The structural organization of sodium borophosphate glasses with composition (NaPO 3 ) 1-x (B 2 O 3 ) x (0.0 e x e 0.3) has been investigated by X-ray photoelectron spectroscopy (XPS), as well as single-and doubleresonance 11 B and 31 P magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. O-1s XPS data provides a quantitative distinction between B-O-B, B-O-P, and P-O-P linkages as well as nonbridging oxygen atoms. 11 B and 31 P MAS NMR data indicate that within the compositional region 0 e x e 0.20 the entire boron inventory is present in the form of anionic BO 4units, resulting in the repolymerization of an equivalent fraction of the phosphate units (conversion of anionic metaphosphate (P (2) ) into neutral branching groups (P (3) ) species. Both XPS as well as 31 P{ 11 B} and 11 B{ 31 P} rotational echo double resonance (REDOR) NMR results reveal strong interactions between the two network formers boron oxide and phosphorus oxide, resulting in the dominant formation of B-O-P linkages. In addition, the shape of the REDOR curve reveals a certain tendency of these linkages to cluster, consistent with a preference of P (3) units to form more than one P-O-B linkage, even at low boron contents. The enhanced degree of network polymerization correlates with a significant increase of the glass transition temperature as a function of boron content.

The structural organization of sodium borophosphate glasses with composition (Na(2)O)(x)(BPO(4))(1-x) (0.25 ≤x≤ 0.55) has been investigated by differential scanning calorimetry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), as well as single- and double resonance (11)B and (31)P magic-angle spinning (MAS) NMR. (11)B MAS-NMR data indicate the dominance of anionic four-coordinated boron units, and (31)P MAS NMR reveals the successive transformation of neutral P(3) into singly charged P(2) units and their further transformation into doubly charged P(1) units at high Na(2)O contents. The quantification of these units provides detailed insight into the competition of the network formers borate and phosphate for the network modifier oxide. At low modifier content (x < 0.35), the anionic species are almost exclusively borate (B(4)) units, whereas at higher sodium concentrations, large numbers of anionic phosphate (P(2) and P(1)) species are formed. O-1s XPS data provide a quantitative distinction between B-O-B, B-O-P, and P-O-P linkages as well as non-bridging oxygen atoms, and comparable numbers can be extracted from (11)B and (31)P MAS-NMR experiments. Both XPS as well as (31)P{(11)B} and (11)B{(31)P} rotational echo double resonance (REDOR) NMR results reveal strong interactions between the two network formers boron oxide and phosphorus oxide, resulting in a preferred formation of B-O-P linkages. For higher Na(2)O contents, however, the successive network modification diminishes this preference, resulting in close-to-statistical network connectivities. Compositional trends of T(g) in the Na(2)O-B(2)O(3)-P(2)O(5) glass forming system can be correlated with the overall network connectedness, expressed by the total number of bridging oxygen atoms per network former species. However, separate linear correlations are observed for different compositional lines, indicating also the relevance of the type of network former linkages present.

Precise determination of DNA concentration without the health risks of intercalating dyes is possible via the optical changes that arise from DNA‐induced aggregation of cationic conjugated polyelectrolytes. Addition of DNA to a conjugated electrolyte containing two fluorophores results in aggregation and fluorescence quenching, inducing a measurable and quantifiable shift from blue‐ to green‐light emission (see figure and inside cover).

The structure of laser glasses in the system (B 2 O 3 ) 0.6 {(Al 2 O 3 ) 0.4-x (Y 2 O 3 ) x } (0.1 e x e 0.25) has been investigated by means of 11 B, 27 Al, and 89 Y solid state NMR as well as Y-3d core-level X-ray photoelectron spectroscopy. 11B magic-angle spinning (MAS) NMR spectra reveal that the majority of the boron atoms are three-coordinated, and a slight increase of four-coordinated boron content with increasing x can be noticed. 27 Al MAS NMR spectra show that the alumina species are present in the coordination states four, five and six. All of them are in intimate contact with both the three-and the four-coordinate boron species and vice versa, as indicated by 11 B/ 27 Al rotational echo double resonance (REDOR) data. These results are consistent with the formation of a homogeneous, nonsegregated glass structure. For the first time, 89 Y solid state NMR has been used to probe the local environment of Y 3+ ions in a glass-forming system. The intrinsic sensitivity problem associated with 89 Y NMR has been overcome by combining the benefits of paramagnetic doping with those of signal accumulation via Carr-Purcell spin echo trains. Both the 89 Y chemical shifts and the Y-3d core level binding energies are found to be rather sensitive to the yttrium bonding state and reveal that the bonding properties of the yttrium atoms in these glasses are similar to those found in the model compounds YBO 3 and YAl 3 (BO 3 ) 4 . Based on charge balance considerations as well as 11 B NMR line shape analyses, the dominant borate species are concluded to be meta-and pyroborate anions.