Antifungal cellulose by capsaicin grafting

Cellulose is one of the most abundant materials in nature. Besides its biological function, cellulose can be extracted from the cell wall and used in several industrial applications. Thus, it can be used in papers, pharmaceuticals, food, cosmetics and innovative materials such as nanocomposites, packaging, coatings and dispersion technology. With the aim of extending cellulose applications and producing so-called “smart” materials, new functionality can be introduced by physical or chemical modifications. Taking into account that capsaicin, the active component of chili peppers, is an excellent antifungal agent, a potential new material could be obtained by chemical reaction between this active compound and cellulose. In this work, capsaicin grafting onto cellulose using polycarboxylic acid as linking agent is proposed. The reaction occurrence was corroborated by Fourier transform infrared spectroscopy and UV–Vis spectrophotometry in reflectance mode. Modified cellulose with <2 wt% of capsaicin shows a strong change in antifungal activity with respect to the unmodified one. This activity was evaluated by the fungal growth inhibition test with two different fungi, Trametes versicolor and Gloeophyllum trabeum. Modified cellulose samples showed a high percentage of fungal growth inhibition, demonstrating the success of the cellulose modification and high antifungal power of the grafting molecule.     

Ultrafast time‐resolved X‐ray absorption spectroscopy of chemical systems

The semiconductor industry continues in its relentless march to miniaturization [1 See, for instance http://www.itrs.net/Links/2007ITRS/2007_Chapters/2007_Lithography.pdf  [Google Scholar]]. Every four years or so, the dimensions of the features on an integrated circuit are halved, yielding an increase in density and functionality of the electronic “chip.” The economic advantages of more devices per unit area outweigh increases in fabrication costs and performance limitations, pushing the industry to seek ever-smaller patterns. At the time of writing (April 2008) advanced devices are patterned with the smallest features hovering around 45 nm, and the next generation of ～32 nm devices is on the horizon. What is perhaps most remarkable is that this level of nanopatterning is achieved with optical imaging tools and processes that use an actinic wavelength of 193 nm, the ArF laser emission line. As taught in any elementary physics textbook, the wavelength of light ultimately limits the achievable optical resolution [2 Hecht, E. and Zajac, A. 2002. Optics. Addison Wesley, : 471–474.  [Google Scholar]]. So how can we pattern 32 nm features using 193 nm radiation?     

Microwave-Assisted Extraction of Curcuma longa L. Oil: Optimization,Chemical Structure and Composition,Antioxidant Activity and Comparison with Conventional Soxhlet Extraction

Curcuma root (Curcuma longa L.) is a very important plant in gastronomy and medicine for its unique antiseptic, anti-inflammatory, antimicrobial and antioxidant properties. Conventional methods for the extraction of curcuma oil require long extraction times and high temperatures that can degrade the active substances. Therefore, the objectives of the present study were: (i) first, to optimize the extraction yield of curcuma oil by applying a Box-Behnken experimental design using surface response methodology to the microwave-assisted extraction (MAE) technique (the independent variables studied were reaction time (10–30 min), microwave power (150–200 W) and curcuma powder/ethanol ratio (1:5–1:20; w/v); and, (ii) second, to assess the total phenolic content (TPC) and their antioxidant activity of the oil (at the optimum conditions point) and compare with the conventional Soxhlet technique. The optimum conditions for the MAE were found to be 29.99 min, 160 W and 1:20 w/v to obtain an optimum yield of 10.32%. Interestingly, the oil extracted by microwave-assisted extraction showed higher TPC and better antioxidant properties than the oil extracted with conventional Soxhlet technique. Thus, it was demonstrated that the method applied for extraction influences the final properties of the extracted Curcuma longa L. oil.     

