present study was to investigate whether ALG-2 plays a crucial role in tumor cell proliferation, migration and tumorigenicity. In this study, we examined the expression of PDCD6 in glioblastoma cell lines and found that ALG-2 was generally expressed in glioblastoma cell lines. We also performed an analysis of an online database and found that high expression of ALG-2 was associated with poor prognosis (p = 0.039). We found that over-expression of ALG2 in glioblastoma could inhibit cell proliferation and, conversely, that down-regulation of ALG2 could promote cell proliferation. Further studies showed that over-expression of ALG2 inhibited the migration of tumor cells, whereas down-regulation of ALG2 promoted tumor cell migration. Finally, in vitro and in vivo studies showed that over-expression of ALG2 inhibited the tumorigenic ability of tumor cells, while down-regulation of ALG2 promoted tumor cell tumorigenic ability. In conclusion, ALG2 has a tumor suppressive role in glioblastoma and might be a potential target for the treatment of glioblastoma. - Highlights: • Low ALG2 expression is indicative of poor prognosis in glioblastoma patients. • ALG2 is required for cell proliferation in GBM cells. • ALG2 is involved in GBM cell migration. • ALG2 is involved in GBM cell self-renewal and tumorigenesis in vitro and in vivo.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Φ 3 theory with F 4 flavor symmetry in 6 – 2ϵ dimensions: 3-loop renormalization and conformal bootstrap

Here, we consider Φ 3 theory in 6 – 2ϵ with F 4 global symmetry. The beta function is calculated up to 3 loops, and a stable unitary IR fixed point is observed. The anomalous dimensions of operators quadratic or cubic in Φ are also computed. We then employ conformal bootstrap technique to study the fixed point predicted from the perturbative approach. For each putative scaling dimension of Φ(Δ Φ ), we obtain the corresponding upper bound on the scaling dimension of the second lowest scalar primary in the 26 representation (Δ 26 2nd ) which appears in the OPE of Φ × Φ. In D = 5.95, we observe a sharp peak on the upper bound curve located at Δ Φ equal to the value predicted by the 3-loop computation. In D = 5, we observe a weak kink on the upper bound curve at (Δ Φ , Δ 26 2nd ) = (1.6, 4).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS2003

Developing Novel Fluorescent Materials with Near Infrared Emission by Using m-Phenylene

Our research focuses on development of novel p-conjugated polymers with desired emission. In the current study, the structure of a highly green-emitting poly[(m-phenylenevinylene)- alt-( p-phenylenevinylene)] has been modified by increasing the content of p-phenylene to achieve red- and infrared-emission. The polymer is synthesized via Wittig-Horner condensation, which is known to lead to trans-olefin linkage. The polymer is soluble in common organic solvents such as toluene, chloroform and THF. The spectroscopic properties of the polymer in both solution and film states will be discussed in comparison with its model compound.

Pang, Yi↗
NASA NTRS2003

Synthesis and Luminescence of Yellow/Orange-Emitting Poly[tris(2,5-dihexyloxy-l,4-phenylenevinylene)-alt-(l,3-phenylenevinylene)]s

Soluble yellow/orange-emitting poly[tris(2,5-dihexyloxy-1,4-phenylenevinylene)-alt- (1,3-phenylenevinylene)] derivatives (6) have been synthesized and characterized. These polymers contain oligo(p-phenylene vinylene) chromophores of equal conjugation length, which are linked to a m-phenylene unit. Optical comparison between 6 and its model compound 8 at room and low temperature reveals the similarity in their absorption and fluorescence band structures. The vibronic band structure of 6 is assigned with the aid of the spectroscopic data for 8 at low temperature. Polymers 6 are electroluminescent with emission lambda (sub max), at approximately 565 nm. By using the device configuration of ITO/PEDOT/6/Ca, the polymer exhibits an external EL efficiency as high as 0.46%.

Liao, Liang↗