Dye molecular aggregation and other interactions on clay mineral surfaces cause phenomena such as methachromasy (change in color), fluorescence enhancement, or quenching, which represent significant changes in the spectral properties of the dye. These phenomena can be used to control the photophysical properties of hybrid systems based on cationic organic dyes. In the present study, the aggregation of two structurally similar cyanine dyes, 3,3’-diethyl-oxocyanine iodide (OxCy) and 3,3’-diethyl-2,2’-thiacyanine iodide (ThCy), in colloidal dispersions of three smectites (saponite, hectorite, and montmorillonite) was studied by absorption and fluorescence spectroscopy for a broad range of dye/smectite loadings. Spectral data were analysed by chemometric methods (principal component analysis, PCA, and multivariate curve resolution, MCR). Detailed analysis of the OxCy absorption spectra by the chemometric methods revealed the formation of two types of oblique aggregates exhibiting light absorption in both H- and J-bands. The existence of such similar aggregates, with similar splitting of excitation energies, appears to be related to the existence of two stable conformational isomers of this dye. On increasing the smectite CEC and dye/smectite loading, fluorescence quenching occurred. The ThCy dye exhibited a stronger tendency for molecular aggregation than OxCy. On increasing the smectite CEC, the formation of oblique aggregates with dominant H-bands also increased. On aging of the hybrid dispersions, equilibria of ThCy aggregates were shifted to the species with dominant J-bands. This behavior had a significant impact on the shape and intensity of the fluorescence emission of the hybrid dispersions. Using different smectites enables control of the dye aggregation and significant change to the photophysical properties of the hybrid systems. These systems can be used for the detailed study of the photophysical properties of cyanine dyes in various states. The colloidal systems with cyanine dyes can be used as precursors for the preparation of novel hybrid materials. In addition, the sensitive response of the photophysical properties of cyanine dyes to the clay mineral surface can be applied to the characterization of clay minerals.

Resonance energy transfer (RET) in hybrid polymer/inorganic/organic layers in saponite films, prepared using the ‘layer-by-layer’ (LBL) method, was studied. This method allows the fabrication of a multicomposite molecular assembly based on electrostatic and/or other intermolecular interactions between the interacting species. The LBL films were designed by sequential deposition including positively charged polycations ( poly(diallyldimethyl ammonium), PDDA) and negatively charged saponite dispersions with donor molecules (rhodamine 6G) and saponite dispersions with acceptor molecules (rhodamine 3B). In this sequence, the layer of saponite donor molecules was placed on an adjacent layer of saponite acceptor molecules, while the layers were separated by inserting a PDDA polycationic layer. The adsorption process was studied using absorption spectroscopy. The linear deposition regime was completed when ten layers had been deposited. The process of REF was studied by fluorescence spectroscopy. In this case the donor molecules – rhodamine 6G – play the role of lightharvesting antennae and transfer the energy to the next layer covered by energy acceptor, i.e. rhodamine 3B molecules. The insertion of polycation layers is rationalized by the adhesion of negatively charged underlying layers and the stabilization of multicomponent systems. The energy transfer efficiency was affected heavily by changing the distances between the adjacent layers.

Targets have been developed to measure supersonic radiation transport in aerogel foams using absorption spectroscopy. The target consists of an aerogel foam uniformly doped with either titanium or scandium inserted into an undoped aerogel foam package. This creates a localized doped foam region to provide spatial resolution for the measurement. Development and characterization of the foams is a key challenge in addition to machining and assembling the two foams so they mate without gaps. The foam package is inserted into a beryllium sleeve and mounted on a gold hohlraum. The target is mounted to a holder created using additive manufacturing and mounted on a stalk. The manufacturing of the components, along with assembly and metrology of the target are described here.

Ammocoetes of sea lamprey (Petromyzon marinus Linnaeus, 1758) from an assumedly pristine tidal freshwater habitat were used for determination of metal levels and accumulation patterns with size. The individuals were collected during the winter of 2011 in river Minho (Iberian Peninsula, Southwest of Europe) and the levels of metals (Cd, Cu, Cr, Fe, Pb, Mn and Zn) in the whole body were analysed by atomic absorption spectrometry. Fe was the metal with highest levels (maximum of 1438 ppm), while Cd and Pb were the lowest accumulated elements (overall means of 0.093±0.065 ppm and 0.259±0.094 ppm, respectively). Larger ammocoetes seemed prone to accumulate Cu, Fe and Mn (P<0.05). Pb and Zn levels also seemed to increase with ammocoetes size; however, statistical differences were not found between size classes (P>0.05).

Distribution, reproductive biology and biochemical composition of Rhopalophthalmus indicus were investigated based on samples collected over a period of one year from Cochin backwater. Rhopalophthalmus indicus was recorded throughout the year with peak abundance during pre-monsoon. The population density was influenced by chlorophyll-a, dissolved oxygen, salinity and water temperature. The species showed periodicity in the abundance and produced more than one generation per year. The number of embryos carried by a single female ranged from six to 13, and was correlated with female body length (P > 0.05), tending to increase with the size of the female. Egg size varied between 0.42 and 0.47 mm, and was independent of female size. Both males and females attain sexual maturity at a length of 8.4 mm. Seasonality is observed in biochemical composition, as mature males and females had higher protein contents, immature stages contained high carbohydrate content and brooding females accumulated more lipids.