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14 pages, 2164 KiB

Open AccessCommunication

On the Use of Laser Fragmentation for the Synthesis of Ligand-Free Ultra-Small Iron Nanoparticles in Various Liquid Environments

by Ondřej Havelka, Martin Cvek, Michal Urbánek, Dariusz Łukowiec, Darina Jašíková, Michal Kotek, Miroslav Černík, Vincenzo Amendola and Rafael Torres-Mendieta

Nanomaterials 2021, 11(6), 1538; https://doi.org/10.3390/nano11061538 - 10 Jun 2021

Cited by 4 | Viewed by 2963

Abstract

Traditionally, the synthesis of nanomaterials in the ultra-small size regime (1–3 nm diameter) has been linked with the employment of excessive amounts of hazardous chemicals, inevitably leading to significant environmentally detrimental effects. In the current work, we demonstrate the potential of laser fragmentation [...] Read more.

Traditionally, the synthesis of nanomaterials in the ultra-small size regime (1–3 nm diameter) has been linked with the employment of excessive amounts of hazardous chemicals, inevitably leading to significant environmentally detrimental effects. In the current work, we demonstrate the potential of laser fragmentation in liquids (LFL) to produce highly pure and stable iron ultra-small nanoparticles. This is carried out by reducing the size of carbonyl iron microparticles dispersed in various polar solvents (water, ethanol, ethylene glycol, polyethylene glycol 400) and liquid nitrogen. The explored method enables the fabrication of ligand-free iron oxide ultra-small nanoparticles with diameter in the 1–3 nm range, a tight size distribution, and excellent hydrodynamic stability (zeta potential > 50 mV). The generated particles can be found in different forms, including separated ultra-small NPs, ultra-small NPs forming agglomerates, and ultra-small NPs together with zero-valent iron, iron carbide, or iron oxide NPs embedded in matrices, depending on the employed solvent and their dipolar moment. The LFL technique, aside from avoiding chemical waste generation, does not require any additional chemical agent, other than the precursor microparticles immersed in the corresponding solvent. In contrast to their widely exploited chemically synthesized counterparts, the lack of additives and chemical residuals may be of fundamental interest in sectors requiring colloidal stability and the largest possible number of chemically active sites, making the presented pathway a promising alternative for the clean design of new-generation nanomaterials. Full article

(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Nanofabrication and Nanomanufacturing)

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15 pages, 5381 KiB

Open AccessFeature PaperArticle

Tailoring Mesoporous Titania Features by Ultrasound-Assisted Sol-Gel Technique: Effect of Surfactant/Titania Precursor Weight Ratio

by Elvira Mahu, Cristina Giorgiana Coromelci, Doina Lutic, Iuliean Vasile Asaftei, Liviu Sacarescu, Valeria Harabagiu and Maria Ignat

Nanomaterials 2021, 11(5), 1263; https://doi.org/10.3390/nano11051263 - 11 May 2021

Cited by 11 | Viewed by 2017

Abstract

A mesoporous titania structure has been prepared using the ultrasound-assisted sol-gel technique in order to find out a way to tailor its structure. The TiO₂ obtained was compared to the same version of titania but synthesized by a conventional sol-gel method with [...] Read more.

A mesoporous titania structure has been prepared using the ultrasound-assisted sol-gel technique in order to find out a way to tailor its structure. The TiO₂ obtained was compared to the same version of titania but synthesized by a conventional sol-gel method with the objective of understanding the effect of ultrasound in the synthesis process. All synthesis experiments were focused on the preparation of a titania photocatalyst. Thus, the anatase photocatalytic active phase of titania was proven by X-ray diffraction. Additionally, the ultrasonation treatment proved to increase the crystallinity of titania samples, being one of the requirements to having good photocatalytic activity for titania. The influence of surfactant/titania precursor weight ratio on the structural (XRD), textural (N₂-sorption measurements), morphological (TEM), surface chemistry (FTIR) and optical properties (UVDR) was investigated. It was observed that the crystallite size, specific surface area, band gap energy and even photocatalytic activity was affected by the synergism occurring between cavitation effect and the surfactant/titania precursor weight ratio. The study yielded interesting great results that could be considered for further application of ultrasound to tailor mesoporous titania features via sol-gel soft template synthesis, against conventional sol-gel process. Full article

