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Assessing Physical Stability of Colloidal Dispersions Using Turbiscan Optical Analyzer
摘要： The physical stability of aqueous colloidal dispersions containing highly concentrated droplets of poorly water-soluble drugs has recently been identified as one of the main considerations in developing amorphous solid dispersions (ASDs). Turbiscan, an instrument based on multiple light scattering technology, was employed for the first time to assess colloidal dispersions with ritonavir as the model compound. The physical instability of ritonavir-rich droplets was monitored directly with and without the presence of candidate polymer additives at different drug concentrations and temperatures. The mechanism of the observed instability was confirmed to be coalescence of liquid droplets, based on the low glass transition temperature of water-saturated amorphous ritonavir determined using a newly developed experimental procedure. Temperature and solvent composition, within the range studied, have little influence on the kinetics of ritonavir coalescence. On the contrary, higher concentration of drug, i.e., more droplets per unit volume, greatly accelerates the coalescence process. In addition, polymers with varying degrees of hydrophobicity resulted in different levels of effectiveness in stabilization which is likely related to the strength of drug-polymer interactions and the corresponding differences in surface adsorption. This work demonstrates that the Turbiscan optical analyzer can be used as a rapid screening tool that provides a first-pass, high-throughput feasibility ranking of different excipients and additives to support the development of ASD formulations.
关键词： nanodroplets,coalescence,glass transition temperature,physical stability,stabilization,amorphous,ritonavir,colloidal dispersions,Turbiscan
更新于2025-09-23 15:22:29
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Light-Induced Shape Morphing of Liquid Metal Nanodroplets Enabled by Polydopamine Coating
摘要： Shape morphing nanosystems have recently attracted much attention and a number of applications are developed, spanning from autonomous robotics to drug delivery. However, the fabrication of such nanosystems remains at an early stage owing to limited choices of strategies and materials. This work reports a facile method to fabricate liquid metal (LM) nanodroplets by sonication of bulk LM in an aqueous dopamine hydrochloride solution and their application in light-induced shape morphing at the nanoscale. In this method, dopamine acts as a surfactant, which stabilizes the LM nanodroplets dispersion during the sonication, and results in downsizing of the nanodroplets. Furthermore, by adding 2-amino-2-(hydroxymethyl)-1,3-propanediol to the suspension, self-polymerization of dopamine molecules occurs, resulting in the formation of polydopamine (PDA)-coated LM nanodroplets. Owing to the high photothermal conversion of the PDA, PDA-coated LM nanodroplets are transformed from spherical shapes to ellipsoids by NIR laser irradiation. This study paves a simple and reliable pathway for the preparation of functional LM nanodroplets and their application as shape-morphing nanosystems.
关键词： light-induced shape morphing,polydopamine,liquid metal nanodroplets,photothermal effect
更新于2025-09-23 15:22:29
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Quantum Dot-Based Hybrid Coacervate Nanodroplets for Ultrasensitive Detection of Hg2+
摘要： Multifunctional organic-inorganic hybrid materials with inherent optical, electrical and/or magnetic properties find tremendous importance in various fields such as sensing, photovoltaics, therapeutics, bio-imaging, and light-emitting devices. Herein, we have fabricated membrane-free organic-inorganic hybrid luminescent coacervate nanodroplets and utilized them towards ultrasensitive detection and efficient removal of mercuric ions (Hg2+) simultaneously. The self-assembly of negatively charged mercaptosuccinic acid (MSA)-capped CdTe quantum dots (QDs) in the presence of positively charged poly(diallyldimethylammonium chloride) (PDADMAC) leads to the formation of luminescent nanodroplets with average size of 430 ± 20 nm. Selective luminescence quenching of these nanodroplets has been observed only in the presence of Hg2+. It has also been observed that the presence of other metal ions does not interfere in the sensing process. Our findings reveal that Hg2+ ions specifically associate with the porous structure of these nanodroplets via electrostatic interactions with the free carboxylate groups of MSA ligands at the surface of CdTe QDs and undergo photoinduced electron transfer (PET) with photoexcited QDs. The limit of detection (LOD) for Hg2+ sensing with our present system is estimated to be 1.32 nM (0.26 ppb), which is significantly lower than most of the earlier reported self-assembled materials. Moreover, these hybrid nanodroplets efficiently sequester trace quantity of Hg2+ from contaminated water. The overall performance of our present system towards Hg2+ remediation is superior over most of the earlier reported hybrid nanocomposites in terms of fast uptake kinetics (within 15 min), ultrasensitive detection (LOD: 0.26 ppb), and high sequestration efficiency (98.3%). Our present findings in particular, the tailorability of surface ligands and inorganic nanoparticles in hybrid nanodroplets provide great advantage for the development of multifunctional nanomaterials for diverse range of applications.
