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24 pages, 2767 KiB

Open AccessArticle

Radiation and Energetic Analysis of Nanofluid Based Volumetric Absorbers for Concentrated Solar Power

by Jan Rudolf Eggers, Eckart Matthias Lange and Stephan Kabelac

Nanomaterials 2018, 8(10), 838; https://doi.org/10.3390/nano8100838 - 16 Oct 2018

Cited by 8 | Viewed by 3723

Abstract

Recently, several publications gave attention to nanofluid based solar absorber systems in which the solar radiation energy is directly absorbed in the volume of the fluid. This idea could provide advantages over conventionally used surface absorbers regarding the optical and thermal efficiency. For [...] Read more.

Recently, several publications gave attention to nanofluid based solar absorber systems in which the solar radiation energy is directly absorbed in the volume of the fluid. This idea could provide advantages over conventionally used surface absorbers regarding the optical and thermal efficiency. For the evaluation of this concept, a numerical approach is introduced and validated in this contribution. The results show that the optical efficiency of a volumetric absorber strongly depends on the scattering behavior of the nanofluid and can reach competitive values only if the particle size distribution is narrow and small. If this is achieved, the surface temperature and therefore the heat loss can be lowered significantly. Furthermore, the surface absorber requires very high Reynolds numbers to transfer the absorbed energy into the working fluid and avoid overheating of the absorber tube. This demand of pumping power can be reduced significantly using the concept of volumetric absorption. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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10 pages, 1845 KiB

Open AccessArticle

Micropatterning of Metal Nanoparticle Ink by Laser-Induced Thermocapillary Flow

by Sewoong Park, Jinhyeong Kwon, Jaemook Lim, Wooseop Shin, Younggeun Lee, Habeom Lee, Hyun-Jong Kim, Seungyong Han, Junyeob Yeo, Seung Hwan Ko and Sukjoon Hong

Nanomaterials 2018, 8(9), 645; https://doi.org/10.3390/nano8090645 - 22 Aug 2018

Cited by 14 | Viewed by 5071

Abstract

Selective laser sintering of metal nanoparticle ink is a low-temperature and non-vacuum technique developed for the fabrication of patterned metal layer on arbitrary substrates, but its application to a metal layer composed of large metal area with small voids is very much limited [...] Read more.

Selective laser sintering of metal nanoparticle ink is a low-temperature and non-vacuum technique developed for the fabrication of patterned metal layer on arbitrary substrates, but its application to a metal layer composed of large metal area with small voids is very much limited due to the increase in scanning time proportional to the metal pattern density. For the facile manufacturing of such metal layer, we introduce micropatterning of metal nanoparticle ink based on laser-induced thermocapillary flow as a complementary process to the previous selective laser sintering process for metal nanoparticle ink. By harnessing the shear flow of the solvent at large temperature gradient, the metal nanoparticles are selectively pushed away from the scanning path to create metal nanoparticle free trenches. These trenches are confirmed to be stable even after the complete process owing to the presence of the accompanying ridges as well as the bump created along the scanning path. As a representative example of a metal layer with large metal area and small voids, dark-field photomask with Alphabetic letters are firstly created by the proposed method and it is then demonstrated that the corresponding letters can be successfully reproduced on the screen by an achromatic lens. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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12 pages, 3629 KiB

Open AccessArticle

Fabrication and Characterization of Multiscale PLA Structures Using Integrated Rapid Prototyping and Gas Foaming Technologies

by Byung Kyu Park, David J. Hwang, Dong Eui Kwon, Tae Jun Yoon and Youn-Woo Lee

Nanomaterials 2018, 8(8), 575; https://doi.org/10.3390/nano8080575 - 27 Jul 2018

Cited by 14 | Viewed by 4166

Abstract

Multiscale structured polymers have been considered as a promising category of functional materials with unique properties. We combined rapid prototyping and gas foaming technologies to fabricate multiscale functional materials of superior mechanical and thermal insulation properties. Through scanning electron microscope based morphological characterization, [...] Read more.

