A 18F radiolabelled Zn(ii) sensing fluorescent probe

A selective fluorescent probe for Zn(ii), AQA-F, has been synthesized. AQA-F exhibits a ratiometric shift in emission of up to 80 nm upon binding Zn(ii) ([AQA-F] = 0.1 mM, [Zn(ii)Cl 2 ] = 0-300 μM). An enhancement of quantum yield from Φ = 4.2% to Φ = 35% is also observed. AQA-F has a binding constant, K d = 15.2 μM with Zn(ii). This probe has been shown to respond to endogenous Zn(ii) levels in vitro in prostate and prostate cancer cell lines. [ 18 F]AQA-F has been synthesized with a radiochemical yield of 8.6% and a radiochemical purity of 97% in 88 minutes. AQA-F shows the potential for a dual modal PET/fluorescence imaging probe for Zn(ii)

Long-term ambient air-stable cubic CsPbBr3 perovskite quantum dots using molecular bromine

We report unprecedented phase stability of cubic CsPbBr3 quantum dots in ambient air obtained by using Br2 as halide precursor. Mechanistic investigation reveals the decisive role of temperature-controlled in situ generated, oleylammonium halide species from molecular halogen and amine for the long term stability and emission tunability of CsPbX3 (X = Br, I) nanocrystals

Surface functionalisation of self-assembled quantum dot microlasers with a DNA aptamer

Surface functionalisation of self-assembled colloidal quantum dot supraparticle lasers with a Thrombin Binding Aptamer (TBA-15) has been demonstrated. Self-assembly of CdSSe/ZnS alloyed core/shell microsphere-shape CQD supraparticles emitting at 630 nm was carried out using an oil-in-water emulsion technique, yielding microspheres with an oleic acid surface and an average diameter of 7.3 ± 5.3 μm. Surface modification of the microspheres was achieved through a ligand exchange with mercaptopropionic acid and subsequent attachment of TBA-15 using EDC/NHS coupling, confirmed by zeta potential and Fourier Transform IR spectroscopy. Lasing functionality between 627 nm and 635 nm was retained post-functionalisation with oleic acid- and TBA-coated microspheres exhibiting laser oscillation with thresholds as low as 4.10 ± 0.37 mJ.cm-2 and 7.23 ± 0.78 mJ.cm-2 respectively

Spectral characterization of a blue light-emitting micro-LED platform on skin-associated microbial chromophores

The therapeutic application of blue light (380 – 500nm) has garnered considerable attention in recent years as it offers a non-invasive approach for the management of prevalent skin conditions including acne vulgaris and atopic dermatitis. These conditions are often characterised by an imbalance in the microbial communities that colonise our skin, termed the skin microbiome. In conditions including acne vulgaris, blue light is thought to address this imbalance through the selective photoexcitation of microbial species expressing wavelength-specific chromophores, differentially affecting skin commensals and thus altering the relative species composition. However, the abundance and diversity of these chromophores across the skin microbiota remains poorly understood. Similarly, devices utilised for studies are often bulky and poorly characterised which if translated to therapy could result in reduced patient compliance. Here, we present a clinically viable micro-LED illumination platform with peak emission 450 nm (17 nm FWHM) and adjustable irradiance output to a maximum 0.55 ± 0.01 W/cm2, dependent upon the concentration of titanium dioxide nanoparticles applied to an accompanying flexible light extraction substrate. Utilising spectrometry approaches, we characterised the abundance of prospective blue light chromophores across skin commensal bacteria isolated from healthy volunteers. Of the strains surveyed 62.5% exhibited absorption peaks within the blue light spectrum, evidencing expression of carotenoid pigments (18.8%, 420–483 nm; Micrococcus luteus, Kocuria spp.), porphyrins (12.5%, 402–413 nm; Cutibacterium spp.) and potential flavins (31.2%, 420–425 nm; Staphylococcus and Dermacoccus spp.). We also present evidence of the capacity of these species to diminish irradiance output when combined with the micro-LED platform and in turn how exposure to low-dose blue light causes shifts in observed absorbance spectra peaks. Collectively these findings highlight a crucial deficit in understanding how microbial chromophores might shape response to blue light and in turn evidence of a micro-LED illumination platform with potential for clinical applications

Conjugated, rod-like viologen oligomers: correlation of oligomer length with conductivity and photoconductivity

An iterative synthesis has been used to produce conjugated, monodisperse, viologen-based aromatic oligomers containing up to 12 aromatic/heterocyclic rings. The methoxy-substituted oligomers were soluble in common organic solvents and could be processed by spin coating. The conductivities of the resulting films (30 to 221 nm thick) increased by more than an order of magnitude as the oligomer length increased from unimer (1, 2.20×10-11 S cm-1) through dimer (2) to trimer (3, 6.87×10-10 S cm-1). The bandgaps of the materials were estimated from the absorption spectra of these thin films. The longest oligomer, 3, exhibited a noticeably narrower bandgap (2.3 eV) than the shorter oligomers (1 and 2 both 2.7 eV). Oligomer 3 also showed photoconductivity under irradiation across a wide range of wavelengths in the visible spectral region. In conjunction with DFT calculations of these systems our results suggest that structurally related viologen-type oligomers may find use in optoelectronic devices

Biotinylated photocleavable semiconductor colloidal quantum dot supraparticle microlaser

