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1449 KiB

Open AccessArticle

by Luciano De Sio, Giulio Caracciolo, Ferdinanda Annesi, Tiziana Placido, Daniela Pozzi, Roberto Comparelli, Alfredo Pane, Maria Lucia Curri, Angela Agostiano and Roberto Bartolino

Nanomaterials 2015, 5(2), 1022-1033; https://doi.org/10.3390/nano5021022 - 09 Jun 2015

Cited by 1 | Viewed by 5467

Abstract

Plasmonic metallic nanoparticles (NPs) represent a relevant class of nanomaterials, which is able to achieve light localization down to nanoscale by exploiting a phenomenon called Localized Plasmon Resonance. In the last few years, NPs have been proposed to trigger DNA release or enhance [...] Read more.

Plasmonic metallic nanoparticles (NPs) represent a relevant class of nanomaterials, which is able to achieve light localization down to nanoscale by exploiting a phenomenon called Localized Plasmon Resonance. In the last few years, NPs have been proposed to trigger DNA release or enhance ablation of diseased tissues, while minimizing damage to healthy tissues. In view of the therapeutic relevance of such plasmonic NPs; a detailed characterization of the electrostatic interaction between positively charged gold nanorods (GNRs) and a negatively charged whole-genome DNA solution is reported. The preparation of the hybrid biosystem has been investigated as a function of DNA concentration by means of ζ-potential; hydrodynamic diameter and gel electrophoresis analysis. The results have pointed out the specific conditions to achieve the most promising GNRs/DNA complex and its photo-thermal properties have been investigated. The overall study allows to envisage the possibility to ingeniously combine plasmonic and biological materials and, thus, enable design and development of an original non invasive all-optical methodology for monitoring photo-induced temperature variation with high sensitivity. Full article

(This article belongs to the Special Issue Nanophotonic Materials)

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1084 KiB

Open AccessArticle

Emission Properties of Fluorescent Nanoparticles Determined by Their Optical Environment

by Kelvin Chung and Snjezana Tomljenovic-Hanic

Nanomaterials 2015, 5(2), 895-905; https://doi.org/10.3390/nano5020895 - 29 May 2015

Cited by 11 | Viewed by 4785

Abstract

The emission rate of a radiating dipole within a nanoparticle is crucially dependent on its surrounding refractive index environment. In this manuscript, we present numerical results on how the emission rates are affected for nanoparticles in a homogenous and substrate environment. These results [...] Read more.

The emission rate of a radiating dipole within a nanoparticle is crucially dependent on its surrounding refractive index environment. In this manuscript, we present numerical results on how the emission rates are affected for nanoparticles in a homogenous and substrate environment. These results are general, applicable to any refractive index distribution and emitter. Full article

(This article belongs to the Special Issue Nanophotonic Materials)

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1009 KiB

Open AccessArticle

Electronic Structure and Magnetism of Mn-Doped ZnO Nanowires

by Fuchun Zhang, Dandan Chao, Hongwei Cui, Weihu Zhang and Weibin Zhang

Nanomaterials 2015, 5(2), 885-894; https://doi.org/10.3390/nano5020885 - 27 May 2015

Cited by 18 | Viewed by 6101

Abstract

The geometric structures, electronic and magnetic properties of Mn-doped ZnO nanowires were investigated using density functional theory. The results indicated that all the calculated energy differences were negative, and the energy of the ground state was 0.229 eV lower than ferromagnetic coupling, which [...] Read more.

The geometric structures, electronic and magnetic properties of Mn-doped ZnO nanowires were investigated using density functional theory. The results indicated that all the calculated energy differences were negative, and the energy of the ground state was 0.229 eV lower than ferromagnetic coupling, which show higher stability in antiferromagnetic coupling. The calculated results indicated that obvious spin splitting phenomenon occurred near the Femi level. The Zn atoms on the inner layer of ZnO nanowires are easily substituted by Mn atoms along the [0001] direction. It was also shown that the Mn²⁺-O²⁻-Mn²⁺ magnetic coupling formed by intermediate O atom was proved to be caused by orbital hybridization between Mn 3d and O 2p states. The magnetic moments were mainly attributed to the unpaired Mn 3d orbitals, but not relevant with doping position of Mn atoms. Moreover, the optical properties of Mn-doped ZnO nanowires exhibited a novel blue-shifted optical absorption and enhanced ultraviolet-light emission. The above results show that the Mn-doped ZnO nanowires are a new type of magneto-optical materials with great promise. Full article

(This article belongs to the Special Issue Nanophotonic Materials)

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2430 KiB

Open AccessArticle

Thermo-Optical Properties of Thin-Film TiO2–Al2O3 Bilayers Fabricated by Atomic Layer Deposition

by Rizwan Ali, Muhammad Rizwan Saleem, Pertti Pääkkönen and Seppo Honkanen

Nanomaterials 2015, 5(2), 792-803; https://doi.org/10.3390/nano5020792 - 18 May 2015

Cited by 20 | Viewed by 9146

Abstract

We investigate the optical and thermo-optical properties of amorphous TiO\(_2\)–Al\(_2\)O\(_3\) thin-film bilayers fabricated by atomic layer deposition (ALD). Seven samples of TiO\(_2\)–Al\(_2\)O\(_3\) bilayers are fabricated by growing Al\(_2\)O\(_3\) films of different thicknesses on the surface of TiO\(_2\) films of constant thickness (100 nm). [...] Read more.

