Diatomite encapsulated AgNPs as novel hair dye cosmetics: Preparation, performance, and toxicity.

Naturally-occurring diatomite has been successfully utilised as a unique encapsulating material to obtain a highly dispersed suspension of uniformly-sized silver nanoparticles (AgNPs). Plant derived gallic acid was used as the reducing and capping agent. High-resolution scanning and transmission electron microscopy results confirmed the attachment of AgNPs on the surface of diatom frustule and maintained an excellent dispersion stability against particle aggregation. The AgNPs obtained were employed for the colouration of bleached human hair owing to the local surface plasmonic absorption (LSPR) of the AgNPs. The effects of Ag/diatomite concentration, dyeing pH, temperature and time on the produced colour were investigated. Hair fibres treated under optimised conditions display good colour fastness toward solar radiation. The morphology and chemical composition of AgNP-dyed hair were determined by energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses. The biocompatibility of the Ag/diatomite composite, AgNPs, and the dyebaths were confirmed by in vitro acute dermal and ocular toxicity tests. The diatomite supporting AgNPs therefore hold good promise and enormous potential to be exploited for sustainable dyeing of human hair.

Algal blooms of the 18th and 19th centuries.

Algal blooms, including those containing cyanobacteria, are of environmental concern due to the toxicities of some of the constituent microorganisms. This compromises the safety of freshwater causing illness in livestock and humans. We present historical accounts of algal blooms occurring during the 18th and 19th centuries indicating that the advent of intensive farming in the 17th century provided nutrients for promoting harmful algal blooms.

Light losses from scattering in luminescent solar concentrator waveguides.

The reductions in the transmission of emission originating from a fluorophore dissolved in a polymer matrix due to light scattering were compared in two forms of planar waveguides used as luminescent solar concentrators: a thin film of poly(methylmethacrylate) (PMMA) spin-coated on a glass plate and a solid PMMA plate of the same dimensions. The losses attributable to light scattering encountered in the waveguide consisting of the thin film of polymer coated on a glass plate were not detectable within experimental uncertainty, whereas the losses in the solid polymer plate were significant. The losses in the solid plate are interpreted as arising from light-scattering centers comprising minute bubbles of vapor/gas, incomplete polymerization or water clusters that are introduced during or after the thermally induced polymerization process.

The photophysics of phenylenevinylene oligomers and self-absorption of their fluorescence in polymer films.

The fluorescence spectra, quantum yields and lifetimes of a series of alkoxy-substituted phenylenevinylene molecules, which serve as short chain oligomer models for poly(p-phenylenevinylene), have been determined in fluid solvents and in a high viscosity polymer matrix. The effects of solvent polarity and a high viscosity molecular environment on the fluorescence yields and spectral shapes have been established. Alkoxy group substitution on the phenyl ring moieties of the molecules has an important effect on the vibronic structures and profiles of the absorption spectra. This was interpreted in terms of hot-band, ground to excited singlet state transitions from energetically closely-spaced torsional vibrational levels of the vinylene double bond in the ground state. The shapes of the absorption bands affect the overlaps of the absorption and fluorescence spectra. This has been quantified as the probability of fluorescence reabsorption in solid polymer films as a function of pathlength. This is an important determinant of the efficacies of these compounds for "harvesting" solar energy in luminescent solar concentrator systems. The reabsorption probabilities of these compounds are lower for all pathlengths than those determined in the same polymer film for the fluorophores, perylene and perylene diimide, which have been considered for concentrating spatially diffuse sunlight.

[Spectroscopic Investigation of Human Hair from Chinese Subjects During UVA Photoageing].

