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22 pages, 1890 KiB

Open AccessArticle

Nanocantilevers with Adjustable Static Deflection and Significantly Tunable Spectrum Resonant Frequencies for Applications in Nanomechanical Mass Sensors

by Ivo Stachiv and Petr Sittner

Nanomaterials 2018, 8(2), 116; https://doi.org/10.3390/nano8020116 - 17 Feb 2018

Cited by 19 | Viewed by 4482

Abstract

Nanocantilevers have become key components of nanomechanical sensors that exploit changes in their resonant frequencies or static deflection in response to the environment. It is necessary that they can operate at a given, but adjustable, resonant frequency and/or static deflection ranges. Here we [...] Read more.

Nanocantilevers have become key components of nanomechanical sensors that exploit changes in their resonant frequencies or static deflection in response to the environment. It is necessary that they can operate at a given, but adjustable, resonant frequency and/or static deflection ranges. Here we propose a new class of nanocantilevers with a significantly tunable spectrum of the resonant frequencies and changeable static deflection utilizing the unique properties of a phase-transforming NiTi film sputtered on the usual nanotechnology cantilever materials. The reversible frequency tuning and the adjustable static deflection are obtained by intentionally changing the Young’s modulus and the interlayer stress of the NiTi film during its phase transformation, while the usual cantilever elastic materials guarantee a high frequency actuation (up to tens of MHz). By incorporating the NiTi phase transformation characteristic into the classical continuum mechanics theory we present theoretical models that account for the nanocantilever frequency shift and variation in static deflection caused by a phase transformation of NiTi film. Due to the practical importance in nanomechanical sensors, we carry out a complete theoretical analysis and evaluate the impact of NiTi film on the cantilever Young’s modulus, static deflection, and the resonant frequencies. Moreover, the importance of proposed NiTi nanocantilever is illustrated on the nanomechanical based mass sensors. Our findings will be of value in the development of advanced nanotechnology sensors with intentionally-changeable physical and mechanical properties. Full article

(This article belongs to the Special Issue Nanomaterials for Sensing Applications)

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13 pages, 3219 KiB

Open AccessArticle

UV-Assisted Photochemical Synthesis of Reduced Graphene Oxide/ZnO Nanowires Composite for Photoresponse Enhancement in UV Photodetectors

by Changsong Chen, Peng Zhou, Na Wang, Yang Ma and Haisheng San

Nanomaterials 2018, 8(1), 26; https://doi.org/10.3390/nano8010026 - 05 Jan 2018

Cited by 33 | Viewed by 6729

Abstract

The weak photon absorption and high recombination rate of electron-hole pairs in disordered zinc oxide nanowires (ZNWs) limit its application in UV photodetection. This limitation can be overcome by introducing graphene sheets to the ZNWs. Herein we report a high-performance photodetector based on [...] Read more.

The weak photon absorption and high recombination rate of electron-hole pairs in disordered zinc oxide nanowires (ZNWs) limit its application in UV photodetection. This limitation can be overcome by introducing graphene sheets to the ZNWs. Herein we report a high-performance photodetector based on one-dimensional (1D) wide band-gap semiconductor disordered ZNWs composited with reduced graphene oxide (RGO) for ultraviolet (UV) photoresponse enhancement. The RGO/ZNWs composites have been successfully synthetized through UV-assisted photochemical reduction of GO in ZNWs suspension. The material characterizations in morphology, Raman scattering, and Ultraviolet-visible light absorption verified the formation of graphene sheets attached in ZNWs network and the enhancement of UV absorption due to the introduction of graphene. In comparison with photodetectors based on pure ZNWs, the photodetectors based on RGO/ZNWs composite exhibit enhanced photoresponse with photocurrent density of 5.87 mA·cm⁻², on/off current ratio of 3.01 × 10⁴, and responsivity of 1.83 A·W⁻¹ when a UV irradiation of 3.26 mW·cm⁻² and 1.0 V bias were used. Theory analysis is also presented to get insight into the inherent mechanisms of separation and transportation of photo-excited carriers in RGO/ZNWs composite. Full article

(This article belongs to the Special Issue Nanomaterials for Sensing Applications)

