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Nano sand filter with functionalized nanoparticles embedded in anodic aluminum oxide templates

View Article: PubMed Central - PubMed

ABSTRACT

Since the ancient Egyptians had used sand as filter media for water purification, its principle has been inherited through generations and it is still being used now in industries. The sand filter consists of sand literally, and the voids within the sand bed are the pores for filtration. Here we present a filtration principle using nanoparticles, so that the voids between the nanoparticles can be considered as effective pores in nanoscale dimension. Anodic aluminum oxide (AAO) membrane has been used as the working template, and the nanoparticles have been injected and embedded within the pores of the AAO template. Nanoparticles with multiple sizes have been used in order to obtain smaller voids. Moreover, the nanoparticles have been functionalized, or electrically charged, with arginine/phenylalanine (RF) peptide group. In this way, filtration performance for charged particles or molecules, such as methylene blue, has been enhanced. Consequently, this study is expected to provide a new principle for fabrication of nano voids, or nano pores, and for filtration in nanoscale dimension.

No MeSH data available.


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Cross sectional view of working templates for every step of embedding nanoparticles.(a) Original AAO template. (b) After embedding with 150 nm particles. (c) After embedding with 150 and 60 nm particles. (d) After embedding with 150, 60 and 24 nm particles.
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f2: Cross sectional view of working templates for every step of embedding nanoparticles.(a) Original AAO template. (b) After embedding with 150 nm particles. (c) After embedding with 150 and 60 nm particles. (d) After embedding with 150, 60 and 24 nm particles.

Mentions: We used commercial anodic aluminum oxide (AAO) membrane filters (Anodisc, Whatman plc.) as working templates, which have nominal pore diameter of 100 nm. This AAO template has asymmetric pores as seen in Fig. 1, where the pores on one side are bigger than those on the other side. And circles are also illustrated together in Fig. 1, which represent spherical particles with diameter of 150 nm. So it is expected that the particles with this size can be injected into the larger pores but they will be trapped, or embedded, inside. Therefore, solution of nanoparticles of 150 nm in diameter was injected firstly with a syringe pump. Then solutions with particles of 60 and 24 nm were injected in sequence. Figure 2 shows cross sectional scanning electron microscopy (SEM) images for every step. However, it needs to be mentioned that these images may not represent the exact arrangement of the nanoparticles in the AAO pores, because many of them have been lost when the AAO template is cut. Though, we could check whether the particles of every size were embedded within the AAO templates or not. Initially, the pores of original AAO template (Fig. 2a) is filled with 150 nm particles (Fig. 2b), and the following images (Fig. 2c and d) show that the smaller particles are occupying the pores of AAO template together. For further investigation on the embedment of the particles in the pore, the particles are required to remain on the cross section as many as possible, when the template is cut. So after the embedment, the template with nanoparticles of 150, 60 and 24 nm was frozen and then cut. By this way, another cross sectional images were obtained (Fig. 3), which should be more close to actual embedment of the particles in the pores. Meanwhile, all the pores need to be filled with the nanoparticles because this template is for filtration or separation. If there exist any empty pores on AAO template, they will be serious defects for the performance. In this study, the particles are transported in liquid solution, which tends to flow toward unoccupied pores naturally. Therefore, it can be expected that all the pores contain nanoparticles inside, without any empty pores. And overall view of the cross section of AAO template is shown in Supplementary Fig. 1. This shows internal structure of the template together with the nanoparticles in the pores.


Nano sand filter with functionalized nanoparticles embedded in anodic aluminum oxide templates
Cross sectional view of working templates for every step of embedding nanoparticles.(a) Original AAO template. (b) After embedding with 150 nm particles. (c) After embedding with 150 and 60 nm particles. (d) After embedding with 150, 60 and 24 nm particles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC5120303&req=5

f2: Cross sectional view of working templates for every step of embedding nanoparticles.(a) Original AAO template. (b) After embedding with 150 nm particles. (c) After embedding with 150 and 60 nm particles. (d) After embedding with 150, 60 and 24 nm particles.
Mentions: We used commercial anodic aluminum oxide (AAO) membrane filters (Anodisc, Whatman plc.) as working templates, which have nominal pore diameter of 100 nm. This AAO template has asymmetric pores as seen in Fig. 1, where the pores on one side are bigger than those on the other side. And circles are also illustrated together in Fig. 1, which represent spherical particles with diameter of 150 nm. So it is expected that the particles with this size can be injected into the larger pores but they will be trapped, or embedded, inside. Therefore, solution of nanoparticles of 150 nm in diameter was injected firstly with a syringe pump. Then solutions with particles of 60 and 24 nm were injected in sequence. Figure 2 shows cross sectional scanning electron microscopy (SEM) images for every step. However, it needs to be mentioned that these images may not represent the exact arrangement of the nanoparticles in the AAO pores, because many of them have been lost when the AAO template is cut. Though, we could check whether the particles of every size were embedded within the AAO templates or not. Initially, the pores of original AAO template (Fig. 2a) is filled with 150 nm particles (Fig. 2b), and the following images (Fig. 2c and d) show that the smaller particles are occupying the pores of AAO template together. For further investigation on the embedment of the particles in the pore, the particles are required to remain on the cross section as many as possible, when the template is cut. So after the embedment, the template with nanoparticles of 150, 60 and 24 nm was frozen and then cut. By this way, another cross sectional images were obtained (Fig. 3), which should be more close to actual embedment of the particles in the pores. Meanwhile, all the pores need to be filled with the nanoparticles because this template is for filtration or separation. If there exist any empty pores on AAO template, they will be serious defects for the performance. In this study, the particles are transported in liquid solution, which tends to flow toward unoccupied pores naturally. Therefore, it can be expected that all the pores contain nanoparticles inside, without any empty pores. And overall view of the cross section of AAO template is shown in Supplementary Fig. 1. This shows internal structure of the template together with the nanoparticles in the pores.

View Article: PubMed Central - PubMed

ABSTRACT

Since the ancient Egyptians had used sand as filter media for water purification, its principle has been inherited through generations and it is still being used now in industries. The sand filter consists of sand literally, and the voids within the sand bed are the pores for filtration. Here we present a filtration principle using nanoparticles, so that the voids between the nanoparticles can be considered as effective pores in nanoscale dimension. Anodic aluminum oxide (AAO) membrane has been used as the working template, and the nanoparticles have been injected and embedded within the pores of the AAO template. Nanoparticles with multiple sizes have been used in order to obtain smaller voids. Moreover, the nanoparticles have been functionalized, or electrically charged, with arginine/phenylalanine (RF) peptide group. In this way, filtration performance for charged particles or molecules, such as methylene blue, has been enhanced. Consequently, this study is expected to provide a new principle for fabrication of nano voids, or nano pores, and for filtration in nanoscale dimension.

No MeSH data available.


Related in: MedlinePlus