Nanomaterials

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3 pages, 180 KiB

Open AccessEditorial

Functional Nanoporous Materials

by Christian Weinberger and Michael Tiemann

Nanomaterials 2020, 10(4), 699; https://doi.org/10.3390/nano10040699 - 7 Apr 2020

Cited by 1 | Viewed by 2346

Abstract

This Special Issue on “Functional Nanoporous Materials” in the MDPI journal nanomaterials features seven original papers [...] Full article

(This article belongs to the Special Issue Functional Nanoporous Materials)

Research

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16 pages, 2869 KiB

Open AccessArticle

Investigation of Well-Defined Pinholes in TiO₂ Electron Selective Layers Used in Planar Heterojunction Perovskite Solar Cells

by Muhammad Talha Masood, Syeda Qudsia, Mahboubeh Hadadian, Christian Weinberger, Mathias Nyman, Christian Ahläng, Staffan Dahlström, Maning Liu, Paola Vivo, Ronald Österbacka and Jan-Henrik Smått

Nanomaterials 2020, 10(1), 181; https://doi.org/10.3390/nano10010181 - 20 Jan 2020

Cited by 22 | Viewed by 5440

Abstract

The recently introduced perovskite solar cell (PSC) technology is a promising candidate for providing low-cost energy for future demands. However, one major concern with the technology can be traced back to morphological defects in the electron selective layer (ESL), which deteriorates the solar [...] Read more.

The recently introduced perovskite solar cell (PSC) technology is a promising candidate for providing low-cost energy for future demands. However, one major concern with the technology can be traced back to morphological defects in the electron selective layer (ESL), which deteriorates the solar cell performance. Pinholes in the ESL may lead to an increased surface recombination rate for holes, if the perovskite absorber layer is in contact with the fluorine-doped tin oxide (FTO) substrate via the pinholes. In this work, we used sol-gel-derived mesoporous TiO₂ thin films prepared by block co-polymer templating in combination with dip coating as a model system for investigating the effect of ESL pinholes on the photovoltaic performance of planar heterojunction PSCs. We studied TiO₂ films with different porosities and film thicknesses, and observed that the induced pinholes only had a minor impact on the device performance. This suggests that having narrow pinholes with a diameter of about 10 nm in the ESL is in fact not detrimental for the device performance and can even, to some extent improve their performance. A probable reason for this is that the narrow pores in the ordered structure do not allow the perovskite crystals to form interconnected pathways to the underlying FTO substrate. However, for ultrathin (~20 nm) porous layers, an incomplete ESL surface coverage of the FTO layer will further deteriorate the device performance. Full article

(This article belongs to the Special Issue Functional Nanoporous Materials)

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18 pages, 4703 KiB

Open AccessArticle

Structural and Electrical Studies for Birnessite-Type Materials Synthesized by Solid-State Reactions

by Nayda P. Arias, María E. Becerra and Oscar Giraldo

Nanomaterials 2019, 9(8), 1156; https://doi.org/10.3390/nano9081156 - 12 Aug 2019

Cited by 22 | Viewed by 3620

Abstract

The focus of this paper is centered on the thermal reduction of KMnO₄ at controlled temperatures of 400 and 800 °C. The materials under study were characterized by atomic absorption spectroscopy, thermogravimetric analysis, average oxidation state of manganese, nitrogen adsorption–desorption, and impedance [...] Read more.

The focus of this paper is centered on the thermal reduction of KMnO₄ at controlled temperatures of 400 and 800 °C. The materials under study were characterized by atomic absorption spectroscopy, thermogravimetric analysis, average oxidation state of manganese, nitrogen adsorption–desorption, and impedance spectroscopy. The structural formulas, found as a result of these analyses, were

K_{0.29}^{+} (M n_{0.84}^{4 +} M n_{0.16}^{3 +}) O_{2.07} \cdot 0.61 H_{2} O

and

K_{0.48}^{+} (M n_{0.64}^{4 +} M n_{0.36}^{3 +}) O_{2.06} \cdot 0.50 H_{2} O

. The N₂ adsorption–desorption isotherms show the microporous and mesoporous nature of the structure. Structural analysis showed that synthesis temperature affects the crystal size and symmetry, varying their electrical properties. Impedance spectroscopy (IS) was used to measure the electrical properties of these materials. The measurements attained, as a result of IS, show that these materials have both electronic and ionic conductivity. The conductivity values obtained at 10 Hz were 4.1250 × 10⁻⁶ and 1.6870 × 10⁻⁴ Ω⁻¹cm⁻¹ for Mn4 at 298 and 423 K respectively. For Mn8, the conductivity values at this frequency were 3.7074 × 10⁻⁷ (298) and 3.9866 × 10⁻⁵ Ω⁻¹cm⁻¹ (423 K). The electrical behavior was associated with electron hopping at high frequencies, and protonic conduction and ionic movement of the K⁺ species, in the interlayer region at low frequencies. Full article