关键词： membrane-free nanodroplets,detection of mercuric ions,sensing,LOD,hybrid nanodroplets
更新于2025-09-23 15:19:57
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Antimicrobial propensity of ultrananocrystalline diamond films with embedded silver nanodroplets
摘要： Ultrananocrystalline diamond (UNCD) layers exhibit excellent mechanical properties and combine chemical inertness with good biological compatibility. Therefore, UNCD is considered a promising material for coating of implants. In this work we present the preparation of thin UNCD films with embedded silver nanodroplets that provide antimicrobial property, addressing another important topic concerning implant surgery, namely the risk of a life threatening bacterial infection. UNCD layers were prepared by microwave plasma-assisted chemical vapor deposition on a silicon substrate. Afterwards, a thin film of silver was deposited on top and treated by rapid thermal annealing (RTA) leading to dewetting and formation of silver nanodroplets on the surface. A second UNCD deposition with a short duration between 5 and 30 min was applied for capping the silver nanoparticles with a thin layer. The sample surfaces were characterized after each step by atomic force microscopy and scanning electron microscopy. The composition of the final samples, including the depth of the incorporated Ag nanodroplets, was analyzed by Auger electron spectroscopy. The impact of the silver layer thickness and the RTA temperature on the nanodroplet morphology was investigated. It was found that after 10 min of capping deposition the silver particles were completely covered with UNCD. In order to study the release of silver ions, the UNCD/Ag/UNCD samples were submerged in deionized water for 7 days at 37 °C, followed by detection of the silver concentration in the aqueous samples by inductively coupled plasma mass spectrometry. The determined concentration was strongly dependent on the thickness of the capping UNCD layer, exhibiting the highest silver content for the sample with the thinnest capping layer. Thus, the UNCD layer thickness can be utilized to control the amount of Ag ions released into the surrounding environment. The antibacterial properties were investigated with bacterial assays of the Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria that were exposed to the samples. All silver containing samples showed significant antimicrobial propensity, whereas the different capping thicknesses affected the time-course dependent antibacterial efficiency.
关键词： antibacterial material,ultrananocrystalline diamond films,silver nanodroplets
更新于2025-09-19 17:15:36
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4s to 5s and 4p photoexcitation dynamics of K atoms from the surface of helium nanodroplets: a theoretical study
摘要： We study the photodissociation of the potassium atom from a superfluid helium nanodroplet upon 5s 2S or 4p 2P excitation using the time-dependent helium density functional method (He-TDDFT). The importance of quantum effects is assessed by comparing the absorption spectrum obtained for a classical or a quantum description of the K atom. In the case of the 5s 2S ' 4s 2S excitation the difference is rather large, and we use a quantum description for the ensuing direct dissociation dynamics. In the case of the 4p 2P ' 4s 2S absorption spectrum, the difference is much smaller, hence a classical description of K is used to describe 4p 2P excitation dynamics. Excitation to the 4p 2S1/2 state leads to the direct dissociation of the K atom, while the 4p 2P3/2 state initially leads to the formation of an exciplex and the 4p 2P1/2 state to a bouncing atom above the droplet surface. Remarkably, electronic relaxation can be observed for the latter two states, leading to spin–orbit relaxation and the binding of the initially departing one-atom excimer as a ring excimer for the 2P3/2 state and to the formation of a bound, ring excimer for the 2P1/2 state.
关键词： potassium,spin-orbit relaxation,quantum effects,helium nanodroplets,exciplex formation,photodissociation
更新于2025-09-19 17:15:36
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Plasmonic Nanobubbles in ‘Armored’ Surface Nanodroplets
摘要： Plasmonic nanobubbles are bubbles that are formed from local heat generated by noble metal nanoparticles under illumination of light at resonance. Understanding the formation and behavior of plasmonic nanobubbles is important for a broad suite of applications that rely on enhanced local heating of nanoparticles, such as in biomedical treatments and solar energy conversion. Here, we investigate formation, growth and dissolution of plasmonic bubbles in a model system of oil nanodroplets in water. Gold nanoparticles were located at the surface of nanodroplets immobilized on a substrate. We followed temporal evolution of plasmonic nanobubbles from ~ 200 nm in radius and above. Our experimental results show that there is an upper limit of the bubble size set by hosting droplet size, beyond which the nanobubbles burst. Nanobubbles grew, following the same growth exponent that was reported for a sub-millimeter bubble in contact with a bulk organic solvent. When the laser was switched off, the nanobubbles could remain for several minutes, much longer than the bubbles formed directly in water. The findings from this work may be valuable for light-driven chemical conversion in droplets or photothermal treatments involving immiscible phases.
关键词： bubble growth,Plasmonic nanobubbles,dissolution dynamics,nanodroplets,laser illumination,gold nanoparticles
更新于2025-09-11 14:15:04