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7224 KiB

Open AccessArticle

H₂S Sensing by Hybrids Based on Nanocrystalline SnO₂ Functionalized with Cu(II) Organometallic Complexes: The Role of the Ligand Platform

by Marina Rumyantseva, Ekaterina Makeeva, Alexander Gaskov, Nikolay Shepel, Svetlana Peregudova, Andrey Khoroshutin, Sergey Tokarev and Olga Fedorova

Nanomaterials 2017, 7(11), 384; https://doi.org/10.3390/nano7110384 - 09 Nov 2017

Cited by 7 | Viewed by 3924

Abstract

This paper deals with the functionalization of nanocrystalline SnO₂ with Cu(II) complexes with organic ligands, aimed at the improvement of sensor selectivity towards gas molecules. For the synthesis of metalorganic/SnO₂ hybrid material complexes of Cu(II) with phthalocyanine, porphyrinines, bipyridine and azadithiacrown [...] Read more.

This paper deals with the functionalization of nanocrystalline SnO₂ with Cu(II) complexes with organic ligands, aimed at the improvement of sensor selectivity towards gas molecules. For the synthesis of metalorganic/SnO₂ hybrid material complexes of Cu(II) with phthalocyanine, porphyrinines, bipyridine and azadithiacrown etherwere used. The analysis of gas sensor properties showed the possibility of increasing the sensitivity and selectivity of hybrid materials in H₂S detection due to the electron transfer from SnO₂ to an adsorbed organic molecule, which changes during the interaction between H₂S and Cu(II) ions. Full article

(This article belongs to the Special Issue Nanomaterials for Sensing Applications)

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5248 KiB

Open AccessArticle

Regulation of the Electroanalytical Performance of Ultrathin Titanium Dioxide Nanosheets toward Lead Ions by Non-Metal Doping

by Junping Zhang, Jianjun Liao, Fan Yang, Ming Xu and Shiwei Lin

Nanomaterials 2017, 7(10), 327; https://doi.org/10.3390/nano7100327 - 14 Oct 2017

Cited by 13 | Viewed by 4443

Abstract

Three non-metallic elements, sulfur, fluorine, and iodine, were used to dope the ultrathin two-dimensional TiO₂ nanosheets, which would regulate their electroanalytical properties toward heavy metal ions. Among these doped materials, fluorine-doped TiO₂ nanosheets shows the highest electrochemical sensitivity and a superior [...] Read more.

Three non-metallic elements, sulfur, fluorine, and iodine, were used to dope the ultrathin two-dimensional TiO₂ nanosheets, which would regulate their electroanalytical properties toward heavy metal ions. Among these doped materials, fluorine-doped TiO₂ nanosheets shows the highest electrochemical sensitivity and a superior detection limit toward Pb(II) when the doping concentration is 10%. When compared with the bare TiO₂ nanosheets, the sensitivity increased by 102%, and the detection limit decreased by 36.4%. Through combining further electrochemical experiments and density-functional theory calculations, the enhanced electrochemical performance stemming from element doping was then investigated in detail. The theoretical calculation demonstrated that fluorine doping could greatly increase the adsorption energy of Pb(II) on the TiO₂ nanosheets and enhance their loading capacity. Both cyclic voltammetric and electrical impedance spectroscopy analysis indicated the enhanced electron transfer rate on the electrode modified by fluorine-doped TiO₂ nanosheets. Further measurement on the desorption performance showed the better stripping response of Pb(II) on the electrode with TiO₂ nanosheets after fluorine doping, which suggests that fluorine doping is beneficial for Pb(II) diffuse onto the electrode surface for the reduction and stripping reaction. Therefore, the element doping of two-dimensional TiO₂ nanosheets provides a facile method to extend the electronic materials toward detection of heavy metal ions in the environment. Full article

(This article belongs to the Special Issue Nanomaterials for Sensing Applications)

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5328 KiB

Open AccessArticle

Three-Dimensional Porous Nitrogen-Doped NiO Nanostructures as Highly Sensitive NO₂ Sensors

by Van Hoang Luan, Huynh Ngoc Tien, Seung Hyun Hur, Jong Hun Han and Wonoh Lee

Nanomaterials 2017, 7(10), 313; https://doi.org/10.3390/nano7100313 - 11 Oct 2017

Cited by 21 | Viewed by 5605

Abstract

Nickel oxide has been widely used in chemical sensing applications, because it has an excellent p-type semiconducting property with high chemical stability. Here, we present a novel technique of fabricating three-dimensional porous nitrogen-doped nickel oxide nanosheets as a highly sensitive NO₂ sensor. [...] Read more.

