The need to characterize different properties of nanomaterials continues to grow rapidly. Since the commercialization of the technique in 2004, Nanoparticle tracking Analysis (NTA) has become increasingly prevalent in a wide variety of different research fields and industrial applications. In this final chapter of the Nanoparticle Tracking Analysis (NTA) application and usage review, we review the reports of Nanoparticle Tracking Analysis in industrial applications including papers and inks, treatments of wastes, filtration and nanobubbles.
The increasing number of nanomaterial based consumer products raises concerns about their possible impact on the environment. Suitable methods for their analysis are a particular problem in this regard. As discussed by Paterson et al. (2011) there is an urgent need for standardized methods and environmental monitoring programs for anthropogenic nanoparticles in order to appropriately assess the risks to biological species due to potential nanoparticle exposure. In doing so they issued a challenge to national and international regulatory and research agencies to help develop standard methods, quality assurance tools, and implement environmental monitoring programs for this class of pollutants thereby generating baseline data that could facilitate the environmental risk assessment evaluations that are currently virtually absent.
In a similar vein, Dean (2012) emphasized the need to produce stable reference materials while preventing agglomeration such that the behavior of the nanomaterials needs to be controlled by modifying the surface of the particles. He suggested that such modified particles could then be “characterized in biological solutions using instrumentation such as Nanoparticle Tracking Analysis (NTA), which offers a unique method for visualizing and analyzing particle size and size distribution by relating the rate of Brownian motion to particle size”. He advocated combining NTA with a label-free, real-time, cell-electronic sensing system to measure changes in cell number following nanoparticle exposure so that nanoparticles in complex suspensions could be characterized in terms of size, distribution, and toxicity
NTA has recently become an ASTM method for the analysis of particle size distribution of nanomaterials in suspension being one of the very few techniques that are able to deal with the measurement of particle size distribution in the nano-size region, The ASTM (2012) guide describes the NTA technique for direct visualization and measurement of Brownian motion, generally applicable in the particle size range from several nanometers until the onset of sedimentation in the sample and is acknowledged as being capable of being routinely applied in industry and academia as both a research and development tool and as a QC method for the characterization of submicron systems.
Given the recognized importance of the subject of nanoparticles and their analysis and the fact that nanoparticles are already used in several consumer products including food, food packaging and cosmetics, and their detection and measurement in food represent a particularly difficult challenge, the European Commission published in October 2011 its recommendation on the definition of ‘nanomaterial’. This will have an impact in many different areas of legislation, such as the European Cosmetic Products Regulation, where the current definitions of nanomaterial will come under discussion regarding how they should be adapted in light of this new definition. This new definition calls for the measurement of the number-based particle size distribution in the 1–100nm size range of all the primary particles present in the sample independently of whether they are in a free, unbound state or as part of an aggregate/agglomerate. Recently, Linsinger et al. (2012) have analyzed the requirements on measurements for the implementation of the European Commission definition of the term 'nanomaterial’.
Calzolai et al. (2012) have subsequently reviewed methods for measuring nanoparticles size distribution in food and consumer products. They gave an overview of the current state of the art, focusing particularly on the suitability of the most used techniques for the size measurement of nanoparticles when addressing this new definition of nanomaterials illustrating the problems to be overcome in measuring nanoparticles in food and consumer products with some practical examples. In assessing NTA and in comparison the other such techniques, they acknowledged that NTA was effective in overcoming the inherent weaknesses of the DLS and static light scattering methods when confronted with mixtures of relatively similarly sized particles and had a number of important advantages including relatively low instrument cost and high sensitivity which can detect nanoparticles at concentrations as low as low as 106 particle/cm3. They did point out however, the inherent limitation of the technique in not being able to detect nanoparticles below 10-20nm meant it did not meet the full requirements of the EU definition and was, furthermore, a technique which required expertise on the part of the operator. In analyzing foodstuffs, Famelart et al. (2013) recently used NTA to determine heat-induced effects on the particle size distribution of casein micelles through the formation of disulphide bonds formed during acid gelation of preheated milk in the presence and absence of N-ethylmaleimide (NEM), a thiol-blocking agent.
The use of engineered nanoparticles as additives to papers and as coatings materials and inks has been increasingly studied over the last few years.
Lamminmäki and her co-workers have described studies using NTA into the reported short timescale inkjet ink component diffusion as an active part of the absorption mechanism into inkjet coatings (Lamminmäki et al., 2011a) and the limitations of current formulations when decreasing the coating layer thickness of papers for inkjet coating. The rate of uptake of inks is strongly related to the number of fine diameter pores in the substrate and is a critical parameter in industrial scale printing processes both in terms of speed and coating density. The results showed that, under the external pressure caused by the surface tension and impact of the ink droplets themselves, the permeability of the coating layer dominates after at least 4msecs from the time of ink application on a high-speed inkjet printing press (Lamminmäki et al., 2011b). She described in detail the various parameters associated with the comparative dynamics of bulk liquid flow and interpolymer diffusion during inkjet ink imbibition in porous coating structures (Lamminmäki, 2012).
Kosmala et al. (2011) have also reported the development of high concentrated aqueous silver nanofluid and inkjet printing on ceramic substrates in which the effect of substrates, printing temperature and dot spacing on the size and morphology of printed silver features was investigated. NTA was used in the analysis of silver nanoparticles and zeta potential in dependence on pH for the nanosilver powders treated with IPA and acetone. The use of high solid loading inks reduces the number of printed layers required for thick, dense and conductive film thus leading to the reduction of the costs and higher efficiency of the printing process.
Laitinen has also described the preparation and characterization of α-methylstyrene–butadiene latexes for paper coating applications (Laitinen et al., 2012), showing that coating colors containing α-methylstyrene seems to have an improved water retention compared to the commercial reference styrene-butadiene latex coating color and the laboratory prepared styrene-butadiene coating color. The particle size of the latex samples was measured using NTA.
Nanocelluloses can be used to fabricate and reinforce hemp fibers. Thus, Dai et al. (2012) developed a novel fabrication which was employed to produce nanocelluloses from natural fibers (hemp) and the developed nanocellulose was then used as a “coupling agent” to modify hemp fibers themselves. The size distribution of nano-particles (nanocellulose) was measured by NTA and results showed that oxidation–sonication developed nanocellulose had wider size range (29–281 nm) than the average size (100–112 nm). Mechanical testing showed that the nanocellulose modification could improve the mechanical properties of natural fibers significantly. The modulus, tensile stress and tensile strain of nanocellulose modified hemp fibers were increased by 36%, 72% and 68%, respectively. Curable biopolymer nanoparticle latex binders have recently been patented for mineral, natural organic or synthetic fiber products and non-woven mats (Tseitlin et al., 2012)
As nanoparticles become more widely spread throughout industry and consumer products, release from, and exposure to, such nanoparticle-containing materials becomes of increasing concern and the subject of intense study. While the toxicity and environmental fate of nanoparticles has been described elsewhere in this document (See Chapter III and IV), specific examples of the use of NTA for sizing and concentration measurement of nanoparticles in development of monitoring protocols as might be applied to industrial products and manufacturing processes are described here.
