{"id":20,"date":"2025-06-25T15:06:36","date_gmt":"2025-06-25T15:06:36","guid":{"rendered":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/chapter\/chapter-1\/"},"modified":"2026-03-16T14:19:55","modified_gmt":"2026-03-16T14:19:55","slug":"chapter-1","status":"publish","type":"chapter","link":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/chapter\/chapter-1\/","title":{"raw":"Chapter 1 - Introduction to Nanotechnology","rendered":"Chapter 1 &#8211; Introduction to Nanotechnology"},"content":{"raw":"The field of nanotechnology is rapidly maturing, with nanomaterials being integrated into a wide variety of applications in electronics, medicine and biotechnology, environmental engineering, and other areas. Nanotechnology development must pass through several stages, from research to commercialization and regulation. At each stage, it is of critical importance to address each of the following questions:\n<ul>\n \t<li><span style=\"font-size: 1em\">How do we define a \"nanomaterial\" when evaluating whether a sample or product contains nanomaterials?<\/span><\/li>\n \t<li>What are the most important properties or behaviors of nanomaterials, and how do we define these properties?<\/li>\n \t<li>Are there reliable analytical methods available to characterize these properties?<\/li>\n \t<li>Are there tools available to train students and workers to implement these methods?<\/li>\n<\/ul>\nThis first chapter of this course book provides a brief overview of key definitions for nanomaterials, examples of applications of nanotechnology, and key nanomaterial properties that enable the function of these products. Subsequent chapters will further build upon these concepts and the other questions listed above.\n<h2>1.1 What is \"nanotechnology\"?<\/h2>\nClear definitions of the terms \"nanotechnology\" and \"nanomaterials\" are necessary to specify samples or products that contain nanomaterials and implement guidelines related to nanomaterials. First, consider the International System of Units (SI) prefix, \"nano\":\n\nThe original version of this chapter contained H5P content. You may want to remove or replace this element.\n\nThe quiz above should affirm that \"nano\" indicates a multiplication factor of 10<sup>-9<\/sup>. However, full units are required for a meaningful definition. Here, the units of interest are nano<span style=\"text-decoration: underline\">meters<\/span> (nm), referring to the physical size or dimensions of an object. The classification \"nanomaterials\" then refers to a material with at least one dimension in the nanoscale range. This definition is still not sufficient to fully define a \"nanomaterial;\" a minimum and maximum number of nanometers is required to define the range. Most typically, these minimum and maximum limits are defined as <span style=\"text-decoration: underline\">1 nm<\/span> and <span style=\"text-decoration: underline\">100 nm<\/span>, respectively. Hence, a \"nanomaterial\" is any material with at least one dimension in the range of 1 nm and 100 nm, and \"nanotechnology\" refers to any product or technology that incorporates nanomaterials.\n\nNanomaterials can be further classified by the number of dimensions that fall within the 1 nm to 100 nm size range:\n<ul>\n \t<li>Nano<span style=\"text-decoration: underline\">particles<\/span> have all three dimensions in the 1 nm to 100 nm size range; for example, spherical nanoparticles have diameters of 1 nm to 100 nm.<\/li>\n \t<li>Nano<span style=\"text-decoration: underline\">rods<\/span>, nano<span style=\"text-decoration: underline\">wires<\/span>, or nano<span style=\"text-decoration: underline\">fibers<\/span> have two dimensions (e.g., the cross-sectional diameter of the rod, wire, or fiber) in the 1 nm to 100 nm size range, whereas the length of the object is larger than 100 nm.<\/li>\n \t<li>Nano<span style=\"text-decoration: underline\">sheets<\/span> have one dimension (e.g., the height or thickness) in the 1 nm to 100 nm range, whereas the legnth and width of the material are larger than 100 nm.<\/li>\n<\/ul>\n<div class=\"textbox shaded\">\n\n<strong>Notes on the lower and upper size bounds for nanomaterials:<\/strong>\n\nA frequent question is why there is a minimum size bound for defining a nanomaterial. Small molecules and ions, such as organic compounds and dissolved salts, have sizes in the range of Angstroms (\u00c5), where 1 \u00c5 = 10<sup>-10<\/sup> m or 0.1 nm. The lower size limit of 1 nm for a nanomaterial hence excludes these molecular or ionic species.