Imaging the Thermal Hysteresis of Single Spin-Crossover Nanoparticles.
25 Aug 2020-Journal of the American Chemical Society (American Chemical Society)-Vol. 142, Iss: 37, pp 15852-15859
TL;DR: Correlations between the hysteresis and the size and morphology of the same individuals further uncovered the significant nanoparticle-to-nanoparticle heterogeneity, with implications for the size-property relationship and rational design of SCO materials with improved performances.
Abstract: The magnetic hysteresis property during the spin transition of spin-crossover (SCO) materials holds great promise for their applications in spin electronics, information storage, thermochromic, and nanophotonic devices. Existing studies often measured the averaged property of a bulk sample consisting of lots of individuals. When considering the significant heterogeneity among different individuals and the inevitable interparticle interactions, ensemble measurement not only blurred the structure-property relationship but also compromised the intrinsic hysteresis property and cyclability. Herein, we employed a recently developed surface plasmon resonance microscopy (SPRM) method to measure the thermal hysteresis curve of single isolated SCO nanoparticles. The thermal-induced spin transition was found to alter the optical contrast of single SCO nanoparticles, which was optically readout using SPRM in a quantitative, nonintrusive, and high-throughput manner. Single nanoparticle measurements revealed an intrinsic transition temperature that was independent of the temperature scan rate and superior stability after over 11 000 cycles of single SCO nanoparticles. Correlations between the hysteresis and the size and morphology of the same individuals further uncovered the significant nanoparticle-to-nanoparticle heterogeneity with implications for the size-property relationship and rational design of SCO materials with improved performance.
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TL;DR: In this paper, the length changes of individual switchable nanoparticles induced thermally by nanosecond laser pulses are compared with time-resolved optical measurements performed on an assembly of these particles.
Abstract: Spin Crossover (SCO) is a promising switching phenomenon when implemented in electronic devices as molecules, thin films or nanoparticles. Among the properties modulated along this phenomenon, optically induced mechanical changes are of tremendous importance as they can work as fast light-induced mechanical switches or allow to investigate and control microstructural strains and fatigability. The development of characterization techniques probing 2 nanoscopic behaviour with high spatio-temporal resolution allows to trigger and visualize such mechanical changes of individual nanoscopic objects. Here we use Ultrafast Transmission Electron Microscopy (UTEM) to precisely probe the length changes of individual switchable nanoparticles induced thermally by nanosecond laser pulses. This allows us to reveal the mechanisms of spin switching, leading to the macroscopic expansion of SCO materials. This study was conducted on individual pure SCO nanoparticles and SCO nanoparticles encapsulating gold nanorods that serve for plasmonic heating under laser pulses. Length changes are compared with time-resolved optical measurements performed on an assembly of these particles.
9 citations
TL;DR: In this article , a thermal-optical imaging technique was proposed to determine the glass transition and rubber-fluid transition temperatures of single isolated polystyrene nanospheres (PSNS) in a high-throughput and nonintrusive manner.
Abstract: An ultrathin surface layer with extraordinary molecular mobility has been discovered and intensively investigated on thin-film polymer materials for decades. However, because of the lack of suitable characterization techniques, it remains largely unexplored whether such a surface mobile layer also exists on individual polymeric nanospheres. Here, we propose a thermal-optical imaging technique to determine the glass transition (Tg) and rubber-fluid transition (Tf) temperatures of single isolated polystyrene nanospheres (PSNS) in a high-throughput and nonintrusive manner for the first time. Two distinct steps, corresponding to the glass transition and rubber-fluid transition, respectively, were clearly observed in the optical trace of single PSNS during temperature ramping. Because the transition temperature and size of the same individuals were both determined, single nanoparticle measurements revealed the reduced apparent Tf and increased Tg of single PSNS on the gold substrate with a decreasing radius from 130 to 70 nm. Further experiments revealed that the substrate effect played an important role in the increased Tg. More importantly, a gradual decrease in the optical signal was detected prior to the glass transition, which was consistent with a surface layer with enhanced molecular mobility. Quantitative analysis further revealed the thickness of this layer to be ∼8 nm. This work not only uncovered the existence and thickness of a surface mobile layer in single isolated nanospheres but also demonstrated a general bottom-up strategy to investigate the structure-property relationship of polymeric nanomaterials by correlating the thermal property (Tg and Tf) and structural features (size) at single nanoparticle level.
5 citations
5 citations
TL;DR: In this article , a dark field microscope (DFM) was used to study the thermal desorption process of I2 from I2-loaded zeolitic imidazolate framework-8 (I2@ZIF-8).
Abstract: Thermogravimetric analysis (TGA) is a key material characterization method for studying the thermal stability and thermochemical process. However, the common TGA for bulk samples lacks sufficient spatial information, which blurs the intrinsic thermal decomposition characteristic and limits the understanding of the structure-performance relationship. Here, we report a dark-field microscope (DFM) method for studying thermal desorption process of I2 from I2-loaded zeolitic imidazolate framework-8 (I2@ZIF-8). Because of the high spatial resolution, DFM enables the imaging and tracking of the local mass loss of I2 in single I2@ZIF-8 particles at different reaction temperatures. We obtain from the DFM images the single-particle thermogravimetric and differential thermogravimetric curves to evaluate the inherent thermal stability of single I2@ZIF-8 particles. We also find the heterogeneous thermal decomposition property among different I2@ZIF-8 particles. Furthermore, we demonstrate the capacity of DFM to quantitatively determine thermal kinetics parameters such as the diffusion coefficient and activation energy of I2 in individual and multiple ZIF-8 particles. These useful results are essential for developing high-efficient porous adsorbents for the capture of I2.