Thus, Sachse et al. (2012) have studied the effect of nanoclay on dust generation during drilling of polymer nanocomposites, using NTA to follow particle size distribution and quantity. While there is currently a lack of information available in the literature on the nano and ultrafine particle emission rates from these, it was shown that the influence of nanoclay on mechanical drilling of PA6 composites, in terms of dust generation, has been reported with more particles in the size range between 175 and 350 nm being generated during drilling of the nanocomposites, these particles deposit in a shorter time. In a similar type of application, Njuguna et al. (2011) have investigated the nanoparticles generated from nanofiller reinforced polymer nanocomposites during structural testing.
Künniger et al. (2010) investigated the consequences for functionality and the aquatic environment of the release of conventional and nano-sized biocides from coated wooden façades during weathering. Extending these studies to show that Ag-NPs are likely transformed to silver complexes, which are considerably less toxic than ionic silver, Künniger et al. (2013), in her comparative study of metallic silver nanoparticles (Ag-NP), most recently compared conventional organic biocides used as transparent, hydrophobic coatings of wooden outdoor façades.
Cabot et al. (2012) have used NTA to monitor changes in tobacco smoke particle size when measured over a series of different time points. The health effects of automotive particulate pollution, specifically related to engineered Pd-nanoparticles, were studied by Wilkinson et al. (2011) using NTA and DLS to track particle aggregation in cell growth media. The measurement of soot-in-oil agglomerates from automotive engines was recently carried out by NTA and compared to TEM (La Rocca et al., 2013). Diluting used sump oil in heptane, both techniques showed that soot-in-oil exists as agglomerates with average size of 120nm but that NTA was able to measure particles in polydisperse solutions and report the size and volume distribution of soot-in-oil aggregates with the advantage of being fast and relatively low cost compared with TEM.
A new SAE Standard (equivalent to MIL-L-21260) covering military engine oils suitable for preservation, break-in, and lubrication of reciprocating internal combustion engines in equipment used in combat/tactical service has recently been proposed in which NTA was used to establish protocols for measuring soot agglomerates size distribution in used automotive lubricant oils (SAE Standard (2013).
Peetsch and Epple (2011) employed DLS, NTA, SEM, energy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), atomic absorption spectroscopy (AAS), thermogravimetric analysis (TG), and elemental analysis in their characterization of the solid components of three desensitizing toothpastes and a mouth wash.
Having established that, to March 2011, there existed over 100 food and food-related nanoproducts, Chen et al. (2012) investigated and developed a simple test for the characterization and preliminary toxicity assay of nano-titanium dioxide additive in sugar-coated chewing gum. Using NTA their results surprisingly showed that the number of food products containing nano-TiO2 (<200 nm) is much larger than known, and consumers have already often been exposed to engineered nanoparticles in daily life and that over 93% of TiO2 in gum is nano-TiO2 and it is unexpectedly easy to come out and be swallowed by a person who chews gum. Similarly, van Landuyt et al. (2013) showed by NTA that nanoscale particles exist in dental abrasives (up to 60vol %) and that dental personnel (and patients) may inhale nano-sized dust particles (<100 nm) during abrasive procedures to shape, finish or remove restorations.
Recognizing that no standard test method is currently available for evaluating the efficiency of personal protective equipment against nanoparticles, in particular in the case of gloves, Dolez et al. (2011) used NTA and other techniques to determine the rate of nanoparticle penetration through protective gloves in conditions simulating glove-nanoparticle occupational interaction. They reported on commercial 15nm TiO2 nanoparticles-powder and colloidal solutions in 1,2-propanediol, ethylene glycol and water and for four types of protective gloves (disposable nitrile and latex as well as unsupported neoprene and butyl rubber gloves) they showed that mechanical deformations and contact with colloidal solution liquid carriers may affect glove materials. Preliminary results obtained with TiO2 powder indicated a possible penetration of nanoparticles through gloves following mechanical deformations.
Textile materials with engineered nanoparticles (ENPs) have excellent properties as they are antibacterial, antimicrobial, water resistant and protective. The textile industry has recognized the importance and the advantages of ENPs, so they now comprise one of the fastest developing branches of processing and are the subject of significant patent activity, some of which employs NTA analysis in the description (Corona et al., 2013). The most important sources of ENPs released to the environment from textiles are textile-industry wastewaters and waters from large hospital or hotel laundries. Rezić (2011) has reviewed analytical techniques for the characterization of ENPs on textiles. In this context, the increasing number of nanomaterial-based consumer products raises concerns about their possible impact on the environment. In assessing the effluent from a commercially available silver nanowashing machine, Farkas et al. (2011) used inductive coupled mass spectrometry (ICP-MS) and TEM to confirm the presence of an average of 10nm silver nanoparticles but employed NTA to determine that 60–100nm particles were also present. The effluent was shown to have negative effects on a natural bacterial community as its abundance was clearly reduced when exposed to the nanowash water and they suggested that if washing machines capable of producing AgNPs become a common feature of households in the future, wastewater will contain significant loadings of AgNPs which might be released into the environment. Ling and Pui (2013) also used NTA to characterize nanoparticles from abrasive waterjet machining (AWM) and electrical discharge machining processes showing a peak size of 100-200 nm and that while the filtration systems of the cleaning systems were found to remove 70 and 90 % the nanoparticles present, the particle concentration of the filtered water from the AWM was still four times higher than that found in regular tap water.
Nanoparticle-containing matrices are being increasingly investigated for the removal of environmental pollutants from industrial process wastewaters. NTA was employed by Prasad et al. (2012) in their study of the adsorption of arsenite (As3+) on nano-sized Fe2O3 waste powder from the steel industry while Savu et al. (2010) earlier assessed the generation of airborne nanoparticulates during pulsed laser welding processes and considered methods for their removal.
Mallampati et al. (2012) demonstrated, in part by employing NTA, the enhanced heavy metal immobilization in soil by grinding with addition of a nanometallic Ca/CaO dispersion mixture. Raychoudhury et al. (2011) assessed the transport of two polyelectrolyte-stabilized zerovalent iron nanoparticles in porous media for the remediation of contaminated subsurface environments. Using DLS, NTA and laser Doppler velocimetry, they measured the aggregate size and surface charge of bare and carboxymethylcellulose-coated nZVI particles.
