Nanometer-sized luminescent semiconductor quantum dots (QDs) have been utilized as imaging and therapeutic agents in a variety of disease settings, including diseases of the central nervous system. QDs have several advantages over traditional fluorescent probes including their small size (5–10 nm), tunable excitation and emission spectra, tailorable surface functionality, efficient photoluminescence, and robust photostability, which are ideal characteristics for in vivo imaging. Although QDs are promising imaging agents in brain-related applications, no systematic evaluation of QD behavior in brain-relevant conditions has yet been done. Therefore, we sought to investigate QD colloidal stability, cellular uptake, and toxicity in vitro, ex vivo, and in vivo in the brain environment. We found that QD behavior is highly dependent on surface functionality and that treatment of cultured organotypic whole hemisphere (OWH) slices with QDs results in dose-dependent toxicity and metallothionein increase, but no subsequent mRNA expression level changes in inflammatory cytokines or other oxidative stress. QDs coated with poly(ethylene glycol) (PEG) were protected from aggregation in neurophysiologically relevant fluids and in tissue, allowing for greater penetration. Importantly, QD behavior differed in cultured slices as compared to monolayer cell cultures, and behavior in cultured slices aligned more closely with that seen in vivo. Irrespective of surface chemistry and brain-relevant platform, non-aggregated QDs were primarily internalized by microglia in a region-dependent manner both in slices and in vivo upon systemic administration. This knowledge will help guide further engineering of candidate QD-based imaging probes for neurological application.
Plasmas at the surface of or inside liquids are of importance for emerging applications, and are often formed with stagnant liquids. Here, the authors present the generation of a direct-current, atmospheric-pressure microplasma at the surface of a liquid water microjet that enables solution species to be transported by forced convection. The water jet is formed by pumping conductive ionic solutions through a plastic capillary tube in a vertically falling geometry, and overcomes Plateau–Rayleigh instabilities by controlling the flow rate, resulting in a constant diameter jet of ∼0.45 mm over lengths of more than 30 mm. Analysis of the electrical characteristics of the complete microplasma-water jet system shows that the current–voltage (I-V) relationship is linear with a large positive slope when the solution conductivity is relatively low. The authors show that the primary contribution to this large resistance is the confined solution geometry. As proof-of-concept, the authors demonstrate that plasmonic Ag nanoparticles can be continuously produced at steady state from solutions of silver nitrate, opening up the possibility of scaled-up production of materials by plasma-liquid processes.
Atheism is a controversial topic, with individuals who identify as atheist reporting high rates of discrimination. Despite increasing literature discussing religious/spiritual views and beliefs, few scholarly discussions of atheism in the counseling field can be found. Counselors need to be made aware of the issues facing atheist clients and educated on the best interventions to use in collaborative work with clients. Counselors should also be prepared to advocate for atheist clients in multiple domains. This article aims to explore the relevant literature around atheism, identify implications for counselors, and provide a path to advocacy for counselors in their work with atheist clients.
A sonochemical Materials Acceleration Platform was implemented to synthesize CdSe nanocrystals under 625 unique conditions (in triplicate) in less than 6 weeks. The modularity of the workflow is adaptable to a variety of applications.
The sonochemical synthesis of CdSe quantum dots (QDs) in a single-liquid bulk phase and in an emulsion-based system is presented. Reactions utilized cadmium oleate and trioctylphosphine selenide precursors and were monitored as a function of sonication time under controlled temperature conditions to isolate the effects of cavitation from those of bulk temperature changes. QD synthesis was found to be slow in the single-phase liquid system (i.e., 1-octadecene) but greatly accelerated in the dispersed system (i.e., emulsions of 1-octadecene in ethylene glycol). It is hypothesized that the emulsion system increases the cavitation efficiency while also delivering acoustic energy in closer proximity to the precursor molecules. The capacity of CdSe production in the emulsion system was found to be 3.8 g/(L h), which is comparable to the typical hot-injection synthesis of CdSe QDs and can likely be further optimized. While the single-phase solvent system was found to produce ultrasmall QDs that exhibit broadband white-light emission, the emulsion system was found to produce welldefined magic-size clusters (MSCs) with photoluminescence quantum yield as high as 34%. Differences in synthesis rate and product properties from the emulsion and single-phase systems were probed by X-ray diffraction, electron microscopy, UV− visible (vis) and photoluminescence spectroscopy, and small-angle X-ray scattering (SAXS). Finally, precise temporal control of the QD synthesis was demonstrated via on−off cycling of the ultrasound waves.
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