\n\nIn the related field of colloid science, the term \"colloid\" denotes matter or a phase (e.g. solid particles, liquid droplets, or gas bubbles) in the size range of 1 to 1000 nm. Hence, nanomaterials represent a subset of colloidal materials. Materials with dimensions larger than the nano- or colloidal size range are referred to as \"bulk\" materials.\n\n<\/div>\n<h2>1.2 Nanotechnology applications<\/h2>\nNanotechnology has applications across a wide range of science and engineering fields. Three examples are highlighted below.\n<h3>1.2.1 Quantum dots for electronic applications<\/h3>\nQuantum dots are semiconductor nanoparticles in which electrons can be excited by light from a valence band to a conduction band. Upon transition back to the valence band, the material emits part of the absorbed excitation energy as light. Materials that can be used to synthesize quantum dots include metal chalcogenides (e.g., CdSe) or carbon for carbon dots. Quantum dots can also be synthesized using multiple materials in a \"core-shell\" structure.\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\"><strong>Interactive Question 1.1<\/strong><\/p>\n\n<\/header>\n<div class=\"textbox__content\">\n\nThe original version of this chapter contained H5P content. You may want to remove or replace this element.\n\n<\/div>\n<\/div>\n<div class=\"textbox shaded\">\n\n<strong>Why are nanoparticles used for this application?<\/strong>\n\nThe nanoscale size of quantum dots is critical to enable the phenomenon of \"quantum confinement,\" resulting in their special optical and electronic properties. The particle size is also important to tune the color (i.e. wavelength) of the light emission from the nanoparticles.\n\n<\/div>\n<h3>1.2.2 Nanoparticles for biomedical applications<\/h3>\nNanoparticles can be utilized for a variety of biomedical applications, from sensing devices for disease detection to vaccines and treatments. Two examples are shown below.\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\"><strong>Interactive Question 1.2<\/strong><\/p>\n\n<\/header>\n<div class=\"textbox__content\">\n\nThe original version of this chapter contained H5P content. You may want to remove or replace this element.\n\n<\/div>\n<\/div>\nThe test strip shown above consists of gold nanoparticles embedded in a test pad. The gold nanoparticles have a strong red color and are functionalized with antibodies that bind to SARS-CoV-2. The sample is applied to the sample test pad (S) and flows down the test strip across the test (T) and control (C) lines. The T line is functionalized with antibodies that bind to another region of the SARS-CoV-2. If SARS-CoV-2 is present in the sample, it will bind to a portion of the gold nanoparticles, then attach onto the T line. The C line is functionalized to bind the nanoparticles regardless of whether SARS-CoV-2 is present. Therefore, nanoparticles should always attach onto the C line in both negative and positive test cases. The image shows a negative test for COVID-19.\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\n<p class=\"textbox__title\"><strong>Interactive Question 1.3<\/strong><\/p>\n\n<\/header>\n<div class=\"textbox__content\">\n\nThe original version of this chapter contained H5P content. You may want to remove or replace this element.\n\n<\/div>\n<\/div>\nThe composition and surface functionalization of the mRNA-loaded lipid nanoparticles shown above can be tuned to optimize their efficacy for the vaccine application. In the image, the surface of the nanoparticle is functionalized with a polymer, polyethylene glycol (PEG), and the bilayer is formed using a phospholipid, distearoylphosphatidylcholine (DSPC).\n<div class=\"textbox shaded\">\n\n<strong>Why are nanoparticles used for these applications?<\/strong>\n\nIn the COVID-19 test strip application, the red color of the gold nanoparticles is a unique feature of their size, which enables the optical phenomenon of \"surface plasmon resonance.\" This phenonemon does not occur for either dissolved gold salts (which yield a transparent yellow solution) or bulk gold. In <strong>Activity 1<\/strong>, you will synthesize gold nanoparticles and observe this dramatic change in sample color as the nanoparticles form. The strong color of the gold nanoparticles enables the test results to be easily visible to users. The ability to functionalize the gold nanoparticles with antibodies and have them easily disperse into the liquid sample to flow down the test strip are also important features for the application.\n\nIn the COVID-19 vaccine, although the mRNA induces the immune response for COVID-19, the lipid nanoparticle carrier is required to protect the mRNA from degradation and to enhance its delivery to the target cells.