Similarly, Cheng et al. (2012) have recently described the synthesis of carbon-coated, porous and water-dispersive Fe3O4 nanocapsules with a diameter of about 120 nm (as determined by NTA) and their excellent performance for heavy metal removal applications. The heavy metals removal test they employed demonstrated the excellent affinity of nanocapsules, the high efficiency for different metals (>90%), 79 mg g−1 adsorption capacity for Pb2+ and ultrafast removal process (Pb2+, 99.57%) within 1 minute).
In developing a simple and rapid room-temperature aerosol deposition method to fabricate TiO2 films for photokilling/photodegradation applications, Park et al. (2012) used NTA to demonstrate a mean size of approximately 1µm on fracturing following impacting a glass substrate to form a functional thin film, a process known as aerosol deposition.
Investigating new techniques for enhanced oil recovery (EOR) Hendraningrat et al. (2012a) have undertaken a glass micromodel experimental study of hydrophilic nanoparticles retention for EOR, in which NTA was used to enumerate particles in both the influent and effluent in a glass micromodel. Further work reported an evaluation of oil recovery using nanofluid injection onto several water-wet Berea sandstone core plugs (Hendraningrat et al., 2012b). Hendraningrat and his colleagues have subsequently carried out and reported numerous further studies in this area in which NTA was used to determine the size, size distribution and concentration of nanoscale particles used in the field of EOR. Li et al. (2013) showed that a hydrophilic silica nanoparticles suspension enabled improved oil recovery by a 2-phase flow system. Hendraningrat also reported a coreflood investigation of nanofluid enhanced oil recovery again in low-medium permeability Berea sandstone (Hendraningrat et al., 2013a and 2013b) as well as comparing the effect of some parameters influencing enhanced oil recovery process using these silica nanoparticles (Hendraningrat et al., 2013c). The latest data regarding these studies has been reported recently: the retention of nanoparticles during flooding experiment in several water-wet Berea cores was investigated in 3 different ways involving continuously increasing pressure during single-phase coreflood experiment with microscopic visualization under SEM integrated with Energy Dispersive X-Ray Spectroscopy (EDX) to distinguish nanoparticles with other elements and NTA particle measurement between influent and effluent (Hendraningrat et al., 2013d).
The ability of the NTA technique to generate high resolution particle size distribution data as well as nanoparticle concentration data makes the technique ideally suited to the testing of filters and filtration processes.
Ling et al. (2011) have used NTA to measure particle (50–500 nm) concentration upstream and downstream of the filter to determine the filtration efficiency of a model membrane filter, the Nucleopore® filter, for application in the purification and disinfection of drinking water as well as removal of NPs in highly pure chemicals used in the industries. NTA measurements were found reliable within a certain concentration limit (about 108–1010 particles/cm3) and they stated that experimental results are comparable with previously published data obtained using an aerosolization method, thus validating the capability of the NTA technique.
Co-workers Boulestreau and Schulz have carried out extensive studies of filtration using NTA as the primary method for testing filter efficiency and performance. Thus, in describing the online analysis of the nanoparticles to prevent membrane fouling by a secondary effluent, Boulestreau et al. (2011a and 2011b) tested NTA in terms of reliability and reproducibility of the device as well as the impact of the prefiltration on the measurements made. They showed that NTA was able to measure the particle size distribution and the absolute particle concentration of particles between 100 and 1000 nm in secondary effluent. Their results showed clearly a relationship between the amount of nanoparticles below 200 nm and the filtration behavior. Further such work by Schultz et al. (2011) on improving understanding and prevention of membrane fouling in treated domestic wastewater used NTA to demonstrate that a combination of ozonation/coagulation showed synergistic effects and which led to an additional decrease of submicron particle content and further improvement of the filtration performance.
More recently Boulestreau and co-workers have described the on-line use of NTA in which it was used to optimize the ozonation and the coagulation conditions in a filter system. They stated that the fact that the absolute size and concentration of the nanoparticles can be observed within a few minutes thus allowing users to detect the effect of ozonation and coagulation on the nanoparticles and that the NTA instrument is “a highly capable device to analyze the nanoparticles” (Boulestreau et al., 2012).
Schulz (2012) described his work on submicron particle analysis to characterize fouling in tertiary membrane filtration in which he tested a combination of pre-ozonation, coagulation and subsequent low-pressure membrane filtration as an option for tertiary wastewater treatment. He showed that “by Nanoparticle Tracking Analysis (NTA) a reliable and reproducible detection of the colloid content in treated domestic wastewaters is possible. The effects of the pre-treatments on submicron particle size distribution and on the absolute concentration can be detected”. The results of his work demonstrated that ozonation and coagulation were found to reduce the content of small colloids < 200 nm by forming larger agglomerates, resulting in a better filterability of the water. A combination of both treatments shows synergetic effects and a further reduction of the particle content as well as of the total fouling resistance was observed. More recently, Boulestreau and Miehe (2013) have published guidelines for the use of online fouling monitoring in tertiary treatment; work carried out under a Project entitled OXERAM 2. In order to improve performance of both polymeric membrane and a microsieve pilot scale process, on-line monitoring was implemented. After a literature review and extensive laboratory testing at the Technical University of Berlin, two instruments were selected as being ideal for this purpose. The first was on-line NTA which was used to give “reliable and reproducible information about the concentration and size distributions of the colloidal fractions in the tested treated domestic wastewater”. The other instrument was a simple turbidometer but which was found to be less informative than NTA. As part of the same project, Godehardt et al. (2013) also used NTA in their study on the role of organic substances in tertiary treatment via oxidation and membrane filtration.
In an unrelated filtration problem, that of fractionation of nanocellulose by a foam filter, NTA was used in an attempt to measure bacterial nanocellulose in a sample of enzymatically pretreated nano-fibrillated cellulose from softwood. The length of nanofibres (many 10s microns) often precluded the analysis of such material though sub-micron nanocrystalline cellulose was accessible to NTA (Tanaka et al., 2012).
Luechinger et al. (2010) earlier described a facile, broadly applicable method to prepare nanoporous silver films between 0.5−5 μm and 30−300 nm using soluble salt nanoparticles as pore templates testing them with filtration of aqueous dispersions of carbon nanoparticles (20 nm primary particle size) at a filtration efficiency of >99.6%.
In a study of the significance of electrostatic protein-polysaccharide interactions using bovine serum albumin (BSA) and sodium alginate (Na-Alginate) to specifically illustrate the contribution of this form of non-covalent network to membrane fouling, NTA was used to help demonstrate that soluble complex formation is governed by lowering zeta-potential sufficiently to enable positively charged micro-regions on the protein to bridge between negatively charged carboxyl groups on the alginate. Neemann et al. (2013).
In his development of a recirculating aquaculture system in which accumulation of fine suspended solids and colloids can be avoided by integrating a membrane filtration unit into the system, Holan et al. (2013a) used NTA to identify how the feeding regime affected membrane performance and fouling phenomena caused by dissolved and submicron colloidal particles in the system and how the membrane impacted general water quality and particle characterization. He further reported on this system in his extended work on the Intensive rearing of cod larvae, Gadus morhua. Holan et al. (2013b) thus showed there is a great potential of implementing a membrane filtration system in aquaculture recycling systems.
