Mechanical rigidity of a shape-memory metal–organic framework increases by crystal downsizing

Tiba, Al A; Conway, Matthew T; Hill, Collin S.; Swenson, Dale C.; MacGillivray, Leonard R.; Tivanski, Alexei V.

doi:10.1039/d0cc05684g

Cited by 5 publications

(16 citation statements)

References 39 publications

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“…Thus, the elastic modulus results for nanocrystals are expected to yield an average response reflective of all planes of the bulk crystal, as previously described. 30,31,[36][37][38] The average elastic modulus and standard deviation values were 0.7 ± 0.2 and 2.1 ± 0.8 GPa for base-modified and unmodified ZIF-8 nanocrystals, respectively. Thus, in situ synthesis of ZIF-8 nanocrystals with triethylamine (Et3N) modulator resulted in a marked three-fold decrease in elastic modulus and a corresponding increase in framework flexibility compared to unmodified ZIF-8.…”

Section: Resultsmentioning

confidence: 97%

“…AFM nanoindentation showed force versus indentation depth plots that were purely elastic, enabling us to fit the stress-strain curve to the JKR elastic contact model. 30,31,[36][37][38] For a given indentation depth past 3 nm, the force applied to the solids was about three times more in the unmodified nanocrystals of ZIF-8 compared to the modified samples (Figure 2c). The average elastic moduli of the nanocrystals were statistically similar within each sample type and were combined into two separate histograms (Figure 2d).…”

Section: Resultsmentioning

confidence: 99%

“…AFM nanoindentation was performed by recording force versus vertical piezo displacement curves to generate force-indentation distance plots that were used to determine the elastic modulus (i.e., Young's modulus, stiffness, rigidity) 30,31,[36][37][38] of individual base-modified ZIF-8 nanocrystals and compared to the mechanical properties of unmodified nanocrystals. Repeated force-indentation plots were collected on eleven individual amine-modified and fourteen unmodified nanocrystals of ZIF-8 at two-four different positions in the approximate center of each crystal.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The acquisition of the force plots and corresponding data analysis were carried out as reported in our previous works. 30,31,[36][37][38] Ar gas sorption measurements were performed on modified and unmodified nanocrystals of ZIF-8 using an Autosorb iQ (Anton Paar QuantaTec, Boynton Beach, FL) with a MP (micropore) analysis station. Samples (100 mg) were activated by degassing for 12 hours at 100 °C followed by ensuring the rise in pressure was no greater than 21 mtorr/min while at activation temperature.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The well-known Cu2(bdc)2(bpy) framework (bdc = 1,4-benzenedicarboxylic acid, bpy = 4,4'-bypridine), which exhibits an adsorption and temperature-mediated shape-memory effect exclusively at the nanoscale, has size-dependent mechanical properties. 30 Specifically, the nanocrystals, 10-30 nm in height, showed a higher elastic modulus than the bulk crystals. However, ZIF-8 nanocrystals 150 nm in height had an elastic modulus that was about 40% lower than the bulk crystals.…”

Section: Introductionmentioning

confidence: 99%

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Supramolecular Modification of a Metal-Organic Framework Increases Flexibility and Switchability: Experimental Insights into Structural Deformation of ZIF-8

Tiba

Perman

MacGillivray

et al. 2022

Preprint

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Use of chemical modulators during the synthesis of a coordination framework is an important strategy to affect and tune properties of porous materials. Herein, we introduce an approach to understanding structural modulation and deformation of soft, porous crystals in the context of gas adsorption by using atomic force microscopy (AFM) nanoindentation and physisorption analysis. Modified nanocrystals of the prototypical zeolitic-imidazolate framework-8 (ZIF-8) were generated in triethylamine (Et3N) via an in-situ supramolecular modulation method. We demonstrate that using triethylamine as a modulator results in a conspicuous decrease in elastic modulus (0.7 ± 0.2 GPa) compared to the unmodified nanocrystals of ZIF-8 (2.1 ± 0.8 GPa). Argon gas adsorption analysis also reveals that the more flexible, amine-modified framework exhibited gradual and cooperative gate-opening structural transitions (P/P0 = 0.33 ± 0.02) compared to the steep and stepwise characteristics of unmodified samples of ZIF-8 (P/P0 = 0.45 ± 0.02). The differences in Argon gas pressure-induced structural deformations correspond to the decrease in elastic modulus of base-modified nanocrystals of ZIF-8, likely a consequence of the impact of Et3N on the relative number of point defects and hydrogen bonds in the framework. Our study demonstrates how a combination of AFM nanoindentation, gas uptake, and spectroscopic characterization can be applied to understand structural and energetic changes upon adsorption in flexible framework materials.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Supramolecular Modification of a Metal-Organic Framework Increases Flexibility and Switchability: Experimental Insights into Structural Deformation of ZIF-8

Tiba

Perman

MacGillivray

et al. 2022

Preprint

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Quantifying the Viscosity of Individual Submicrometer Semisolid Particles Using Atomic Force Microscopy

Madawala,

Lee,

Kaluarachchi

et al. 2023

Anal. Chem.