\n\n<\/div>\n<h3>1.2.3 Nanoparticles for environmental applications<\/h3>\nNanoparticles can be used for environmental applications, including water treatment to remove contaminants. These nanoparticles can be applied both in engineered settings, such as a water treatment facility, or natural settings, as in <em>in situ<\/em> remediation of sites with contaminated groundwater.\n\n[caption id=\"attachment_19\" align=\"aligncenter\" width=\"1024\"]<img class=\"wp-image-18 size-large\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/15\/2025\/06\/Chapter01_TiO2PhotocatalyticReactor-1024x739.jpg\" alt=\"Photographs and diagram of a photocatalytic reactor with a composite material comprised of TiO2 affixed on SiO2.\" width=\"1024\" height=\"739\"> <strong>Figure 1.1. <\/strong>Photographs and diagram of a photocatalytic reactor with a composite material comprised of TiO<sub>2<\/sub> nanoparticles affixed to a SiO<sub>2<\/sub> substrate (reprinted under a CC-BY license from Cabezuelo et al., <em>Applied Materials Today<\/em> <strong>2023<\/strong>, 35, 101947, DOI: <a href=\"https:\/\/doi.org\/10.1016\/j.apmt.2023.101947\" target=\"_blank\" rel=\"noopener\">0.1016\/j.apmt.2023.101947<\/a>)[\/caption]\n\n<strong>Figure 1.1<\/strong> depicts a photoreactor that utilizes metal oxide semiconductor nanoparticles, such as titanium dioxide (TiO<sub>2<\/sub>) nanoparticles, for degradation of organic contaminants in water. These photocatalytic nanoparticles are activated by ultraviolet light to excite an electron from a valence to a conduction band, resulting in separation of the electron from a proton (\"hole\"). Both the electron and the hole can react with oxygen or water to form reactive oxygen species that then react with the contaminants to induce degradation. The electron or hole can also react directly with contaminants adsorbed at the nanoparticle surface. Affixing the nanoparticles onto a fixed substrate or larger particles enables easy removal from the treated water.\n\n[caption id=\"attachment_19\" align=\"aligncenter\" width=\"500\"]<img class=\"wp-image-19 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/15\/2026\/03\/Chapter01_EZVI-Diagram.gif\" alt=\"Transmission electron microscope image of zerovalent iron nanoparticles emusified in micron-sized oil droplets.\" width=\"500\" height=\"662\"> <strong>Figure 1.2.<\/strong> Transmission electron microscope image of nanoscale zerovalent iron particles emusified in micron-sized oil droplets, and schematic of the emulsion (reprinted with permisson from Quinn, J. et al., <em>Environ. Sci. Technol.<\/em> <strong>2005<\/strong>, 39, 5, 1309\u20131318, DOI: <a href=\"https:\/\/doi.org\/10.1021\/es0490018\" target=\"_blank\" rel=\"noopener\">10.1021\/es0490018<\/a>).[\/caption]\n\n<strong>Figure 1.2 <\/strong>depicts the\u00a0<em>in situ<\/em> remediation of toxic chlorinated solvents in groundwater usinig emulsified zerovalent iron (Fe<sup>0<\/sup>) nanoparticles. The nanoparticles act as strong reducing agents to degrade the contaminants by reductive dehalogenation. Delivery of the nanoparticles within micron-scale oil drops as a colloidal emulsion allows the nanoparticles to mix thoroughly into the chlorinated solvent, which separates from groundwater as a non-aqueous phase liquid (NAPL). Another approach for enhanced delivery is to functionalize the nanoparticles with a polymeric surface coating, which drives the nanoparticles to the NAPL-water interface, along with enhancing transport through the soil media to the contaminated zone.\n<div class=\"textbox shaded\">\n\n<strong>Why are nanoparticles used for these applications?<\/strong>\n\nIn the photoreactor application, the reactivity of the TiO<sub>2<\/sub> material is a nanoparticle-specific phenomenon. Other beneficial features include the ease of separating the particles from the treated water (as opposed to using dissolved chemical reagents), and the catalytic nature of the particles (i.e., they are not consumed in the reaction process).\n\nIn the groundwater remediation application, only the <strong>surface<\/strong> atoms of the reactive iron particles are in contact with the chorinated solvent, whereas the atoms comprising the <b>volume or mass <\/b>of iron within the interior are not exposed and hence unavailable for reaction. Nanoparticles have a much higher surface area per mass than larger particles or bulk materials. This property enables more efficient material use.