The generation, measurement, and applied technologies of extremely small bubbles, so-called nano- and micro–bubbles, with diameter ranging from tens of nanometer to tens of micrometer, are evolving innovatively in recent years. Nano-bubble technologies have already been implemented in actual applications such as facility cleaning, solar cell manufacturing process, plant growth, etc., and its application is considered to have the possibility to expand to wider range of fields, such as water treatment processing, environment, civil engineering, beverage, food, pharmaceutical, medical, cosmetic, plant cultivation, agriculture, fisheries, cleaning, decontamination, and also manufacturing of future functional materials. Therefore nano- and micro–bubble technology is expected to become one of the key players in major industries of the future. The existence of surface nanobubbles is becoming established following many different investigations from a number of groups. Far less common are reports of the existence of bulk nanobubbles. It has been argued that this is because they are considered less stable in bulk or that appropriate techniques for their investigation have not yet been developed.
However, NTA is proving to be particularly adept at the detection and analysis (size, size distribution, number concentration) of these relatively low concentration structures of extremely small size (compared to ‘conventional’ bubbles).
Seddon has recently and comprehensively reviewed the area of nanobubbles at surfaces and in bulk, and has considered the current understanding of their formation, stability, physicochemical properties and current and future applications (Seddon et al., 2012). In principle, a nanobubble in the bulk should be less stable than one of the same volume at an interface. The bulk nanobubble has a larger gas/liquid interface to allow diffusion of gas out of the bubble. Also, the curvature of the bubble surface is greater, thus leading to a greater pressure differential across the interface for a bulk bubble of the same volume. Nonetheless, several groups have presented evidence for their existence and the most startling evidence for bulk nanobubbles is the recent work which reports small nitrogen, methane and argon bulk nanobubbles of radius 50 nm that are stable for up to 2 weeks. The bulk nanobubbles, which were produced by mechanical means that led to extreme supersaturation, were imaged from freeze-fracture replicas by SEM and were produced in such large quantities that the bulk density of the solution was substantially reduced.
It is noteworthy, however, that questions still remain over whether deeply sub-micron bubbles are what they are assumed to be. In a recent thought-provoking study Sedlak and Rak (2013) have shown that in solutions of low molar mass compounds and mixtures of liquids, large-scale inhomogeneities exist but which are not nanobubbles in all cases. Thus, despite the fact that in textbooks, undersaturated solutions of low molar mass compounds and mixtures of freely miscible liquids are considered as homogeneous at larger length scales exceeding appreciably dimensions of individual molecules, growing experimental evidence reveals that it is not the case. Large-scale structures with sizes on the order of 100 nm are present in degassed solutions and mixtures used in everyday life and research practice (e.g. atmospheric pressure), especially in aqueous systems. These mesoscale inhomogeneities are long-lived and their (relatively slow) formation kinetics can be monitored upon mixing the components using NTA. These results support experimental results obtained in earlier light scattering studies and, indeed, such results have been obtained (especially in 50:50 mixtures of water and ethanol) by the scientists responsible for the development of NTA (data not published).
Most of the work to date involving NTA analysis of nanobubbles has been carried out in Japan. Thus Takaya et al.(2011) described the formation of nanobubbles by water electrolysis and their analysis with NTA, while Kikuchi et al. (2011) investigated their stability and weight having determined their size distribution with NTA.
Uchida et al. (2011) used TEM observations of nanobubbles and their capture of impurities in wastewater. They generated a nanobubble solution by introducing pure O2 gas into the ultra-high purity water with a micro/nano bubble generator and used NTA to measure the resulting number concentration, estimated to be on the order of 107 cm-3 of solution under the same sample preparation conditions. Ushida also investigated the efficiency with which nanobubbles could replace detergents in the washing of laundry given it has been estimated that mechanical work has been found to account for 50% of the washing effect and nanobubbles can achieve the same mechanical action. A combination of nanobubbles and reduced detergency resulted in a 10% increase in washing efficiency (Uchida et al., 2011). Ushida et al. (2012) have recently investigated the drag reduction effect of nanobubble mixture flows through micro-orifices and capillaries in which the nanobubble-containing mixture was shown to contain 1.0 vol% nanobubbles by NTA. The results of studies using nanobubble mixtures for water and glycerol which were passed through several sizes of micro-orifices and capillaries suggested that the addition of nanobubbles to a liquid results in excellent drag reduction. Ushida also extended this work to include several types of nanobubble mixtures (nanobubble/water, nanobubble/surfactant and nanobubble/polymer) and discussed factors including slip wall, interfacial tension effect, electric interface phenomenon and elasticity (Ushida et al., 2013).
Uehara and Yano (2011) have reported magnetized nanobubble water formed under a pulsed-magnetic field and Liu et al. (2013) have recently investigated the mechanism of nanobubbles’ physiological activity promotion with proton nuclear magnetic resonance (pNMR) relaxation time measurements. According to the experiment results, the number of nanobubbles had a positive correlation with the spin-spin relaxation time (T2) value of the water, which meant introducing nanobubbles could increase the mobility of water in bulk. These results suggested that the nanobubbles in water could influence the physical properties of water and that it could contribute to one of the explanations for the mechanism of nanobubble’s promotion effect on physiological activity of living organisms. The hydroponic experiment showed that the nanobubbles themselves could greatly promote the growth of barley and that nanobubble technology was possibly feasible to be used in hydroponic cultivation of vegetables as a new technology in agriculture applications. NTA was used to measure the bubble size diameters, a crucial parameter in understanding the effects they exhibited.
It is interesting to note that methods for the production and apparatus for the generation of nanobubbles, and in which NTA is used for analysis for supporting data, is currently the subject of recent patent activity (e.g. Ryu, 2012; Tsuji, 2012 and Tsuji et al., 2013; Lynn, 2013a and 2013b).
Numerous industrial applications of the use of nanobubbles are beginning to appear in the rapidly growing body of literature on the subject of nanobubbles. Those in which NTA is central to their analysis include studies on applications as diverse as petrochemicals and fuels, building materials and remediation of contaminated land sites and aquaculture. Ueda et al. (2013) described the use of water containing air bubbles with a diameter around 100 nm (nanobubbled water) on removal of radioactive carbon from granule conglomerate, asphalt and concrete contaminated sites in Fukushima, Japan. In a wide ranging study of the efficacy of water containing nanobubbles of air or oxygen gas as generated using a nanobubble aerator, Ebina et al. (2013) showed significant (compared to normal water) increases in growth (plant height, leaf length and fresh weight) of Brassica campestris grown using nanobubbled water; weight and length of DBA1/J mice free-fed nanobubbled water, as well as sweetfish and rainbow trout grown in nanobubbled water.