(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Nanofabrication and Nanomanufacturing)

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23 pages, 7617 KiB

Open AccessFeature PaperArticle

Numerical Modelling of the Optical Properties of Plasmonic and Latex Nanoparticles to Improve the Detection Limit of Immuno-Turbidimetric Assays

by Giuliano Coletta and Vincenzo Amendola

Nanomaterials 2021, 11(5), 1147; https://doi.org/10.3390/nano11051147 - 28 Apr 2021

Cited by 7 | Viewed by 3059

Abstract

Turbidimetric assays with latex nanoparticles are widely applied for the detection of biological analytes, because of their rapidity, low cost, reproducibility, and automatization. However, the detection limit can be lowered only at the price of a reduced dynamic range, due to the rapid [...] Read more.

Turbidimetric assays with latex nanoparticles are widely applied for the detection of biological analytes, because of their rapidity, low cost, reproducibility, and automatization. However, the detection limit can be lowered only at the price of a reduced dynamic range, due to the rapid saturation of the light scattering signal at high analyte concentration. Here, we use numerical calculations to investigate the possibility of increasing the performance of immuno-turbidimetric assays without compromising the measurement dynamic range, by combining plasmonic (gold, silver) and latex nanoparticles. Our modelling results show that plasmonic nanoparticles are compatible with a large signal change even when small aggregates are formed, i.e., at low analyte concentration. The working principle relies on the remarkable modification of the surface plasmon band when noble metal nanoparticles form oligomers, and also when latex particles are included in the aggregate. At high analyte concentration, when larger aggregates form, the latex particles can provide the required linear response of standard immuno-turbidimetric assays. Thus, the combination of the two components can be a successful strategy to improve the detection limit and the dynamic range, while maintaining all the advantages of the homogeneous immuno-turbidimetric assays. Full article

(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Nanofabrication and Nanomanufacturing)

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13 pages, 2717 KiB

Open AccessArticle

Fabrication and Characterization of Double- and Single-Clamped CuO Nanowire Based Nanoelectromechanical Switches

by Liga Jasulaneca, Alexander I. Livshits, Raimonds Meija, Jelena Kosmaca, Raitis Sondors, Matiss M. Ramma, Daniels Jevdokimovs, Juris Prikulis and Donats Erts

Nanomaterials 2021, 11(1), 117; https://doi.org/10.3390/nano11010117 - 06 Jan 2021

Cited by 10 | Viewed by 2098

Abstract

Electrostatically actuated nanoelectromechanical (NEM) switches hold promise for operation with sharply defined ON/OFF states, high ON/OFF current ratio, low OFF state power consumption, and a compact design. The present challenge for the development of nanoelectromechanical system (NEMS) technology is fabrication of single nanowire [...] Read more.

Electrostatically actuated nanoelectromechanical (NEM) switches hold promise for operation with sharply defined ON/OFF states, high ON/OFF current ratio, low OFF state power consumption, and a compact design. The present challenge for the development of nanoelectromechanical system (NEMS) technology is fabrication of single nanowire based NEM switches. In this work, we demonstrate the first application of CuO nanowires as NEM switch active elements. We develop bottom-up and top-down approaches for NEM switch fabrication, such as CuO nanowire synthesis, lithography, etching, dielectrophoretic alignment of nanowires on electrodes, and nanomanipulations for building devices that are suitable for scalable production. Theoretical modelling finds the device geometry that is necessary for volatile switching. The modelling results are validated by constructing gateless double-clamped and single-clamped devices on-chip that show robust and repeatable switching. The proposed design and fabrication route enable the scalable integration of bottom-up synthesized nanowires in NEMS. Full article

(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Nanofabrication and Nanomanufacturing)

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19 pages, 2300 KiB

Open AccessArticle

Comprehensive Density Functional Theory Studies of Vibrational Spectra of Carbonates

by Yurii N. Zhuravlev and Victor V. Atuchin

Nanomaterials 2020, 10(11), 2275; https://doi.org/10.3390/nano10112275 - 17 Nov 2020

Cited by 32 | Viewed by 2954

Abstract

Within the framework of the density functional theory (DFT) and the hybrid functional B3LYP by means of the CRYSTAL17 program code, the wavenumbers and intensities of normal oscillations of MgCO₃, CaCO₃, ZnCO₃, CdCO₃ in the structure [...] Read more.

