41 research outputs found
Synthesis and Characterization of MOFâDerived Structures: Recent Advances and Future Perspectives
Due to their facile tunability, metalâorganic frameworks (MOFs) are employed as precursors and templates to construct advanced functional materials with unique and desired chemical, physical, mechanical, and morphological properties. By tuning MOF precursor composition and manipulating conversion processes, various MOFâderived materials commonly known as MOF derivatives can be constructed. The possibility of controlled and predictable properties makes MOF derivatives a preferred choice for numerous advanced technological applications. The innovative synthetic designs besides the plethora of interdisciplinary characterization approaches applicable to MOF derivatives provide the opportunity to perform a myriad of experiments to explore the performance and offer key insight to develop the next generation of advanced materials. Though there are many published works of literature describing various synthesis and characterization techniques of MOF derivatives, it is still not clear how the synthesis mechanism works and what are the best techniques to characterize these materials to probe their properties accurately. In this review, the recent development in synthesis techniques and mechanisms for a variety of MOF derivates such as MOFâderived metal oxides, porous carbon, composites/hybrids, and sulfides is summarized. Furthermore, the details of characterization techniques and fundamental working principles are summarized to probe the structural, mechanical, physiochemical, electrochemical, and electronic properties of MOF and MOF derivatives. The future trends and some remaining challenges in the synthesis and characterization of MOF derivatives are also discussed
Simultaneous quantification of Youngâs modulus and dispersion forces with nanoscale spatial resolution
Many advances in polymers and layered materials rely on a precise understanding of the local interactions between adjacent molecular or atomic layers. Quantifying dispersion forces at the nanoscale is particularly challenging with existing methods often time consuming, destructive, relying on surface averaging or requiring bespoke equipment. Here, we present a non-invasive method able to quantify the local mechanical and dispersion properties of a given sample with nanometer lateral precision. The method, based on atomic force microscopy (AFM), uses the frequency shift of a vibrating AFM cantilever in combination with established contact mechanics models to simultaneously derive the Hamaker constant and the effective Youngâs modulus at a given sample location. The derived Hamaker constant and Youngâs modulus represent an average over a small (typically <100) number of molecules or atoms. The oscillation amplitude of the vibrating AFM probe is used to select the length-scale of the features to analyse, with small vibrations able to resolve the contribution of sub-nanometric defects and large ones exploring effectively homogeneous areas. The accuracy of the method is validated on a range of 2D materials in air and water as well as on polymer thin films. We also provide the first experimental measurements of the Hamaker constant of HBN, MoT2, WSe2 and polymer films, verifying theoretical predictions and computer simulations. The simplicity and robustness of the method, implemented with a commercial AFM, may support a broad range of technological applications in the growing field of polymers and nanostructured materials where a fine control of the van der Waals interactions is crucial to tune their properties
Force reconstruction from tapping mode force microscopy experiments
Fast, accurate, and robust nanomechanical measurements are intensely studied in materials science, applied physics, and molecular biology. Amplitude modulation force microscopy (tapping mode) is the most established nanoscale characterization technique of surfaces for air and liquid environments. However, its quantitative capabilities lag behind its high spatial resolution and robustness. We develop a general method to transform the observables into quantitative force measurements. The force reconstruction algorithm has been deduced on the assumption that the observables (amplitude and phase shift) are slowly varying functions of the tipâsurface separation. The accuracy and applicability of the method is validated by numerical simulations and experiments. The method is valid for liquid and air environments, small and large free amplitudes, compliant and rigid materials, and conservative and non-conservative forces.This work was funded by the Spanish Ministry of Economy (MINECO) through grant CSD2010â00024 and the European Research Council ERC-AdG-340177 (3DNanoMech)
Opportunities and challenges for biosensors and nanoscale analytical tools for pandemics: COVID-19
Biosensors and nanoscale analytical tools have shown a huge growth in literature in the
past 20 years, with a large number of reports on the topic of âultra-sensitiveâ, âcosteffectiveâ
and âearly-detectionâ tools with a potential of âmass-productionâ cited on the
web of science. Yet none of these tools are commercially available in the market or
practically viable for mass production and use in pandemic diseases such as COVID-19.
In this context, we review the technological challenges and opportunities of current
bio/chemical sensors and analytical tools by critically analyzing the bottlenecks which have
hindered the implementation of advanced sensing technologies in pandemic diseases. We
also describe in brief COVID-19 by comparing it with other pandemic strains such as
SARS and MERS for the identification of features that enable biosensing. Moreover, we
discuss visualization and characterization tools that can potentially be used not only for
sensing applications but also assist in speeding up the drug discovery and vaccine
development process. Furthermore, we discuss the emerging monitoring mechanism,
namely wastewater-based epidemiology, for early warning of the outbreak, focusing on
sensors for rapid and on-site analysis of SARS-COV-2 in sewage. To conclude, we provide holistic insights into challenges associated with the quick translation of sensing
technologies, policies, ethical issues, technology adoption, and an overall outlook of the
role of the sensing technologies in pandemics