Nanodroplets that encapsulate a perfluoropentane (PFP) core will transition upon exposure to ultrasound pulses into gas microbubbles, which will rapidly expand and collapse resulting in disruption of cells similar to the histotripsy process but at a significantly lower acoustic pressure. Thus, in attempting to develop an image-guided, targeted ultrasound ablation technique by combining histotripsy with nanodroplets that can be selectively delivered to tumor cells, Vlaisavljevich et al. (2013) used NTA in the preparation of nanodroplets with an average diameter of 204 nm at 37 °C by self-assembly of an amphiphilic triblock copolymer around a PFP core, followed by cross-linkage of the polymer shell forming stable nanodroplets. Using a high speed camera to monitor microbubble generation, the peak negative pressure threshold needed to generate bubbles >50 μm in agarose phantoms containing nanodroplets was measured to be 10.8 MPa, which is significantly lower than the 28.8 MPa observed using ultrasound pulses alone. High speed images also showed that cavitation microbubbles produced from the nanodroplets displayed expansion and collapse similar to histotripsy alone at higher pressures. Nanodroplet-mediated histotripsy created consistent, well-defined fractionation of red blood cells in agarose tissue phantoms at 10 Hz pulse repetition frequency; similar to the lesions generated by histotripsy alone but at a significantly lower pressure. These results support their hypothesis and demonstrate the potential of using nanodroplet-mediated histotripsy for targeted cell ablation.
Finally, nanobubbles of air have been introduced into gas oil for energy saving and environmental load reduction of diesel engines. After the micro air-bubbles were separated from the nano air-bubbles in a mixing tank, diesel engine performance test with a common-rail injection system was tested. The results showed a 3% reduction in a brake specific fuel consumption (BSFC), 1% rise in charging efficiency and a slight reduction in the density of exhaust smoke (Nakatake et al., 2013). Similarly, Oh et al. (2013) investigated the effect of hydrogen nanobubble addition on the combustion characteristics of a gasoline engine. Using NTA to demonstrate a mean diameter and concentration of hydrogen nanobubble in the gasoline blend of 149 nm and about 11x108 particles/mL, respectively, the results showed that the power of a gasoline engine with hydrogen nanobubble gasoline blend was improved by 4.0 % in comparison with conventional gasoline at an engine load of 40 %. Also, BSFC was improved, from 291.10 g/kWh for the conventional gasoline, to 269.48 g/kWh for the hydrogen nanobubble gasoline blend, at the engine load of 40%.
Unsworth et al. (2010) first reported the use of NTA in studying the tribology of CFR-PEEK in hips and knees when generated at 0.5, 10 and 25 million wear test cycles. As the test progressed, the number of particles reduced and the dominant particle size increased from about 40nm to approx. 200 nm. AFM showed some particles as large as 3µm to co-exist. The same group also reported on a tribological and particle debris study of as-cast and heat treated CoCrMo alloy (Kinbrum et al., 2010).
More than 400,000 primary hip and knee replacement surgeries are performed each year in the United States. From these procedures, approximately 0.5–3% will become infected and when considering revision surgeries, this rate has been found to increase significantly. Sinclair et al. (2012) accordingly developed a broad spectrum polymer-released antimicrobial coating (Cationic Steroidal Antimicrobial-13 (CSA-13)) for the prevention of resistant strain bacterial infections. Following manufacturing, CSA-13 was micronized using a jet mill and the resultant particle size distribution was measured using NTA.
Patel et al. (2012) have studied cobalt-based orthopaedic alloys and explored the relationship between the forming route, microstructure and tribological performance using NTA to generate data on the mode of wear particle debris size distribution.
Hydroxyapatite (Ca10(PO4)6(OH)2)is a bioactive ceramic which is found in the mineral phase of bone tissue and is known for its great potential in tissue engineering applications. For this reason, this material can be applied as particle aggregates on ceramic slurry, coating or film on materials with a poorer biological response than hydroxyapatite. Rodrigues et al. (2012) obtained hydroxyapatite gel by the sol-gel process and applied it as nanoparticle aggregation in a mixture of hydroxyapatite and tricalcium phosphate to form a ceramic slurry. This process, the polymer foam replication technique, was used to produce scaffolds which are used in tissue engineering. While the nanoparticles size before firing was approximately 5nm, NTA showed the crystallite size after calcination was approximately 63nm.
ASTM E2834 - 12 (2012) Standard Guide for Measurement of Particle Size Distribution of Nanomaterials in Suspension by Nanoparticle Tracking Analysis (NTA), Active Standard ASTM E2834 Developed by Subcommittee: E56.02|Book of Standards Volume: 14.02, DOI: 10.1520/E2834-12
Boulestreau M, Raspati GS, Miehe U (2011a) Online analysis of the nanoparticles to prevent membrane fouling by a secondary effluent, 6th IWA Specialist Conference on Membrane Technology for Water & Wastewater Treatment, 4-7 October 2011 Eurogress Aachen, Germany
Boulestreau M, Schulz G, Miehe U and Jekel K (2011b) Submicron particle analysis to characterize fouling in tertiary membrane filtration, 6th IWA Specialist Conference on Membrane Technology for Water & Wastewater Treatment, 4-7 October 2011 Eurogress Aachen, Germany
Boulestreau M, Miehe U, Lesjean B (2012) Online analysis of the nanoparticles size distribution in a treated and untreated secondary effluent, EuroNanoTox 5th Late Summer Workshop "Nanoparticles and Nanomaterials in Aquatic Systems" 28 September - 1 October 2010 in Schloss Maurach, Lake Constance