Within the framework of the density functional theory (DFT) and the hybrid functional B3LYP by means of the CRYSTAL17 program code, the wavenumbers and intensities of normal oscillations of MgCO₃, CaCO₃, ZnCO₃, CdCO₃ in the structure of calcite; CaMg(CO₃)₂, CdMg(CO₃)₂, CaMn(CO₃)₂, CaZn(CO₃)₂ in the structure of dolomite; BaMg(CO₃)₂ in the structure of the norsethite type; and CaCO₃, SrCO₃, BaCO₃, and PbCO₃ in the structure of aragonite were calculated. Infrared absorption and Raman spectra were compared with the known experimental data of synthetic and natural crystals. For lattice and intramolecular modes, linear dependences on the radius and mass of the metal cation are established. The obtained dependences have predictive power and can be used to study solid carbonate solutions. For trigonal and orthorhombic carbonates, the linear dependence of wavenumbers on the cation radius R_M (or M–O distance) is established for the infrared in-plane bending mode: 786.2–65.88·R_M and Raman in-plane stretching mode: 768.5–53.24·R_M, with a correlation coefficient of 0.87. Full article

(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Nanofabrication and Nanomanufacturing)

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Review

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31 pages, 22082 KiB

Open AccessEditor’s ChoiceReview

Materials, Electrical Performance, Mechanisms, Applications, and Manufacturing Approaches for Flexible Strain Sensors

by Fei Han, Min Li, Huaiyu Ye and Guoqi Zhang

Nanomaterials 2021, 11(5), 1220; https://doi.org/10.3390/nano11051220 - 05 May 2021

Cited by 39 | Viewed by 6742

Abstract

With the recent great progress made in flexible and wearable electronic materials, the upcoming next generation of skin-mountable and implantable smart devices holds extensive potential applications for the lifestyle modifying, including personalized health monitoring, human-machine interfaces, soft robots, and implantable biomedical devices. As [...] Read more.

With the recent great progress made in flexible and wearable electronic materials, the upcoming next generation of skin-mountable and implantable smart devices holds extensive potential applications for the lifestyle modifying, including personalized health monitoring, human-machine interfaces, soft robots, and implantable biomedical devices. As a core member within the wearable electronics family, flexible strain sensors play an essential role in the structure design and functional optimization. To further enhance the stretchability, flexibility, sensitivity, and electricity performances of the flexible strain sensors, enormous efforts have been done covering the materials design, manufacturing approaches and various applications. Thus, this review summarizes the latest advances in flexible strain sensors over recent years from the material, application, and manufacturing strategies. Firstly, the critical parameters measuring the performances of flexible strain sensors and materials development contains different flexible substrates, new nano- and hybrid- materials are introduced. Then, the developed working mechanisms, theoretical analysis, and computational simulation are presented. Next, based on different material design, diverse applications including human motion detection and health monitoring, soft robotics and human-machine interface, implantable devices, and biomedical applications are highlighted. Finally, synthesis consideration of the massive production industry of flexible strain sensors in the future; different fabrication approaches that are fully expected are classified and discussed. Full article

(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Nanofabrication and Nanomanufacturing)

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22 pages, 3602 KiB

Open AccessReview

Charge Transfer and Biocompatibility Aspects in Conducting Polymer-Based Enzymatic Biosensors and Biofuel Cells

by Simonas Ramanavicius and Arunas Ramanavicius

Nanomaterials 2021, 11(2), 371; https://doi.org/10.3390/nano11020371 - 02 Feb 2021

Cited by 117 | Viewed by 6220

Abstract

Charge transfer (CT) is a very important issue in the design of biosensors and biofuel cells. Some nanomaterials can be applied to facilitate the CT in these bioelectronics-based devices. In this review, we overview some CT mechanisms and/or pathways that are the most [...] Read more.

