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2 pages, 162 KiB

Open AccessEditorial

Special Issue: State-of-the-Art Nanophotonic and Optical Nanomaterials in China

by Kun Huang and Heping Zeng

Nanomaterials 2022, 12(13), 2270; https://doi.org/10.3390/nano12132270 - 1 Jul 2022

Viewed by 1211

Abstract

In recent years, the fields of nanophotonics and nano-optics have been greatly fueled by rapid advancements in photonic science and technology, especially by the emergence of novel optical nanomaterials and new functional nanostructures [...] Full article

(This article belongs to the Special Issue State-of-the-Art Nanophotonic and Optical Nanomaterials in China)

Research

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21 pages, 7511 KiB

Open AccessArticle

Hydrogenated Amorphous Titania with Engineered Surface Oxygen Vacancy for Efficient Formaldehyde and Dye Removals under Visible-Light Irradiation

by Guang Feng, Mengyun Hu, Botao Wu, Shencheng Shi, Shuai Yuan, Yanan Li and Heping Zeng

Nanomaterials 2022, 12(5), 742; https://doi.org/10.3390/nano12050742 - 22 Feb 2022

Cited by 5 | Viewed by 2005

Abstract

Hydrogenated crystalized TiO_2−x with oxygen vacant (O_V) doping has attracted considerable attraction, owing to its impressive photoactivity. However, amorphous TiO₂, as a common allotrope of titania, is ignored as a hydrogenated templet. In this work, hydrogenated amorphous TiO [...] Read more.

Hydrogenated crystalized TiO_2−x with oxygen vacant (O_V) doping has attracted considerable attraction, owing to its impressive photoactivity. However, amorphous TiO₂, as a common allotrope of titania, is ignored as a hydrogenated templet. In this work, hydrogenated amorphous TiO_2−x (HAm-TiO_2−x) with engineered surface O_V and high surface area (176.7 cm² g⁻¹) was first prepared using a unique liquid plasma hydrogenation strategy. In HAm-TiO_2−x, we found that O_V was energetically retained in the subsurface region; in particular, the subsurface O_V-induced energy level preferred to remain under the conduction band (0.5 eV) to form a conduction band tail and deep trap states, resulting in a narrow bandgap (2.36 eV). With the benefits of abundant light absorption and efficient photocarrier transportation, HAm-TiO_2−x coated glass has demonstrated superior visible-light-driven self-cleaning performances. To investigate its formaldehyde photodegradation under harsh indoor conditions, HAm-TiO_2−x was used to decompose low-concentration formaldehyde (~0.6 ppm) with weak-visible light (λ = 600 nm, power density = 0.136 mW/cm²). Thus, HAm-TiO_2−x achieved high quantum efficiency of 3 × 10⁻⁶ molecules/photon and photoactivity of 92.6%. The adsorption capabilities of O₂ (−1.42 eV) and HCHO (−1.58 eV) in HAm-TiO_2−x are both largely promoted in the presence of subsurface O_V. The surface reaction pathway and formaldehyde decomposition mechanism over HAm-TiO_2−x were finally clarified. This work opened a promising way to fabricate hydrogenated amorphous photocatalysts, which could contribute to visible-light-driven photocatalytic environmental applications. Full article

(This article belongs to the Special Issue State-of-the-Art Nanophotonic and Optical Nanomaterials in China)

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10 pages, 2542 KiB

Open AccessArticle

Preparation of Bimodal Silver Nanoparticle Ink Based on Liquid Phase Reduction Method

by Zhiheng Yu, Tiancheng Zhang, Kaifeng Li, Fengli Huang and Chengli Tang

Nanomaterials 2022, 12(3), 560; https://doi.org/10.3390/nano12030560 - 6 Feb 2022

Cited by 18 | Viewed by 2612

Abstract

Improving the conductivity of metal particle inks is a hot topic of scientific research. In this paper, a method for preparing metal-filled particles was proposed. By adding filled particles to the ink, the size distribution of particles could be changed to form a [...] Read more.