Since ultraviolet radiation is one of the major environmental factors that cause photoageing/photodamage, human hair, including both dyed and undyed hair, are subject to color change following extended exposure to sunlight. In the work described in this paper, six samples of human hair from Chinese volunteers that included untreated, bleached and dyed were subjected to accelerated ageing by exposure to UVA (320～400 nm) radiation. Changes to their chemical compositions during photoageing were non-destructively characterized by reflectance, 3D-fluorescence and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopies. These techniques, together with a quantitative analysis of the photosensitized generation of hydrogen peroxide, were used to assess the effects of different hair color and bleaching/dyeing treatments on the light stability of hair fibers. The results suggest that UVA irradiation can induce the production of hydrogen peroxide via a type Ⅱ mechanism (electron transfer interaction between photosensitive protein groups in their excited states) and subsequent reaction with oxygen, resulting in photo-oxidative degradation of surface protein and pigments of the hair fiber. Hair fibers of natural or artificial color respond differently in terms of color change during photoageing. Natural white and gray hair fibers exhibited the usual photoyellowing; and chemically black-dyed and bleached hairs showed photofading and additional photobleaching, respectively. Irradiation of hair in the wet state was found to accelerate photodegradation. Chemical bleaching and oxidative dyeing processes were shown to promote the photoinduced production of hydrogen peroxide, which contribute to a higher level of oxidative stress and thereby affects the photostability of human hair. Pigment molecules in hair, including both the natural pigmentation of melanin and that produced by artificial dyes, are suggested to play a dual role, both in the production and in the scavenging of oxygen free radicals. The work is designed to contribute to the establishment of spectroscopic methods for assessing the extent of hair photodamage as well as providing a sound experimental data basis for the research and development of improved hair dyes and after-dye products for the Chinese cosmetic market.

Synthesis and solution aggregation studies of a suite of mixed neutral and zwitterionic chromophores for second-order nonlinear optics.

We report details of the synthesis of a series of bi- and trichromophores. These compounds contain mixtures of chromophores that have zwitterionic (ZWI) and neutral ground state (NGS) components covalently attached to each other. The neutral ground state moieties are based on dyes with aniline donors--such as Disperse Red 1--whereas the zwitterionic components are derived from chromophores with pro-aromatic donors such as 1,4-dihydropyridinylidene. By combining both ZWI and NGS components, we aim to develop novel compounds for nonlinear optics in which there is an enhancement of the overall hyperpolarizability coupled with a decrease in the net dipole moment. Thus, this approach should eliminate the electrostatic effects that result when only one type of chromophore is used, and so reduce the likelihood of undesirable aggregation occurring. This, in turn, should enable us to realize organic materials with large macroscopic optical nonlinearities. An analysis of the UV-vis results suggests that there is a strong dependence on solvent polarity that determines whether the embedded constituents should be treated as discrete elements; in low polarity solvents, there appear to be strong intramolecular interactions occurring, particularly when a 1,4-quinolinylidene-based donor is used in the ZWI component.

Sesquiterpenes from the inner bark of the silver birch and the paper birch.

The compositions of the mixtures of sesquiterpenoids, largely hydrocarbons that were found in the inner bark of the silver birch, Betula pendula Roth and the paper birch, Betulapapyrifera Marshall, grown in New Zealand were analyzed by SPME-GCMS. The major components of the volatile oil from the inner bark of B. pendula were trans alpha-bergamotene (31%) and alpha-santalene (19%). This composition was quite different from that of the oil from the branches, buds and leaves of the same species from Turkey, but was very similar to that of the oil from the bark of B. pubescens from Russia. The major components of the oil from the inner bark of B. papyrifera were trans alpha-bergamotene (18%), ar-curcumene (12%), E-beta-farnesene (12%), Z-beta-farnesene (10%) and cis-alpha-bergamotene (8%).

Coumarins in Phormium (New Zealand flax) fibers: their role in fluorescence and photodegradation.