\n\n<\/div>\n<h2>1.3 Key properties of nanomaterials<\/h2>\nConsidering the example applications above, there are several key properties or behaviors of nanomaterials that are important in enabling their effective use:\n<ul>\n \t<li>Size (e.g., diameter for spherical nanoparticles; length and diameter for nanorods; length, width, and thickness for nanosheets)<\/li>\n \t<li>Shape or morphology (e.g., nanosphere, nanorod, nanosheet)<\/li>\n \t<li>Structure (e.g., homogeneous vs. core-shell)<\/li>\n \t<li>Composition \u2014 including the core material forming the nanomaterial, surface composition (adsorbates), and species carried by or embedded within the nanomaterial<\/li>\n \t<li>Surface charge<\/li>\n<\/ul>\nThese properties can strongly impact the resulting behaviors of the nanomaterial:\n<ul>\n \t<li>Colloidal stability, i.e., the tendency of the nanomaterials to remain separated in suspension or to form agglomerates or aggregates<\/li>\n \t<li>Interactions with light, i.e., optical or electronic properties<\/li>\n \t<li>Chemical reactivity<\/li>\n<\/ul>\nGiven the importance of these properties and behaviors, it is critical to have characterization methods suitable to measure these properties, and the corequisite knowledge on how to best implement these methods and interpret the results.","rendered":"<p>The field of nanotechnology is rapidly maturing, with nanomaterials being integrated into a wide variety of applications in electronics, medicine and biotechnology, environmental engineering, and other areas. Nanotechnology development must pass through several stages, from research to commercialization and regulation. At each stage, it is of critical importance to address each of the following questions:<\/p>\n<ul>\n<li><span style=\"font-size: 1em\">How do we define a &#8220;nanomaterial&#8221; when evaluating whether a sample or product contains nanomaterials?<\/span><\/li>\n<li>What are the most important properties or behaviors of nanomaterials, and how do we define these properties?<\/li>\n<li>Are there reliable analytical methods available to characterize these properties?<\/li>\n<li>Are there tools available to train students and workers to implement these methods?<\/li>\n<\/ul>\n<p>This first chapter of this course book provides a brief overview of key definitions for nanomaterials, examples of applications of nanotechnology, and key nanomaterial properties that enable the function of these products. Subsequent chapters will further build upon these concepts and the other questions listed above.<\/p>\n<h2>1.1 What is &#8220;nanotechnology&#8221;?<\/h2>\n<p>Clear definitions of the terms &#8220;nanotechnology&#8221; and &#8220;nanomaterials&#8221; are necessary to specify samples or products that contain nanomaterials and implement guidelines related to nanomaterials. First, consider the International System of Units (SI) prefix, &#8220;nano&#8221;:<\/p>\n<p>The original version of this chapter contained H5P content. You may want to remove or replace this element.<\/p>\n<p>The quiz above should affirm that &#8220;nano&#8221; indicates a multiplication factor of 10<sup>-9<\/sup>. However, full units are required for a meaningful definition. Here, the units of interest are nano<span style=\"text-decoration: underline\">meters<\/span> (nm), referring to the physical size or dimensions of an object. The classification &#8220;nanomaterials&#8221; then refers to a material with at least one dimension in the nanoscale range. This definition is still not sufficient to fully define a &#8220;nanomaterial;&#8221; a minimum and maximum number of nanometers is required to define the range. Most typically, these minimum and maximum limits are defined as <span style=\"text-decoration: underline\">1 nm<\/span> and <span style=\"text-decoration: underline\">100 nm<\/span>, respectively. Hence, a &#8220;nanomaterial&#8221; is any material with at least one dimension in the range of 1 nm and 100 nm, and &#8220;nanotechnology&#8221; refers to any product or technology that incorporates nanomaterials.<\/p>\n<p>Nanomaterials can be further classified by the number of dimensions that fall within the 1 nm to 100 nm size range:<\/p>\n<ul>\n<li>Nano<span style=\"text-decoration: underline\">particles<\/span> have all three dimensions in the 1 nm to 100 nm size range; for example, spherical nanoparticles have diameters of 1 nm to 100 nm.<\/li>\n<li>Nano<span style=\"text-decoration: underline\">rods<\/span>, nano<span style=\"text-decoration: underline\">wires<\/span>, or nano<span style=\"text-decoration: underline\">fibers<\/span> have two dimensions (e.g., the cross-sectional diameter of the rod, wire, or fiber) in the 1 nm to 100 nm size range, whereas the length of the object is larger than 100 nm.