Luminescent supraparticles of colloidal semiconductor nanocrystals can act as microscopic lasers and are hugely attractive for biosensing, imaging, and drug delivery. However, biointerfacing these to increase functionality while retaining their main optical properties remains an unresolved challenge. Here, we propose and demonstrate red-emitting, silica-coated CdS xSe 1−x/ZnS colloidal quantum dot supraparticles functionalized with a biotinylated photocleavable ligand. The success of each step of the synthesis is confirmed by scanning electron microscopy, energy dispersive X-ray and Fourier transform infrared spectroscopy, ζ-potential, and optical pumping measurements. The capture and release functionality of the supraparticle system is proven by binding to a neutravidin functionalized glass slide and subsequently cleaving off after UV-A irradiation. The biotinylated supraparticles still function as microlasers; e.g., a 9 μm diameter supraparticle has oscillating modes around 625 nm at a threshold of 58 mJ/cm 2. This work is a first step toward using supraparticle lasers as enhanced labels for bionano applications

Biotinylated photocleavable semiconductor colloidal quantum dot supraparticle microlaser

Luminescent supraparticles of colloidal semiconductor nanocrystals can act as microscopic lasers and are hugely attractive for biosensing, imaging, and drug delivery. However, biointerfacing these to increase functionality while retaining their main optical properties remains an unresolved challenge. Here, we propose and demonstrate red-emitting, silica-coated CdSxSe1−x/ZnS colloidal quantum dot supraparticles functionalized with a biotinylated photocleavable ligand. The success of each step of the synthesis is confirmed by scanning electron microscopy, energy dispersive X-ray and Fourier transform infrared spectroscopy, ζ-potential, and optical pumping measurements. The capture and release functionality of the supraparticle system is proven by binding to a neutravidin functionalized glass slide and subsequently cleaving off after UV-A irradiation. The biotinylated supraparticles still function as microlasers; e.g., a 9 μm diameter supraparticle has oscillating modes around 625 nm at a threshold of 58 mJ/cm2. This work is a first step toward using supraparticle lasers as enhanced labels for bionano applications

From photoinduced to dark cytotoxicity via an octahedral cluster hydrolysis

Octahedral molybdenum and tungsten clusters have potential biological applications in photodynamic therapy and bioimaging. However, poor solubility and hydrolysis stability of these compounds hinder their application. The first water-soluble photoluminescent octahedral tungsten cluster [{W6I8}(DMSO)6](NO3)4 was synthesised and demonstrated to be at least one order of magnitude more stable towards hydrolysis than its molybdenum analogue. Biological studies of the compound on larynx carcinoma cells suggest that it has a significant photoinduced toxicity, while the dark toxicity increases with the increase of the degree of hydrolysis. The increase of the dark toxicity is associated with the in situ generation of nanoparticles that clog up the cisternae of rough endoplasmic reticulum

Self-assembled cadmium-free semiconductor microspheres based on colloidal quantum dots

A method for the fabrication of cadmium-free, photoluminescent (PL) quantum dot supracrystal microspheres (MS) is implemented, creating red emitting MS. The overall aim is to characterise and develop MS acting as optical microresonators, and to explore their applications in miniature lasers for bioimaging and biosensing using non-toxic semiconductor materials. Fabrication of whispering gallery mode (WGM) microlasers via self-assembly of colloidal quantum dots (CQDs) has been previously achieved with the caveat of employing toxic metals, and resulting in MS with low solubility [1,2]. Non-toxic InP/ZnS CQDs represent a heavy-metal free alternative for luminescent applications and have been demonstrated as a laser material [3]. By utilising the self-assembly of oleate capped CQDs via an oil-in-water emulsion technique, MS were formed and suspended in water with polyvinyl alcohol as a surfactant. The following step included the addition of polyvinylpyrrolildone, then ammonia and tetraethyl orthosilicate for a thin (<5 nm) coating of silica to allow for improved solubility in water. The MS characterisation consisted of: (i) optical microscope imaging to ascertain the size and size distribution of 5-45 µm; (ii) UV-visible absorption spectroscopy and Scanning Electron Microscopy; (iii) optical pumping with a 355 nm, 5 ns pulsed Nd:YAG laser at a 10 Hz repetition rate with a beam spot area of 2.6 ± 1.5 x10-5 cm2 for PL spectra measurements. Optical pumping demonstrated the resulting MS PL ability, which differs significantly from their QD precursor’s comparatively Gaussian PL. Details of the results of the MS synthesis and of the optical characterisation at different wavelengths will be discussed

Surface modification of self-assembled semiconductor quantum dot microlasers

Microlasers self-assembled entirely from colloidal quantum dots (CQDs) have been recently reported [1,2]. Surface functionalisation of such lasers, which has not been shown before, is essential for realising their biosensing potential. Here, we demonstrate an approach for the surface modification of self-assembled microlasers with streptavidin which can act as a platform for further functionalisation or sensing by exploiting the avidin–biotin interaction. Bottom-up self-assembly of orange-emitting CdSSe/ZnS CQDs was carried out using an oilin-water emulsion technique [1,2], yielding microspheres with an oleic acid surface that are insoluble in water. A ligand exchange with 3-mercaptopropionic acid (MPA) was carried out [3] to put a carboxylic acid group on the surface of the microspheres for the streptavidin to bind to [4]. Ligand exchange and streptavidin modification was indicated with FTIR and UVvis measurements. Microsphere size remained between 1 and 20 µm throughout the functionalisation process as measured by optical microscopy. Microspheres were optically pumped with a 355nm, 5ns pulsed Nd:YAG laser at a 10 Hz repetition rate with a beam spot area 2.6 ± 1.5 x10-5 cm². Oleate- and streptavidin-coated spheres, with diameters of 9.1 µm and 11.5 µm respectively, exhibited lasing with thresholds of 1.9 µJ and 8.7 µJ respectively. Figure 1(a) shows the threshold curve for the streptavidin-capped microsphere and Figure 1(b) shows its emission spectra above and below threshold. Lowering the threshold of the streptavidin coated microspheres to match oleate-coated spheres is required but the fact functionalised spheres can lase is promising for future applications