We investigate the optical and thermo-optical properties of amorphous TiO\(_2\)–Al\(_2\)O\(_3\) thin-film bilayers fabricated by atomic layer deposition (ALD). Seven samples of TiO\(_2\)–Al\(_2\)O\(_3\) bilayers are fabricated by growing Al\(_2\)O\(_3\) films of different thicknesses on the surface of TiO\(_2\) films of constant thickness (100 nm). Temperature-induced changes in the optical refractive indices of these thin-film bilayers are measured by a variable angle spectroscopic ellipsometer VASE\textsuperscript{\textregistered}. The optical data and the thermo-optic coefficients of the films are retrieved and calculated by applying the Cauchy model and the linear fitting regression algorithm, in order to evaluate the surface porosity model of TiO\(_2\) films. The effects of TiO\(_2\) surface defects on the films' thermo-optic properties are reduced and modified by depositing ultra-thin ALD-Al\(_2\)O\(_3\) diffusion barrier layers. Increasing the ALD-Al\(_2\)O\(_3\) thickness from 20 nm to 30 nm results in a sign change of the thermo-optic coefficient of the ALD-TiO\(_2\). The thermo-optic coefficients of the 100 nm-thick ALD-TiO\(_2\) film and 30 nm-thick ALD-Al\(_2\)O\(_3\) film in a bilayer are (0.048 \(\pm\) 0.134) \(\times 10 ^{-4} {^\circ}\mathrm {C}^{-1}\) and (0.680 \(\pm\) 0.313) \(\times 10^{-4} {^\circ} \mathrm {C}^{-1}\), respectively, at a temperature \(T = 62 ^\circ \mathrm{C}\). Full article

(This article belongs to the Special Issue Nanophotonic Materials)

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1503 KiB

Open AccessArticle

Band Structure Simulations of the Photoinduced Changes in the MgB₂:Cr Films

by Iwan V. Kityk, Anatolii O. Fedorchuk, Katarzyna Ozga and Nasser S. AlZayed

Nanomaterials 2015, 5(2), 541-553; https://doi.org/10.3390/nano5020541 - 02 Apr 2015

Cited by 2 | Viewed by 4855

Abstract

An approach for description of the photoinduced nonlinear optical effects in the superconducting MgB₂:Cr₂O₃ nanocrystalline film is proposed. It includes the molecular dynamics step-by-step optimization of the two separate crystalline phases. The principal role for the photoinduced nonlinear [...] Read more.

An approach for description of the photoinduced nonlinear optical effects in the superconducting MgB₂:Cr₂O₃ nanocrystalline film is proposed. It includes the molecular dynamics step-by-step optimization of the two separate crystalline phases. The principal role for the photoinduced nonlinear optical properties plays nanointerface between the two phases. The first modified layers possess a form of slightly modified perfect crystalline structure. The next layer is added to the perfect crystalline structure and the iteration procedure is repeated for the next layer. The total energy here is considered as a varied parameter. To avoid potential jumps on the borders we have carried out additional derivative procedure. Full article

(This article belongs to the Special Issue Nanophotonic Materials)

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4903 KiB

Open AccessArticle

Unidirectional Wave Propagation in Low-Symmetric Colloidal Photonic-Crystal Heterostructures

by Vassilios Yannopapas

Nanomaterials 2015, 5(1), 376-385; https://doi.org/10.3390/nano5010376 - 19 Mar 2015

Cited by 9 | Viewed by 5378

Abstract

We show theoretically that photonic crystals consisting of colloidal spheres exhibit unidirectional wave propagation and one-way frequency band gaps without breaking time-reversal symmetry via, e.g., the application of an external magnetic field or the use of nonlinear materials. Namely, photonic crystals with low [...] Read more.