Multiscale structured polymers have been considered as a promising category of functional materials with unique properties. We combined rapid prototyping and gas foaming technologies to fabricate multiscale functional materials of superior mechanical and thermal insulation properties. Through scanning electron microscope based morphological characterization, formation of multiscale porous structure with nanoscale cellular pores was confirmed. Improvement in mechanical strength is attributed to rearrangement of crystals within CO₂ saturated grid sample. It is also shown that a post-foaming temperature higher than the glass transition temperature deteriorates mechanical strength, providing process guidelines. Thermal decomposition of filament material sets the upper limit of temperature for 3D printed features, characterized by simultaneous differential scanning calorimetry and thermogravimetric analysis. Porosity of the fabricated 3D structured polylactic acid (PLA) foam is controllable by suitable tuning of foaming conditions. The fabricated multiscale 3D structures have potential for thermal insulation applications with lightweight and reasonable mechanical strength. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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9 pages, 1987 KiB

Open AccessArticle

Enhanced Thermoelectric Conversion Efficiency of CVD Graphene with Reduced Grain Sizes

by Gyumin Lim, Kenneth David Kihm, Hong Goo Kim, Woorim Lee, Woomin Lee, Kyung Rok Pyun, Sosan Cheon, Phillip Lee, Jin Young Min and Seung Hwan Ko

Nanomaterials 2018, 8(7), 557; https://doi.org/10.3390/nano8070557 - 22 Jul 2018

Cited by 23 | Viewed by 5926

Abstract

The grain size of CVD (Chemical Vapor Deposition) graphene was controlled by changing the precursor gas flow rates, operation temperature, and chamber pressure. Graphene of average grain sizes of 4.1 µm, 2.2 µm, and 0.5 µm was synthesized in high quality and full [...] Read more.

The grain size of CVD (Chemical Vapor Deposition) graphene was controlled by changing the precursor gas flow rates, operation temperature, and chamber pressure. Graphene of average grain sizes of 4.1 µm, 2.2 µm, and 0.5 µm was synthesized in high quality and full coverage. The possibility to tailor the thermoelectric conversion characteristics of graphene has been exhibited by examining the grain size effect on the three elementary thermal and electrical properties of σ, S, and k. Electrical conductivity (σ) and Seebeck coefficients (S) were measured in a vacuum for supported graphene on SiO₂/Si FET (Field Effect Transistor) substrates so that the charge carrier density could be changed by applying a gate voltage (

V_{G}

). Mobility (µ) values of 529, 459, and 314 cm²/V·s for holes and 1042, 745, and 490 cm²/V·s for electrons for the three grain sizes of 4.1 µm, 2.2 µm, and 0.5 µm, respectively, were obtained from the slopes of the measured σ vs.

V_{G}

graphs. The power factor (PF), the electrical portion of the thermoelectric figure of merit (ZT), decreased by about one half as the grain size was decreased, while the thermal conductivity (k) decreased by one quarter for the same grain decrease. Finally, the resulting ZT increased more than two times when the grain size was reduced from 4.1 µm to 0.5 µm. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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16 pages, 3262 KiB

Open AccessArticle

Study on the Performance of Nano-Titanium Nitride-Coated Stainless Steel Electrodes in Electro-Fenton Systems

by Yita Wang and Youchen Lin

Nanomaterials 2018, 8(7), 494; https://doi.org/10.3390/nano8070494 - 5 Jul 2018

Cited by 12 | Viewed by 5065

Abstract

The electro-Fenton (EF) process is a type of electrochemical oxidation process; ·OH radicals are generated on the cathode using electricity and decolorize dye wastewaters. Most studies on EF systems in the past have focused on the operating parameters of this process. In recent [...] Read more.

