Schiff base capped gold nanoparticles for transition metal cation sensing in organic media

We report a fast and ultrasensitive colorimetric method for the detection of transition metal ions (Fe³⁺, Cu²⁺, Ni²⁺) in a mixture of toluene-acetonitrile using Schiff base functionalized gold nanoparticles. We achieved limits of detection for the three metal ions at least two orders of magnitude lower than the EU recommended limits. Finally, our methodology was assessed for the determination of nickel in the organic waste of a relevant industrial reaction.

Highly luminescent gold nanoparticles: effect of ruthenium distance for nanoprobes with enhanced lifetimes

The photophysical properties of gold nanoparticles, AuNPs, with sizes of 13, 50 and 100 nm in diameter, coated with surface-active ruthenium complexes have been studied to investigate the effect of the distance of the ruthenium luminescent centre from the gold surface. Luminescence lifetimes of the three ruthenium probes, RuS1, RuS6 and RuS12, with different length spacer units between the surface active groups and the ruthenium centre were taken. The metal complexes were attached to AuNP13, AuNP50 and AuNP100 via thiol groups using a method of precoating the nanoparticles with a fluorinated surfactant. The luminescence lifetime of the longer spacer unit complex, RuS12, was enhanced by 70% upon attachment to the AuNP when compared to the increase of the short and medium linker unit complexes, RuS1 (20%) and (RuS6 40%) respectively. The effect of the surfactant in the lifetime increase of the ruthenium coated AuNPs was shown to be larger for the medium spacer probe, RuS6. There was no effect of the change of the size of the AuNPs from 13 to 50 or 100 nm.

The impact of structural variation in simple lanthanide binding peptides

A series of di-, tri- and tetra-peptides were synthesised using l- and d-glutamic acid in order to determine the effects of peptide length and stereochemistry on lanthanide binding affinity.

High coating of Ru(II) complexes on gold nanoparticles for single particle luminescence imaging in cells

Gold nanoparticles are efficiently labelled with a luminescent ruthenium complex, producing 13 and 100 nm diameter, monodisperse red-emissive imaging probes with luminescence lifetimes prolonged over the molecular unit. Single, 100 nm particles are observed in whole cell luminescence imaging which reveals their biomolecular association with chromatin in the nucleus of cancer cells.

Evaluation of quinoline as a remote sensitiser for red and near-infrared emissive lanthanide(III) ions in solution and the solid state

In order to evaluate quinoline as a remote sensitiser, we have prepared a DTPA based ligand, H3L, bearing quinoline bisamide arms for the complexation of a range of lanthanide(III) ions to give the neutral complexes LnLwhere Ln(3+) = Y(3+), Eu(3+), Sm(3+), Tb(3+), Er(3+), Yb(3+), Nd(3+), Gd(3+). Detection of the phosphorescence signal exhibited by the GdLcomplex at 77 K confirmed that the triplet energy level of the sensitiser at 21,190 cm(-1) was suitable for the indirect population of a range of lanthanide luminescent states. A full photophysical analysis of the complexes reveals that SmL and EuL display red emission when excited through the ligand-based absorption band centred at 330 nm, extending the excitation to violet light around 370 nm. We demonstrate that quinoline sensitizes near-infrared emission in the YbL, ErL and NdL complexes, in powder form as well as in solution. Most importantly, the luminescence for YbL and NdL was sufficiently efficient to be detected in non-deuterated solvent.

pH-controlled delivery of luminescent europium coated nanoparticles into platelets

Water soluble, luminescent gold nanoparticles are delivered into human platelets via a rapid, pH-controlled mechanism using a pH low insertion peptide, pHLIP. The approach introduces cocoating of gold nanoparticles with a europium luminescent complex, EuL and the pHLIP peptide to give pHLIP•EuL•Au. The 13-nm diameter gold nanoparticles act as a scaffold for the attachment of both the luminescent probe and the peptide to target delivery. Their size allows delivery of approximately 640 lanthanide probes per nanoparticle to be internalized in human platelets, which are not susceptible to transfection or microinjection. The internalization of pHLIP•EuL•Au in platelets, which takes just minutes, was studied with a variety of imaging modalities including luminescence, confocal reflection, and transmission electron microscopy. The results show that pHLIP•EuL•Au only enters the platelets in low pH conditions, pH 6.5, mediated by the pHLIP translocation across the membrane, and not at pH 7.4. Luminescence microscopy images of the treated platelets show clearly the red luminescence signal from the europium probe and confocal reflection microscopy confirms the presence of the gold particles. Furthermore, transmission electron microscopy gives a detailed insight of the internalization and spatial localization of the gold nanoparticles in the platelets. Thus, we demonstrate the potential of the design to translocate multimodal nanoparticle probes into cells in a pH dependent manner.