1. Introduction

Recently, the peculiarities of metamaterials and nanoparticles are used in the construction of new devices for optoelectronics [1]. The research on photonic terahertz and microwave electromagnetic devices by using the nonlinear properties of metamaterials has been summarized. The periodicity of the building blocks of metamaterials which are smaller than the light wavelength was taken into consideration. The nanoparticle devices can be used for the localization of cavity fields, in particular surface plasmon resonance (SPR) [2]. Some of the phenomena originated by the uncommon wave dynamics in near-zero photonics and their fundamental and technological implications on different subfields of optics and metamaterials are presented in Ref. [3].

We analyzed the contact surfaces between the contaminated fluid and optical metamaterials, like photonic crystals or unordered granules, inserted inside the "core tube" of the decontamination reactor. In this case, the dispersive optical systems connected with the liquid volume through evanescent field improve the contact zones between UV radiation and pathogens. The dynamic treatment regime of translucent liquids that flow through decontamination core tube filled up with metamaterials is discussed. Moreover, the static treatment regime is analyzed, in which the fluids filling up the free spaces between metamaterial's elements keep motionless. When increasing the dimension of metamaterial elements, the decontamination rate decreases due to the increasing of

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One expects a large increase of the observed effects when passing from simple lamps to laser irradiation, that is, incoherent to coherent light sources. Also, significant improvement is expected when using optical fibers for evanescent wave generation instead of, or in parallel with, quartz microspheres. Our results prove that the energy emerging via evanescent waves from multistructures under dynamic irradiation is not in any case lost but used in this particular case for the efficient antimicrobial action. This can contribute to a positive balance of light propagation through optical metamaterials and fiber metamaterials in view of valorizing all

The approach presented in this chapter proposes a new method of decontamination using metamaterials consisting of microspheres and optical fibers structures with various topologies. The proposed method secures a substantial gain in the decontamination contact surfaces between the contaminated fluid and metamaterials, inserted inside the "core tube" of the decontamination reactor during the light (UV) propagation. The efficient decontamination using the evanescent zones of metamaterials opens new perspectives, not simply for new and innovative research applications, but besides opens novel ways for fundamental studies. The cumulative effect of UV radiation in contact with contaminated liquid depends on the refractive index of metamaterial and liquid, as well as optical properties of pathogens. A decontamination complementary effect depends on the probable trapping of liquid microparticles into the evanescent zone of optical fibers or microspheres in photon crystal structures [7, 8]. In this case, throughout the wave's propagation in nanofibers, a predilection for trapping and manipulating microparticles (viruses and bacteria) along the optical fibers occurs. The trapping of dielectric particles along the fibers was observed and revealed a new perspective on the capabilities of trapping the viruses, bacteria, and other microorganisms which can be present in contaminated liquids. Several techniques are proposed in order to destroy undesirable viral or bacterial particles [9]. These methods mainly used the UV lamp radiation for sterilization, but, quite often, they induced damaging effects and issues connected with the penetration depth. For instance, the 253 nm radiation effectively disinfects the surface, but sometimes, this emission could harm not just the viral particles and bacteria, but also mammalian cells [10–14]. When the intensity of UV irradiation is increased, the decontamination is always associated with mutation and shadowing effects, or damage of the viral nucleic acids and protein shells [11–14]. In other cases, radiation of microwave origin is proposed, but the absorption is not considered efficient because the energy

These drawbacks can be overcome by solving-related problems. The first one is associated with the UV radiation penetration depth. To solve this, it is required to propose an optical

distance between elements and the weaker penetration of the radiation into the liquid.

resources with maximum efficiency.

is mostly transferred to water and not to the viral particles [12].

One concern in pathogen decontamination is the need of a new effective method of radiation interaction with microorganisms [4–6]. An open surface of a translucent fluid exposed to radiation cannot provide the expected solution, due to the difficulty to irradiate pathogens inside the liquid volume as an immanent self-absorption. In this case, the total contact surface in quasiperiodical structures comes to be proportional to the surface of one element multiplied by the number of elements. Accordingly, the decontamination volume increases due to the large dispersion of light in these metamaterials, being proportional to the surface of one element multiplied to their number and UV-C light penetration depth through the translucent contaminated fluid.