(This article belongs to the Special Issue Functional Nanoporous Materials)

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11 pages, 2261 KiB

Open AccessCommunication

Synthesis of Porous Organic Polymers with Tunable Amine Loadings for CO₂ Capture: Balanced Physisorption and Chemisorption

by Xueying Kong, Shangsiying Li, Maria Strømme and Chao Xu

Nanomaterials 2019, 9(7), 1020; https://doi.org/10.3390/nano9071020 - 17 Jul 2019

Cited by 40 | Viewed by 5682

Abstract

The cross-coupling reaction of 1,3,5-triethynylbenzene with terephthaloyl chloride gives a novel ynone-linked porous organic polymer. Tethering alkyl amine species on the polymer induces chemisorption of CO₂ as revealed by the studies of ex situ infrared spectroscopy. By tuning the amine loading content [...] Read more.

The cross-coupling reaction of 1,3,5-triethynylbenzene with terephthaloyl chloride gives a novel ynone-linked porous organic polymer. Tethering alkyl amine species on the polymer induces chemisorption of CO₂ as revealed by the studies of ex situ infrared spectroscopy. By tuning the amine loading content on the polymer, relatively high CO₂ adsorption capacities, high CO₂-over-N₂ selectivity, and moderate isosteric heat (Q_st) of adsorption of CO₂ can be achieved. Such amine-modified polymers with balanced physisorption and chemisorption of CO₂ are ideal sorbents for post-combustion capture of CO₂ offering both high separation and high energy efficiencies. Full article

(This article belongs to the Special Issue Functional Nanoporous Materials)

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14 pages, 25689 KiB

Open AccessArticle

Growth and Functionalization of Particle-Based Mesoporous Silica Films and Their Usage in Catalysis

by Pei-Hsuan Wu, Peter Mäkie, Magnus Odén and Emma M. Björk

Nanomaterials 2019, 9(4), 562; https://doi.org/10.3390/nano9040562 - 6 Apr 2019

Cited by 10 | Viewed by 3985

Abstract

We report the formation of mesoporous films consisting of SBA-15 particles grown directly onto substrates and their usage as catalysts in esterification of acetic acid and ethanol. The film thickness was altered between 80 nm and 750 nm by adding NH₄F [...] Read more.

We report the formation of mesoporous films consisting of SBA-15 particles grown directly onto substrates and their usage as catalysts in esterification of acetic acid and ethanol. The film thickness was altered between 80 nm and 750 nm by adding NH₄F to the synthesis solution. The salt also affects the formation rate of the particles, and substrates must be added during the formation of the siliceous network in the solution. Various substrate functionalizations were tested and hydrophobic substrates are required for a successful film growth. We show that large surfaces (> 75 cm²), as well as 3D substrates, can be homogenously coated. Further, the films were functionalized, either with acetic acid through co-condensation, or by coating the films with a thin carbon layer through exposure to furfuryl alcohol fumes followed by carbonization and sulfonation with H₂SO₄. The carbon-coated film was shown to be an efficient catalyst in the esterification reaction with acetic acid and ethanol. Due to the short, accessible mesopores, chemical variability, and possibility to homogenously cover large, rough surfaces. the films have a large potential for usage in various applications such as catalysis, sensing, and drug delivery. Full article

(This article belongs to the Special Issue Functional Nanoporous Materials)

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15 pages, 5424 KiB

Open AccessArticle

Near-Infrared Surface-Enhanced Raman Scattering on Silver-Coated Porous Silicon Photonic Crystals

by Marko Škrabić, Marin Kosović, Marijan Gotić, Lara Mikac, Mile Ivanda and Ozren Gamulin

Nanomaterials 2019, 9(3), 421; https://doi.org/10.3390/nano9030421 - 12 Mar 2019

Cited by 28 | Viewed by 4451

Abstract

Surface-enhanced Raman scattering (SERS) with near-infrared (NIR) excitation offers a safe way for the detection and study of fragile biomolecules. In this work, we present the possibility of using silver-coated porous silicon photonic crystals as SERS substrates for near-infrared (1064 nm) excitation. Due [...] Read more.

