scholarly journals Size control and shape evolution of single-twinned platinum nanocrystals in a room temperature colloidal synthesis

CrystEngComm ◽  
2014 ◽  
Vol 16 (42) ◽  
pp. 9907-9914 ◽  
Author(s):  
Milena Osmić ◽  
Joanna Kolny-Olesiak ◽  
Katharina Al-Shamery
Keyword(s):  
Room Temperature ◽  
Size Control ◽  
Colloidal Synthesis ◽  
Shape Evolution ◽  
Platinum Nanocrystals

Device Applications of Solution Processed MIR Semiconductor Nanocrystal Thin Films

2021 ◽  
Author(s):  
◽  
Matt Cryer
Keyword(s):  
Thermal Imaging ◽  
Room Temperature ◽  
Spray Deposition ◽  
Low Cost ◽  
Semiconductor Nanocrystals ◽  
Colloidal Synthesis ◽  
Noisy Environment ◽  
Air Exposure ◽  
Solution Processed

<p>Colloidal semiconductor nanocrystals (NCs) with bandgaps less than 1 eV allow the development of mid wave infrared (MIR) sensitive detectors that exploit the benefits of colloidal materials, primarily bandgap selection and solution deposition. Additionally, the electrical behaviour of these films can be examined for characteristics that can increase the functionality of NC based detectors.  The production of devices that are designed to be competitive as ultra-low-cost, room temperature MIR detectors, operating with photonic, rather than thermal detection is detailed. The evolution of the colloidal synthesis, spray deposition methods, substrate materials and post deposition treatments used here lead to highly robust and high performing devices. These devices demonstrate a “colour” sensitivity down to 300 nm in the MIR (≈10 % of scale), with superior responsivities for this class of device, up to 0.9 AW⁻¹, and competitive specific detectivity up to 8 × 10⁹ Jones at 200 Hz and 300 K. Furthermore, these devices utilise a cheap and robust substrate material that allows operation after deformation up to 45 ° without degradation over many cycles. These devices offer a template for ultra-low-cost MIR detectors with performance that rivals microbolometers but with better measurement speed and spectral sensitivity. As such these devices showcase the key advantages of using colloidal NCs in MIR applications.  Planar and fully air processed thin film devices that demonstrate photo-induced memristive behaviour and can be used as a transistors, photode-tectors or memory devices are investigated. Following long term (60 h) air exposure, unpackaged NC films develop reliable memristive characteristics in tandem with temperature, gate and photoresponse. On/off ratios of more than 50 are achieved and the devices show long term stability, producing repeatable metrics over days of measurement. The on/off behaviour is shown to be dependent on previous charge flow and carrier density, implying memristive rather than switching behaviour. These observations are described within a long term trap filling model. This work represents an advance in the integration of NC films into electronic devices, which may lead to the development of multi-functional electronic components.  Building on the previous work the steps taken to move from a planar device, that works well in controlled conditions, to a multi-pixel sensor that can demonstrate MIR video imaging at room temperature in a noisy environment are shown. This is achieved with a 15 pixel detector that consists only of a polymer substrate and solution patterned NC pixels. This device can detect a 373 K object with the device at 298 K in a noisy environment. This performance is enabled by photogain at 5 V bias that reaches a maximum External Quantum Efficiency (EQE) of 1940 ± 290 % for a pixel with a 3.3 µm bandgap. Through the use of four separate bandgaps it is shown that “multicolour” thermal imaging systems can deliver another layer of information, on top of intensity, to the user. The behaviour of the system is examined under use and it is shown that the photoconductive device behaves as expected with regards to bias, and that trap enabled gain is sensitive to total incident flux, more than the spectral energy distribution of the target. Finally, it is shown that solution patterned QD fabrication methods can deliver electrical reproducibility between pixels that is sufficient to allow an imaging plane of multiple pixels.  The somewhat neglected tin chalcogenide semiconductor nanocrystals are investigated and inverse MIR detection at room temperature is demonstrated with planar, solution and airprocessed PbSnTe and SnTe QD devices. The detection mechanism is shown to be mediated by an interaction between MIR radiation and the vibrational stretches of adsorbed hydroxyl species at the oxdised NC surface. Devices are shown to possess mAW⁻¹ responsivity via a reduction in film conductance due to MIR radiation and, unlike classic MIR photoconductors, are unaffected by visible wavelengths. As such these devices offer the possibility of MIR thermal imaging that has an intrinsic solution to the blinding caused by higher energy light sources.  In summary, it is shown that semiconductor NCs with an all ambient fully solution processed deposition and ligand exchange procedure can be used to create simple, robust and cheap devices that are beginning to demonstrate metrics on par with current commercial thermal detector systems. It is also shown that these devices can under certain circumstances demonstrate novel behaviours that offer the prospects of enhanced or novel functionality.</p>