We show theoretically that photonic crystals consisting of colloidal spheres exhibit unidirectional wave propagation and one-way frequency band gaps without breaking time-reversal symmetry via, e.g., the application of an external magnetic field or the use of nonlinear materials. Namely, photonic crystals with low symmetry such as the monoclinic crystal type considered here as well as with unit cells formed by the heterostructure of different photonic crystals show significant unidirectional electromagnetic response. In particular, we show that the use of scatterers with low refractive-index contrast favors the formation of unidirectional frequency gaps which is the optimal route for achieving unidirectional wave propagation. Full article

(This article belongs to the Special Issue Nanophotonic Materials)

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Review

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1357 KiB

Open AccessReview

Origin and Future of Plasmonic Optical Tweezers

by Jer-Shing Huang and Ya-Tang Yang

Nanomaterials 2015, 5(2), 1048-1065; https://doi.org/10.3390/nano5021048 - 12 Jun 2015

Cited by 52 | Viewed by 10120

Abstract

Plasmonic optical tweezers can overcome the diffraction limits of conventional optical tweezers and enable the trapping of nanoscale objects. Extension of the trapping and manipulation of nanoscale objects with nanometer position precision opens up unprecedented opportunities for applications in the fields of biology, [...] Read more.

Plasmonic optical tweezers can overcome the diffraction limits of conventional optical tweezers and enable the trapping of nanoscale objects. Extension of the trapping and manipulation of nanoscale objects with nanometer position precision opens up unprecedented opportunities for applications in the fields of biology, chemistry and statistical and atomic physics. Potential applications include direct molecular manipulation, lab-on-a-chip applications for viruses and vesicles and the study of nanoscale transport. This paper reviews the recent research progress and development bottlenecks and provides an overview of possible future directions in this field. Full article

(This article belongs to the Special Issue Nanophotonic Materials)

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4922 KiB

Open AccessReview

Optical and Structural Properties of Si Nanocrystals in SiO2 Films

by Timur Nikitin and Leonid Khriachtchev

Nanomaterials 2015, 5(2), 614-655; https://doi.org/10.3390/nano5020614 - 22 Apr 2015

Cited by 42 | Viewed by 8967

Abstract

Optical and structural properties of Si nanocrystals (Si-nc) in silica films are described. For the SiOx (x < 2) films annealed above 1000 °C, the Raman signal of Si-nc and the absorption coefficient are proportional to the amount of elemental Si detected by [...] Read more.

Optical and structural properties of Si nanocrystals (Si-nc) in silica films are described. For the SiOx (x < 2) films annealed above 1000 °C, the Raman signal of Si-nc and the absorption coefficient are proportional to the amount of elemental Si detected by X-ray photoelectron spectroscopy. A good agreement is found between the measured refractive index and the value estimated by using the effective-medium approximation. The extinction coefficient of elemental Si is found to be between the values of crystalline and amorphous Si. Thermal annealing increases the degree of Si crystallization; however, the crystallization and the Si–SiO2 phase separation are not complete after annealing at 1200 °C. The 1.5-eV PL quantum yield increases as the amount of elemental Si decreases; thus, this PL is probably not directly from Si-nc responsible for absorption and detected by Raman spectroscopy. Continuous-wave laser light can produce very high temperatures in the free-standing films, which changes their structural and optical properties. For relatively large laser spots, the center of the laser-annealed area is very transparent and consists of amorphous SiO2. Large Si-nc (up to ∼300 nm in diameter) are observed in the ring around the central region. These Si-nc lead to high absorption and they are typically under compressive stress, which is connected with their formation from the liquid phase. By using strongly focused laser beams, the structural changes in the free-standing films can be made in submicron areas. Full article

(This article belongs to the Special Issue Nanophotonic Materials)

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1992 KiB

Open AccessReview

Magneto-Plasmonics and Resonant Interaction of Light with Dynamic Magnetisation in Metallic and All-Magneto-Dielectric Nanostructures

by Ivan S. Maksymov

Nanomaterials 2015, 5(2), 577-613; https://doi.org/10.3390/nano5020577 - 09 Apr 2015

Cited by 80 | Viewed by 10919

Abstract

A significant interest in combining plasmonics and magnetism at the nanoscale gains momentum in both photonics and magnetism sectors that are concerned with the resonant enhancement of light-magnetic-matter interaction in nanostructures. These efforts result in a considerable amount of literature, which is difficult [...] Read more.

A significant interest in combining plasmonics and magnetism at the nanoscale gains momentum in both photonics and magnetism sectors that are concerned with the resonant enhancement of light-magnetic-matter interaction in nanostructures. These efforts result in a considerable amount of literature, which is difficult to collect and digest in limited time. Furthermore, there is insufficient exchange of results between the two research sectors. Consequently, the goal of this review paper is to bridge this gap by presenting an overview of recent progress in the field of magneto-plasmonics from two different points of view: magneto-plasmonics, and magnonics and magnetisation dynamics. It is expected that this presentation style will make this review paper of particular interest to both general physical audience and specialists conducting research on photonics, plasmonics, Brillouin light scattering spectroscopy of magnetic nanostructures and magneto-optical Kerr effect magnetometry, as well as ultrafast all-optical and THz-wave excitation of spin waves. Moreover, readers interested in a new, rapidly emerging field of all-dielectric nanophotonics will find a section about all-magneto-dielectric nanostructures. Full article

(This article belongs to the Special Issue Nanophotonic Materials)

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