Improving the conductivity of metal particle inks is a hot topic of scientific research. In this paper, a method for preparing metal-filled particles was proposed. By adding filled particles to the ink, the size distribution of particles could be changed to form a bimodal distribution structure in accordance with Horsfield’s stacking model. The filling particles had small volume and good fluidity, which could fill the gaps between the particles after printing and improve its electrical conductivity without significantly changing the metal solid content in the ink. Experimental results show that the silver content of the ink slightly increased from 15 wt% to 16.5 wt% after adding filled particles. However, the conductivity of the ink was significantly improved, and after sintering, the resistivity of the ink decreased from 70.2 μΩ∙cm to 31.2 μΩ∙cm. In addition, the filling particles prepared by this method is simple and has a high material utilization rate, which could be applied to the preparation of other kinds of metal particle inks. Full article

(This article belongs to the Special Issue State-of-the-Art Nanophotonic and Optical Nanomaterials in China)

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8 pages, 14629 KiB

Open AccessArticle

Enhancement of Terahertz Radiation by Surface Plasmons Based on CdTe Thin Films

by Huiyan Kong, Luyi Huang, Min Li, Ling Zhang and Heping Zeng

Nanomaterials 2022, 12(2), 290; https://doi.org/10.3390/nano12020290 - 17 Jan 2022

Cited by 2 | Viewed by 1965

Abstract

Terahertz (THz) time-domain spectroscopy (TDS) is a powerful tool used to characterize the surface/interface of materials, and semiconductor/metal interfaces can generate THz emission through ultrafast optical excitation, which can be further improved through the optical excitation of surface plasmons. Here, we assembled cadmium [...] Read more.

Terahertz (THz) time-domain spectroscopy (TDS) is a powerful tool used to characterize the surface/interface of materials, and semiconductor/metal interfaces can generate THz emission through ultrafast optical excitation, which can be further improved through the optical excitation of surface plasmons. Here, we assembled cadmium telluride (CdTe) on an AuAg alloy (Au₂₅Ag₇₅, wt.%) substrate and obtained five times stronger THz emission compared with silicon substrate, and found that the enhancement can be tuned by controlling the thickness of the semiconductor materials and plasmonic metal substrates. We believe that our results not only promote the development of THz emission enhancement, but also provide a straightforward way of producing small, thin, and more efficient terahertz photonic devices. Full article

(This article belongs to the Special Issue State-of-the-Art Nanophotonic and Optical Nanomaterials in China)

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14 pages, 4058 KiB

Open AccessArticle

Thin-Film Solar Cells Based on Selenized CuSbS₂ Absorber

by Minghao Zhao, Junsheng Yu, Lijuan Fu, Youwei Guan, Hua Tang, Lu Li and Jiang Cheng

Nanomaterials 2021, 11(11), 3005; https://doi.org/10.3390/nano11113005 - 9 Nov 2021

Cited by 12 | Viewed by 2705

Abstract

Copper antimony sulfide (CuSbS₂) has attracted significant interest as an earth-abundant photovoltaic absorber. However, the efficiency of the current CuSbS₂ photovoltaic device is too low to meet the requirement of a large-scale application. In this study, selenylation was introduced to [...] Read more.

Copper antimony sulfide (CuSbS₂) has attracted significant interest as an earth-abundant photovoltaic absorber. However, the efficiency of the current CuSbS₂ photovoltaic device is too low to meet the requirement of a large-scale application. In this study, selenylation was introduced to optimize the band structure and improve the device performance. Selenized CuSbS₂ [CuSbS₂(Se)] films were realized using porous CuSbS₂ films prepared by spray deposition with a post-treatment in Se vapor. The as-prepared CuSbS₂(Se) films exhibited a compact structure. X-ray diffraction and elemental analysis confirmed the effective doping of Se into the lattice by substituting a part of S in CuSbS₂. Elemental analysis revealed a gradient distribution for Se from the top surface to the deeper regions, and the substitution rate was very high (>39%). Dark J–V characteristics and AC impedance spectroscopy analysis showed that selenylation significantly reduced the carrier recombination center. As a result, the selenized CuSbS₂ device exhibited a significant efficiency improvement from 0.12% to 0.90%, which is much higher than that of the simply annealed device (0.46%), indicating this technique is a promising approach to improve the performance of CuSbS₂ solar cells. Full article

