A hierarchical nanoparticle strategy to simultaneously gain super Raman signal amplification, high uniformity, and reproducibility is presented. Using hollow Au-Ag alloy nanourchins, an ultrahigh sensitivity, e.g., down to 1 fM concentrations for DEHP molecule is obtained. A small standard deviation of <10% is achieved by simply dropping and evaporating sub-100 nm nanourchins onto a substrate.

Highly Sensitive, Uniform, and Reproducible Surface‐Enhanced Raman Spectroscopy from Hollow Au‐Ag Alloy Nanourchins

Catalytic behavior of metal–organic frameworks in the Knoevenagel condensation reaction

A new method for quantifying the intensity of the C=C band of dimethacrylate dental monomers in their FTIR and Raman spectra.

The Raman spectra (3200-10 cm−1) of dichloroacetyl fluoride (CHCL2CFO) of the gas, liquid (with qualitative depolarization ratios) and solid were recorded. The infrared spectra (3200-30 cm−1) of the gas and solid were also obtained. All of these data indicate a trans/gauche equilibrium in the gas and liquid whereas only the gauche conformation remains in the solid. A complete vibrational assignment is proposed for both conformers based on the Raman depolarization data, infrared band contours, group frequencies and normal coordinate calculations. From the studies of the Raman spectra at various temperatures, the enthalpy difference between the stable conformers was determined to be 315 ± 68 cm−1 (0.90 ± 0.19 kcal mol−1) (1 kcal = 4.184 kJ) and 180 ± 4 cm−1 (0.51 ± 0.01 kcal mol−1) for the gas and liquid, respectively, with the trans conformer being more stable in the gas but the gauche conformer more stable in the liquid. These experimental results are compared to those obtained from ab initio Hartree-Fock gradient calculations with the RHF/3-21G* and RHF/6-31G* basis sets, and to the corresponding quantities obtained for some similar molecules.

Raman and infrared spectra, conformational stability, barriers to internal rotation, ab initio calculations and vibrational assignment of dichloroacetyl fluoride

Publisher Summary This chapter examines important aspects of the synthesis, electrical, and optical properties of conducting polymers. There are a variety of routes toward the synthesis of polyacetylene. These syntheses can be classified into four categories: catalytic polymerization of acetylene, noncatalytic polymerization of acetylene, catalytic polymerization of monomers other than acetylene, and, finally, precursor methods. Many chemical reaction schemes have been proposed for polyaromatics and they can be classified as—(1) direct oxidation of benzene, (2) organometallic coupling, (3) precursor methods, and (4) electrochemical syntheses. There are several approaches toward the preparation of poly(p-phenylene vinylene) (FPV), which can be classified as direct and precursor methods. Several of these methods have been applied to synthesize heterocyclic derivatives, alkoxy-substituted poly(thienylene vinylene), and poly(furylene vinylene). Several types of π-electron systems have shown very interesting features in the electrical transport properties. The charge-transfer complexes consisting of electron-donating and electron-withdrawing organic molecules have a wide range of exciting electronic properties of low-dimensional systems. The typical sp2-carbon-rich systems such as intercalated graphite, carbon-60, and carbon nanotubes display a wide range of behavior from metals to insulators.

Synthesis, electrical, and optical properties of conjugated polymers

The far infrared spectrum of gaseous chloroacetyl fluoride, CH2ClC(O)F, has been recorded at a resolution of 0.10 cm−1 in the 350 to 35 cm−1 region. The fundamental asymmetric torsional frequencies of the more stable trans (two halogen atoms oriented trans to one another) and high energy gauche (Cl–C–C=O torsional dihedral angle of 122°) have been observed at 86.5 and 48.8 cm−1, respectively, each with excited states falling to lower frequency. From these data the asymmetric torsional potential function governing internal rotation about the C–C bond has been determined. This potential function is consistent with torsional potential coefficients of: V1=350±12, V2=306±6, V3=420±1, V4=44±1, and V6=2±1 cm−1. The trans to gauche, gauche to gauche, and gauche to trans barriers have been determined to be 796, 245, and 271 cm−1, respectively, with an energy difference between the conformations of 525±24 cm−1 (1.50±0.07 kcal/mol). From studies of the Raman spectrum at variable temperatures the conformational energ...