The use of optical metamaterials with periodical structures to act against undesired microorganisms (viruses, bacteria, and yeast) existing in translucent liquids and gases is proposed. Studies were devoted to the topological effect of individual metamaterial elements on the modification of UV (ultraviolet) absorption of evanescent waves dispersed in the optical contact zones, as a function of granule size and geometry. The decontamination rate also depends on the packing and optical properties of metamaterial elements, as well as on the optical properties of contaminated liquids and microorganisms inside them. Different situations were investigated, when quartz (SiO2) or glass metamaterials with dimensions of about 0.5–3 mm are separately placed into a quartz core tube, of about 2.7 cm diameter and 90 cm length, of decontamination equipment. Quartz granules transmit UV light (240–400 nm) of the Hg lamp and ensure an efficient microbial decontamination of translucent liquids and gases. We herewith demonstrate the efficient antimicrobial action of the evanescent waves dispersed around quartz metamaterial elements inside contaminated translucent fluids.

The decontamination rate was studied in different configurations of metamaterials such as microspheres and unordered granules, with the aim to obtain an efficient contact zone of the contaminated liquids with UV radiation. This effect can be boosted by the manipulation of microorganisms along the optical fibers or around microspheres. A special trapping zone could be identified by exploration of high-density viruses and bacteria interaction with metamaterials in order to annihilate pathogens.

We herewith propose a model for structures with optical periodicity characterized by large free spaces among elements and fitting evanescent zone. This proves essential for decontamination of fluids that flow close to surface of microspheres or optical fibers. Here, one should asses the adherence of liquids to surface, evanescent field penetration depth inside contaminated fluid, and coefficient of absorption of light radiation by microorganisms.

We analyzed the contact surfaces between the contaminated fluid and optical metamaterials, like photonic crystals or unordered granules, inserted inside the "core tube" of the decontamination reactor. In this case, the dispersive optical systems connected with the liquid volume through evanescent field improve the contact zones between UV radiation and pathogens. The dynamic treatment regime of translucent liquids that flow through decontamination core tube filled up with metamaterials is discussed. Moreover, the static treatment regime is analyzed, in which the fluids filling up the free spaces between metamaterial's elements keep motionless. When increasing the dimension of metamaterial elements, the decontamination rate decreases due to the increasing of distance between elements and the weaker penetration of the radiation into the liquid.

1. Introduction

170 Advanced Surface Engineering Research

ments inside contaminated translucent fluids.

metamaterials in order to annihilate pathogens.

and coefficient of absorption of light radiation by microorganisms.

Recently, the peculiarities of metamaterials and nanoparticles are used in the construction of new devices for optoelectronics [1]. The research on photonic terahertz and microwave electromagnetic devices by using the nonlinear properties of metamaterials has been summarized. The periodicity of the building blocks of metamaterials which are smaller than the light wavelength was taken into consideration. The nanoparticle devices can be used for the localization of cavity fields, in particular surface plasmon resonance (SPR) [2]. Some of the phenomena originated by the uncommon wave dynamics in near-zero photonics and their fundamental and technological

implications on different subfields of optics and metamaterials are presented in Ref. [3].