The genus Phormium (New Zealand flax) has fiber possessing a high content of lignin and, like other lignocellulosic materials, it is subject to photodegradation. Photoproducts in the fiber absorbing over a broad spectral region from ∼370 to 600nm are observed as a result of exposure to near-UV radiation from 350 to 400 nm. Irradiation was shown to produce hydrogen peroxide and this can account, at least in part, for the photo-oxidation manifested in changes in the reflectance spectra of the fibers. Unirradiated solid fibers and their aqueous extracts exhibit fluorescence with excitation maxima at 350-360nm and emission maxima at 440 nm. The fluorescence spectra of the fibers change following exposure to near-UV radiation with the major fluorophore being substantially photodegraded, evidenced by a substantial loss of emission between 410 and 480nm, which is largely responsible for the yellow and duller appearance of the fiber. Analysis of the aqueous extracts of the fibers, using electron-spray ionization mass spectroscopy of aqueous extracts, showed the presence of coumarin, hydroxycoumarin and a number of substituted hydroxycoumarins. The spectral distributions of the fluorescence associated with the unirradiated fibers and their aqueous extracts are consistent with them originating from a number of 7-hydroxycoumarins present.

The effect of molecular environment on the photoisomerization of urocanic acid.

Urocanic acid, imidazole propenoic acid, is a metabolic product of histidine, which accumulates in skin and is excreted in sweat. It absorbs UV radiation at wavelengths shorter than 340 nm, and its principal photochemical reaction is a trans-cis isomerization about the propenyl double bond. This isomerization to the biologically active cis isomer is implicated in the photoinduced suppression of the immune system of skin. The kinetics of the trans --> cis photoisomerization of urocanic acid has been determined in a number of solvents, spanning a range of polarities. The initial rates of isomerization and the photostationary trans-cis compositions, in all solvents except water, correlate linearly with solvent polarity. This indicates that the isomerization proceeds through a polar intermediate that is stabilized by coulombic interactions with the molecular environment.

The fluorescence and photostabilities of naturally occurring isoflavones.

The 5,7-dihydroxyisoflavones do not emit detectable fluorescence and are significantly more photostable than the two 7-hydroxy-5-deoxyisoflavones, daidzein and formononetin. The latter isoflavones emit fluorescence that depends on the basicity of the solution and the polarity of the solvent. Comparison of the spectral distributions of the emission in methanol in the presence and absence of base indicates that it originates from the conjugate anion excited singlet states. The fluorescence of daidzein and formononetin exhibit large Stokes shifts to longer wavelengths in methanol, ethanol, hexanol and acetonitrile and the magnitudes of these shifts increase with solvent polarity. This indicates that the emission originates from excited singlet states with much larger dipole moments than those of the corresponding ground states. Values of 8.3 D and 6.5 D were determined for daidzein and formononetin respectively. The photostabilities of formononetin and daidzein both increase with increasing solvent polarity and in corresponding solvents, the photostability of daidzein is higher than that of formononetin, behaviour which is attributed to the greater antioxidant activity of daidzein.

The effect of UV absorbing sunscreens on the reflectance and the consequent protection of skin.

The in vivo reflectance spectra of Caucasian skin, coated with preparations containing sunscreen vehicle, vehicle with olive oil and vehicle with the UVB and UVA absorbers 2-ethylhexyl-4-methoxycinnamate and 4-t-butyl-4'-methoxydibenzoylmethane were determined. All preparations reduced the reflectance of skin throughout the UVA spectral range (320 to 400 nm), with the sunscreen preparations containing the UVB and UVB plus UVA absorbers reducing the reflectance more than the sunscreen vehicle alone. This phenomenon, which facilitates the penetration of UV radiation to the lower epidermis and dermal layers of skin and therefore lessens sunscreen efficacy, is attributed to optical coupling mediated by refractive index matching of the sunscreen to the upper epidermis. The greater reduction in skin diffuse reflectance caused by sunscreens containing methoxycinnamate is associated with this compound's high refractive index. Also, by determining the excitation spectra of the autofluorescence originating from the dermal layer of skin, the transmission spectra of the various components of sunscreen on skin were established, and these were in good general agreement with previously published spectra.