Many novel fluorescent nanomaterials exhibit radically different optical properties compared to organic fluorophores that are still the most extensively used class of fluorophores in biology today. Assessing the practical impact of these optical differences for bioimaging experiments is challenging due to a lack of published quantitative benchmarking data. This study therefore directly and quantitatively compares the brightness and photostability of representatives from seven classes of fluorescent materials in spectroscopy and fluorescence microscopy experiments for the first time. These material classes are: organic dyes, semiconductor quantum dots, fluorescent beads, carbon dots, gold nanoclusters, nanodiamonds, and nanorubies. The relative brightness of each material is determined and the minimum material concentrations required to generate sufficient contrast in a fluorescence microscopy image are assessed. The influence of optical filters used for imaging is also discussed and suitable filter combinations are identified. The photostability of all materials is determined under typical imaging conditions and the number of images that can be acquired is inferred. The results are expected to facilitate the transition of novel fluorescent materials from physics and chemistry into biology laboratories.

We demonstrate a magnetocaloric ferrofluid based on a gadolinium saturated liquid metal matrix, using a gallium-based liquid metal alloy as the solvent and suspension medium. The material is liquid at room temperature, while exhibiting spontaneous magnetization and a large magnetocaloric effect. The magnetic properties were attributed to the formation of gadolinium nanoparticles suspended within the liquid gallium alloy, which acts as a reaction solvent during the nanoparticle synthesis. High nanoparticle weight fractions exceeding 2% could be suspended within the liquid metal matrix. The liquid metal ferrofluid shows promise for magnetocaloric cooling due to its high thermal conductivity and its liquid nature. Magnetic and thermoanalytic characterizations reveal that the developed material remains liquid within the temperature window required for domestic refrigeration purposes, which enables future fluidic magnetocaloric devices. Additionally, the observed formation of nanometer-sized metallic particles within the supersaturated liquid metal solution has general implications for chemical synthesis and provides a new synthetic pathway toward metallic nanoparticles based on highly reactive rare earth metals.

A new analysis of depolarized dynamic light scattering data is presented, which allows the unambiguous determination of rotational and translational diffusions coefficients of nanorods in suspension. By visualizing data scaling, purely translational diffusive motions can be isolated from vertically polarized scattering, allowing the unique determination of rotational diffusion from the depolarized scattering. The method is applied to nanorods with four different aspect ratios, and compared with theoretical predictions. Diffusion coefficients obtained show good agreement with calculations based on the direct measurements of rod length and diameter. Where the theories are shown to be valid, the method allows the measurement of statistically meaningful particle sizes and aspect ratios.

The photocontrollable antibacterial and biofilm modulatory activity of a panel of light responsive carbohydrate-based surfactants is reported.