The electro-Fenton (EF) process is a type of electrochemical oxidation process; ·OH radicals are generated on the cathode using electricity and decolorize dye wastewaters. Most studies on EF systems in the past have focused on the operating parameters of this process. In recent years, the influence of electrode performance on the EF process has begun to receive more attention. In this study, direct nitridation was used to prepare titanium nitride powders, which were thereafter coated on an SUS304 stainless steel substrate. The performance of this system in the treatment of rhodamine B dye wastewaters via the EF process was investigated. The experimental methods used in this work include: (1) scanning electron microscopy (SEM); (2) X-ray diffraction (XRD); (3) electrochemical Tafel curves; (4) linear sweep voltammetry (LSV); (5) and cyclic voltammetry (CV). It was shown that high-purity TiN can be formed at nitriding temperatures above 900 °C, and the strength of the (111) crystal plane increases with the increase in nitriding temperature; the TiN coating effectively activates the reactive surface of the electrode owing to its porous structure. In terms of corrosion resistance, the corrosion potential and corrosion current of the TiN 1000 °C/SUS304 electrode were 116.94 mV and 205 nA/cm², respectively, and the coating had a coating porosity of 0.89 × 10⁻⁷. As compared with SUS304 stainless steel, the TiN 1000 °C/SUS304 composite electrode had a significantly greater degree of corrosion resistance and exhibited higher redox activity in LSV tests. This composite electrode could achieve a decolorization rate of 49.86% after 30 min, and 94.46% after 120 min. In summary, the TiN 1000 °C/SUS304 composite electrode is very stable and has excellent decolorization efficacy in the EF process. Our findings will serve as a useful reference for future studies on EF electrodes. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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10 pages, 3546 KiB

Open AccessArticle

Cutting-Processed Single-Wall Carbon Nanotubes with Additional Edge Sites for Supercapacitor Electrodes

by Teayeop Kim, Mun Kyoung Kim, Yunjeong Park, Eunpa Kim, Jangho Kim, Wonhyoung Ryu, Hyung Mo Jeong and Kyunghoon Kim

Nanomaterials 2018, 8(7), 464; https://doi.org/10.3390/nano8070464 - 26 Jun 2018

Cited by 9 | Viewed by 5158

Abstract

Carbon nanotubes are frequently selected for supercapacitors because of their major intrinsic properties of mechanical and chemical stability, in addition to their excellent electrical conductivity. However, electrodes using carbon nanotubes suffer from severe performance degradation by the phenomenon of re-stacking during fabrication, which [...] Read more.

Carbon nanotubes are frequently selected for supercapacitors because of their major intrinsic properties of mechanical and chemical stability, in addition to their excellent electrical conductivity. However, electrodes using carbon nanotubes suffer from severe performance degradation by the phenomenon of re-stacking during fabrication, which hinders ion accessibility. In this study, short single-wall carbon nanotubes were further shortened by sonication-induced cutting to increase the proportion of edge sites. This longitudinally short structure preferentially exposes the active edge sites, leading to high capacitance during operation. Supercapacitors assembled using the shorter-cut nanotubes exhibit a 7-fold higher capacitance than those with pristine single-wall nanotubes while preserving other intrinsic properties of carbon nanotubes, including excellent cycle performance and rate capability. The unique structure suggests a design approach for achieving a high specific capacitance with those low-dimensional carbon materials that suffer from re-stacking during device fabrication. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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9 pages, 2009 KiB

Open AccessArticle

The Effect of Light Intensity, Temperature, and Oxygen Pressure on the Photo-Oxidation Rate of Bare PbS Quantum Dots

by Huiyan Liu, Qian Dong and Rene Lopez

Nanomaterials 2018, 8(5), 341; https://doi.org/10.3390/nano8050341 - 18 May 2018

Cited by 11 | Viewed by 5277

Abstract

The oxidation speed of PbS quantum dots has been a subject of controversy for some time. In this study, we reveal the precise functional form of the oxidation rate constant for bare quantum dots through analysis of their photoluminescence as a function of [...] Read more.

The oxidation speed of PbS quantum dots has been a subject of controversy for some time. In this study, we reveal the precise functional form of the oxidation rate constant for bare quantum dots through analysis of their photoluminescence as a function of temperature, oxygen pressure, and excitation-laser intensity. The combined effect of these factors results in a reduced energy barrier that allows the oxidation to proceed at a high rate. Each absorbed photon is found to have a 10⁻⁸ probability of oxidizing a PbS atomic pair. This highlights the importance of photo-excitation on the speed of the oxidation process, even at low illumination conditions. The procedure used here may set up a quantitative standard useful for characterizing the stability of quantum dots coated with ligands/linkers, and to compare different protection schemes in a fair quantitative way. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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9 pages, 1924 KiB

Open AccessArticle

ZnO/CuO/M (M = Ag, Au) Hierarchical Nanostructure by Successive Photoreduction Process for Solar Hydrogen Generation

by Jinhyeong Kwon, Hyunmin Cho, Jinwook Jung, Habeom Lee, Sukjoon Hong, Junyeob Yeo, Seungyong Han and Seung Hwan Ko

Nanomaterials 2018, 8(5), 323; https://doi.org/10.3390/nano8050323 - 12 May 2018

Cited by 20 | Viewed by 5429

Abstract

To date, solar energy generation devices have been widely studied to meet a clean and sustainable energy source. Among them, water splitting photoelectrochemical cell is regarded as a promising energy generation way for splitting water molecules and generating hydrogen by sunlight. While many [...] Read more.