One concern in pathogen decontamination is the need of a new effective method of radiation interaction with microorganisms [4–6]. An open surface of a translucent fluid exposed to radiation cannot provide the expected solution, due to the difficulty to irradiate pathogens inside the liquid volume as an immanent self-absorption. In this case, the total contact surface in quasiperiodical structures comes to be proportional to the surface of one element multiplied by the number of elements. Accordingly, the decontamination volume increases due to the large dispersion of light in these metamaterials, being proportional to the surface of one element multiplied to their number and UV-C light penetration depth through the translucent contaminated fluid. The use of optical metamaterials with periodical structures to act against undesired microorganisms (viruses, bacteria, and yeast) existing in translucent liquids and gases is proposed. Studies were devoted to the topological effect of individual metamaterial elements on the modification of UV (ultraviolet) absorption of evanescent waves dispersed in the optical contact zones, as a function of granule size and geometry. The decontamination rate also depends on the packing and optical properties of metamaterial elements, as well as on the optical properties of contaminated liquids and microorganisms inside them. Different situations were investigated, when quartz (SiO2) or glass metamaterials with dimensions of about 0.5–3 mm are separately placed into a quartz core tube, of about 2.7 cm diameter and 90 cm length, of decontamination equipment. Quartz granules transmit UV light (240–400 nm) of the Hg lamp and ensure an efficient microbial decontamination of translucent liquids and gases. We herewith demonstrate the efficient antimicrobial action of the evanescent waves dispersed around quartz metamaterial ele-

The decontamination rate was studied in different configurations of metamaterials such as microspheres and unordered granules, with the aim to obtain an efficient contact zone of the contaminated liquids with UV radiation. This effect can be boosted by the manipulation of microorganisms along the optical fibers or around microspheres. A special trapping zone could be identified by exploration of high-density viruses and bacteria interaction with

We herewith propose a model for structures with optical periodicity characterized by large free spaces among elements and fitting evanescent zone. This proves essential for decontamination of fluids that flow close to surface of microspheres or optical fibers. Here, one should asses the adherence of liquids to surface, evanescent field penetration depth inside contaminated fluid, One expects a large increase of the observed effects when passing from simple lamps to laser irradiation, that is, incoherent to coherent light sources. Also, significant improvement is expected when using optical fibers for evanescent wave generation instead of, or in parallel with, quartz microspheres. Our results prove that the energy emerging via evanescent waves from multistructures under dynamic irradiation is not in any case lost but used in this particular case for the efficient antimicrobial action. This can contribute to a positive balance of light propagation through optical metamaterials and fiber metamaterials in view of valorizing all resources with maximum efficiency.

The approach presented in this chapter proposes a new method of decontamination using metamaterials consisting of microspheres and optical fibers structures with various topologies. The proposed method secures a substantial gain in the decontamination contact surfaces between the contaminated fluid and metamaterials, inserted inside the "core tube" of the decontamination reactor during the light (UV) propagation. The efficient decontamination using the evanescent zones of metamaterials opens new perspectives, not simply for new and innovative research applications, but besides opens novel ways for fundamental studies. The cumulative effect of UV radiation in contact with contaminated liquid depends on the refractive index of metamaterial and liquid, as well as optical properties of pathogens. A decontamination complementary effect depends on the probable trapping of liquid microparticles into the evanescent zone of optical fibers or microspheres in photon crystal structures [7, 8]. In this case, throughout the wave's propagation in nanofibers, a predilection for trapping and manipulating microparticles (viruses and bacteria) along the optical fibers occurs. The trapping of dielectric particles along the fibers was observed and revealed a new perspective on the capabilities of trapping the viruses, bacteria, and other microorganisms which can be present in contaminated liquids. Several techniques are proposed in order to destroy undesirable viral or bacterial particles [9]. These methods mainly used the UV lamp radiation for sterilization, but, quite often, they induced damaging effects and issues connected with the penetration depth. For instance, the 253 nm radiation effectively disinfects the surface, but sometimes, this emission could harm not just the viral particles and bacteria, but also mammalian cells [10–14]. When the intensity of UV irradiation is increased, the decontamination is always associated with mutation and shadowing effects, or damage of the viral nucleic acids and protein shells [11–14]. In other cases, radiation of microwave origin is proposed, but the absorption is not considered efficient because the energy is mostly transferred to water and not to the viral particles [12].