Boulestreau M and Miehe U (2013) Guidelines for the use of online fouling monitoring in tertiary treatment Project acronym: OXERAM 2, VW Wasserbetriebe – 2013, http://www.kompetenz-wasser.de/fileadmin/user_upload/pdf/forschung /OXERAM/D3.1_OXERAM__Online_fouling_monitoring_through_particle_size_analysis.pdf
Cabot R, Hawke J, McAughey J, Dickens C (2012), Dissolution Measurements of Smoke Particles in a Liquid Based Suspension, Poster V13, Drug Delivery to the Lungs 22, Edinburgh, 7 – 9 December 2011
Calzolai L, Gilliland D & Rossi F (2012): Measuring nanoparticles size distribution in food and consumer products: a review, Food Additives & Contaminants: Part A, 29:8, 1183-1193
Chen X.-X, Cheng B, Yang Y.-X, Cao A, Liu J.-H, Du L.-J, Liu Y, Zhao Y and Wang H (2012), Characterization and Preliminary Toxicity Assay of Nano-Titanium Dioxide Additive in Sugar-Coated Chewing Gum. Small. doi: 10.1002/smll.201201506
Cheng K, Zhou Y-M, Sun Z-Y, Hu H-B, Zhong H, Kong X-K and Chen Q-W (2012) Synthesis of carbon-coated, porous and water-dispersive Fe3O4 nanocapsules and their excellent performance for heavy metal removal applications, Dalton Trans., 2012, Advance Article, DOI: 10.1039/C2DT12312F
Corona A, Clark TK, Dupont JS, Hall NL (2013) Fabric Care Compositions, US Patent 20,130,109,612 Publication Date: 05/02/2013
Dai D, Fan M, Collins P (2012) Fabrication of nanocelluloses from hemp fibers and their application for the reinforcement of hemp fibers, Industrial Crops and Products, Volume 44, January 2013, Pages 192–199 http://dx.doi.org/10.1016/j.indcrop.2012.11.010,
Dean L (2012) Size Matters, Chemistry International July-August 2012, p6-9
Dolez P, Vinches L, Wilkinson K, Plamondon P and Vu-Khanh T (2011) Development of a test method for protective gloves against nanoparticles in conditions simulating occupational use, Journal of Physics: Conference Series Volume 304 Number 1 doi: 10.1088/1742-6596/304/1/012066
Ebina K, Shi K, Hirao M, Hashimoto J, Kawato Y, et al.. (2013) Oxygen and Air Nanobubble Water Solution Promote the Growth of Plants, Fishes, and Mice. PLoS ONE 8(6): e65339. doi:10.1371/journal.pone.0065339
Farkas J, Peter H, Christian P, Gallego-Urrea JA, Hassellöv M, Tuoriniemi J, Gustafsson S, Olsson E, Hylland K and Thomas KV (2011) Characterization of the effluent from a nanosilver producing washing machine, Environment International, Article in Press, doi:10.1016/j.envint.2011.03.006
Famelart M.-H, Le NHT, Croguennec T and Rousseau F (2013), Are disulphide bonds formed during acid gelation of preheated milk?. International Journal of Food Science & Technology. doi: 10.1111/ijfs.12174
Godehardt M, Aschermann G, Jekel IM (2013) Role of organic substances in tertiary treatment via oxidation and membrane filtration Project acronym: OXERAM 2, http://www.kompetenz-wasser.de/fileadmin/user_upload/pdf/forschung/OXERAM/D4.2_OXERAM_-_Role_of_organic_substances_-_TU_Berlin.pdf
Hendraningrat L, Shidong L, Suwarno S and Torsæter O (2012a) A Glass Micromodel Experimental Study of Hydrophilic Nanoparticles Retention for EOR Project, SPE Russian Oil and Gas Exploration and Production Technical Conference and Exhibition, 16-18 October 2012, Moscow, Russia
Hendraningrat L, Engeset B, Suwarno S and Torsæter O (2012b) Improved Oil Recovery by Nanofluids Flooding: An Experimental Study , 2012 SPE Kuwait International Petroleum Conference and Exhibition, Dec 10 - 12, 2012 , Kuwait City, Kuwait, ISBN 978-1-61399-263-0
Hendraningrat L, Li S, and Torsæter O (2013a) A Coreflood Investigation of Nanofluid Enhanced Oil Recovery in Low-Medium Permeability Berea Sandstone, 2013 SPE International Symposium on Oilfield Chemistry, Apr 08 - 10, 2013 2013, The Woodlands, TX, USA, DOI 10.2118/164106
Hendraningrat L, Li S, Torsæter O (2013b) A Coreflood Investigation of Nanofluid Enhanced Oil Recovery, Journal of Petroleum Science and Engineering, Available online 1 August 2013, http://dx.doi.org/10.1016/j.petrol.2013.07.003
Hendraningrat L, Li S, and Torsæter O (2013c), Effect of Some Parameters Influencing Enhanced Oil Recovery Process using Silica Nanoparticles: An Experimental Investigation, SPE Reservoir Characterization and Simulation Conference and Exhibition, Sep 16 - 18, 2013 2013, Beach Rotana Hotel, Abu Dhabi, UAE, DOI 10.2118/165955-MS
Hendraningrat L, Engeset B, Suwarno S, Li S and Torsæter O (2013d) Laboratory Investigation Of Porosity And Permeability Impairments In Berea Sandstones Due To Hydrophilic Nanoparticle Retention, International Symposium of the Society of Core Analysts held in Napa Valley, California, USA, 16-19 September, 2013. SCA2013-062.
Holan AB, Wold PA, Leiknes TO (2013) Membrane performance and fouling behavior of membrane bioreactors installed in marine recirculating aquaculture systems, Aquacultural Engineering, Available online 23 October 2013, http://dx.doi.org/10.1016/j.aquaeng.2013.10.002
Holan AB, Wold PA, Leiknes TO (2013) Intensive rearing of cod larvae (Gadus morhua) in recirculating aquaculture systems (RAS) implementing a membrane bioreactor (MBR) for enhanced colloidal particle and fine suspended solids removal, Aquacultural Engineering, Available online 24 October 2013, http://dx.doi.org/10.1016/j.aquaeng.2013.10.001
Kikuchi K, Ioka A, Oku T, Tanaka Y, Saihara Y and Ogumi Z (2011) Stability and weight of oxygen nanobubbles obtained with water electrolysis, Proc 61st Annual Meeting of the International Society of Electrochemistry, September 26th - October 1st, 2010, Nice, France
Kinbrum A; Vasilliou K; Lee SM and Unsworth A (2010) A tribological and particle debris study of as-cast and heat treated CoCrMo alloy, Journal of Bone and Joint Surgery - British Volume, Vol 92-B, Issue SUPP_I, 101.
