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 [{W I }(DMSO) ](NO ) 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.

We report unprecedented phase stability of cubic CsPbBr 3 quantum dots in ambient air obtained by using Br 2 as halide precursor. Mechanistic investigation reveals the decisive role of temperaturecontrolled in situ generated, oleylammonium halide species from molecular halogen and amine for the long term stability and emission tunability of CsPbX 3 (X ¼ Br, I) nanocrystals.High photoluminescence quantum yield (PL QY), narrow emission linewidth, tunable band gap, large diffusion lengths and low exciton binding energies are some of the key attributes of all-inorganic caesium lead halide perovskite nanocrystals (LHP NCs) i.e., CsPbX 3 , X ¼ I, Br, This novel class of NCs has been shown to be highly "defect tolerant", i.e. defect states are either shallow or localized in the valence or the conduction band. 1,2 Unlike conventional semiconductor NCs, the rigorous passivation of their surface via formation of core/shell structures or other methods is not required to achieve high QY. These LHP NCs are promising building blocks for light emitting diode, 3,4 solar cell, 5,6 laser, 7 photocatalysis 8 and detector. 9 Despite the recent surge of studies on CsPbX 3 perovskite NCs, a persisting drawback is their poor phase stability in ambient air. For example, cubic (a) "black" phase CsPbI 3 (E g ¼ 1.73 eV) perovskite NCs undergo rapid phase transformation to nonluminescent orthorhombic (d) "yellow" phase in ambient condition ( Fig. S1 †) leading to undesired changes of the band gap, optical and electrical properties. 6,10,11 Similarly, cubic (a) CsPbBr 3 (E g ¼ 2.25 eV) is unstable at ambient condition. 12 For successful integration of these materials into devices, the issue of long-term phase stability must thus be addressed. 6,13 Most of the reported strategies involve the use of additives such as halide salt, 12 phosphinic acid, 14 ammonium halide, 11 2,2 0 -iminodibenzoic acid 15 sulphides and metal ions 16 and polymers 5 or via special post-synthetic purication step. 6,10 Herein, we report the rst synthesis of highly stable, cubic a-CsPbBr 3 perovskite NCs using Br 2 as an independent halide precursor. In a typical synthesis, lead acetate is dissolved in 1-octadecene in the presence of oleyl amine (OAm) and oleic acid (OA). To this solution, Br 2 (warning: handle the liquid Br 2 in fume hood, Br 2 vapors are toxic) and caesium oleate solutions (both dissolved in ODE) are sequentially added. Phase stability and emission colour tunability are achieved by controlling the reaction temperature (75-200 C) and amount of Br 2 (0.6-1.2 mmol) under air-free synthetic condition (cf. ESI; Experimental section †). The "three-precursor" nature 16-18 of our synthetic scheme allows for independent tuning of the amount of the individual elements viz., Cs + , Pb 2+ and X À ions and in turn, allows for the precise control over the surface chemistry. 17 Highly crystalline, monodisperse 7.62 AE 1.0 nm sized cubic a-CsPbBr 3 NCs (Fig. 1a) were synthesised under optimized conditions using Cs : Pb : Br 2 ratio of 1 : 1 : 6 at 200 C. Highresol...

A novel SERS/fluorescent multimodal imaging probe for mitochondria has been synthesised using 12 nm diameter gold nanoparticles (AuNP) surface functionalised with a rhodamine thiol derivative ligand. The normal pH‐dependent fluorescence of the rhodamine‐based ligand is inversed when it is conjugated with the AuNP and higher emission intensity is observed at basic pH. This switch correlates to a pKa at pH 6.62, which makes it an ideal candidate for a pH‐sensitive imaging probe in the biological range (pH 6.5–7.4). The observed pH sensitivity of the ligand when attached to the AuNP is thought to be due to the formation of a spirolactam ring, going from positively charged (+18 mV) to negatively charged (−60 mV) as the pH is changed from acidic to basic. Additionally, conjugation of the ligand to the AuNP serves to enhance the Raman signal of the rhodamine ligand through surface‐enhanced Raman scattering (SERS). Confocal microscopy has shown that the probe enters HEK293 (kidney), A2780 (ovarian cancer) and Min6 (pancreatic beta) cells within an hour and a half incubation time. The probe was shown to localise in the mitochondria, thus providing a novel pH‐dependent SERS/fluorescent multimodal imaging probe for mitochondria.

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)Cl2] = 0-300 μM). An enhancement of quantum yield from Φ = 4.2% to Φ = 35% is also observed. AQA-F has a binding constant, Kd = 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. [18F]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).

A novel approach for synthesizing silica-coated colloidal quantum dot supracrystal microsphere lasers is demonstrated. These lasers consist of red-emitting CdSxSe1-x/ZnS quantum dots that act as both the laser medium and the cavity, and have great potential for biosensing, bioimaging, and integrated photonics.