Effect of Solvents upon the Absorption Spectra of Dyes. V. Water as Solvent: Quantitative Examination of the Dimerization Hypothesis

1944 ◽  
Vol 66 (12) ◽  
pp. 2003-2009 ◽  
Author(s):  
S. E. Sheppard ◽  
A. L. Geddes
Keyword(s):  
Absorption Spectra ◽  
Effect Of Solvents ◽  
Water As Solvent ◽  
Quantitative Examination

THEORETICAL CHARACTERS OF MgX (X = Te, Se, S AND O) CLUSTERS

2010 ◽  
Vol 19 (04) ◽  
pp. 695-701 ◽  
Author(s):  
SHUHONG XU ◽  
CHUNLEI WANG ◽  
YIPING CUI
Keyword(s):  
Dipole Moment ◽  
Absorption Spectra ◽  
Raman Spectra ◽  
Density Functional ◽  
Nbo Analysis ◽  
Time Dependent ◽  
Theoretical Level ◽  
Functional Theory ◽  
Regular Change ◽  
Water As Solvent

At DFT/B3LYP/LANL2DZ theoretical level, a series of MgX clusters with Mg3X3 hexagon, Mg4X4-t tetrahedron and Mg4X4-o octagon conformations are investigated. Their wavelengths of absorption spectra are calculated with time-dependent Density Functional Theory (TDDFT) using water as solvent. Firstly, the lowest vibrational frequencies, bond lengths, Dipole Moment and Raman spectra of them present regular change. Dipole Moment result shows that different clusters have different charges. From Raman spectra, we have discovered that they correlate with the conformation and variety of clusters. Conformations of MgO clusters have different optimizing characters with MgS , MgSe and MgTe molecules. Secondly, through Molecular Orbital and Nature Bond Orbital (NBO) analysis, we have found that all these clusters are materials with wider gaps. MgTe structures have stronger bonding. Besides, MgO have different transition from the other clusters. The order of wavelengths of absorption spectra is MgTe > MgSe > MgS . In a word, except MgO molecules, these clusters have similar or regular characters. These results are significant for experimental study of MgX nanocrystals.

Effect of Solvents on Controlling the Photophysical Properties of Poly[2-Methoxy-5-(2’-Ethylhexyloxy)-1,4-Phenylenevinylene] (MEH-PPV) Nanoparticle

2017 ◽  
Vol 16 ◽  
pp. 56-59
Author(s):  
Ruttayapon Potai ◽  
Rakchart Traiphol
Keyword(s):  
Absorption Spectra ◽  
Solvent Effects ◽  
Conjugated Polymer ◽  
Photophysical Properties ◽  
Conjugation Length ◽  
Simple Method ◽  
Chain Packing ◽  
Solvent Interactions ◽  
Effect Of Solvents ◽  
Chain Conformations

Abstract. This study focuses on detailed investigation of solvent effects on controlling photophysical properties of poly [2-methoxy,5-(2’-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) nanoparticles prepared by using reprecipitation techniques. In this work, the MEH-PPV polymer is dissolved in various solvents, including chlorobenzene (CRB), toluene (TOL) and pyridine (PYR). The polymers in solutions adopt different conformations (i.e. collapsed or extended coils), depending on local polymer-solvent interactions. The differences of chain conformations cause the variations of chain packing within the nanoparticles. The majority of nanoparticles exhibit diameter of about 65-70 nm. The photophysical properties of MEH-PPV nanoparticles varied with type of solvents. The absorption spectra of nanoparticles exhibit a broad pattern with a long red tail at about 550 nm, indicating the formation of inter-and/or intrachain aggregates within the nanoparticles. However, the nanoparticle from TOL system shows blueshift of λmax, corresponding to the decrease of conjugation length due to the existence of collapsed coil. The photoluminescence (PL) spectra of MEH-PPV nanoparticles show consistent result with the shift of λmax to about 590 nm and vibronic shoulder at about 640 nm. The PL patterns vary with the type of solvents. In addition, the PL patterns depend on the variations of excitation wavelengths. These discrepancies indicated the variation of chain conformation and degree of aggregation within the nanoparticles. Our results demonstrate the simple method to prepare the conjugated polymer nanoparticle with different photophysical properties by changing solvents.

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