<\/li>\n<li>Nano<span style=\"text-decoration: underline\">sheets<\/span> have one dimension (e.g., the height or thickness) in the 1 nm to 100 nm range, whereas the legnth and width of the material are larger than 100 nm.<\/li>\n<\/ul>\n<div class=\"textbox shaded\">\n<p><strong>Notes on the lower and upper size bounds for nanomaterials:<\/strong><\/p>\n<p>A frequent question is why there is a minimum size bound for defining a nanomaterial. Small molecules and ions, such as organic compounds and dissolved salts, have sizes in the range of Angstroms (\u00c5), where 1 \u00c5 = 10<sup>-10<\/sup> m or 0.1 nm. The lower size limit of 1 nm for a nanomaterial hence excludes these molecular or ionic species.<\/p>\n<p>In the related field of colloid science, the term &#8220;colloid&#8221; denotes matter or a phase (e.g. solid particles, liquid droplets, or gas bubbles) in the size range of 1 to 1000 nm. Hence, nanomaterials represent a subset of colloidal materials. Materials with dimensions larger than the nano- or colloidal size range are referred to as &#8220;bulk&#8221; materials.<\/p>\n<\/div>\n<h2>1.2 Nanotechnology applications<\/h2>\n<p>Nanotechnology has applications across a wide range of science and engineering fields. Three examples are highlighted below.<\/p>\n<h3>1.2.1 Quantum dots for electronic applications<\/h3>\n<p>Quantum dots are semiconductor nanoparticles in which electrons can be excited by light from a valence band to a conduction band. Upon transition back to the valence band, the material emits part of the absorbed excitation energy as light. Materials that can be used to synthesize quantum dots include metal chalcogenides (e.g., CdSe) or carbon for carbon dots. Quantum dots can also be synthesized using multiple materials in a &#8220;core-shell&#8221; structure.<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\"><strong>Interactive Question 1.1<\/strong><\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>The original version of this chapter contained H5P content. You may want to remove or replace this element.<\/p>\n<\/div>\n<\/div>\n<div class=\"textbox shaded\">\n<p><strong>Why are nanoparticles used for this application?<\/strong><\/p>\n<p>The nanoscale size of quantum dots is critical to enable the phenomenon of &#8220;quantum confinement,&#8221; resulting in their special optical and electronic properties. The particle size is also important to tune the color (i.e. wavelength) of the light emission from the nanoparticles.<\/p>\n<\/div>\n<h3>1.2.2 Nanoparticles for biomedical applications<\/h3>\n<p>Nanoparticles can be utilized for a variety of biomedical applications, from sensing devices for disease detection to vaccines and treatments. Two examples are shown below.<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\"><strong>Interactive Question 1.2<\/strong><\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>The original version of this chapter contained H5P content. You may want to remove or replace this element.<\/p>\n<\/div>\n<\/div>\n<p>The test strip shown above consists of gold nanoparticles embedded in a test pad. The gold nanoparticles have a strong red color and are functionalized with antibodies that bind to SARS-CoV-2. The sample is applied to the sample test pad (S) and flows down the test strip across the test (T) and control (C) lines. The T line is functionalized with antibodies that bind to another region of the SARS-CoV-2. If SARS-CoV-2 is present in the sample, it will bind to a portion of the gold nanoparticles, then attach onto the T line. The C line is functionalized to bind the nanoparticles regardless of whether SARS-CoV-2 is present. Therefore, nanoparticles should always attach onto the C line in both negative and positive test cases. The image shows a negative test for COVID-19.<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\"><strong>Interactive Question 1.3<\/strong><\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>The original version of this chapter contained H5P content. You may want to remove or replace this element.<\/p>\n<\/div>\n<\/div>\n<p>The composition and surface functionalization of the mRNA-loaded lipid nanoparticles shown above can be tuned to optimize their efficacy for the vaccine application. In the image, the surface of the nanoparticle is functionalized with a polymer, polyethylene glycol (PEG), and the bilayer is formed using a phospholipid, distearoylphosphatidylcholine (DSPC).<\/p>\n<div class=\"textbox shaded\">\n<p><strong>Why are nanoparticles used for these applications?<\/strong><\/p>\n<p>In the COVID-19 test strip application, the red color of the gold nanoparticles is a unique feature of their size, which enables the optical phenomenon of &#8220;surface plasmon resonance.