Synthetic routes, characterization and photophysical properties of luminescent, surface functionalized nanodiamonds

The functionalization of small diameter (ca. 50 nm) polycarboxylated nanodiamond particles using amide coupling methodologies in both water and acetonitrile solvent has been investigated. In this manner, the surfaces of nanodiamond particles were adorned with different luminescent moieties, including a green fluorescent 1,8-naphthalimide species (Nap-1), and a red emitting ruthenium(II) tris-bipyridine complex (Ru-1), as well as dual functionalization with both luminophores. Comprehensive characterization of the surface functionalized nanodiamonds has been achieved using a combination of dynamic light scattering, nanoparticle tracking analysis, transmission electron microscopy, X-ray photoelectron spectroscopy, zeta potential measurements, microwave plasma atomic emission spectroscopy and time-resolved photophysics. The tendency of the functionalized nanodiamonds to aggregate reflects the degree of surface substitution, yielding small aggregates with typical particle sizes ca. 150 nm. This is likely to be driven by the reduction of the zeta potential, concomitant with the conversion of surface charged carboxylate groups to neutral amide functions. The results show that luminescent nanodiamond materials can be synthesised with tuneable photophysical properties

Non-centrosymmetric alignment of optically nonlinear dyes

Langmuir-Blodgett (LB) film structures of the two-legged dye, (E)-4-[2-alkanoyloxyphenyl) ethenyl]-N-docosylpyridinium iodide, CHC(O)OCHCHCHCHNCH I, are dependent upon the alkanoyl group, there being a cross-over from a centrosymmetric Y-type arrangement to a non-centrosymmetric Z-type arrangement as n increases. The second-harmonic intensity from films comprising an even number of layers is negligible for 1 ≤ n ≤ 10, increases with the number of LB layers when n ≥ 12 and is greatly reduced when n = 21. The two-legged molecules adopt a 'stretched' rather than a 'U-shaped' configuration and there is a tendency towards an antiparallel alignment within layers as the length of the alkanoyl group approaches that of the second alkyl chain. The stearoyloxy homologue (n = 17) has a layer thickness, from ellipsometry, of 52 Å and an in-plane area, from grazing incidence synchrotron diffraction, of 19.72 ± 0.04 Å molecule

2,4-Bis[4-(N,N-dibutylamino)phenyl]squaraine: X-ray crystal structure of a centrosymmetric dye and the second-order non-linear optical properties of its non-centrosymmetric Langmuir-Blodgett films

Crystals of the title compound exist as a green monoclinic phase [space group P2/c with a=9.046(1), b=19.615(2), c=9.055(1) Å, β=116.107(5)°, Z=2] and a purple triclinic phase. The chromophore is both planar and centrosymmetric and its dimensions indicate a tendency towards a quinoidal structure with extensive delocalisation. The Langmuir-Blodgett (LB) films show two types of aggregation with absorption maxima at 655 nm and 540 nm. These monolayers also exhibit strong second harmonic generation (SHG) comparable to the intensity from films of hemicyanine dyes. The anomalous non-linear optical properties are attributed to a serendipitous non-centrosymmetric packing arrangement within the films and to an intermolecular charge transfer contribution to the bulk second-order susceptibility

Towards dual SPECT/optical bioimaging with a mitochondrial targeting, Tc-99m(i) radiolabelled 1,8-naphthalimide conjugate

A series of six different 1,8-naphthalimide conjugated dipicolylamine ligands (L1-6) have been synthesised and characterised. The ligands possess a range of different linker units between the napthalimide fluorophore and dipcolylamine chelator which allow the overall lipophilicity to be tuned. A corresponding series of Re(i) complexes have been synthesised of the form fac-[Re(CO)3(L1-6)]BF4. The absorption and luminescence properties of the ligands and Re(i) complexes were dominated by the intramolecular charge transfer character of the substituted fluorophore (typically absorption ca. 425 nm and emission ca. 520 nm). Photophysical assessments show that some of the variants are moderately bright. Radiolabelling experiments using a water soluble ligand variant (L5) were successfully undertaken and optimised with fac-[99mTc(CO)3(H2O)3]+. Confocal fluorescence microscopy showed that fac-[Re(CO)3(L5)]+ localises in the mitochondria of MCF-7 cells. SPECT/CT imaging experiments on naïve mice showed that fac-[99mTc(CO)3(L5)]+ has a relatively high stability in vivo but did not show any cardiac uptake, demonstrating rapid clearance, predominantly via the biliary system along with a moderate amount cleared renally.status: publishe