(This article belongs to the Special Issue State-of-the-Art Nanophotonic and Optical Nanomaterials in China)

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8 pages, 2855 KiB

Open AccessFeature PaperArticle

Distance-Dependent Fluorescence Resonance Energy Transfer Enhancement on Nanoporous Gold

by Lianmin Cui, Ling Zhang and Heping Zeng

Nanomaterials 2021, 11(11), 2927; https://doi.org/10.3390/nano11112927 - 1 Nov 2021

Cited by 7 | Viewed by 2579

Abstract

Fluorescence resonance energy transfers (FRET) between cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) on nanoporous gold (NPG) are systematically investigated by controlling the distance between NPG and fluorescent proteins with polyelectrolyte multilayers. The FRET between CFP and YFP is significantly enhanced [...] Read more.

Fluorescence resonance energy transfers (FRET) between cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) on nanoporous gold (NPG) are systematically investigated by controlling the distance between NPG and fluorescent proteins with polyelectrolyte multilayers. The FRET between CFP and YFP is significantly enhanced by NPG, and the maximum enhancement is related to both ligament size of NPG and the distance between NPG and proteins. With the optimized distance, 18-fold FRET enhancement was obtained on NPG compared to that on glass, and the conversion efficiency is about 90%. The potential to tune the characteristic energy transfer distance has implications for applications in nanophotonic devices and provides a possible way to design sensors and light energy converters. Full article

(This article belongs to the Special Issue State-of-the-Art Nanophotonic and Optical Nanomaterials in China)

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10 pages, 4571 KiB

Open AccessFeature PaperArticle

Tilted Nano-Grating Based Ultra-Compact Broadband Polarizing Beam Splitter for Silicon Photonics

by Haipeng Liu, Jijun Feng, Jinman Ge, Shanqing Zhuang, Shuo Yuan, Yishu Chen, Xiaojun Li, Qinggui Tan, Qinghua Yu and Heping Zeng

Nanomaterials 2021, 11(10), 2645; https://doi.org/10.3390/nano11102645 - 8 Oct 2021

Cited by 13 | Viewed by 2237

Abstract

An ultra-compact broadband silicon polarizing beam splitter is proposed based on a tilted nano-grating structure. A light cross coupling can be realized for transverse-magnetic mode, while the transverse-electric light can almost completely output from the through port. The length of the coupling region [...] Read more.

An ultra-compact broadband silicon polarizing beam splitter is proposed based on a tilted nano-grating structure. A light cross coupling can be realized for transverse-magnetic mode, while the transverse-electric light can almost completely output from the through port. The length of the coupling region is only 6.8 μm, while an extinction ratio of 23.76 dB can be realized at a wavelength of 1550 nm. As a proof of concept, the device was fabricated by a commercial silicon photonic foundry. It can realize a 19.84 dB extinction ratio and an 80 nm working bandwidth with an extinction ratio of larger than 10 dB. The presented device also shows a good fabrication tolerance to the structure deviations, which is favorable for its practical applications in silicon photonics. Full article

(This article belongs to the Special Issue State-of-the-Art Nanophotonic and Optical Nanomaterials in China)

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11 pages, 7663 KiB

Open AccessArticle

Plasmon Enhanced Second Harmonic Generation from ZnO Nanofilms on Vertical Au Nanorod Arrays

by Qiang Ma, Chengda Pan, Yingxian Xue, Zhiyun Fang, Shiyu Zhang, Botao Wu and E Wu

Nanomaterials 2021, 11(10), 2597; https://doi.org/10.3390/nano11102597 - 2 Oct 2021

Cited by 3 | Viewed by 2313

Abstract

Vertically aligned gold nanorod arrays have attracted much attention for their fascinating optical properties. Different from longitudinal surface plasmon wavelength (LSPW) and edge-to-edge spacing of gold nanorods, the role of gold nanorod diameter in plasmonic enhancement ability of vertical gold nanorod arrays has [...] Read more.

