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Polarization of Colloidal CdSe Quantum Dots
Nguyen Quang Liem,Le Quang Phuong,Ung Thi Dieu Thuy,Tran Thi Kim Chi,Do Xuan Thanh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3
The effects of the polarization of colloidal CdSe QDs on the optical transitions are discussed based on systematic studies of a colloidal CdSe-based QDs system as a function of the net QDs' polarity/polarization and of the solvent's polarity. The polarization of the QD/ligand complexes makes them water-soluble after appropriate cleaning processes. The polarization of the bare CdSe QDs is reasonably thought to originate from dangling bonds at the surfaces of the dots. Passivation of the Se dangling bond by hydrogen generated from ultraviolet irradiation of the CdSe QDs in water is clearly observed to cause a spectral blueshift and a photoluminescence enhancement.
CePO4:Tb Nanoparticles: Preparation, Structure and Optical Properties
Nguyen Vu Thanh,Tran Kim Anh,Nguyen Quang Liem,Nguyen Huu Quan,Nguyen The Khoi 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Nanocrystals of CePO4:Tb were prepared by reacting the corresponding metal chlorides, phos- phoric acid and trioctylamine at 200℃ in tris(2-ethylhexyl) phosphate (TEHP). The samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). The photoluminescence (PL) and the absorption spectra of CePO4:Tb nanoparticles will be presented. The PL spectra are described by using the well-known 5D4 - 7FJ transitions (J = 6, 5, 4, 3 ···) of Tb3+ ions with the strongest emission at 543 nm for J = 5. The dependence of PL intensity on Tb3+ concentration has been investigated. Nanocrystals of CePO4:Tb were prepared by reacting the corresponding metal chlorides, phos- phoric acid and trioctylamine at 200℃ in tris(2-ethylhexyl) phosphate (TEHP). The samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). The photoluminescence (PL) and the absorption spectra of CePO4:Tb nanoparticles will be presented. The PL spectra are described by using the well-known 5D4 - 7FJ transitions (J = 6, 5, 4, 3 ···) of Tb3+ ions with the strongest emission at 543 nm for J = 5. The dependence of PL intensity on Tb3+ concentration has been investigated.
Design and growth of InAsP metamorphic buffers for InGaAs thermophotovoltaic cells
Nguyen Thuy Thi,Kim Yeongho,Park Suho,이상준,Jo Hyun Jun,Kim Jong Su,Nguyen Liem Quang,Kim Eui-Tae 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.78 No.11
The structural and optical properties of InAsxP1-x metamorphic buffers grown by metal–organic chemical vapor deposition on InP (100) substrates have been investigated. High-resolution X-ray reciprocal space mapping around the (115) InP lattice point reveals that the strain relaxations of the InAsxP1-x with x = 0.5, 0.55, and 0.7 are 98%, 92%, and 96%, while the lateral correlation lengths are 17, 62, and 28 nm, respectively. The optical bandgap energy of the InAsP derived from photoreflectance (PR) measurements decreases from 0.819 to 0.621 eV at 300 K when increasing As composition from x = 0.5 to 0.7. The bowing parameter for the optical bandgap of the InAsP is increased with increasing As composition, which is attributable to the increased spontaneous CuPt-type ordering in InAsP. It is found from the excitation power-dependent PR measurement that the InAsxP1-x layers have different degrees of the bandgap redshift due to the reduced thermal conductivity caused by crystal imperfections generated during the strain relaxation process.
Linh Nhat Nguyen,Neha Kaushik,Pradeep Bhartiya,Sintayehu Kebede Gurmessa,김화정,Liem Quang Nguyen,Nagendra Kumar Kaushik,최은하 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.100 No.-
The development of an efficient tumor-specific therapeutic approach, which functions against theprimary tumor and also repairs the host immune system to eradicate distant tumors, remains a clinicalissue. Herein, this study focuses on the use of polydopamine-coated gold nanoparticles (Au@PDA NPs)that showed excellent selectivity towards cancer cells. The Au@PDA NPs were prepared by a plasmasynthesis method with a short reaction time and minimize the use of chemicals. Prominently, Au@PDANPs not only exhibited high cellular internalization but also stimulated immunogenic cell death (ICD) inaggressive breast carcinoma cells. Moreover, it was observed that damage-associated molecular patterns(DAMPs) were released by damaged cells together with the autophagy process after Au@PDA NPsexposure, which acted as endogenous danger signals to regulate the consequent immune response. Thisstudy highlights the novel mechanism of Au@PDA NPs-triggered anti-tumor immunity againstimmunosuppressive cancers, demonstrated the potential of the Au@PDA NPs for cancer immunotherapy.
Temperature-Dependent Photoluminescence and Absoprtion of CdSe Quantum dots Embedded in PMMA
Tran Thi Kim Chi,Ung Thi Dieu Thuy,Nguyen Quang Liem,Man Hoai Nam,Do Xuan Thanh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Photoluminescence and absorption studies of CdSe quantum dots in polymethylmethacrylate (PMMA) were carried out in the temperature range 14 - 310 K. We found an anomalously discontinuous variation of the photoluminescence intensity and the peak position around 50 K. Two different kinds of states, whose populations are temperature-dependent, are proposed as the origins for the emissions at lower and higher temperatures. The absorption exhibited a temperature-dependent behavior similar to that of the photoluminescence.O Photoluminescence and absorption studies of CdSe quantum dots in polymethylmethacrylate (PMMA) were carried out in the temperature range 14 - 310 K. We found an anomalously discontinuous variation of the photoluminescence intensity and the peak position around 50 K. Two different kinds of states, whose populations are temperature-dependent, are proposed as the origins for the emissions at lower and higher temperatures. The absorption exhibited a temperature-dependent behavior similar to that of the photoluminescence.O
Thuy, Ung Thi Dieu,Chae, Weon-Sik,Yang, Won-Geun,Liem, Nguyen Quang North-Holland 2017 Optical materials Vol.66 No.-
<P><B>Abstract</B></P> <P>This paper reports the metal-induced fluorescence property on the CdTe/CdS core/shell quantum dots (QDs), which exhibit the systematic band-gap transition from type-I to type-II with increasing shell thickness, near porous silver membrane by using time-resolved fluorescence lifetime imaging microscopy (FLIM). The results revealed that notable fluorescence enhancement came from the closed location to the cavity of the porous silver metal due to an increase in the local electromagnetic fields at the cavity. In the cases of the type-II CdTe/CdS QDs, interestingly, multiple exciton generation can be an additional factor for the lifetime reduction and fluorescence amplification compared to the type-I QDs. Without CdS shell, the strong interaction between the bare core CdTe QDs and silver caused emission quenching.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Luminescence enhancement up to 5- and 10-times for type-I and type-II CdTe/CdS QDs at local cavity region of <I>p</I>-Ag membranes. </LI> <LI> The luminescence enhancement in type-I CdTe/CdS QDs is due to the accelerated optical fields; while, that in type-II CdTe/CdS QDs is reasonably attributed to both the accelerated radiative recombination and the enhanced absorption mechanisms. </LI> <LI> The metal-induced absorption enhancement and plausible multiexciton generation in the type-I and type-II CdTe/CdS QDs make them very promising for optical signal amplification and solar energy conversion applications. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>