scholarly journals Device Applications of Solution Processed MIR Semiconductor Nanocrystal Thin Films

2021 ◽  
Author(s):  
◽  
Matt Cryer
Keyword(s):  
Thermal Imaging ◽  
Room Temperature ◽  
Spray Deposition ◽  
Low Cost ◽  
Semiconductor Nanocrystals ◽  
Colloidal Synthesis ◽  
Noisy Environment ◽  
Air Exposure ◽  
Solution Processed

<p>Colloidal semiconductor nanocrystals (NCs) with bandgaps less than 1 eV allow the development of mid wave infrared (MIR) sensitive detectors that exploit the benefits of colloidal materials, primarily bandgap selection and solution deposition. Additionally, the electrical behaviour of these films can be examined for characteristics that can increase the functionality of NC based detectors.  The production of devices that are designed to be competitive as ultra-low-cost, room temperature MIR detectors, operating with photonic, rather than thermal detection is detailed. The evolution of the colloidal synthesis, spray deposition methods, substrate materials and post deposition treatments used here lead to highly robust and high performing devices. These devices demonstrate a “colour” sensitivity down to 300 nm in the MIR (≈10 % of scale), with superior responsivities for this class of device, up to 0.9 AW⁻¹, and competitive specific detectivity up to 8 × 10⁹ Jones at 200 Hz and 300 K. Furthermore, these devices utilise a cheap and robust substrate material that allows operation after deformation up to 45 ° without degradation over many cycles. These devices offer a template for ultra-low-cost MIR detectors with performance that rivals microbolometers but with better measurement speed and spectral sensitivity. As such these devices showcase the key advantages of using colloidal NCs in MIR applications.  Planar and fully air processed thin film devices that demonstrate photo-induced memristive behaviour and can be used as a transistors, photode-tectors or memory devices are investigated. Following long term (60 h) air exposure, unpackaged NC films develop reliable memristive characteristics in tandem with temperature, gate and photoresponse. On/off ratios of more than 50 are achieved and the devices show long term stability, producing repeatable metrics over days of measurement. The on/off behaviour is shown to be dependent on previous charge flow and carrier density, implying memristive rather than switching behaviour. These observations are described within a long term trap filling model. This work represents an advance in the integration of NC films into electronic devices, which may lead to the development of multi-functional electronic components.  Building on the previous work the steps taken to move from a planar device, that works well in controlled conditions, to a multi-pixel sensor that can demonstrate MIR video imaging at room temperature in a noisy environment are shown. This is achieved with a 15 pixel detector that consists only of a polymer substrate and solution patterned NC pixels. This device can detect a 373 K object with the device at 298 K in a noisy environment. This performance is enabled by photogain at 5 V bias that reaches a maximum External Quantum Efficiency (EQE) of 1940 ± 290 % for a pixel with a 3.3 µm bandgap. Through the use of four separate bandgaps it is shown that “multicolour” thermal imaging systems can deliver another layer of information, on top of intensity, to the user. The behaviour of the system is examined under use and it is shown that the photoconductive device behaves as expected with regards to bias, and that trap enabled gain is sensitive to total incident flux, more than the spectral energy distribution of the target. Finally, it is shown that solution patterned QD fabrication methods can deliver electrical reproducibility between pixels that is sufficient to allow an imaging plane of multiple pixels.  The somewhat neglected tin chalcogenide semiconductor nanocrystals are investigated and inverse MIR detection at room temperature is demonstrated with planar, solution and airprocessed PbSnTe and SnTe QD devices. The detection mechanism is shown to be mediated by an interaction between MIR radiation and the vibrational stretches of adsorbed hydroxyl species at the oxdised NC surface. Devices are shown to possess mAW⁻¹ responsivity via a reduction in film conductance due to MIR radiation and, unlike classic MIR photoconductors, are unaffected by visible wavelengths. As such these devices offer the possibility of MIR thermal imaging that has an intrinsic solution to the blinding caused by higher energy light sources.  In summary, it is shown that semiconductor NCs with an all ambient fully solution processed deposition and ligand exchange procedure can be used to create simple, robust and cheap devices that are beginning to demonstrate metrics on par with current commercial thermal detector systems. It is also shown that these devices can under certain circumstances demonstrate novel behaviours that offer the prospects of enhanced or novel functionality.</p>