Vertically aligned gold nanorod arrays have attracted much attention for their fascinating optical properties. Different from longitudinal surface plasmon wavelength (LSPW) and edge-to-edge spacing of gold nanorods, the role of gold nanorod diameter in plasmonic enhancement ability of vertical gold nanorod arrays has rarely been explored. In this work, we selected gold nanorods with similar LSPW but two different diameters (22 and 41 nm), the optical properties of which are dominated by absorption and scattering cross sections, respectively. The vertically aligned arrays of these gold nanorods formed by evaporation self-assembly are coupled with nonlinear ZnO nanocrystal films spin-coated on their surfaces. It was found that the gold nanorod array with a larger diameter can enhance the second harmonic generation (SHG) of ZnO nanofilm by a factor of 27.0, while it is about 7.3 for the smaller gold nanorod array. Theoretical simulations indicate that such stronger enhancement of the larger vertical gold nanorod array compared with the smaller one is due to its stronger scattering ability and greater extent of near-field enhancement at SHG fundamental wavelength. Our work shows that the diameter of gold nanorods is also an important factor to be considered in realizing strong plasmon enhancement of vertically aligned gold nanorod arrays. Full article

(This article belongs to the Special Issue State-of-the-Art Nanophotonic and Optical Nanomaterials in China)

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15 pages, 10675 KiB

Open AccessArticle

Variation of Signal Reflection on Electrodes of Silicon Mach-Zehnder Modulators: Influence of Nanoscale Variation and Mitigation Strategies

by Zhaobang Zeng, Ding Ding, Qianyi Gao, Nan Yang, Peiyan Zhao and Wei Jiang

Nanomaterials 2021, 11(2), 499; https://doi.org/10.3390/nano11020499 - 16 Feb 2021

Cited by 2 | Viewed by 3074

Abstract

Driving signal reflection on traveling wave electrodes (TWEs) is a critical issue in Mach–Zehnder modulators. Fabrication variation often causes a random variation in the electrode impedance and the signal reflection, which induces modulation characteristics variation. The variation of reflection could be intertwined with [...] Read more.

Driving signal reflection on traveling wave electrodes (TWEs) is a critical issue in Mach–Zehnder modulators. Fabrication variation often causes a random variation in the electrode impedance and the signal reflection, which induces modulation characteristics variation. The variation of reflection could be intertwined with the variation of other electrode characteristics, such as microwave signal attenuation, resulting in complexity. Here, we characterize the (partial) correlation coefficients between the reflection and modulation characteristics at different bit rates. Decreasing correlation at higher bit rates is observed. Device physics analysis shows how the observed variation can be related to nanoscale variation of material properties, particularly in the embedded diode responsible for electro-optic modulation. We develop a detailed theory to analyze two variation modes of the diode (P-i-N diode or overlapping P/N regions), which reveal insight beyond simplistic diode models. Microwave signal attenuation tends to reduce the correlation with on-electrode reflection, particularly at high bit rates. The theory shows the relative importance of conductor-induced attenuation and “dielectric”-induced attenuation, with different dependence on the frequency and fabrication variation. Strategies on how to mitigate the effect of variation for better fabrication tolerance are discussed by considering three key factors: pre-shift in structural design, bias condition, and fabrication control accuracy. Full article

(This article belongs to the Special Issue State-of-the-Art Nanophotonic and Optical Nanomaterials in China)

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