&#8221; This phenonemon does not occur for either dissolved gold salts (which yield a transparent yellow solution) or bulk gold. In <strong>Activity 1<\/strong>, you will synthesize gold nanoparticles and observe this dramatic change in sample color as the nanoparticles form. The strong color of the gold nanoparticles enables the test results to be easily visible to users. The ability to functionalize the gold nanoparticles with antibodies and have them easily disperse into the liquid sample to flow down the test strip are also important features for the application.<\/p>\n<p>In the COVID-19 vaccine, although the mRNA induces the immune response for COVID-19, the lipid nanoparticle carrier is required to protect the mRNA from degradation and to enhance its delivery to the target cells.<\/p>\n<\/div>\n<h3>1.2.3 Nanoparticles for environmental applications<\/h3>\n<p>Nanoparticles can be used for environmental applications, including water treatment to remove contaminants. These nanoparticles can be applied both in engineered settings, such as a water treatment facility, or natural settings, as in <em>in situ<\/em> remediation of sites with contaminated groundwater.<\/p>\n<figure id=\"attachment_19\" aria-describedby=\"caption-attachment-19\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"wp-image-18 size-large\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/15\/2025\/06\/Chapter01_TiO2PhotocatalyticReactor-1024x739.jpg\" alt=\"Photographs and diagram of a photocatalytic reactor with a composite material comprised of TiO2 affixed on SiO2.\" width=\"1024\" height=\"739\" srcset=\"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-content\/uploads\/sites\/15\/2025\/06\/Chapter01_TiO2PhotocatalyticReactor-1024x739.jpg 1024w, https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-content\/uploads\/sites\/15\/2025\/06\/Chapter01_TiO2PhotocatalyticReactor-300x216.jpg 300w, https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-content\/uploads\/sites\/15\/2025\/06\/Chapter01_TiO2PhotocatalyticReactor-768x554.jpg 768w, https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-content\/uploads\/sites\/15\/2025\/06\/Chapter01_TiO2PhotocatalyticReactor-65x47.jpg 65w, https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-content\/uploads\/sites\/15\/2025\/06\/Chapter01_TiO2PhotocatalyticReactor-225x162.jpg 225w, https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-content\/uploads\/sites\/15\/2025\/06\/Chapter01_TiO2PhotocatalyticReactor-350x253.jpg 350w, https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-content\/uploads\/sites\/15\/2025\/06\/Chapter01_TiO2PhotocatalyticReactor.jpg 1228w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-19\" class=\"wp-caption-text\"><strong>Figure 1.1. <\/strong>Photographs and diagram of a photocatalytic reactor with a composite material comprised of TiO<sub>2<\/sub> nanoparticles affixed to a SiO<sub>2<\/sub> substrate (reprinted under a CC-BY license from Cabezuelo et al., <em>Applied Materials Today<\/em> <strong>2023<\/strong>, 35, 101947, DOI: <a href=\"https:\/\/doi.org\/10.1016\/j.apmt.2023.101947\" target=\"_blank\" rel=\"noopener\">0.1016\/j.apmt.2023.101947<\/a>)<\/figcaption><\/figure>\n<p><strong>Figure 1.1<\/strong> depicts a photoreactor that utilizes metal oxide semiconductor nanoparticles, such as titanium dioxide (TiO<sub>2<\/sub>) nanoparticles, for degradation of organic contaminants in water. These photocatalytic nanoparticles are activated by ultraviolet light to excite an electron from a valence to a conduction band, resulting in separation of the electron from a proton (&#8220;hole&#8221;). Both the electron and the hole can react with oxygen or water to form reactive oxygen species that then react with the contaminants to induce degradation. The electron or hole can also react directly with contaminants adsorbed at the nanoparticle surface. Affixing the nanoparticles onto a fixed substrate or larger particles enables easy removal from the treated water.<\/p>\n<figure id=\"attachment_19\" aria-describedby=\"caption-attachment-19\" style=\"width: 500px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"wp-image-19 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/15\/2026\/03\/Chapter01_EZVI-Diagram.gif\" alt=\"Transmission electron microscope image of zerovalent iron nanoparticles emusified in micron-sized oil droplets.\" width=\"500\" height=\"662\" \/><figcaption id=\"caption-attachment-19\" class=\"wp-caption-text\"><strong>Figure 1.2.