体相纳米气泡及其研究进展

纳米气泡是直径在1μm以下的气泡,已被证明可以在固液界面、体相中长期稳定存在.基于跨越气液界面的拉普拉斯压强定理,气泡无法保持热力学稳定,将在微秒的尺度上消失.然而,大量试验报道,体相纳米气泡可以长时间稳定存在.目前,关于纳米气泡的产生技术、表征手段和相关的稳定机制已被世界各国的课题组竞相报道.该综述对现有纳米气泡的研...     

纳米气泡制备和检测方法研究进展

纳米气泡凭借独特的物理化学性质和生理活性引起了国内外的广泛关注,其在废水处理、土壤和地下水修复、矿物浮选、动植物生长以及生物医学等领域具有良好的发展空间和应用前景.近年来,随着各类技术的不断进步,人们对纳米气泡的研究工作取得了一系列成果,尤其是在纳米气泡的形成机制和测定方法方面.文中概述了目前国内外纳米气泡常用的制备方...     

纳米级超声造影剂的理论研究进展

为了克服超声造影剂中微米级气泡尺寸较大的局限性,大量研究人员对超声应用的替代造影剂(纳米级造影剂)进行了研究。随着生物纳米技术的飞速发展,纳米级超声造影剂在诊断与治疗领域有着广阔的发展前景。与超声造影剂中的微米级气泡相比,纳米级造影剂粒径较小,渗透能力极强,可以通过血管内皮间隙,进而可以实现血管外病变部位的显影。文中详细论述了超声造影剂在超声作用下的行为以及2种主要的纳米级造影剂:纳米气泡和纳米液滴造影剂,对其理论研究进展进行了总结,并提出了目前仍存在的一些问题及其未来的研究方向。     

非对称通道内亲疏水结构影响下的纳米气泡滑移效应

目的 研究非对称性通道中亲疏水表面结构影响下纳米气泡特征与边界滑移之间的关系,以实现良好的流体减阻效果.方法 采用二元体系分子动力学方法,研究纳米气泡在通道流动中产生的滑移减阻效应.首先建立上下壁面非对称微通道模型,通过考虑微通道流动传热过程,探究纳米气泡影响下的微通道界面速度滑移现象.结果 保持亲水下壁面高度以及上下...     

Visualizing Piezoelectricity on 2D Crystals Nanobubbles

2D crystals with noncentrosymmetric structures exhibit piezoelectric properties that show great potential for applications in energy conversion and electromechanical devices. Quantitative visualization of piezoelectric field spatial distribution is expected to offer a better understanding of macroscopic piezoelectricity, yet remains to be realized. Here, a technique of mapping piezoelectric potential on 2D materials bubbles based on the measurements of surface potential using kelvin probe force microscope is reported. By using odd number of layers hexagonal boron nitride and MoS₂ nanobubbles, strain-induced piezoelectric potential profiles are quantitatively visualized on the bubbles. The obtained piezoelectric coefficient is 3.4 ± 1.2 × 10⁻¹⁰ C m⁻¹ and 3.3 ± 0.2 × 10⁻¹⁰ C m⁻¹ for hBN and MoS₂, in agreement with the values reported. On the contrary, homogeneous distribution of surface potential is measured on even number of layers crystals bubbles where the crystal's inversion symmetry is restored. Using such technique, in situ visualization of photogenerated charge carrier separation under piezoelectric potential is also achieved, which offers a platform of investigating the coupling between piezoelectricity and photoelectric effect, and an approach of tuning piezoelectric field. The present work should aid the understanding of local piezoelectric potential and its various affecting factors including substrate doping and external stimuli, and give insights for designing piezoelectric nanodevices based on 2D nanobubbles.     

纳米技术在微细粒矿物浮选中的应用

主要阐述了疏水性纳米粒子与纳米气泡在微细粒矿物浮选中的研究进展以及纳米技术在浮选废水中的发展态势.指出了纳米技术选矿应加大疏水性纳米粒子对矿浆中微细粒难选矿物特殊的捕获和识别效应等选矿工艺的研究,纳米气泡和气核对矿物疏水表面的相互作用是影响浮选技术指标的关键因素.讨论了疏水性纳米粒子作为浮选捕收剂的补收能力以及纳米技术处理浮选废水的原理与应用,结合了当今纳米粒子、纳米气泡在浮选研究领域最前沿的技术和成果,展望了其在微细粒级难选矿物分选方向的发展前景.     