Nickel oxide has been widely used in chemical sensing applications, because it has an excellent p-type semiconducting property with high chemical stability. Here, we present a novel technique of fabricating three-dimensional porous nitrogen-doped nickel oxide nanosheets as a highly sensitive NO₂ sensor. The elaborate nanostructure was prepared by a simple and effective hydrothermal synthesis method. Subsequently, nitrogen doping was achieved by thermal treatment with ammonia gas. When the p-type dopant, i.e., nitrogen atoms, was introduced in the three-dimensional nanostructures, the nickel-oxide-nanosheet-based sensor showed considerable NO₂ sensing ability with two-fold higher responsivity and sensitivity compared to non-doped nickel-oxide-based sensors. Full article

(This article belongs to the Special Issue Nanomaterials for Sensing Applications)

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3823 KiB

Open AccessArticle

Reduced Graphene Oxides: Influence of the Reduction Method on the Electrocatalytic Effect towards Nucleic Acid Oxidation

by Daniela F. Báez, Helena Pardo, Ignacio Laborda, José F. Marco, Claudia Yáñez and Soledad Bollo

Nanomaterials 2017, 7(7), 168; https://doi.org/10.3390/nano7070168 - 04 Jul 2017

Cited by 45 | Viewed by 5174

Abstract

For the first time a critical analysis of the influence that four different graphene oxide reduction methods have on the electrochemical properties of the resulting reduced graphene oxides (RGOs) is reported. Starting from the same graphene oxide, chemical (CRGO), hydrothermal (hTRGO), electrochemical (ERGO), [...] Read more.

For the first time a critical analysis of the influence that four different graphene oxide reduction methods have on the electrochemical properties of the resulting reduced graphene oxides (RGOs) is reported. Starting from the same graphene oxide, chemical (CRGO), hydrothermal (hTRGO), electrochemical (ERGO), and thermal (TRGO) reduced graphene oxide were produced. The materials were fully characterized and the topography and electroactivity of the resulting glassy carbon modified electrodes were also evaluated. An oligonucleotide molecule was used as a model of DNA electrochemical biosensing. The results allow for the conclusion that TRGO produced the RGOs with the best electrochemical performance for oligonucleotide electroanalysis. A clear shift in the guanine oxidation peak potential to lower values (~0.100 V) and an almost two-fold increase in the current intensity were observed compared with the other RGOs. The electrocatalytic effect has a multifactorial explanation because the TRGO was the material that presented a higher polydispersity and lower sheet size, thus exposing a larger quantity of defects to the electrode surface, which produces larger physical and electrochemical areas. Full article

(This article belongs to the Special Issue Nanomaterials for Sensing Applications)

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2951 KiB

Open AccessArticle

A Large-Area Nanoplasmonic Sensor Fabricated by Rapid Thermal Annealing Treatment for Label-Free and Multi-Point Immunoglobulin Sensing

by Hana Tzu-Han Lin, Chuan-Kai Yang, Chi-Chen Lin, Albert Meng-Hsin Wu, Lon A. Wang and Nien-Tsu Huang

Nanomaterials 2017, 7(5), 100; https://doi.org/10.3390/nano7050100 - 02 May 2017

Cited by 12 | Viewed by 5000

Abstract

Immunoglobulins are important biomarkers to evaluate the immune status or development of infectious diseases. To provide timely clinical treatments, it is important to continuously monitor the level of multiple immunoglobulins. Localized surface plasmon resonance (LSPR)-based nanoplasmonic sensors have been demonstrated for multiplex immunoglobulins [...] Read more.