<\/strong> Transmission electron microscope image of nanoscale zerovalent iron particles emusified in micron-sized oil droplets, and schematic of the emulsion (reprinted with permisson from Quinn, J. et al., <em>Environ. Sci. Technol.<\/em> <strong>2005<\/strong>, 39, 5, 1309\u20131318, DOI: <a href=\"https:\/\/doi.org\/10.1021\/es0490018\" target=\"_blank\" rel=\"noopener\">10.1021\/es0490018<\/a>).<\/figcaption><\/figure>\n<p><strong>Figure 1.2 <\/strong>depicts the\u00a0<em>in situ<\/em> remediation of toxic chlorinated solvents in groundwater usinig emulsified zerovalent iron (Fe<sup>0<\/sup>) nanoparticles. The nanoparticles act as strong reducing agents to degrade the contaminants by reductive dehalogenation. Delivery of the nanoparticles within micron-scale oil drops as a colloidal emulsion allows the nanoparticles to mix thoroughly into the chlorinated solvent, which separates from groundwater as a non-aqueous phase liquid (NAPL). Another approach for enhanced delivery is to functionalize the nanoparticles with a polymeric surface coating, which drives the nanoparticles to the NAPL-water interface, along with enhancing transport through the soil media to the contaminated zone.<\/p>\n<div class=\"textbox shaded\">\n<p><strong>Why are nanoparticles used for these applications?<\/strong><\/p>\n<p>In the photoreactor application, the reactivity of the TiO<sub>2<\/sub> material is a nanoparticle-specific phenomenon. Other beneficial features include the ease of separating the particles from the treated water (as opposed to using dissolved chemical reagents), and the catalytic nature of the particles (i.e., they are not consumed in the reaction process).<\/p>\n<p>In the groundwater remediation application, only the <strong>surface<\/strong> atoms of the reactive iron particles are in contact with the chorinated solvent, whereas the atoms comprising the <b>volume or mass <\/b>of iron within the interior are not exposed and hence unavailable for reaction. Nanoparticles have a much higher surface area per mass than larger particles or bulk materials. This property enables more efficient material use.<\/p>\n<\/div>\n<h2>1.3 Key properties of nanomaterials<\/h2>\n<p>Considering the example applications above, there are several key properties or behaviors of nanomaterials that are important in enabling their effective use:<\/p>\n<ul>\n<li>Size (e.g., diameter for spherical nanoparticles; length and diameter for nanorods; length, width, and thickness for nanosheets)<\/li>\n<li>Shape or morphology (e.g., nanosphere, nanorod, nanosheet)<\/li>\n<li>Structure (e.g., homogeneous vs. core-shell)<\/li>\n<li>Composition \u2014 including the core material forming the nanomaterial, surface composition (adsorbates), and species carried by or embedded within the nanomaterial<\/li>\n<li>Surface charge<\/li>\n<\/ul>\n<p>These properties can strongly impact the resulting behaviors of the nanomaterial:<\/p>\n<ul>\n<li>Colloidal stability, i.e., the tendency of the nanomaterials to remain separated in suspension or to form agglomerates or aggregates<\/li>\n<li>Interactions with light, i.e., optical or electronic properties<\/li>\n<li>Chemical reactivity<\/li>\n<\/ul>\n<p>Given the importance of these properties and behaviors, it is critical to have characterization methods suitable to measure these properties, and the corequisite knowledge on how to best implement these methods and interpret the results.<\/p>\n","protected":false},"author":1,"menu_order":1,"template":"","meta":{"pb_show_title":"","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[48],"contributor":[],"license":[],"class_list":["post-20","chapter","type-chapter","status-publish","hentry","chapter-type-standard"],"part":17,"_links":{"self":[{"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/pressbooks\/v2\/chapters\/20","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":1,"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/pressbooks\/v2\/chapters\/20\/revisions"}],"predecessor-version":[{"id":21,"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/pressbooks\/v2\/chapters\/20\/revisions\/21"}],"part":[{"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/pressbooks\/v2\/parts\/17"}],"metadata":[{"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/pressbooks\/v2\/chapters\/20\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/wp\/v2\/media?parent=20"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/pressbooks\/v2\/chapter-type?post=20"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/wp\/v2\/contributor?post=20"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/nanoengineering\/wp-json\/wp\/v2\/license?post=20"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}