Kosmala R. Wright Q. Zhang and Kirby P (2011) Synthesis of silver nano particles and fabrication of aqueous Ag inks for inkjet printing , Materials Chemistry and Physics, Article in Press; doi:10.1016/j.matchemphys.2011.05.064
Künniger T, Fischer A, Gerecke A, Heeb M, Kunz P, Ulrich A and Vonbank R (2010) Release of Conventional and Nano-Sized Biocides from Coated Wooden Façades during Weathering: Consequences for Functionality and Aquatic Environment, Proceedings of the International Convention of Society of Wood Science and Technology and United Nations Economic Commission for Europe – Timber Committee, October 11-14, 2010, Geneva, Switzerland, Paper NT-5
Künniger T, Gerecke AC, Ulrich A, Huch A, Vonbank R, Heeb M, Wichser A, Haag R, Kunz P, Faller M (2013) Release and environmental impact of silver nanoparticles and conventional organic biocides from coated wooden façades, Environmental Pollution, Volume 184, January 2014, Pages 464–471 http://dx.doi.org/10.1016/j.envpol.2013.09.030
La Rocca A, Di Liberto G, Shayler P, Parmenter CDJ, Fay MW (2013) Application of nanoparticle tracking analysis platform for the measurement of soot-in-oil agglomerates from automotive engines,Tribology International, http://dx.doi.org/10.1016/j.triboint.2013.09.018
Laitinen A, Alkio M, Forsström U, Harlin A, Heikkinen H, Kaunisto J, Kokko A, Rautkoski H, Räsänen L (2012) Preparation and characterization of α-methylstyrene–butadiene latexes for paper coating applications, Progress in Organic Coatings, Volume 75, Issue 4, December 2012, Pages 411–419
Lamminmäki T; Kettle J; Puukko P; Ridgwa CJ; Gane PAC (2011a) Short timescale inkjet ink component diffusion: An active part of the absorption mechanism into inkjet coatings, Journal of Colloid and Interface Science, vol. 365(2012):1, pp. 222-235. http://dx.doi.org/10.1016/j.jcis.2011.08.045
Lamminmaki T, Kettle J, Rautkoski H, Kokko A and Gane P (2011b) Limitations of Current Formulations when Decreasing the Coating Layer Thickness of Papers for Inkjet Printing, Ind. Eng. Chem. Res., Article ASAP, DOI: 10.1021/ie102114s Publication Date (Web): May 9, 2011
Lamminmäki T (2012) The comparative dynamics of bulk liquid flow and interpolymer diffusion during inkjet ink imbibition in porous coating structures, PhD Thesis, VTT Finland, ISBN 978-951-38-7456-8 (URL: http://www.vtt.fi/publications/index.jsp)
Li S, Hendraningrat L, Torsæter O (2013) Improved Oil Recovery by Hydrophilic Silica Nanoparticles Suspension: 2-Phase Flow Experimental Studies, 6th International Petroleum Technology Conference, Mar 26 - 28, 2013 2013, Beijing, China, DOI 10.2523/16707-MS
Ling TY, Wang J and Pui DYH (2011) Measurement of filtration efficiency of Nuclepore filters challenged with polystyrene latex nanoparticles: experiments and modeling, Journal of Nanoparticle Research, DOI: 10.1007/s11051-011-0529-2,Online First™
Ling TY and Pui DYH (2013) Characterization of Nanoparticles from Abrasive Waterjet Machining and Electrical Discharge Machining Processes, Environ. Sci. Technol., Just Accepted Manuscript, DOI: 10.1021/es402593y
Linsinger T, Roebben G, Rossi F, Gilliland D, Gibson N, Klein C, Calzolai L (2012) Requirements on measurements for the implementation of the European Commission definition of the term 'nanomaterial', JRC Reference Report, http://publications.jrc.ec.europa.eu/repository/bitstream/111111111/26399/1/irmm_nanomaterials%20%28online%29.pdf
Luechinger NA., Walt SGand Stark WJ (2010) Printable Nanoporous Silver Membranes, Chem. Mater., 2010, 22 (17), pp 4980–4986
Liu S, Kawagoe Y, Makino Y, Oshita S (2013) Effects of nanobubbles on the physicochemical properties of water: The basis for peculiar properties of water containing nanobubbles, Chemical Engineering Science, Available online 11 February 2013 http://dx.doi.org/10.1016/j.ces.2013.02.004
Lynn DW (2013a) Ozonated Liquid Dispensing Unit, US Patent 20,130,142,704, 2013
Lynn, DW (2013b) Ozonated Liquid Production And Distribution Systems, United States Patent Application 20130195725
Mallampati SR, Mitoma Y, Okuda T, Sakita S, Kakeda M (2012) Enhanced heavy metal immobilization in soil by grinding with addition of nanometallic Ca/CaO dispersion mixture, Chemosphere, http://dx.doi.org/10.1016/j.chemosphere.2012.06.030
Neemann F, Rosenberger S, Jefferson B, McAdam EJ (2013) Non-covalent protein-polysaccharide interactions and their influence on membrane fouling, Journal of Membrane Science, Available online 5 July 2013, http://dx.doi.org/10.1016/j.memsci.2013.06.054
Nakatake Y, Kisu S, Shigyo K, Eguchi T, Watanabe T (2013) Effect of nano air-bubbles mixed into gas oil on common-rail diesel engine, Energy, http://dx.doi.org/10.1016/j.energy.2013.06.065
Njuguna J, Sachse S, Silva F, Irfan A, Michałowski S, Pielichowski Kf, Kazmina O, Ermini V, Zhu H and Blázquez M (2011) Investigations into nanoparticles generated from nanofiller reinforced polymer nanocomposites during structural testing, Safety issues of nanomaterials along their life cycle, Symposium at LEITAT Technological Center, Barcelona (Spain). 4th and 5th May 2011
Oh SH, Yoon SH, Song H, Guen Han J, Kim J-M (2013) Effect of hydrogen nanobubble addition on combustion characteristics of gasoline engine, International Journal of Hydrogen Energy, Available online 4 October 2013, http://dx.doi.org/10.1016/j.ijhydene.2013.09.063
Park J-J, Lee J-G, Kim D-Y, Hong J-H, Kim J-J, Hong S and Yoon SS (2012) Antibacterial and Water Purification Activities of Self-Assembled Honeycomb Structure of Aerosol Deposited Titania Film, Environ. Sci. Technol., Just Accepted Manuscript DOI: 10.1021/es3037252
Patel B, Favaro G, Inam F, Reece MJ, Angadji A, Bonfield W, Huang J and Edirisinghe M (2012) Cobalt-based orthopaedic alloys: Relationship between forming route, microstructure and tribological performance, Materials Science and Engineering: C http://dx.doi.org/10.1016/j.msec.2012.03.012
Paterson G, Macken A and Thomas KV (2011) The need for standardized methods and environmental monitoring programs for anthropogenic nanoparticles, , Anal. Methods, 2011, Advance Article, DOI: 10.1039/C1AY05157A
Peetsch A and Epple M (2011), Characterization of the solid components of three desensitizing toothpastes and a mouth wash. Materialwissenschaft und Werkstofftechnik, 42: 131–135. DOI: 10.1002/mawe.201100744