Surface-enhanced Raman scattering (SERS) with near-infrared (NIR) excitation offers a safe way for the detection and study of fragile biomolecules. In this work, we present the possibility of using silver-coated porous silicon photonic crystals as SERS substrates for near-infrared (1064 nm) excitation. Due to the deep penetration of NIR light inside silicon, the fabrication of photonic crystals was necessary to quench the band gap photoluminescence of silicon crystal, which acts as mechanical support for the porous layer. Optimal parameters of the immersion plating process that gave maximum enhancement were found and the activity of SERS substrates was tested using rhodamine 6G and crystal violet dye molecules, yielding significant SERS enhancement for off-resonant conditions. To our knowledge, this is the first time that the 1064 nm NIR laser excitation is used for obtaining the SERS effect on porous silicon as a substrate. Full article

(This article belongs to the Special Issue Functional Nanoporous Materials)

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25 pages, 3541 KiB

Open AccessArticle

Vibration and Buckling of Shear Deformable Functionally Graded Nanoporous Metal Foam Nanoshells

by Yufei Zhang and Fei Zhang

Nanomaterials 2019, 9(2), 271; https://doi.org/10.3390/nano9020271 - 15 Feb 2019

Cited by 25 | Viewed by 3263

Abstract

This article aims to investigate free vibration and buckling of functionally graded (FG) nanoporous metal foam (NPMF) nanoshells. The first-order shear deformation (FSD) shell theory is adopted and the theoretical model is formulated by using Mindlin’s most general strain gradient theory, which can [...] Read more.

This article aims to investigate free vibration and buckling of functionally graded (FG) nanoporous metal foam (NPMF) nanoshells. The first-order shear deformation (FSD) shell theory is adopted and the theoretical model is formulated by using Mindlin’s most general strain gradient theory, which can derive several well-known simplified models. The symmetric and unsymmetric nanoporosity distributions are considered for the structural composition. Hamilton’s principle is employed to deduce the governing equations as well as the boundary conditions. Then, via the Navier solution technique, an analytical solution for the free vibration and buckling of FG NPMF nanoshells is presented. Afterwards, a detailed parametric analysis is conducted to highlight the effects of the nanoporosity coefficient, nanoporosity distribution, length scale parameter, and geometrical parameters on the mechanical behaviors of FG NPMF nanoshells. Full article

(This article belongs to the Special Issue Functional Nanoporous Materials)

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11 pages, 2674 KiB

Open AccessArticle

Straightforward Immobilization of Phosphonic Acids and Phosphoric Acid Esters on Mesoporous Silica and Their Application in an Asymmetric Aldol Reaction

by Christian Weinberger, Tatjana Heckel, Patrick Schnippering, Markus Schmitz, Anpeng Guo, Waldemar Keil, Heinrich C. Marsmann, Claudia Schmidt, Michael Tiemann and René Wilhelm

Nanomaterials 2019, 9(2), 249; https://doi.org/10.3390/nano9020249 - 12 Feb 2019

Cited by 17 | Viewed by 5970

Abstract

The combined benefits of moisture-stable phosphonic acids and mesoporous silica materials (SBA-15 and MCM-41) as large-surface-area solid supports offer new opportunities for several applications, such as catalysis or drug delivery. We present a comprehensive study of a straightforward synthesis method via direct immobilization [...] Read more.

The combined benefits of moisture-stable phosphonic acids and mesoporous silica materials (SBA-15 and MCM-41) as large-surface-area solid supports offer new opportunities for several applications, such as catalysis or drug delivery. We present a comprehensive study of a straightforward synthesis method via direct immobilization of several phosphonic acids and phosphoric acid esters on various mesoporous silicas in a Dean–Stark apparatus with toluene as the solvent. Due to the utilization of azeotropic distillation, there was no need to dry phosphonic acids, phosphoric acid esters, solvents, or silicas prior to synthesis. In addition to modeling phosphonic acids, immobilization of the important biomolecule adenosine monophosphate (AMP) on the porous supports was also investigated. Due to the high surface area of the mesoporous silicas, a possible catalytic application based on immobilization of an organocatalyst for an asymmetric aldol reaction is discussed. Full article

(This article belongs to the Special Issue Functional Nanoporous Materials)

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