Characterization and Application of Nanomaterials (2022) Volume 5 Issue 1 doi:10.24294/can.v5i1.1680 59 Review Article Nanotechnology, architecture and art Adriana Lira Oliver1*, Alicia Oliver2 1 Facultad de Arquitectura, Universidad Nacional Autónoma de México, Mexico. E-mail: adrianali- ra@post.harvard.edu 2 Instituto de Física, Universidad Nacional Autónoma de México, Mexico ABSTRACT In the past three decades, nanotechnology has attracted extensive attention. People have many expectations on the utilization of nanotechnology in medicine, but unfortunately, these expectations are unlikely to be realized. In the field of nanotechnology, the niche for building commercial products has not been developed yet. However, metal nanoparti- cles have attracted people’s attention since ancient times because of their optical properties, which are very different from those of bulk metals. By understanding the origin of these optical properties and using current technology, these nanoparticles can be manipulated to build a palette. Using micro measurement equipment, the palette can be printed with very good resolution. Keywords: Metal Nanoparticles; Plasma; Photoprinting ARTICLE INFO Received: 7 January 2022 Accepted: 26 February 2022 Available online: 9 March 2022 COPYRIGHT Copyright © 2022 Adriana Lira Oliver, et al. EnPress Publisher LLC. This work is li- censed under the Creative Commons At- tribution-NonCommercial 4.0 International License (CC BY-NC 4.0). https://creativecommons.org/licenses/by-nc/ 4.0/ 1. Introduction In the past decade, the word “nanotechnology” has appeared on countless occasions, referring to great inventions that will change our lives. Unfortunately, we live in a world that is distorted by mass media transmission. We believe that the trivialization of the term nanotech- nology is due to two basic factors: (1) after an important discovery, scientists’ emotions confuse them and sometimes have high expecta- tions for future applications; and (2) the media exaggerate the news coverage of this discovery. Therefore, the new discoveries realized by science through dissemination to others distort the meaning of social life and produce high expectations that are often difficult to achieve. At the end of the Second World War, the great potential of nuclear energy emerged. It is generally believed that nuclear energy will solve human problems in this regard, but it didn’t happen. In the 1980s, when the high-temperature superconductor was discovered, the superconductivity of this material was higher than the temperature of liquid helium, higher than -269 °C. It was also said that the energy problem would be solved to a great extent: in our daily life, the current of a conductor is expected to be maintained indefinitely, but this did not happen. However, it is undeniable that apart from its negative uses, nuclear energy is beneficial to people’s lives in many ways. On the other hand, at more accessible temperatures, such as -196 °C, superconductivity has opened up a new research field. The same is true for nanotechnology. There is no doubt that nanotechnology is bringing great benefits to the fields of biomedi- cine, energy, environment, and photonics (aimed at replacing electron- ics). 60 Metal nanoparticles, due to their surface plas- mon resonance characteristics, produce a very strong near nanoscale electric field at nano distance, making them high-sensitivity and high-resolution sensors in two-state systems and photonics[1,2]. In order to understand what we are going to write about architecture and art, we must first un- derstand what nanotechnology is. 2. Nanotechnology Nanotechnology originates from the under- standing of nanostructures in nanoscience. From the perspective of size, the nanostructure is a collection of atoms or molecules, and its size is on the non-metrological scale (1 nm = 10−9 meters, 1000 times that of 1 micron). A cell with a size between 5 and 50 microns is tens of thousands of times larger than what we mean by nanostructures. However, nanostructures have always existed and been pro- duced. But these structures were not understood until a few years ago. For nanoscience, the nanostructures that make up nanotechnology are those basic elements, whether atoms or basic crystal cells. In nanoscale aggregates, they show character- istics different from the mass properties we are used to in our daily life. Not all nanostructures show characteristics different from large volume struc- tures, so these characteristics are not considered in nanotechnology. At present, however, nano-sized materials, whether or not they have properties dif- ferent from those in large volume, are considered a part of nanotechnology products. In the field of ar- chitecture, there are few truly commercialized and large-scale nanotechnology products. This paper describes the real nanotechnology materials used in architecture and the materials currently being de- veloped for printing. 