Strongly white-emitting (lambda(max) = 495 +/- 10 nm) D- and L- penicillamine capped CdS nanoparticles, which show strong circular dichroism in the range 200-390 nm, have been prepared.

We report and explain circular dichroism in semiconductor quantum dots. CdS nanocrystals capped with penicillamine enantiomers were prepared and found to be both highly luminescent and optically active. No new features in circular dichroism were observed as the nanocrystal grew larger. Density functional calculations reveal that penicillamine strongly distorts surface Cd, transmitting an enantiomeric structure to the surface layers and associated electronic states. The quantum dot core is found to remain undistorted and achiral.

Chiral quantum dots (QDs) are expected to have a range of potential applications in photocatalysis, as specific antibacterial and cytotoxic drug-delivery agents, in assays, as sensors in asymmetric synthesis and enantioseparation, and as fluorescent chiral nanoprobes in biomedical and analytical technologies. In this protocol, we present procedures for the synthesis of chiral optically active QD nanostructures and their quality control using spectroscopic studies and transmission electron microscopy imaging. We closely examine various synthetic routes for the preparation of chiral CdS, CdSe, CdTe and doped ZnS QDs, as well as of chiral CdS nanotetrapods. Most of these nanomaterials can be produced by a very fast (70 s) microwave-induced heating of the corresponding precursors in the presence of D- or L-chiral stabilizing coating ligands (stabilizers), which are crucial to generating optically active chiral QDs. Alternatively, chiral QDs can also be produced via the conventional hot injection technique, followed by a phase transfer in the presence of an appropriate chiral stabilizer. We demonstrate that the properties, structure and behavior of chiral QD nanostructures, as determined by various spectroscopic techniques, strongly depend on chiral stabilizers and that the chiral effects induced by them can be controlled via synthetic procedures.

Aging population ratios are rising significantly. Health monitoring systems (HMS) in smart environments have evolved rapidly to become a viable alternative to traditional healthcare solutions. The aim of HMS is to not only reduce costs but to also provide timely e-health services to individuals wishing to maintain their independence. In this way, elderly people can avoid, for as long as possible, any interaction with healthcare institutions (e.g. nursing homes and hospitals), which in turn reduces pressure on the health system. To fully realise this vision of seamless e-health services supporting people in need of them, a number of challenges that need further investigation still exist. To this end, we provide an overview of the current state of the art for smart health monitoring systems. We review HMS in smart environments from a general perspective and with a particular focus on systems for the elderly and dependent people. We look at the challenges for these systems from the perspective of developing the technology itself, system requirements, system design and modelling. We present a consolidated picture of the most important functions and services offered by HMS for monitoring and detecting human behaviour including its concepts, approaches, and processing techniques. Moreover, we provide an extensive, in-depth analysis and evaluation of the existing research findings in the area of e-health systems. Finally, we present challenges and open issues facing the smart HMS field and we make recommendations on how to improve future systems.

Using microwave irradiation, water soluble, optically active, penicillamine (Pen) capped CdSe nanocrystals with broad spectral distribution (430-780 nm) of photoluminescence have been produced and studied by a range of instrumental techniques including absorption, circular dichroism and both steady state and time resolved photoluminescence spectroscopy. The photoluminescence of these nanocrystals is attributed to emission from surface defect states. The decay of the excited state in the nanosecond region, which can be analysed as a triple exponential, depends strongly on the emission wavelength selected, but only weakly on the excitation wavelength. Graphical Abstract: IntroductionChirality is a common occurrence in the natural world and chiraln compounds are very important in chemistry, biology, pharmacology and medicine. It has also been envisaged that chirality could play an important role in nanotechnology. 1,2 The majority of existing research in this field has been focused on chiral organic, metallorganic and biological molecules and their supramolecular structures, 3 while research in the area of chiral inorganic nanoparticles is still in the very early stage of its development. For example, there has been some work involving chiral optically active metallic gold 4,5 and silver 6,7 nanoparticles, as well as carbon nanotubes. 8,9 However, there are currently only a few recent papers dealing with chiral light emitting semiconducting nanocrystals (quantum dots). [10][11][12][13][14] In general over the last decade much attention has been directed towards II-VI type CdS, CdTe and CdSe quantum dots (QDs). [15][16][17][18][19] It is the ability to fine-tune their optical properties by chemical control of their size and shape (i.e. their degree of quantum confinement) which makes quantum dots particularly interesting. This level of optical control combined with QDs' resistance to photobleaching and their high level of solubility in practically any solvent (depending on the stabiliser used) make these nanomaterials potentially suited for roles as divergent as light emitting diodes, 20 biological sensors 21 and photovoltaic devices. [22][23][24] Thiol group containing amino acids have proved to be excellent stabilisers, with L-cysteine becoming one of the popular surface capping molecules for CdX (X ¼ S, Se, and Te) nanoparticles. 18,[25][26][27][28][29][30][31] In addition this use of stereospecific chiral stabilising molecules opened another avenue of interest in the area of quantum dot research, as chirality is a key factor in biological and biochemical interactions. Due to their unique photophysical properties, we believe that chiral QDs have a range of potential applications in photonics and biochemistry. 13,32,33 The main aim of our work is to develop novel chiral CdSe based QDs by using chiral stabilisers and to investigate the properties of these materials. Here we report the synthesis and detailed spectroscopic studies of new penicillamine stabilised CdSe QDs, which have been prepared using the dextrorota...