scholarly journals Size Control in the Colloidal Synthesis of Plasmonic Magnesium Nanoparticles

2021 ◽  
Author(s):  
Elizabeth R. Hopper ◽  
Thomas M. R. Wayman ◽  
Jérémie Asselin ◽  
Bruno Pinho ◽  
Christina Boukouvala ◽  
...  
Keyword(s):  
Size Control ◽  
Colloidal Synthesis ◽  
Magnesium Nanoparticles

scholarly journals Synthesis and Characterization of Silicon and Germanium Nanocrystals and Titanium Disulphide Nanostructures

2021 ◽  
Author(s):  
◽  
Sujay Prabakar
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Size Control ◽  
Synthesis And Characterization ◽  
One Pot ◽  
Lithium Aluminium ◽  
Germanium Nanocrystals ◽  
Fluorescent Whitening Agents ◽  
Silicon And Germanium

<p>This thesis is concerned with the synthesis and characterization of nanostructured materials in the solution, in particular silicon and germanium nanocrystals, their applica-tion as fluorescent whitening agents and titanium disulphide nanostructures. The aim of this research with regards to the synthesis of silicon and germanium nanocrystals was to obtain size control and provide functionality using simple room temperature solution techniques. In the case of the nanostructures of titanium disulphide, the focus was to synthesize in the colloid using simple one-pot bench top techniques. The above were realized with chemical techniques in the solution using organic solvents and surfactants to control their size. The morphology, chemical composition and crystal structure of the synthesized nanomaterials were characterized using techniques such as High Resolution Transmission Electron Microscopy (HRTEM), Selected Area Electron Diffraction (SAED), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectrosco-py (EDX) and Optical Spectroscopies. Whilst chapter one is a brief introduction of the thesis, chapter two talks in detail about the various characterization techniques used in this research.  Chapter three of the thesis focuses on the synthesis of alkyl- and amine-functionalized silicon nanocrystals using a microemlusion technique. The effect of reducing agents, surfactants and precursors on particle size was studied. The surfactant C12E5 was found to be very effective in producing silicon nanocrystals that were freestanding and pure. Whilst the hydride reducing agents lithium aluminium hydride and lithium tri-ethyl borohydride were found to be effective in synthesizing nanocrystals of narrow size distribution, it was found that using silicon tetrachloride yielded smaller particles compared to silicon tetrabromide.  The fourth chapter in the theses is concerned with the synthesis and characterization of germanium nanocrystals by both microemulsion and high temperature techniques. Using lithium aluminium hydride; a strong reducing agent, very small nanocrystals were obtained, whilst weaker reductants such as sodium borohydride produced larger nano-crystals. Another effective method to control the particle size of germanium nanocrystals was found to be by varying the concentration of precursor. The germanium nanocrystals which were amine capped were found to luminesce in the blue and were used to image HePG2 cells. Toxicity studies on these nanocrystals proved their relative non-toxicity. The high temperature experiments, though not as flexible as the room temperature syntheses were found to facilitate a certain degree of size control.  Chapter five of the theses deal with the application of silicon and germanium nanocrys-tals as fluorescent whitening agents in wool fabrics. Both nanocrystals, when applied to the fabric were found to emit matching blue fluorescence that was demonstrated to be more suited to improving the brightness properties of fabric than the commercial fluo-rescing whitening agent Uvitex. In particular Silicon-amine and Silicon-hexene functionalized nanocrystal (low concentration) treated fabrics were found to have improved color stability against both UVA and UVB radiation. The treated fabrics were in addition found to maintain a stable color than untreated fabric. Silicon-amine treated fabrics were found to have a stable color even after 48h exposures to UVA radiation. It should be noted that this is the first evidence of the application of group IV semiconductor nanocrystals as fluorescing whitening agents.  The sixth chapter of this thesis deals with the one-pot synthesis of titanium disulphide nanostructures using both coordinating and non-coordinating solvents and their subse-quent characterization. By varying the injection temperature of the titanium source into the 1-Octadecene sulphur solution, two different morphologies were synthesized. Two different pathways were suggested for the formation of the flower-like and flake-like morphologies; an instant nucleation to form titanium disulphide flakes whilst spherical nuclei to form flower-like nanostructures. The flower-like nanostructures were found to have higher BET surface area compared to the flake-like nanostructures and previously reported surface areas for analogous TiS₂ nanostructures. Whilst using oleylamine as solvent, the low temperature injection yielded hollow spheres of TiS₂ and the high temperature injection, fullerene-like nanoparticles of TiS₂. The property of oleylamine to selectively bind to the nanostructure surface in conjunction with the effect of injection temperature was understood to be behind the growth of these nanostructures. The synthesis of flower-like and flake-like morphologies by solution phase techniques were the first evidence of this kind for titanium disulphide and provides a new and exciting material for a variety of applications.  A final chapter on conclusions and recommendations for future work is then presented.</p>

