Enhanced optical sensing of anions with amide-functionalized gold nanoparticles

A gold nanoparticle surface-modified with amide ligands shows enhanced optical sensing of anions: the detection limit is increased by about three orders of magnitude higher than that originally expected from the anion binding ability of neutral amide ligands.     

Isotope-dependent crystalline phases at ambient temperature: Spectroscopic and calorimetric evidence for a deuteration-induced phase transition at 320 K in α-DCrO2

The heat capacities of HCrO₂ and DCrO₂ have been measured at temperatures between 5 and 360 K. A lambda anomaly occurred at 320 K for DCrO₂ but not for HCrO₂. Infrared spectra were recorded at temperatures between 5 and 405 K. The spectrum of DCrO₂ changed at 320 K with respect to the peak wave-number and splitting of some of the vibrations, while those of HCrO₂ depended smoothly on temperature. These experimental results are discussed in terms of a deuteration-induced phase transition.     

Hole drilling in stainless steel and silicon by femtosecond pulses at low pressure

We report on the ablation and hole drilling in stainless steel SUS304 and Si by femtosecond pulses (wavelength 800 nm; pulse duration >80 fs) at the room and low (5 Torr) air pressure ambient. It was found that the quality of surface processing is improved at low pressure avoiding debris formation. The improvement is due to suppression of the conical emission, resulting from the air optical breakdown at a pre-surface area of sample. Debris-free processing of the movable Si-MEMS components is demonstrated. Techniques for the precise measurement of focal spot size and pulse duration are discussed. PACS 87.80.Mj; 78.66.Bz; 42.62.Cf; 61.82.Bg; 61.80.-x     

Resonance Raman effect in thiourea

Raman spectra of thiourea have been observed in H₂O and D₂O solutions with the exciting laser beams of 514.5, 488.0, 457.9, 363.8, 325.0, and 257.3 nm. The resonance Raman excitation profile of the 729-cm^?1 line has been examined in the region of the 237-nm absorption band ($\text{π}{}_{\mathrm{<mtext>CS</mtext>}}{}^1\text{← π}{}_{\mathrm{<mtext>CS</mtext>}}$) by use of a solvent shift of the absorption band instead of by changing the wavelength of the exciting beam. The depolarization degree of this line was measured and its overtone Raman line was also observed. On the basis of the results of these experiments, it has been concluded that the 729-cm^?1 Raman line, assignable to the CS stretching vibration, derives its intensity solely from the 237-nm band when it is excited at 257.3 or 325.0 nm. On exciting in the region 363.8–514.5 nm, however, contributions of the higher-frequency bands are predominant rather than the contribution from the 237-nm band. The Raman line at 1520 cm^?1 of thiourea-d₄ is assignable to the NCN antisymmetric stretching vibration. From its excitation profile, its intensity has been considered to come from a vibronic coupling between the excited electronic states of the 220-nm ($\text{π}{}_{\mathrm{<mtext>CS</mtext>}}{}^1\text{← π}{}_{\mathrm{<mtext>N</mtext>}}\text{? π}{}_{\mathrm{<mtext>N</mtext>}}$) and the 197-nm ($\text{π}{}_{\mathrm{<mtext>CS</mtext>}}{}^1\text{← π}{}_{\mathrm{<mtext>N</mtext>}}\text{+ π}{}_{\mathrm{<mtext>N</mtext>}}$) bands.     

Overtones of liquid benzene in the visible region by direct absorbance measurement

The absorption bands arising from overtones of the CH stretching vibration of liquid benzene were measured up to the v = 0–9 transition. The transition energies at the band maxima are expressed by a cubic equation. Their bandwidths and oscillator strengths are discussed.     

Calorimetric and dielectric studies of a phase transition in thallium dihydrogen phosphate: A nearly critical case

The heat capacity of thallium dihydrogen phosphate was measured from 12 to 300 K. A lambda anomaly with a small first order discontinuity was found at 229.76 K with the integrated enthalpy and entropy changes equal to 370 J mol^-1 and 1.8 J K^-1 mol^-1, respectively. The entropy discontinuity at the first order transition is 0.25 J K^-1 mol^-1. The Landau theory of phase transitions of the second kind reproduces closely the temperature dependence of the anomalous heat capacity. This, together with the small discontinuity in the entropy, implies that the phase transition is close to a classical critical point of higher order. The relative dielectric permittivity ?_r(b) along the b-axis at 1 kHz is anomalously large and strongly temperature dependent, while the ?_r(a¹) and ?_r(c) are not. A broad absorption centered at 1700 cm^-1 was observed in the infrared absorption spectrum, indicating presence of hydrogen bonding of the length ～ 0.25 nm. Occurrence of a phase transition at 127 ± 2 K was suggested by differential thermal analysis of thallium dideuterium phosphate.     

Fabrication of fine-pitch TiO<Subscript>2</Subscript>-organic hybrid dot arrays using multi-photon absorption of femtosecond pulses

Surface corrugation has been photo-induced in a single-step process in hybrid sol-gel thin films. A model based on elastic deformation under photo-induced stress is developed to explain relief formation in this material. Computation is carried out with finite-element software. Theoretical and experimental values of relief amplitude variation with film thickness and grating period agree for small deformations. Mass transfer from illuminated to non-illuminated areas has to be associated with the elastic model to account for surface corrugation in the case of large photo-induced deformation. A comparison with a fluid mechanics model is presented. PACS 81.65.C; 81.20.F; 81.40.L     

Creation of hoop- and bowl-shaped benzenoid systems by selective detraction of [60]fullerene conjugation. [10]cyclophenacene and fused corannulene derivatives

Selective penta-addition of a methylcopper reagent followed by addition of a phenylcopper reagent to a suitably modified synthetic intermediate results in creation of 40pi-electron systems-hoop- and bowl-shaped cyclic benzenoid compounds, [10]cyclophenacene, and dibenzo-fused corannulene derivatives. The 40pi-electron cyclophenacene derivatives have been found to be chemically stable, yellow-colored, luminescent (560 nm), and EPR-silent. X-ray crystallographic analysis provided precision structural data sets. The dibenzo-fused corannulene derivatives exhibit blue-green (460 nm) to red (649 nm) fluorescence.