3. Metal nanoparticles and plasma Plasma is a new branch of science. The term was coined by a group of scientists at the California Institute of Technology in 2000[3]. Plasma refers to the surface plasma that produces light when being hit by metal particles. We know that light is an electromagnetic wave composed of oscillating elec- tric and magnetic fields. When the electric field of the wave acts on the metal nanoparticles, the free electrons of the super surface metal oscillate with the electric field of the wave. Through some physi- cal mechanisms, the nanoparticles absorb a large amount of light. At some wavelengths, this absorp- tion occurs in a privileged form, which is called surface plasmon resonance. This phenomenon only occurs when the size of metal particles is much smaller than the wavelength of the incident light, from some nanometers to 100 nm, so it will not oc- cur in a large volume of materials[4]. This particu- larity bestows these nanoparticles’ interesting opti- cal properties in nonlinear optics[5], photonics[6], and biomedicine[1,7]. Interestingly, this phenomenon leads to the absorption of metal nanoparticles in the ultraviolet and visible regions. In special cases, nanoparticles over 100 nm absorb in the infrared range of the electromagnetic spectrum[8]. 4. Light and color Light is an electromagnetic wave, which is part of the electromagnetic spectrum. The electromag- netic spectrum is very broad, including wavelengths ranging from picometers to kilometers. In this large range, light occupies the so-called visible region, which is a very small region of the electromagnetic spectrum. White visible light disperses through a prism and is separated into its component colors. This is because visible light consists of wave- lengths between 380 and 780 nm, which are per- ceived by the eyes and detected as color in our brain. We know that the color of objects is caused by the different lengths they absorb and the different lengths reflected by other objects and detected by the eyes. Therefore, metal nanoparticles up to 100 nm absorb the visible light band and show a color that metals do not have in a large volume. 5. The wonderful world of color in metal nanoparticles In the previous section, we have said that met- al nanoparticles selectively absorb visible light at some visible wavelengths. Specifically, this absorp- tion is carried out in some nanoscale to 100 na- noscale structures. In addition, nanoparticles can 61 have different shapes. According to the size and shape of nanoparticles, surface plasmon resonance, when the light is absorbed to the greatest extent, can move and expand in the spectrum, so as to change the color. We know that if it absorbs blue light, the color will turn yellow. This is why the surface plasmon resonance wavelength of silver nanoparti- cles embedded in glass with a spherical diameter of about 10 nm is 380 nm and the width extends to blue. This is why these nanoparticles appear yel- low. If the size and shape of these particles change, surface plasmon resonance can occur at higher or lower wavelengths, or can be expanded according to the situation to produce different colors. If the green color is absorbed, the color will be red. An- other example is gold nanoparticles. If these nano- particles are spherical, they are between 4 nm and 20 nm, and their surface plasmon resonance is 520 nm. Therefore, they have strong absorption of green, making them look red. If their size increases to about 90 nm, they will appear blue. Nanoparticles can have a range of bright colors depending on their shape and size. Figure 1 shows a series of solutions containing metal nanoparticles of different elements of different shapes and sizes. When these nanopar- ticles are embedded in glass, they will show differ- ent colors according to the nanoparticles involved. Figure 1. Metal nanoparticles in solution. Source: José I. García Laureiro, isqch. Blog promotion of In- stitute of Chemical Synthesis and homogeneous catalysis Higher Scientific Research Council (CSIC) of the University of Zara- goza, Spain. 6. Design of nanodevices The synthesis of metal nanoparticles can be carried out by chemical or physical methods. It is relatively simple to synthesize in an aqueous solu- tion by chemical method. The color is really bright. As early as 1875, Michael Faraday already had the solutions. He first described these colors scientifi- cally, referring to very small particles with optical properties different from large volume metals. One physical method is ion implantation. Through the particle accelerator, the required metal atoms are introduced into the dielectric one-to-one[9]. The ob- tained material is then treated at a high temperature and special atmosphere. Figure 2 shows two dif- ferent amounts of high-purity silica-implanted gold. These materials were obtained at the Pelletron Ac- celerator Laboratory of the UNAMA Institute of Physics. Although the properties of metal nanoparticles had already be explained in the 19th century, the discipline of nanoscience