Development of a continuous membrane nanobubble generation method applicable in liquid food processing

A novel continuous nanobubble generation method was developed using a commercial ceramic membrane as a nanobubble generator. CO₂ and air were infused externally across the ceramic membrane (pore size 50 nm) into the water flowing inside the ceramic membrane tube. Infusion of each gas was done in a single (20 s) and multiple passes (180 s) at 20–21°C. Results showed that gaseous nanobubbles could be generated even in a single pass. Low power ultrasound (200 kHz, 30W) was applied for the rapid assessment of nanobubble stability. Single-pass ultrasound treatment of the samples was carried out at two levels: 2.6 and 5.1 J mL⁻¹. Among the samples in which gases were infused for multiple passes, air nanobubbles were found more stable than CO₂. In contrast, an opposite trend was observed in those samples in which gases were infused in the single-pass only (20 s). This process has the potential to be applied to food processing industries, such as to enhance the products’ sensory attributes, the efficiency of membrane separation, food drying and liquid food transportation systems.     

Role of mineral flotation technology in improving bitumen extraction from mined Athabasca oil sands—II. Flotation hydrodynamics of water-based oil sand extraction

Bitumen flotation hydrodynamics in water-based oil sand extraction is critically reviewed by comparing aeration of oil sand slurries with mineral flotation. The role of the two-stage particle-bubble attachment model in flotation is emphasized as a means to accelerate bitumen flotation recovery. It involves the generation of micro/nanobubbles and their frosting on hydrophobic bitumen droplets, followed by their attachment to a flotation-size bubble via its coalescence with the nanobubbles frosted on the bitumen. Nanobubble generation by hydrodynamic cavitation demonstrates that the size of nanobubbles can be reduced, and the number of nanobubbles increased by fast liquid flow, intensified agitation, high dissolved gas content and surfactant concentration. The mechanism of pre-existing gas nuclei in enhancing nanobubble generation by cavitation is utilized to produce a large volume of stabilized nanobubbles for practical flotation, by continuously recirculating the stream through a gas saturation tank or a cavitation tube. The aeration of oil sand slurries in hydrotransport pipelines is analyzed based on its similarity to dissolved air flotation. Bitumen extraction recovery increased significantly with the presence of nanobubbles in the system. The role of improved flotation hydrodynamics in bitumen recovery is briefly discussed in terms of the Suncor operation using flotation columns to process oil sand middling streams. Future research should be directed at understanding bitumen flotation kinetics, optimizing size ranges of nanobubbles for maximized flotation recovery, minimizing wearing of cavitation tubes in industrial operations, and intensifying the role of in-situ nanobubble nucleation on hydrophobic particles/bitumen droplets in flotation, especially for bitumen extraction from underperforming oil sands.     

Effect of CO2 nanobubbles incorporation on the viscosity reduction of fruit juice concentrate and vegetable oil

Viscosity is one of key parameters to handle liquid food during processing and transport. In this work, viscosities of apple juice concentrate (APJC) and canola oil (CANO) injected with CO₂ nanobubbles (NBs), having size ranged approximately from 50 to 850 nm, were investigated. A significant (P ≤ 0.05) viscosity reduction was observed by up to 18% and 10% in APJC and CANO, respectively, after the NBs injection. When being stored at ambient (23 °C) and refrigerated (4 °C) temperatures for 7 days, the reduction effect on viscosities of samples treated with NBs tended to diminish in accordance with the growth of NBs’ size and the decrease of dissolved CO₂ concentration. Besides, the suspension of CO₂ NBs insignificantly affected pH, total soluble solid content of APJC, as well as densities of APJC and CANO. These findings suggested that utilisation of NBs can be a feasible mean to reduce viscosity and enhance processing efficiency of food fluids.     

Ultrasound-Based Molecular Imaging of Tumors with PTPmu Biomarker-Targeted Nanobubble Contrast Agents

Ultrasound imaging is a widely used, readily accessible and safe imaging modality. Molecularly-targeted microbubble- and nanobubble-based contrast agents used in conjunction with ultrasound imaging expand the utility of this modality by specifically targeting and detecting biomarkers associated with different pathologies including cancer. In this study, nanobubbles directed to a cancer biomarker derived from the Receptor Protein Tyrosine Phosphatase mu, PTPmu, were evaluated alongside non-targeted nanobubbles using contrast enhanced ultrasound both in vitro and in vivo in mice. In vitro resonant mass and clinical ultrasound measurements showed gas-core, lipid-shelled nanobubbles conjugated to either a PTPmu-directed peptide or a Scrambled control peptide were equivalent. Mice with heterotopic human tumors expressing the PTPmu-biomarker were injected with PTPmu-targeted or control nanobubbles and dynamic contrast-enhanced ultrasound was performed. Tumor enhancement was more rapid and greater with PTPmu-targeted nanobubbles compared to the non-targeted control nanobubbles. Peak tumor enhancement by the PTPmu-targeted nanobubbles occurred within five minutes of contrast injection and was more than 35% higher than the Scrambled nanobubble signal for the subsequent two minutes. At later time points, the signal in tumors remained higher with PTPmu-targeted nanobubbles demonstrating that PTPmu-targeted nanobubbles recognize tumors using molecular ultrasound imaging and may be useful for diagnostic and therapeutic purposes.