Conformational stability, barriers to internal rotation, vibrational assignment, and ab initio calculations of chloroacetyl fluoride

Barriers to internal rotation, vibrational assignment, and ab initio calculations for chloroacetyl chloride

The Raman (3200 to 10 cm−1) and far infrared (380 to 60 cm−1) spectra of gaseous fluorocyclobutane,c-C4H7F, have been recorded. A series of Q-branches observed in both of these spectra beginning at 166 cm−1 with successive transitions falling to lower frequencies have been assigned to the ring puckering vibrations of both the low energy equatorial and high energy axial conformers. These data have been fit to an asymmetric potential function of the form:V (cm−1)=(1.76±0.05)103X+(4.88±0.28)104X2+(2.12 ±0.16)103 exp(−5.66±0.41)10X2 with a reduced mass function ofg44= 0.00386−0.00295X+0.03485X2+0.1228X3 +0.3459X4, whereX is the ring puckering coordinate. Utilizing this potential, the difference between the puckering angles for the two conformers was calculated to be 4° with the equatorial conformer having the larger value of 28°. This potential function is consistent with an energy difference between the equatorial and axial forms of 447 cm−1 (1.28 kcal/mol) and a barrier to ring inversion from the equatorial to the axial conformation of 713 cm−1 (2.04 kcal/mol). Experimental values for the enthalpy difference between the two conformers have been determined for both the liquid (400±30 c−1) and gas (413±43 cm−1) from investigations of the Raman spectra at variable temperatures. The conformational stability, enthalpy difference, structural parameters, and fundamental vibrational frequencies, which have been determined experimentally, are compared to those obtained from ab initio Hartree-Fock calculations employing the 3-21G, 6-31 G*, and 6-31 G** basis sets.

Spectra and structure of small ring compounds. LIX

Spectra and structure of small ring compounds. LI. Infrared and Raman spectra, vibrational assignment and ab initio calculations of 1,1-dicyanocyclobutane

The Raman (3500–10 cm−1) and far-infrared (400–70 cm−1) spectra of solid 1,1-dicyanocyclopropane have been recorded. The molecular structure of cyclopropane, cyanocyclopropane and 1,1-dicyanocyclopropane have been calculated by ab initio methods at the 4-31G basis set level. The harmonic force fields for cyanocyclopropane and 1,1-dicyanocyclopropane have also been calculated using the same basis set. By the combination of experimental data and normal coordinate calculations with scaled ab initio force constants, the vibrational assignments for these two molecules have been revised. Discrepancies between the previously reported and present assignments are discussed. The molecular structures of cyanocyclopropane and 1,1-dicyanocyclopropane obtained in this work are compared with the molecular structure of cyclopropane.

Spectra and structure of small ring compounds. LII—Raman and far‐infrared spectra of solid 1,1‐dicyanocyclopropane and ab initio calculations of cyclopropane, cyanocyclopropane and 1,1‐dicyanocyclopropane

Wenyun Zhao

Papers

Conformational stability, barriers to internal rotation, vibrational assignment, and ab initio calculations of chloroacetyl fluoride

Barriers to internal rotation, vibrational assignment, and ab initio calculations for chloroacetyl chloride

Spectra and structure of small ring compounds. LIX

Spectra and structure of small ring compounds. LI. Infrared and Raman spectra, vibrational assignment and ab initio calculations of 1,1-dicyanocyclobutane

Spectra and structure of small ring compounds. LII—Raman and far‐infrared spectra of solid 1,1‐dicyanocyclopropane and ab initio calculations of cyclopropane, cyanocyclopropane and 1,1‐dicyanocyclopropane