Prasad B, Ghosh C, Chakraborty A, Bandyopadhyay N and Ray RK (2011) Adsorption of arsenite (As3+) on nano-sized Fe2O3 waste powder from the steel industry, Desalination, DOI:10.1016/j.desal.2011.01.081 Article in Press
Raychoudhury T, Naja G and Ghoshal S (2010) Assessment of Transport of Two Polyelectrolyte-Stabilized Zerovalent Iron Nanoparticles in Porous Media , Journal of Contaminant Hydrology, in press , doi:10.1016/j.jconhyd.2010.09.005
Rezić I (2011) Determination of engineered nanoparticles on textiles and in textile wastewaters, TrAC Trends in Analytical Chemistry, Article in Press, Accepted Manuscript doi:10.1016/j.trac.2011.02.017
Rodrigues LR, d`Ávila MA, Monteiro FJM, de Carvalho Zavaglia CAm (2012) Synthesis and characterization of nanocrystalline hydroxyapatite gel and its application as scaffold aggregation, Materials Research, ahead of print Epub Oct 02, 2012 Print version ISSN 1516-1439, http://dx.doi.org/10.1590/S1516-14392012005000124
Ryu, S-r (2012) Method and apparatus for generating nano-bubbles in liquid ,United States Patent Application 20120086137
Sachse S, Silva F, Zhu H, Irfan A, Leszczynska A, Pielichowski K, Ermini V, Blazquez M, Kuzmenko O and Njuguna J (2012) The Effect of Nanoclay on Dust Generation during Drilling of PA6 Nanocomposites, Journal of Nanomaterials, Volume 2012, Article ID 189386, 8 pages, doi:10.1155/2012/189386
SAE: A Novel Diagnostics Tool for Measuring Soot Agglomerates Size Distribution in Used Automotive Lubricant Oils (2013) http://topics.sae.org/lubricants/standards/
Savu D, I. Birdeanu CV and Savu S (2010) Laser welding of low friction nanostructured sintered composites: technical and environmental aspects, International Journal of Microstructure and Materials Properties, Volume 5, Number 2-3, p261 – 275
Schulz M, Godehardt M, Boulestreau M, Ernst M, Miehe U, Lesjean B and Jekel M (2011) Analysis of nanoparticles in treated domestic wastewater for improved understanding and prevention of membrane fouling, 6th IWA Specialist Conference on Membrane Technology for Water & Wastewater Treatment, 4-7 October 2011 Eurogress Aachen, Germany
Schulz M (2012) Submicron particle analysis to characterize fouling in tertiary membrane filtration, Diplomarbeit, Technische Universitat Berlin, Institut fur Technischen Umweltschutz Berlin, April 2012
Seddon JRT, Lohse D, Ducker WA and Craig VSJ (2012) A Deliberation on Nanobubbles at Surfaces and in Bulk, ChemPhysChem 2012, 13, 2179 – 2187
Sedlak M and Rak D (2013) Large-Scale Inhomogeneities in Solutions of Low Molar Mass Compounds and Mixtures of Liquids: Supramolecular Structures or Nanobubbles?, J. Phys. Chem. B, Just Accepted Manuscript, DOI: 10.1021/jp4002093, Publication Date (Web): February 1, 2013
Sinclair KD, Pham TX, Farnsworth RW, Williams DL, Loc-Carrillo C, Horne LA, Ingebretsen SH, Bloebaum RD. (2012) Development of a broad spectrum polymer-released antimicrobial coating for the prevention of resistant strain bacterial infections. J Biomed Mater Res Part A 2012:00A:000–000.
Takaya M., Kikuchi K, Oku T, Tanaka Y, Saihara Y and Ogumi Z (2011) Interface structure of oxygen nanobubble, Proc 61st Annual Meeting of the International Society of Electrochemistry, September 26th - October 1st, 2010, Nice, France
Tanaka A, Hjelt T, Sneck A & Korpela A (2012) Fractionation of Nanocellulose by Foam Filter, Separation Science and Technology, Volume 47, Issue 12, pages 1771-1776 DOI:10.1080/01496395.2012.661825
Tseitlin A, Van Alstyne D, Bloembergen S (2012) Curable biopolymer nanoparticle latex binder for mineral, natural organic, or synthetic fiber products and non-woven mats, United States Patent Application 20120309246
Tsuji H, Tsuji Y, Oka T; Sugi S, Torii M, Miyao H, Nakayama Y, Torii T, Mori M (2012) Composition And Process For Production Thereof, United States Patent Application 20120128749
Tsuji, H; Tsuji Y, Oka T, Miyao H, Liauw D (2013) Extraction method using ultra fine bubbles and liquid extracts obtained thereof, United States Patent Application 20130045934, Publication Date: 02/21/2013
Uchida T, Oshita S, Ohmori M, Tsuno T, Soejima K, Shinozaki S, Take Y and Mitsuda K (2011) Transmission electron microscopic observations of nanobubbles and their capture of impurities in wastewater, Nanoscale Research Letters 6:295
Ueda Y, Tokuda Y, Fujimura S, Nihei N and Oka T (2013) Cesium Transfer from Granule Conglomerate, Asphalt, and Concrete Using Water Containing Nano-Sized Air Bubbles, ECS Trans. 2013 volume 50, issue 22, 1-6, doi: 10.1149/05022.0001ecst
Uehara K and Yano Y (2011) Magnetized Nanobubble Water Formed Under Pulsed-Magnetic Field, IEEE Transactions on Magnetics, Volume: 47 Issue:10, 2604 – 2607
Unsworth A; Scholes SC; Kinbrum A and Inman IA (2010) Tribology of CFR-PEEK in Hips and Knees, Journal of Bone and Joint Surgery - British Volume, Vol 92-B, Issue SUPP_I, 174.
Ushida A, Hasegawa T, Amaki K, Nakajima T, Takahashi N and Narumi T (2011), Investigation On Washing Effects For Nano-Bubble/Surfactant Mixtures In An Alternating Flow, Transactions of The Japan Society of Mechanical Engineers Series B, Vol. 77, No. 777 (2011), pp.1219-1228
Ushida A, Hasegawa T, Nakajima T, Uchiyama H, Narumi T (2012) Drag reduction effect of nanobubble mixture flows through micro-orifices and capillaries, Experimental Thermal and Fluid Science,
Ushida A, Hasegawa T, Narumi T, Nakajima T (2013) Flow properties of nanobubble mixtures passing through micro-orifices, International Journal of Heat and Fluid Flow, Available online 17 February 2013, http://dx.doi.org/10.1016/j.ijheatfluidflow.2013.01.013
Van Landuyt KL, Hellack B, Van Meerbeek B, Peumans M, Hoet P, Wiemann M, Kuhlbusch TAJ, Asbach C (2013) Nanoparticle release from dental composites, Acta Biomaterialia, Available online 10 October 2013
Vlaisavljevich E, Durmaz YY, Maxwell A, ElSayed M, Xu Z (2013), Nanodroplet-Mediated Histotripsy for Image-guided Targeted Ultrasound Cell Ablation, Theranostics, 2013; 3(11):802-815. doi: 10.7150/thno.6717
Wilkinson KE, Palmberg L, Witasp E, Kupczyk M, Feliu NT, Seisenbaeva GA, Fadeel B, Dahlén SE and Kessler V (2011) Solution Engineered Pd-Nanoparticles: Model for Health Effect Studies of Automotive Particulate Pollution, ACS Nano, Just Accepted Manuscript • DOI: 10.1021/nn1032664 • Publication Date (Web): 08 June 2011