and nanotechnology has only emerged recently after completely repeatable synthesis and analysis methods have been devel- oped. This is the result of scientific and technologi- cal progress. The synthetic methods of these sys- tems, both physical and chemical, have made great progress. Nowadays, people are designing the parti- cles to be manufactured. If coupled with the ex- traordinary scientific instruments in the 20th century, a series of analytical methods would be able to produce microscale materials; this progress would usher in the nanoscale ear at a faster pace. For ex- ample, the emergence of nanoparticles expedites the development of ultra-high-resolution transmission electron microscopy. This technology enables us to view the location of nanoparticles and their atoms (Figure 3). On the other hand, really complex cal- culations have been carried out on desktop comput- ers, so that they can simulate and predict what shapes correspond to surface plasmon resonance so as to determine its specific optical characteristics. This makes it possible to produce dispersible mate- rials with very special properties. Figure 2. High-purity silica with spherical gold nanoparticles with an average diameter of 10 nm. (a) Low gold ion inflow. (b) High gold ion inflow. Source: authors’ images. 62 Figure 3. High-resolution transmission electron microscopy micrograph of gold nanoparticles in ion-implanted silicon. Source: authors’ image. Therefore, at present, science and technology al- low the use of nanostructures to design, operate and, in some cases, build devices for different applica- tions[10]. 7. There is nothing new in the sun Colored glass and colored glass beads have always attracted people. Humans have learned to make colored glass since ancient times. The main glass products are colored bead necklaces. As early as 1200 BC, Egypt had a blue or green transparent glass. Of course, it was also in Egypt people found out that adding metal oxides to molten glass would produce beautiful colors. However, the people who did glassblowing are Phoenicians. During the Ro- man Empire, the manufacture of glass products spread throughout the empire and Germany. Figure 4. Likugo Rome Cup at British Museum. (a) Illumina- tion on the observer’s side. (b) Rear illumination relative to the observer. Source: Figures (a) and (b) were photographed by John Bode and Mary Ranran, respectively. In ancient times, craftsmen were already uti- lizing nanotechnology in producing glass products with colors. An indisputable example is the beauti- ful Likugo cup in Rome. The cup was made in the 4th century AD, and its owner had been troubled by the influence of light on the cup for a long time. When illuminated from the observer’s side, it shows green emerald (Figure 4(a)), and the glass looks opaque, but when illuminated from the back relative to the observer, it shows translucent and bright red (Figure 4(b)). The secret was discovered in 1990. Small fragments of the glass were analyzed by electron microscope. The results showed that the glass contained a very accurate mixture of gold and silver particles below 50 nm. Through the invention of this cup, we can deduce that knowledge of con- temporary nanotechnology was practiced and uti- lized in manufacturing products in ancient times. Perhaps, the most famous building of nano- technology is the glass window of the Gothic ca- thedral. Gothic architecture originated in northern France in Normandy in the 12th century. It first spread to the kingdom of France, and then to the Holy Roman Empire. This new architectural style engendered a new form of buildings that were in- fused with different proportions of Romanesque and Gothic architecture styles: thinner and higher vaults. In order to withstand the thrust of the vault, the ar- chitects designed buttresses with stumps. The exte- rior wall has a huge gap, and the interior wall pro- duces greater brightness. This gave rise to what is known today, the medieval glass art that embodies its colorful interior. The Holy Church in central Paris is a good example. The walls of this building, which was built in the early 13th century, were re- placed by huge windows covered with glass (Fig- ure 5). Figure 5. Holy Church of Paris. Source: Photograph by B. Didier. 63 The bright indoor environment brings a very special effect to the atmosphere. Unlike the effect produced by a normal window, the window used in the building can let all the white light in the solar radiation pass through. These craftsmen, the origi- nal nanotechnology experts, know very well what to put in the molten glass and their proportions to ob- tain the whole color range of the glass. Even today, we still appreciate the richness of these works of art (Figure 6). Figure 6. The glass windows of Cologne Cathedral. Source: Photograph by Jan van der Crabben. Figure 7. Schematic diagram of the plasma pixel configuration of aluminum nano disk: (a) different arrangement of nanodisk in size and spacing; (b) palette of the basic layout of nanodisk; (c) a hybrid palette that provides different sizes of nanodiscs with a spacing of one pixel; and (d) a palette that combines the size and spacing of nanodiscs into one pixel. Source: Adapted with the permission of Tan et al.