To date, solar energy generation devices have been widely studied to meet a clean and sustainable energy source. Among them, water splitting photoelectrochemical cell is regarded as a promising energy generation way for splitting water molecules and generating hydrogen by sunlight. While many nanostructured metal oxides are considered as a candidate, most of them have an improper bandgap structure lowering energy transition efficiency. Herein, we introduce a novel wet-based, successive photoreduction process that can improve charge transfer efficiency by surface plasmon effect for a solar-driven water splitting device. The proposed process enables to fabricate ZnO/CuO/Ag or ZnO/CuO/Au hierarchical nanostructure, having an enhanced electrical, optical, photoelectrochemical property. The fabricated hierarchical nanostructures are demonstrated as a photocathode in the photoelectrochemical cell and characterized by using various analytic tools. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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15 pages, 3853 KiB

Open AccessArticle

Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li–O₂ Batteries

by Amrita Chatterjee, Siu Wing Or and Yulin Cao

Nanomaterials 2018, 8(5), 308; https://doi.org/10.3390/nano8050308 - 7 May 2018

Cited by 9 | Viewed by 4926 | Correction

Abstract

As a step towards efficient and cost-effective electrocatalytic cathodes for Li–O₂ batteries, highly porous hausmannite-type Mn₃O₄ hollow nanocages (MOHNs) of a large diameter of ~250 nm and a high surface area of 90.65 m²·g⁻¹ were synthesized [...] Read more.

As a step towards efficient and cost-effective electrocatalytic cathodes for Li–O₂ batteries, highly porous hausmannite-type Mn₃O₄ hollow nanocages (MOHNs) of a large diameter of ~250 nm and a high surface area of 90.65 m²·g⁻¹ were synthesized and their physicochemical and electrochemical properties were studied in addition to their formation mechanism. A facile approach using carbon spheres as the template and MnCl₂ as the precursor was adopted to suit the purpose. The MOHNs/Ketjenblack cathode-based Li–O₂ battery demonstrated an improved cyclability of 50 discharge–charge cycles at a specific current of 400 mA·g⁻¹ and a specific capacity of 600 mAh·g⁻¹. In contrast, the Ketjenblack cathode-based one can sustain only 15 cycles under the same electrolytic system comprised of 1 M LiTFSI/TEGDME. It is surmised that the unique hollow nanocage morphology of MOHNs is responsible for the high electrochemical performance. The hollow nanocages were a result of the aggregation of crystalline nanoparticles of 25–35 nm size, and the mesoscopic pores between the nanoparticles gave rise to a loosely mesoporous structure for accommodating the volume change in the MOHNs/Ketjenblack cathode during electrocatalytic reactions. The improved cyclic stability is mainly due to the faster mass transport of the O₂ through the mesoscopic pores. This work is comparable to the state-of-the-art experimentations on cathodes for Li–O₂ batteries that focus on the use of non-precious transition materials. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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13 pages, 15926 KiB

Open AccessArticle

Thylakoid-Deposited Micro-Pillar Electrodes for Enhanced Direct Extraction of Photosynthetic Electrons

by DongHyun Ryu, Yong Jae Kim, Seon Il Kim, Hyeonaug Hong, Hyun S. Ahn, Kyunghoon Kim and WonHyoung Ryu

Nanomaterials 2018, 8(4), 189; https://doi.org/10.3390/nano8040189 - 25 Mar 2018

Cited by 17 | Viewed by 6205

Abstract

Photosynthesis converts solar energy to electricity in a highly efficient manner. Since only water is needed as fuel for energy conversion, this highly efficient energy conversion process has been rigorously investigated. In particular, photosynthetic apparatus, such as photosystem II (PSII), photosystem I (PSI), [...] Read more.