Magnetic properties of nanotextured greigite.

2020 ◽  
Author(s):  
Barbara Lesniak ◽  
Michalis Charilaou ◽  
Andreas Gehring
Keyword(s):  
Magnetic Properties ◽  
Room Temperature ◽  
Magnetic Measurements ◽  
Resonance Field ◽  
Uniaxial Anisotropy ◽  
Temperature Cycling ◽  
Morphological Properties ◽  
Colloidal Synthesis ◽  
Contour Plot ◽  
Resonance Spectroscopy

&lt;p&gt;Greigite (Fe&lt;sub&gt;3&lt;/sub&gt;S&lt;sub&gt;4&lt;/sub&gt;) is a ferrimagnetic mineral widespread in sedimentary environments, commonly found in lacustrine and marine sediments that records ancient geomagnetic field variations and environmental processes. However, its magnetic properties are not yet well understood due to the lack of a single crystal greigite suitable for magnetic measurements. In particular, the dependency of its magnetic properties with respect to structural and morphological properties remains uncertain.&lt;/p&gt;&lt;p&gt;In the present study, we analyzed the structural and magnetic properties of synthetic, polycrystalline greigite formed by controlled colloidal synthesis [Rhodes et al. 2017]. X-ray diffractometry and transition electron microscopy reveal that greigite forms flakes of about 100 nm that consist of epitaxial intergrown nanoparticles with a mean coherence length of 19 nm. Therefore, our synthetic greigite can be considered as polycrystalline flakes with a nanotexture.&lt;/p&gt;&lt;p&gt;The saturation magnetization (M&lt;sub&gt;s&lt;/sub&gt;) of the nanotextured greigite is 32.7 Am&lt;sup&gt;2&lt;/sup&gt;kg&lt;sup&gt;-1 &lt;/sup&gt;and the coercivity is B&lt;sub&gt;c&lt;/sub&gt; = 41 mT. The M&lt;sub&gt;s&lt;/sub&gt; is about 45% below the value for relatively large, synthetic crystal and this in turn is probably caused by the nanotexture, e.g., interfaces between nanocrystallites. The ratios M&lt;sub&gt;r.&lt;/sub&gt;/M&lt;sub&gt;S&lt;/sub&gt; = 0.54 and B&lt;sub&gt;ar&lt;/sub&gt;/B&lt;sub&gt;Sc&lt;/sub&gt; = 1.33 indicate single-domain (SD) particles with pre-dominant uniaxial anisotropy [Roberts 1995]. The FORC diagram at room temperature shows an oval contour plot supporting that the flakes are nanotextured with interacting SD particles. The hysteresis parameters B&lt;sub&gt;c&lt;/sub&gt; and M&lt;sub&gt;S&lt;/sub&gt; continuously increase upon cooling to 10 K.&lt;/p&gt;&lt;p&gt;Low-temperature cycling of the magnetization between 300 and 10 K in fields between 10 mT and 1000 mT shows the expected behavior for ferrimagnets with the superposition of the cooling and warming curves at fields B &amp;#179; 500 mT. At weaker fields a slight magnetic induction upon warming is found and the relative increase in magnetization is field dependent. This irreversibility most likely stems from the magnetization of the nanoparticle interfaces and their interactions in the flakes.&lt;/p&gt;&lt;p&gt;Ferromagnetic resonance spectroscopy (FMR) at room temperature shows a resonance field B&lt;sub&gt;res&lt;/sub&gt;= 213 mT and linewidth DB = 160 mT. Upon cooling the B&lt;sub&gt;res&lt;/sub&gt; decreases continuously down to 50 K followed by a pronounced shift to lower values down to 10 K. The shift goes along with markedly linewidth broadening. The discontinuity of the spectral parameters at T &lt; 50 K points to a change in the effective anisotropy of the flakes most likely due to changes of the magnetocrystalline and the interaction anisotropies in the nanotexture, because the shape anisotropy of the polycrystalline flakes undergoes no significant change.&amp;#160;&lt;/p&gt;&lt;p&gt;In summary, the magnetic properties of greigite can be critically affected by the nanotexture. The response of the nanotexture to the magnetization and anisotropy properties can be taken to identify and characterize greigite nanoparticles in natural environments and to critically evaluate their use for paleomagnetic studies.&lt;/p&gt;&lt;p&gt;Rhodes, Jordan M., et al. &quot;Phase-controlled colloidal syntheses of iron sulfide nanocrystals via sulfur precursor reactivity and direct pyrite precipitation.&quot;&amp;#160;Chemistry of Materials&amp;#160;29.19 (2017): 8521-8530.&lt;/p&gt;&lt;p&gt;Roberts, Andrew P. &quot;Magnetic properties of sedimentary greigite (Fe3S4).&quot;&amp;#160;Earth and Planetary Science Letters&amp;#160;134.3-4 (1995): 227-236.&lt;/p&gt;