Immunoglobulins are important biomarkers to evaluate the immune status or development of infectious diseases. To provide timely clinical treatments, it is important to continuously monitor the level of multiple immunoglobulins. Localized surface plasmon resonance (LSPR)-based nanoplasmonic sensors have been demonstrated for multiplex immunoglobulins detection. However, the sensor fabrication process is usually slow and complicated, so it is not accessible for large-area and batch fabrication. Herein, we report a large-area (2 cm × 2 cm) nanofabrication method using physical vapor deposition followed by a rapid thermal annealing treatment. To optimize the sensor performance, we systematically characterized three fabrication conditions, including (1) the deposition thickness; (2) the maximum annealing temperature, and (3) the annealing time. The corresponding absorbance spectrum profile and surface morphology of the nanostructures were observed by a UV-VIS spectrometer and atomic force microscopy. We then tested the sensitivity of the sensor using a glucose solution at different concentrations. The results showed that the sensor with 10 nm gold deposition thickness under 5-min 900 °C rapid thermal annealing can achieve the highest sensitivity (189 nm RIU⁻¹). Finally, we integrated this nanoplasmonic sensor with a microchannel and a motorized stage to perform a 10-spot immunoglobulin detection in 50 min. Based on its real-time, dynamic and multi-point analyte detection capability, the nanoplasmonic sensor has the potential to be applied in high-throughput or multiplex immunoassay analysis, which would be beneficial for disease diagnosis or biomedical research in a simple and cost-effective platform. Full article

(This article belongs to the Special Issue Nanomaterials for Sensing Applications)

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5001 KiB

Open AccessArticle

Calcination Method Synthesis of SnO2/g-C3N4 Composites for a High-Performance Ethanol Gas Sensing Application

by Jianliang Cao, Cong Qin, Yan Wang, Bo Zhang, Yuxiao Gong, Huoli Zhang, Guang Sun, Hari Bala and Zhanying Zhang

Nanomaterials 2017, 7(5), 98; https://doi.org/10.3390/nano7050098 - 29 Apr 2017

Cited by 40 | Viewed by 7413

Abstract

The SnO₂/g-C₃N₄ composites were synthesized via a facile calcination method by using SnCl₄·5H₂O and urea as the precursor. The structure and morphology of the as-synthesized composites were characterized by the techniques of X-ray diffraction [...] Read more.

The SnO₂/g-C₃N₄ composites were synthesized via a facile calcination method by using SnCl₄·5H₂O and urea as the precursor. The structure and morphology of the as-synthesized composites were characterized by the techniques of X-ray diffraction (XRD), the field-emission scanning electron microscopy and transmission electron microscopy (FESEM and TEM), energy dispersive spectrometry (EDS), thermal gravity and differential thermal analysis (TG-DTA), and N₂-sorption. The analysis results indicated that the as-synthesized samples possess the two dimensional structure. Additionally, the SnO₂ nanoparticles were highly dispersed on the surface of the g-C₃N₄ nanosheets. The gas-sensing performance of the as-synthesized composites for different gases was tested. Moreover, the composite with 7 wt % g-C₃N₄ content (SnO₂/g-C₃N₄-7) exhibits an admirable gas-sensing property to ethanol, which possesses a higher response and better selectivity than that of the pure SnO2-based sensor. The high surface area of the SnO2/g-C3N4 composite and the good electronic characteristics of the two dimensional graphitic carbon nitride are in favor of the elevated gas-sensing property. Full article

(This article belongs to the Special Issue Nanomaterials for Sensing Applications)

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Review

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4737 KiB

Open AccessFeature PaperReview

Lanthanide-Doped Nanoparticles for Diagnostic Sensing

by Song Yeul Lee, Min Lin, Aeju Lee and Yong Il Park

Nanomaterials 2017, 7(12), 411; https://doi.org/10.3390/nano7120411 - 23 Nov 2017

Cited by 39 | Viewed by 7982

Abstract

Lanthanide-doped nanoparticles exhibit unique optical properties, such as a long luminescence lifetime (up to several milliseconds), sharp emission peaks, and upconversion luminescence over the range of wavelengths from near-infrared to visible. Exploiting these optical properties, lanthanide-doped nanoparticles have been widely utilized for cellular [...] Read more.

Lanthanide-doped nanoparticles exhibit unique optical properties, such as a long luminescence lifetime (up to several milliseconds), sharp emission peaks, and upconversion luminescence over the range of wavelengths from near-infrared to visible. Exploiting these optical properties, lanthanide-doped nanoparticles have been widely utilized for cellular and small animal imaging with the absence of background autofluorescence. In addition, these nanoparticles have advantages of high signal-to-noise ratio for highly sensitive and selective diagnostic detection. In this review, we summarize and discuss recent progress in the development of highly sensitive diagnostic methods using lanthanide-doped nanoparticles. Combined with a smartphone, portable luminescence detecting platforms could be widely applied in point-of-care tests. Full article

(This article belongs to the Special Issue Nanomaterials for Sensing Applications)

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