Photosynthesis converts solar energy to electricity in a highly efficient manner. Since only water is needed as fuel for energy conversion, this highly efficient energy conversion process has been rigorously investigated. In particular, photosynthetic apparatus, such as photosystem II (PSII), photosystem I (PSI), or thylakoids, have been isolated from various plants to construct bio-hybrid anodes. Although PSII or PSI decorated anodes have shown potentials, there still remain challenges, such as poor stability of PSII-based systems or need for electron donors other than water molecules of PSI-based systems. Thylakoid membranes are relatively stable after isolation and they contain all the necessary photosynthetic apparatus including the PSII and PSI. To increase electrical connections between thylakoids and anodes, nanomaterials such as carbon nanotubes, nanowires, nanoparticles, or graphene have been employed. However, since they rely on the secondary electrical connections between thylakoids and anodes; it is desired to achieve larger direct contacts between them. Here, we aimed to develop micro-pillar (MP) array anodes to maximize direct contact with thylakoids. The thylakoid morphology was analyzed and the MP array was designed to maximize direct contact with thylakoids. The performance of MP anodes and a photosynthetic fuel cell based on MP electrodes was demonstrated and analyzed. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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7 pages, 846 KiB

Open AccessArticle

A Brief Note on the Magnetowetting of Magnetic Nanofluids on AAO Surfaces

by Yu-Chin Chien and Huei Chu Weng

Nanomaterials 2018, 8(2), 118; https://doi.org/10.3390/nano8020118 - 20 Feb 2018

Cited by 14 | Viewed by 4611

Abstract

In magnetowetting, the material properties of liquid, surface morphology of solid, and applied external field are three major factors used to determine the wettability of a liquid droplet on a surface. For wetting measurements, an irregular or uneven surface could result in a [...] Read more.

In magnetowetting, the material properties of liquid, surface morphology of solid, and applied external field are three major factors used to determine the wettability of a liquid droplet on a surface. For wetting measurements, an irregular or uneven surface could result in a significant experimental uncertainty. The periodic array with a hexagonal symmetry structure is an advantage of the anodic aluminum oxide (AAO) structure. This study presents the results of the wetting properties of magnetic nanofluid sessile droplets on surfaces of various AAO pore sizes under an applied external magnetic field. Stable, water-based magnetite nanofluids are prepared by combining the chemical co-precipitation with the sol-gel technique, and AAO surfaces are then generated by anodizing the aluminum sheet in the beginning. The influence of pore size and magnetic field gradient on the magnetowetting of magnetic nanofluids on AAO surfaces is then investigated by an optical test system. Experimental results show that increasing the processing voltage of AAO templates could result in enhanced non-wettability behavior; that is, the increase in AAO pore size could lead to the increase in contact angle. The contact angle could be reduced by the applied magnetic field gradient. In general, the magnetic field has a more significant effect at smaller AAO pore sizes. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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4998 KiB

Open AccessArticle

Rationally Controlled Synthesis of CdSe_xTe_1−x Alloy Nanocrystals and Their Application in Efficient Graded Bandgap Solar Cells

by Shiya Wen, Miaozi Li, Junyu Yang, Xianglin Mei, Bin Wu, Xiaolin Liu, Jingxuan Heng, Donghuan Qin, Lintao Hou, Wei Xu and Dan Wang

Nanomaterials 2017, 7(11), 380; https://doi.org/10.3390/nano7110380 - 8 Nov 2017

Cited by 28 | Viewed by 4502

Abstract

CdSe_xTe_1−x semiconductor nanocrystals (NCs), being rod-shaped/irregular dot-shaped in morphology, have been fabricated via a simple hot-injection method. The NCs composition is well controlled through varying molar ratios of Se to Te precursors. Through changing the composition of the CdSe_x [...] Read more.