scholarly journals pH Dependence of Size Control in Gold Nanoparticles Synthesized at Room Temperature

2018 ◽  
Vol 34 (5) ◽  
pp. 2305-2312 ◽  
Author(s):  
Shohifah Annur ◽  
Sri Juari Santosa ◽  
Nurul Hidayat Aprilita
Keyword(s):  
Gold Nanoparticles ◽  
Ascorbic Acid ◽  
Room Temperature ◽  
Ph Dependence ◽  
Size Control ◽  
Spherical Shape ◽  
Alkaline Condition ◽  
Transmission Electron ◽  
Particle Size Analyzer ◽  
Spherical Gold Nanoparticles

We have developed the spherical gold nanoparticles (AuNPs) with different size at room temperature using L-ascorbic acid as a reducing agent. Controlling pH of L-ascorbic acid from 2.0 to 10.0 caused the decreasing of AuNPs size when measured using particle size analyzer. The alkaline condition leads to increase the reactivity of L-ascorbic acid even at room temperature. The homogeneous AuNPs were achieved even the synthesis was conducted at different pH of L-ascorbic acid (pH 2.0 to 12.0). The investigation using Transmission Electron Microscopy (TEM) confirmed that AuNPs performed a spherical shape. SEM-EDX measurement performed a strong characteristic peak of Au appeared at 2.0 keV. This research could be used to control of AuNPs size when synthesized at room temperature. The AuNPs obtained at optimum condition was stable up to 3 months.

Room temperature colloidal synthesis of CsPbBr3 nanowires with tunable length, width and composition

2018 ◽  
Vol 6 (29) ◽  
pp. 7797-7802 ◽  
Author(s):  
Yi Liu ◽  
Mingrui Guo ◽  
Shun Dong ◽  
Xiuling Jiao ◽  
Ting Wang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Colloidal Synthesis ◽  
Single Crystalline ◽  
Colloidal Method ◽  
Length Width ◽  
Precursor Powders

We developed a room temperature ligand-assisted colloidal method to synthesize single-crystalline CsPbBr3 nanowires (NWs) directly from precursor powders.

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