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Atmospheric aerosols' viscosities can vary significantly depending on their composition, mixing states, relative humidity (RH) and temperature. The diffusion time scale of atmospheric gases into an aerosol is largely governed by its viscosity, which in turn influences heterogeneous chemistry and climate-relevant aerosol effects. Quantifying the viscosity of aerosols in the semisolid phase state is particularly important as they are prevalent in the atmosphere and have a wide range of viscosities. Currently, direct viscosity measurements of submicrometer individual atmospheric aerosols are limited, largely due to the inherent size limitations of existing experimental techniques. Herein, we present a method that utilizes atomic force microscopy (AFM) to directly quantify the viscosity of substrate-deposited individual submicrometer semisolid aerosol particles as a function of RH. The method is based on AFM force spectroscopy measurements coupled with the Kelvin−Voigt viscoelastic model. Using glucose, sucrose, and raffinose as model systems, we demonstrate the accuracy of the AFM method within the viscosity range of ∼10 4 −10 7 Pa s. The method is applicable to individual particles with sizes ranging from tens of nanometers to several micrometers. Furthermore, the method does not require prior knowledge on the composition of studied particles. We anticipate future measurements utilizing the AFM method on atmospheric aerosols at various RH to aid in our understanding of the range of aerosols' viscosities, the extent of particle-to-particle viscosity variability, and how these contribute to the particle diversity observable in the atmosphere.

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Engineering a Mechanoactive Fibrous Substrate with Enhanced Efficiency in Regulating Stem Cell Tenodifferentiation

Guo

Wang

Tang

et al. 2022

ACS Appl. Mater. Interfaces

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Electrospun-aligned fibers in ultrathin fineness have previously demonstrated a limited capacity in driving stem cells to differentiate into tendon-like cells. In view of the tendon’s mechanoactive nature, endowing such aligned fibrous structure with mechanoactivity to exert in situ mechanical stimulus by itself, namely, without any forces externally applied, is likely to potentiate its efficiency of tenogenic induction. To test this hypothesis, in this study, a shape-memory-capable poly(l-lactide-co-caprolactone) (PLCL) copolymer was electrospun into aligned fibrous form followed by a “stretching-recovery” shape-programming procedure to impart shape memory capability. Thereafter, in the absence of tenogenic supplements, human adipose-derived stem cells (ADSCs) were cultured on the programmed fibrous substrates for a duration of 7 days, and the effects of constrained recovery resultant stress-stiffening on cell morphology, proliferation, and tenogenic differentiation were examined. The results indicate that the in situ enacted mechanical stimulus due to shape memory effect (SME) did not have adverse influence on cell viability and proliferation, but significantly promoted cellular elongation along the direction of fiber alignment. Moreover, it revealed that tendon-specific protein markers such as tenomodulin (TNMD) and tenascin-C (TNC) and gene expression of scleraxis (SCX), TNMD, TNC, and collagen I (COL I) were significantly upregulated on the mechanoactive fibrous substrate with higher recovery stress compared to the counterparts. Mechanistically, the Rho/ROCK signaling pathway was identified to be involved in the substrate self-actuation-induced enhancement in tenodifferentiation. Together, these results suggest that constrained shape recovery stress may be employed as an innovative loading modality to regulate the stem cell tenodifferentiation by presenting the fibrous substrate with an aligned tendon-like topographical cue and an additional mechanoactivity. This newly demonstrated paradigm in modulating stem cell tenodifferentiation may improve the efficacy of tendon tissue engineering strategy for tendon healing and regeneration.

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Mechanical rigidity of a shape-memory metal–organic framework increases by crystal downsizing

Abstract: Soft porous nanocrystals with a pronounced shape-memory effect exhibit a three-fold increase in elastic modulus compared to the microcrystalline counterpart as determined by atomic force microscopy nanoindentation. The increase in...

Cited by 5 publications

References 39 publications

Supramolecular Modification of a Metal-Organic Framework Increases Flexibility and Switchability: Experimental Insights into Structural Deformation of ZIF-8

Supramolecular Modification of a Metal-Organic Framework Increases Flexibility and Switchability: Experimental Insights into Structural Deformation of ZIF-8

Quantifying the Viscosity of Individual Submicrometer Semisolid Particles Using Atomic Force Microscopy

Engineering a Mechanoactive Fibrous Substrate with Enhanced Efficiency in Regulating Stem Cell Tenodifferentiation

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