CdSe_xTe_1−x semiconductor nanocrystals (NCs), being rod-shaped/irregular dot-shaped in morphology, have been fabricated via a simple hot-injection method. The NCs composition is well controlled through varying molar ratios of Se to Te precursors. Through changing the composition of the CdSe_xTe_1−x NCs, the spectral absorption of the NC thin film between 570–800 nm is proved to be tunable. It is shown that the bandgap of homogeneously alloyed CdSe_xTe_1−x active thin film is nonlinearly correlated with the different compositions, which is perceived as optical bowing. The solar cell devices based on CdSe_xTe_1−x NCs with the structure of ITO/ZnO/CdSe/CdSe_xTe_1−x/MoO_x/Au and the graded bandgap ITO/ZnO/CdSe(w/o)/CdSe_x_Te_1−x/CdTe/MoO_x/Au are systematically evaluated. It was found that the performance of solar cells degrades almost linearly with the increase of alloy NC film thickness with respect to ITO/ZnO/CdSe/CdSe_0.2Te_0.8/MoO_x/Au. From another perspective, in terms of the graded bandgap structure of ITO/ZnO/CdSe/CdSe_xTe_1−x/CdTe/MoO_x/Au, the performance is improved in contrast with its single-junction analogues. The graded bandgap structure is proved to be efficient when absorbing spectrum and the solar cells fabricated under the structure of ITO/ZnO/CdSe_0.8Te_0.2/CdSe_0.2Te_0.8/CdTe/MoO_x/Au indicate power conversion efficiency (PCE) of 6.37%, a value among the highest for solution-processed inversely-structured CdSe_xTe_1−x NC solar cells. As the NC solar cells are solution-processed under environmental conditions, they are promising for fabricating solar cells at low cost, roll by roll and in large area. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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3392 KiB

Open AccessArticle

Enhancing Photovoltaic Performance Using Broadband Luminescent Down-Shifting by Combining Multiple Species of Eu-Doped Silicate Phosphors

by Wen-Jeng Ho, Yu-Tang Shen, Jheng-Jie Liu, Bang-Jin You and Chun-Hung Ho

Nanomaterials 2017, 7(10), 340; https://doi.org/10.3390/nano7100340 - 21 Oct 2017

Cited by 26 | Viewed by 4614

Abstract

This paper demonstrates the application of a broadband luminescent downshifting (LDS) layer with multiple species of europium (Eu)-doped silicate phosphors using spin-on film technique to enhance the photovoltaic efficiency of crystalline silicon solar cells. The surface morphology of the deposited layer was examined [...] Read more.

This paper demonstrates the application of a broadband luminescent downshifting (LDS) layer with multiple species of europium (Eu)-doped silicate phosphors using spin-on film technique to enhance the photovoltaic efficiency of crystalline silicon solar cells. The surface morphology of the deposited layer was examined using a scanning electron microscope (SEM). The chemical composition of the Eu-doped silicate phosphors was analyzed using energy-dispersive X-ray spectroscopy (EDS). The fluorescence emission of the Eu-doped silicate phosphors was characterized using photoluminescence (PL) measurements at room temperature. We also compared the optical reflectance and external quantum efficiency (EQE) response of cells with combinations of various Eu-doped phosphors species. The cell coated with two species of Eu-doped phosphors achieved a conversion efficiency enhancement (∆η) of 19.39%, far exceeding the ∆η = 15.08% of the cell with one species of Eu-doped phosphors and the ∆η = 8.51% of the reference cell with the same silicate layer without Eu-doped phosphors. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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7647 KiB

Open AccessArticle

Upcycling Waste Lard Oil into Vertical Graphene Sheets by Inductively Coupled Plasma Assisted Chemical Vapor Deposition

by Angjian Wu, Xiaodong Li, Jian Yang, Changming Du, Wangjun Shen and Jianhua Yan

Nanomaterials 2017, 7(10), 318; https://doi.org/10.3390/nano7100318 - 12 Oct 2017

Cited by 21 | Viewed by 5326

Abstract

Vertical graphene (VG) sheets were single-step synthesized via inductively coupled plasma (ICP)-enhanced chemical vapor deposition (PECVD) using waste lard oil as a sustainable and economical carbon source. Interweaved few-layer VG sheets, H₂, and other hydrocarbon gases were obtained after the decomposition [...] Read more.