These drawbacks can be overcome by solving-related problems. The first one is associated with the UV radiation penetration depth. To solve this, it is required to propose an optical system, which allows reaching large penetration of the radiation inside contaminated liquids (or gases). Second, it is needed to use the method of selective short pulse decontamination [9, 12, 13] for the estimation of the potential penetration depth in translucent liquids. For example, in Refs. [12, 13], the authors proposed a photonic approach for selective neutralization of viruses. In Ref. [12], a near-infrared (IR) ultrashort pulsed (USP) subpicoseconds fiber laser source is used instead of UV lamps to avoid IR absorption. This UPS targets only the weak links on the protein shells of viral particles. By selecting the appropriate laser parameters, the authors reveal that it is possible to damage the protein shells, conducting to their inactivation, but without affecting mammalian cells. More exactly, they demonstrated that this method can discriminate and inactivate viral particles, from nonpathogenic viruses such as M13 bacteriophage and tobacco mosaic virus (TMV) to pathogenic ones like human papillomavirus (HPV) and human immunodeficiency virus (HIV). Concomitantly, the sensitive materials, for example, human Jurkat T cells, human red blood cells, and mouse dendritic cells, keep unaffected. In Ref. [13], a mechanical model is proposed. It has a normal mode where it oscillates around its equilibrium geometry. By selecting the visible or near-IR laser pulse duration to be shorter or near to the normal oscillation period, the authors of Ref. [12] have demonstrated that a single beam excitation laser pulse can bring a macroparticle, as for example, a virus, into oscillation by impulsive stimulated Raman [14]. It is worthy to mention that similar coherent Raman effect for larger frequencies of UV pulses is used for diagnostics of the various biomolecules (e.g., lipids) with optical equipment [15, 16].

seven pyrimidine dimers per viral genome in SV40, which is sufficient to strongly inhibit viral DNA synthesis [24]. Thymine dimers formed within short pulse of UV excitation are properly oriented [19]. Only a few percent of the thymine doublets are expected to be favorably sited for

Figure 1. (A) Dimer bond generation under UV-C radiation of DNA according to Ref. [22] and (B) two-dimension potential with two minimums. First minimum corresponds to nondimer DNA and second minimum is similar to the

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a. Figure 2(A) explains the dimerization process for a thymine doublet having the appropriate orientation. The two most common conformations of DNA are A-DNA and B-DNA. Molecular orientations can fluctuate due to A and B conformations and vibrational or other movements of the DNA molecule. The average twist angle between consecutive base pairs varies with a few degrees only between the A and B conformations. The minor amount of conformational variation in A-DNA versus B-DNA explicates the superior

b. UV could induce cross-links between nonadjacent thymine besides cross-links between adjacent thymine, as illustrated in Figure 2(B). Cross-linking than can be produced between the nucleotides and proteins in the viruses' capsid could damage the capsid of

c. Cross-linking with cytosine and guanine requires higher energy because of three hydrogen bonds instead of two for thymine/adenine bonds. Accordingly, the thymine dimers are predominant. Thymine may also induce links with proteins, including the ones in the capsid (as is the case for viruses), as illustrated in Figure 2(C). Other biological molecules with unsaturated bonds such as coenzymes, hormones, and electron carriers are prone to UV damage. In RNA (prokaryotic cells, eukaryotic cells, or viruses), uracil replaces thymine. The inactivation of RNA viruses is accompanied by cross-linking between the uracil nucleotides and the generation of uracil dimers [25]. These dimers could damage the capsid of RNA viruses, too. There exist limited quantitative data about the specific damage of DNA produced by UV absorption. Ref. [25] demonstrated that the UV exposure of mengovirus induces a fast formation of uracil dimers. This seemed to be the main source of virus inactivation. During 10 min of UV irradiation, a maximum of 9% of the total uracil dimers of the viral DNA are formed. Studies also demonstrated that irradiated viral RNA

reaction and dimerization at the moment of UV excitation.

dimer phototransformation of DNA under the UV-C radiation.

resistance of A-DNA to cyclobutene pyrimidine dimer.

DNA viruses.