Charge transfer (CT) is a very important issue in the design of biosensors and biofuel cells. Some nanomaterials can be applied to facilitate the CT in these bioelectronics-based devices. In this review, we overview some CT mechanisms and/or pathways that are the most frequently established between redox enzymes and electrodes. Facilitation of indirect CT by the application of some nanomaterials is frequently applied in electrochemical enzymatic biosensors and biofuel cells. More sophisticated and still rather rarely observed is direct charge transfer (DCT), which is often addressed as direct electron transfer (DET), therefore, DCT/DET is also targeted and discussed in this review. The application of conducting polymers (CPs) for the immobilization of enzymes and facilitation of charge transfer during the design of biosensors and biofuel cells are overviewed. Significant attention is paid to various ways of synthesis and application of conducting polymers such as polyaniline, polypyrrole, polythiophene poly(3,4-ethylenedioxythiophene). Some DCT/DET mechanisms in CP-based sensors and biosensors are discussed, taking into account that not only charge transfer via electrons, but also charge transfer via holes can play a crucial role in the design of bioelectronics-based devices. Biocompatibility aspects of CPs, which provides important advantages essential for implantable bioelectronics, are discussed. Full article

(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Nanofabrication and Nanomanufacturing)

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27 pages, 7924 KiB

Open AccessReview

Ultracentrifugation Techniques for the Ordering of Nanoparticles

by Xufeng Xu and Helmut Cölfen

Nanomaterials 2021, 11(2), 333; https://doi.org/10.3390/nano11020333 - 27 Jan 2021

Cited by 17 | Viewed by 5024

Abstract

A centrifugal field can provide an external force for the ordering of nanoparticles. Especially with the knowledge from in-situ characterization by analytical (ultra)centrifugation, nanoparticle ordering can be rationally realized in preparative (ultra)centrifugation. This review summarizes the work back to the 1990s, where intuitive [...] Read more.

A centrifugal field can provide an external force for the ordering of nanoparticles. Especially with the knowledge from in-situ characterization by analytical (ultra)centrifugation, nanoparticle ordering can be rationally realized in preparative (ultra)centrifugation. This review summarizes the work back to the 1990s, where intuitive use of centrifugation was achieved for the fabrication of colloidal crystals to the very recent work where analytical (ultra)centrifugation is employed to tailor-make concentration gradients for advanced materials. This review is divided into three main parts. In the introduction part, the history of ordering microbeads in gravity is discussed and with the size of particles reduced to nanometers, a centrifugal field is necessary. In the next part, the research on the ordering of nanoparticles in analytical and preparative centrifugation in recent decades is described. In the last part, the applications of the functional materials, fabricated from centrifugation-induced nanoparticle superstructures are briefly discussed. Full article

(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Nanofabrication and Nanomanufacturing)

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20 pages, 5546 KiB

Open AccessReview

Generation of Supra-Wavelength Grooves in Femtosecond Laser Surface Structuring of Silicon

by Jijil JJ Nivas and Salvatore Amoruso

Nanomaterials 2021, 11(1), 174; https://doi.org/10.3390/nano11010174 - 12 Jan 2021

Cited by 26 | Viewed by 3335

Abstract

Extensive research work has been carried out on the generation and application of laser-induced periodic surface structures (LIPSS). LIPSS with a sub-wavelength period generated by femtosecond laser irradiation, generally indicated as ripples, have been extensively investigated. Instead, the other ordered surface structures characterized [...] Read more.

Extensive research work has been carried out on the generation and application of laser-induced periodic surface structures (LIPSS). LIPSS with a sub-wavelength period generated by femtosecond laser irradiation, generally indicated as ripples, have been extensively investigated. Instead, the other ordered surface structures characterized by a supra-wavelength period, indicated as grooves, have been much less studied. Grooves typically form at larger irradiance levels or for higher number of laser pulses. Here, we report a comprehensive overview of recent investigations on the supra-wavelength grooves formed on crystalline silicon irradiated by femtosecond laser pulses. The authors’ recent experimental work is mainly addressed giving an explicit picture of the grooves generation process, namely illustrating the influence of the various experimental parameters, including, e.g., polarization, wavelength, fluence and repetition rate of the laser beam as well as number of laser pulses hitting the surface of the material. The effect of irradiation of a static or moving target and of the environmental conditions (e.g., vacuum or air ambient) will also be discussed. Finally, possible mechanisms envisaged to explain grooves formation and still open issues are briefly discussed. Full article

(This article belongs to the Special Issue 10th Anniversary of Nanomaterials—Recent Advances in Nanofabrication and Nanomanufacturing)

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