Vertical graphene (VG) sheets were single-step synthesized via inductively coupled plasma (ICP)-enhanced chemical vapor deposition (PECVD) using waste lard oil as a sustainable and economical carbon source. Interweaved few-layer VG sheets, H₂, and other hydrocarbon gases were obtained after the decomposition of waste lard oil. The influence of parameters such as temperature, gas proportion, ICP power was investigated to tune the nanostructures of obtained VG, which indicated that a proper temperature and H₂ concentration was indispensable for the synthesis of VG sheets. Rich defects of VG were formed with a high

I_{D} / I_{G}

ratio (1.29), consistent with the dense edges structure observed in electron microscopy. Additionally, the morphologies, crystalline degree, and wettability of nanostructure carbon induced by PECVD and ICP separately were comparatively analyzed. The present work demonstrated the potential of our PECVD recipe to synthesize VG from abundant natural waste oil, which paved the way to upgrade the low-value hydrocarbons into advanced carbon material. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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2148 KiB

Open AccessArticle

Rapid Evaporation of Water on Graphene/Graphene-Oxide: A Molecular Dynamics Study

by Qibin Li, Yitian Xiao, Xiaoyang Shi and Shufeng Song

Nanomaterials 2017, 7(9), 265; https://doi.org/10.3390/nano7090265 - 7 Sep 2017

Cited by 87 | Viewed by 8841

Abstract

To reveal the mechanism of energy storage in the water/graphene system and water/grapheme-oxide system, the processes of rapid evaporation of water molecules on the sheets of graphene and graphene-oxide are investigated by molecular dynamics simulations. The results show that both the water/graphene and [...] Read more.

To reveal the mechanism of energy storage in the water/graphene system and water/grapheme-oxide system, the processes of rapid evaporation of water molecules on the sheets of graphene and graphene-oxide are investigated by molecular dynamics simulations. The results show that both the water/graphene and water/grapheme-oxide systems can store more energy than the pure water system during evaporation. The hydroxyl groups on the surface of graphene-oxide are able to reduce the attractive interactions between water molecules and the sheet of graphene-oxide. Also, the radial distribution function of the oxygen atom indicates that the hydroxyl groups affect the arrangement of water molecules at the water/graphene-oxide interface. Therefore, the capacity of thermal energy storage of the water/graphene-oxide system is lower than that of the water/graphene system, because of less desorption energy at the water/graphene-oxide interface. Also, the evaporation rate of water molecules on the graphene-oxide sheet is slower than that on the graphene sheet. The Leidenfrost phenomenon can be observed during the evaporation process in the water/grapheme-oxide system. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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5561 KiB

Open AccessArticle

Highly Efficient and Stable Organic Solar Cells via Interface Engineering with a Nanostructured ITR-GO/PFN Bilayer Cathode Interlayer

by Ding Zheng, Lili Zhao, Pu Fan, Ran Ji and Junsheng Yu

Nanomaterials 2017, 7(9), 233; https://doi.org/10.3390/nano7090233 - 23 Aug 2017

Cited by 7 | Viewed by 6297

Abstract

An innovative bilayer cathode interlayer (CIL) with a nanostructure consisting of in situ thermal reduced graphene oxide (ITR-GO) and poly[(9,9-bis(3′-(N,N-dimethylamion)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl) fluorene] (PFN) has been fabricated for inverted organic solar cells (OSCs). An approach to prepare a CIL of high [...] Read more.

An innovative bilayer cathode interlayer (CIL) with a nanostructure consisting of in situ thermal reduced graphene oxide (ITR-GO) and poly[(9,9-bis(3′-(N,N-dimethylamion)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl) fluorene] (PFN) has been fabricated for inverted organic solar cells (OSCs). An approach to prepare a CIL of high electronic quality by using ITR-GO as a template to modulate the morphology of the interface between the active layer and electrode and to further reduce the work function of the electrode has also been realized. This bilayer ITR-GO/PFN CIL is processed by a spray-coating method with facile in situ thermal reduction. Meanwhile, the CIL shows a good charge transport efficiency and less charge recombination, which leads to a significant enhancement of the power conversion efficiency from 6.47% to 8.34% for Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl} (PTB7):[6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM)-based OSCs. In addition, the long-term stability of the OSC is improved by using the ITR-GO/PFN CIL when compared with the pristine device. These results indicate that the bilayer ITR-GO/PFN CIL is a promising way to realize high-efficiency and stable OSCs by using water-soluble conjugated polymer electrolytes such as PFN. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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575 KiB

Open AccessCommunication

Phonon Transport through Nanoscale Contact in Tip-Based Thermal Analysis of Nanomaterials

by Jay Dulhani and Bong Jae Lee

Nanomaterials 2017, 7(8), 200; https://doi.org/10.3390/nano7080200 - 28 Jul 2017

Cited by 10 | Viewed by 4077

Abstract

Nanomaterials have been actively employed in various applications for energy and sustainability, such as biosensing, gas sensing, solar thermal energy conversion, passive radiative cooling, etc. Understanding thermal transports inside such nanomaterials is crucial for optimizing their performance for different applications. In order to [...] Read more.