Rydberg states in the condensed phase studied by fluorescence depletion spectroscopy

Higher Rydberg states of NO trapped in rare gas matrices have been studied by inducing Rydberg-Rydberg transitions from the lowest Rydberg state and detecting its fluorescence depletion. This technique unravels Rydberg states, which cannot be accessed by ground state absorption. However, no clear cut Rydberg series show up. The data show a compression of the n-(n + 1) splittings between Rydberg states, as well as of the splittings. The results are rationalised in terms of the quantum defect model and the lack of extended Rydberg series is due to the compression of high-n Rydberg states in a tiny energy region below the ionisation potential. Finally, fluorescence depletion data of NO trapped in amorphous sites (the so-called red sites) of solid Ar can be interpreted in terms of the gas phase NO-Ar van der Waals data. A general discussion on the fate of Rydberg states in van der Waals complexes, in liquids, and in solids is presented in an attempt to relate the data in these different media. Received 28 July 1999 and Received in final form 8 November 1999     

Réactivité des cinnamoyl-3 pyrones-2 vis à vis des amines primaires

The reaction of primary amines (methylamine, isopropylamine, benzylamine) in neutral medium, on 3-cinnamoyl-2-pyrones gave 7-amino-3,5-dioxo-l,6-octadienes 2 . The formation of these compounds is presumed to occur via nucleophilic attack of amines with a ring opening reaction followed by decarboxylation. Their structures were determined unambiguously by ¹H, ¹³C nmr spectroscopy, elemental analysis and mass spectrometry.     

Fluorescence and phosphorescence from individual molecules excited by local electron tunneling

Using the highly localized current of electrons tunneling through a double barrier scanning tunneling microscope junction, we excite luminescence from a selected C60 molecule in the surface layer of fullerene nanocrystals grown on an ultrathin NaCl film on Au(111). In the observed fluorescence and phosphorescence spectra, pure electronic as well as vibronically induced transitions of an individual C60 molecule are identified, leading to unambiguous chemical recognition on the single-molecular scale.     

Femtosecond fluorescence and intersystem crossing in rhenium(I) carbonyl-bipyridine complexes

Ultrafast electronic-vibrational relaxation upon excitation of the singlet charge-transfer b (1)A' state of [Re(L)(CO) 3(bpy)] ( n ) (L = Cl, Br, I, n = 0; L = 4-Et-pyridine, n = 1+) in acetonitrile was investigated using the femtosecond fluorescence up-conversion technique with polychromatic detection. In addition, energies, characters, and molecular structures of the emitting states were calculated by TD-DFT. The luminescence is characterized by a broad fluorescence band at very short times, and evolves to the steady-state phosphorescence spectrum from the a (3)A" state at longer times. The analysis of the data allows us to identify three spectral components. The first two are characterized by decay times tau 1 = 85-150 fs and tau 2 = 340-1200 fs, depending on L, and are identified as fluorescence from the initially excited singlet state and phosphorescence from a higher triplet state (b (3)A"), respectively. The third component corresponds to the long-lived phosphorescence from the lowest a (3)A" state. In addition, it is found that the fluorescence decay time (tau 1) corresponds to the intersystem crossing (ISC) time to the two emissive triplet states. tau 2 corresponds to internal conversion among triplet states. DFT results show that ISC involves electron exchange in orthogonal, largely Re-localized, molecular orbitals, whereby the total electron momentum is conserved. Surprisingly, the measured ISC rates scale inversely with the spin-orbit coupling constant of the ligand L, but we find a clear correlation between the ISC times and the vibrational periods of the Re-L mode, suggesting that the latter may mediate the ISC in a strongly nonadiabatic regime.     

A femtosecond fluorescence study of vibrational relaxation and cooling dynamics of UV dyes

We present a femtosecond broad-band fluorescence up-conversion study of the vibrational relaxation dynamics of two UV chromophores, 2,5-diphenyloxazole (PPO) and para-terphenyl (pTP), pumped with a large excess of vibrational energy (>2000 cm(-1)). The band narrowing of the transient fluorescence spectrum reflects a biphasic cooling process in a few hundreds of fs and a few ps. In the sub-ps regime, our data suggest a structural rearrangement in the excited state, followed by thermalization of the excess energy. These dynamics affect the fluorescence spectra of PPO and pTP in different ways. In PPO, the damping of a low frequency vibrational wavepacket and a significant sub-ps narrowing of the band characterize the vibrational relaxation. In pTP, the latter is faster and appears as a red shift with distortion of the band in <200 fs.