[11]. 8. Modern nanotechnology and color palette The color image reproduction system uses fil- ters and prisms to disperse light of different wave- lengths. With the miniaturization of integrated de- vices, the research on the image sensor is growing exponentially. The pursuit of high efficiency, low power consumption, and small size poses a great challenge to the traditional system. 64 In the previous section, it was explained that the surface plasmon resonance of metal nanoparti- cles absorbs light and makes these nanoparticles reflect the light of a certain color. In 2014, scientists from several institutions in Singapore built devices containing specific arrangements of aluminum nanodisks of different sizes with different spatial arrangements[11]. In this way, they built plasma pix- els to form a palette. Each pixel contains four nano- disks of different sizes to create a basic palette. By changing the distance between them and the size of the nanodisk, different colors and tones can be cre- ated and converted into the colors and tones of the palette. These nanostructures were obtained by forming nanocolumns on silicon substrate by elec- tron beam lithography. Aluminium with a thickness of 20 nm was deposited on silicon substrate by electron beam lithography. The size of each pixel is 800 × 800 nm. As shown in Figure 7(a), the basic tray is composed of aluminum nanodisks with the same spacing but different sizes. Other colors and tones can be generated using the same size and different spacing. Finally, the palette is enhanced by a com- bination of size, space, and layout geometry. Fig- ure 7(b) shows the arrangement of the basic tray, in which only the size changes, the disc diameter is 40 to 330 nm, the step diameter is 10 nm, and the fixed spacing is 400 nm. Figure 7(c) shows how the change in size is intertwined with the change in Di, where D in each pixel (two nanodisks of one size and two nanodisks of another size) = 80 to 220 nm, with each step of 10 nm. The fixed spacing on the same pixel is 400 nm, 800 × 800 nm, which enrich- es the palette. In Figure 7(d), the color palette is formed by changing the size (d = 80 to 220 nm) and spacing (s = D + 50 to 400 nm) in steps of 10 and 20 nm, respectively, in the arrangement of four nanodiscs in 800 × 800 nm pixels. Figure 8. Using different strategies of plasma palette to reproduce Monet’s sunrise painting: (a) reproduce the original as the input image; (b) copy using only the “primary plasma colors” palette; (c) use the extended palette to reproduce the painting more realistically; (d) enlarge the details in panel (c); and (e) scanning electron microscope micrograph that shows the pixels in different arrays of alu- minum nanodisks. Source: Adapted with permission of Tan et al.[11]. 65 These combinations of aluminum nanodisks in pixels produce plasma in the visible palette. In order to show the versatility of their plasma palette contained in the microstructure, these scien- tists created photo prints of Monet’s famous paint- ing dawn. A copy of the original is shown in Figure 8(a). In Figure 8(b), printing is performed using a limited (basic) plasma palette. In Figure 8(c), photo printing with a wider color range can be obtained using an extended palette (a combination of pixel and nanodisk size and spacing). The degree of re- peatability is impressive for a micron device, as obtained in the described work. Figure 8(d) shows the details, and Figure 8(e) shows a scanning elec- tron microscope micrograph of pixels with different arrangements of nanodisks. Compared with their gold or silver counter- parts, aluminum nanoparticles are very durable and much cheaper. Therefore, microdevices with these characteristics have a huge market prospect. 9. Conclusion The optical properties of metal nanoparticles are very different from those of large-volume metal nanoparticles. It was first used to decorate objects and is now used as high-resolution photonic micro- devices. From the perspective of architecture and art, the charm of color and the effect of light have always influenced mankind. Conflict of interest The authors declared no conflict of interest. References 1. Heydari E, Mabbot S, Thompson D. Engineering molecularly-active nano-plasmonic surfaces for DNA detection via colorimetry and Raman scatter- ing. Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications XIII. Book series: Pro- ceedings of SPIE 2016; 9721: 972105. 2. Kim HS, Lee BH, Oh GY. Significantly enhanced sensitivity of surface plasmon resonance sensor with self-assembled metallic nanoparticles. Journal of Nanophotonics 2016; 10: 026012. 3. Atwater HA. The promise of plasmonics. Scientific American 2007; 296: 56–63. 4. 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