4 citations
TL;DR: In this paper, the authors employ a dark-field microscopy (DFM) method for in situ imaging the adsorption process of I- on single Cu2O microparticles to reveal the acid activation mechanism.
4 citations
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TL;DR: In this article, the transition temperature of transition metal compounds can be fine tuned using an approach based on the concept of a molecular alloy, and it is possible to design a compound for which room temperature falls in the middle of the thermal hysteresis loop.
Abstract: Some 3dn (4 ≤ n ≤ 7) transition metal compounds exhibit a cooperative transition between a low-spin (LS) and a high-spin (HS) state. This transition is abrupt and occurs with a thermal hysteresis, which confers a memory effect on the system. The intersite interactions and thus the cooperativity are magnified in polymeric compounds such as [Fe(Rtrz)3]A2·nH2O in which the Fe2+ ions are triply bridged by 4-R-substituted-1,2,4-triazole molecules. Moreover, in these compounds, the spin transition is accompanied by a well-pronounced change of color between violet in the LS state and white in the HS state. The transition temperatures of these materials can be fine tuned, using an approach based on the concept of a molecular alloy. In particular, it is possible to design a compound for which room temperature falls in the middle of the thermal hysteresis loop. These materials have many potential applications, for example, as temperature sensors, as active elements of various types of displays, and in information storage and retrieval.
1,934 citations
TL;DR: In particular, the amount of generated heat and temperature increase depends on the number of colloidal nanoparticles in a complex and the shape and organization of the nanoparticles as mentioned in this paper, which suggests new possibilities for measuring heat release at the nanoscale.
1,201 citations
TL;DR: This critical review discusses recent work in the field of molecule-based spin crossover materials with a special focus on these emerging issues, including chemical synthesis, physical properties and theoretical aspects as well (223 references).
Abstract: Recently we assisted a strong renewed interest in the fascinating field of molecular spin crossover complexes by (1) the emergence of nanosized spin crossover materials through direct synthesis of coordination nanoparticles and nanopatterned thin films as well as by (2) the use of novel sophisticated high spatial and temporal resolution experimental techniques and theoretical approaches for the study of spatiotemporal phenomena in cooperative spin crossover systems. Besides generating new fundamental knowledge on size-reduction effects and the dynamics of the spin crossover phenomenon, this research aims also at the development of practical applications such as sensor, display, information storage and nanophotonic devices. In this critical review, we discuss recent work in the field of molecule-based spin crossover materials with a special focus on these emerging issues, including chemical synthesis, physical properties and theoretical aspects as well (223 references).
1,084 citations
TL;DR: The field of molecular magnetism is rapidly evolving towards the use of magnetic molecules and molecule-based magnetic materials in physics-driven and nanotechnology-driven fields, in particular molecular spintronics, quantum technologies, metal-organic frameworks (MOFs) and 2D materials as discussed by the authors.
Abstract: The field of molecular magnetism is rapidly evolving towards the use of magnetic molecules and molecule-based magnetic materials in physics-driven and nanotechnology-driven fields, in particular molecular spintronics, quantum technologies, metal–organic frameworks (MOFs) and 2D materials. In molecular spintronics, the goal is the development of a new generation of spintronic devices based on molecular materials or, in the longer term, on one or a few molecules. In the area of quantum technologies, the milestones reached in the design of molecular spin qubits with long quantum coherence times and in the implementation of quantum operations have raised expectations for the use of molecular spin qubits in quantum computation. MOFs and 2D materials are two classes of materials for which magnetism has been, until very recently, an elusive property; molecular materials with attractive properties and functionalities are now starting to be developed in both areas. In MOFs, single-molecule magnets and spin crossover complexes can be integrated into the nodes of the framework, within the pores or both, sometimes giving rise to smart magnetic materials or to hybrid materials exhibiting synergistic combinations of properties. 2D molecular-based magnets can provide a platform to study magnetism in the 2D limit and exhibit superior properties compared with their inorganic analogues in terms of chemical stability and tunability. This Review discusses the expansion of the field of molecular magnetism from the chemical design and physical study of single-molecule magnets and multifunctional magnetic materials towards physics- and nanotechnology-driven areas, in particular molecular spintronics, quantum technologies, metal–organic frameworks and 2D materials.
494 citations
TL;DR: The observation of spin crossover with thermal hysteresis loops of more than a few Kelvin remains relatively uncommon and unpredictable, so is a relatively underdeveloped, but important, area for spin crossover, particularly for memory applications.
Abstract: The observation of spin crossover with thermal hysteresis loops of more than a few Kelvin remains relatively uncommon and unpredictable, so is a relatively underdeveloped, but important, area of spin crossover, particularly for memory applications. Lessons learnt regarding the origins, and the practicalities of the proper study and reporting, of thermal hysteresis loops are considered and explained, from a synthetic chemists perspective, after a general introduction to the field of spin crossover.
414 citations