Nanomaterials have been actively employed in various applications for energy and sustainability, such as biosensing, gas sensing, solar thermal energy conversion, passive radiative cooling, etc. Understanding thermal transports inside such nanomaterials is crucial for optimizing their performance for different applications. In order to probe the thermal transport inside nanomaterials or nanostructures, tip-based nanoscale thermometry has often been employed. It has been well known that phonon transport in nanometer scale is fundamentally different from that occurred in macroscale. Therefore, Fourier’s law that relies on the diffusion approximation is not ideally suitable for describing the phonon transport occurred in nanostructures and/or through nanoscale contact. In the present study, the gray Boltzmann transport equation (BTE) is numerically solved using finite volume method. Based on the gray BTE, phonon transport through the constriction formed by a probe itself as well as the nanoscale contact between the probe tip and the specimen is investigated. The interaction of a probe and a specimen (i.e., treated as a substrate) is explored qualitatively by analyzing the temperature variation in the tip-substrate configuration. Besides, each contribution of a probe tip, tip-substrate interface, and a substrate to the thermal resistance are analyzed for wide ranges of the constriction ratio of the probe. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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Open AccessArticle

Multi-Shaped Ag Nanoparticles in the Plasmonic Layer of Dye-Sensitized Solar Cells for Increased Power Conversion Efficiency

by Da Hyun Song, Ho-Sub Kim, Jung Sang Suh, Bong-Hyun Jun and Won-Yeop Rho

Nanomaterials 2017, 7(6), 136; https://doi.org/10.3390/nano7060136 - 4 Jun 2017

Cited by 26 | Viewed by 6731

Abstract

The use of dye-sensitized solar cells (DSSCs) is widespread owing to their high power conversion efficiency (PCE) and low cost of manufacturing. We prepared multi-shaped Ag nanoparticles (NPs) and introduced them into DSSCs to further enhance their PCE. The maximum absorption wavelength of [...] Read more.

The use of dye-sensitized solar cells (DSSCs) is widespread owing to their high power conversion efficiency (PCE) and low cost of manufacturing. We prepared multi-shaped Ag nanoparticles (NPs) and introduced them into DSSCs to further enhance their PCE. The maximum absorption wavelength of the multi-shaped Ag NPs is 420 nm, including the shoulder with a full width at half maximum (FWHM) of 121 nm. This is a broad absorption wavelength compared to spherical Ag NPs, which have a maximum absorption wavelength of 400 nm without the shoulder of 61 nm FWHM. Therefore, when multi-shaped Ag NPs with a broader plasmon-enhanced absorption were coated on a mesoporous TiO₂ layer on a layer-by-layer structure in DSSCs, the PCE increased from 8.44% to 10.22%, equivalent to an improvement of 21.09% compared to DSSCs without a plasmonic layer. To confirm the plasmon-enhanced effect on the composite film structure in DSSCs, the PCE of DSSCs based on the composite film structure with multi-shaped Ag NPs increased from 8.58% to 10.34%, equivalent to an improvement of 20.51% compared to DSSCs without a plasmonic layer. This concept can be applied to perovskite solar cells, hybrid solar cells, and other solar cells devices. Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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2 pages, 165 KiB

Open AccessCorrection

Correction: Chatterjee, A.; et al. Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li–O₂ Batteries. Nanomaterials 2018, 8, 308

by Amrita Chatterjee, Siu Wing Or and Yulin Cao

Nanomaterials 2018, 8(10), 748; https://doi.org/10.3390/nano8100748 - 20 Sep 2018

Cited by 1 | Viewed by 2459

Abstract

The authors wish to add the following information to this paper [...] Full article

(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)

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