@article{as2024investigation,

title = {Investigation of the Multiple Doping of Citric Acid and Chitosan in Nanofiber for Enhancement of a Quartz Crystal Microbalance-Based Ammonia Sensor},

author = {Ahmad Hasan As’ ari and Rizky Aflaha and Laila Katriani and Ahmad Kusumaatmaja and Rike Yudianti and Kuwat Triyana},

url = {https://link.springer.com/article/10.1007/s11664-024-11646-0},

doi = {https://doi.org/10.1007/s11664-024-11646-0},

year  = {2024},

date = {2024-12-19},

urldate = {2024-12-19},

journal = {Journal of Electronic Materials},

pages = {1--13},

publisher = {Springer},

abstract = {Herein, the use of multiple doping of citric acid (CA) and chitosan (CS) in polyacrylonitrile (PAN) nanofibers over a quartz crystal microbalance is investigated as a method for enhancing the performance of an ammonia sensor at room temperature. It was found that the PAN/CA/CS sensor has superior sensitivity and better selectivity. The PAN/CA/CS sensor demonstrated sensitivity of (0.629 ± 0.005) Hz ppm−1, which increased by 2.75 times compared to the PAN/CA sensor and 39 times compared to the PAN sensor. Chitosan doping also resulted in better selectivity, as shown by the decreased response of the PAN/CA/CS sensor compared to the PAN/CA sensor to other analytes including formaldehyde (−147%), acetic acid (−22%), ethanol (−19%), methanol (−15%), and acetone (−1%). The viscoelastic properties of chitosan might be responsible for the anti-Sauerbrey phenomena behind the enhanced selectivity. The detection and adsorption mechanisms of the fabricated sensors towards ammonia were studied using adsorption kinetics and isotherms. The adsorption kinetics varied and exhibited the limits of the high-concentration region of each sensor. Moreover, all the fabricated sensors followed the Freundlich adsorption isotherm with different adsorption processes, which were confirmed by scanning electron microscopy, x-ray diffraction, and Fourier transform infrared spectroscopy concerning the morphology, crystal structure, and active groups after the loading of citric acid and chitosan. Thus, the use of multiple doping can improve the sensor abilities, as well as causing changes in the detection and adsorption mechanisms.},

keywords = {Adsorption, Ammonia, Chitosan, Nanofiber, openQCM, QCM, Quartz Crystal Microbalance},

pubstate = {published},

tppubtype = {article}

}

@article{dedecker2025selective,

title = {Selective Adsorption and Separation of C 6 Hydrocarbons: The Role of Structural Flexibility and Functionalization in Zeolitic Imidazolate Frameworks},

author = {Kevin Dedecker and Martin Drobek and Anne Julbe},

url = {https://pubs.rsc.org/en/content/articlehtml/2025/lf/d4lf00388h},

doi = {https://doi.org/10.1039/D4LF00388H},

year  = {2024},

date = {2024-12-19},

urldate = {2024-12-19},

journal = {RSC Applied Interfaces},

publisher = {Royal Society of Chemistry},

abstract = {This study investigates the selective adsorption and separation of C6 hydrocarbons (benzene, cyclohexane, and n-hexane) by zeolitic imidazolate frameworks (ZIFs), focusing on their structural flexibility and functionalization. ZIF-8_CH3 and ZIF-8_Br were synthesized and compared, indicating distinct adsorption behaviors. ZIF-8_CH3 showed higher uptake for benzene (9.5 molecules per unit cell) and n-hexane (8.0 mlc uc−1) compared to cyclohexane (1.0 mlc uc−1). In contrast, ZIF-8_Br exhibited enhanced adsorption for cyclohexane (5.0 mlc uc−1) and reduced n-hexane uptake (0.5 mlc uc−1). Computational simulations supported these findings, identifying the involved host–guest interactions. Ideal adsorbed solution theory analysis confirmed that ZIF-8_CH3 demonstrated virtually zero uptake of cyclohexane from binary mixtures containing either n-hexane or benzene, while ZIF-8_Br exhibited negligible adsorption of n-hexane from its mixtures with cyclohexane or benzene. It was concluded that bromine functionalization in ZIF-8_Br increased structural rigidity and selectivity for aromatic compounds. These results highlight the crucial role of functionalization and gate-opening phenomena in ZIFs to achieve efficient volatile organic compound capture and separation where traditional adsorbents may not be effective.},

keywords = {Adsorption, benzene, cyclohexane, hydrocarbons, n-hexane, openQCM, QCM, Quartz Crystal Microbalance},

pubstate = {published},

tppubtype = {article}

}

@article{hunter2024covalent,

title = {Covalent Capture of Nanoparticle-Stabilized Oil Droplets via Acetal Chemistry Using a Hydrophilic Polymer Brush},

author = {Saul J Hunter and Evelin Csányi and Joshua JS Tyler and Mark A Newell and Matthew AH Farmer and Camery Ma and George Sanderson and Graham J Leggett and Edwin C Johnson and Steven P Armes},

url = {https://pubs.acs.org/doi/full/10.1021/acs.langmuir.4c03897},

doi = {https://doi.org/10.1021/acs.langmuir.4c03897},

year  = {2024},

date = {2024-12-06},

urldate = {2024-01-01},

journal = {Langmuir},

publisher = {ACS Publications},

abstract = {We report the capture of nanosized oil droplets using a hydrophilic aldehyde-functional polymer brush. The brush was obtained via aqueous ARGET ATRP of a cis-diol-functional methacrylic monomer from a planar silicon wafer. This precursor was then selectively oxidized using an aqueous solution of NaIO4 to introduce aldehyde groups. The oil droplets were prepared by using excess sterically stabilized diblock copolymer nanoparticles to prepare a relatively coarse squalane-in-water Pickering emulsion (mean droplet diameter = 20 μm). This precursor was then further processed via high-pressure microfluidization to produce ∼200 nm squalane droplets. We demonstrate that adsorption of these nanosized oil droplets involves acetal bond formation between the cis-diol groups located on the steric stabilizer chains and the aldehyde groups on the brush. This interaction occurs under relatively mild conditions and can be tuned by adjusting the solution pH. Hence this is a useful model system for understanding oil droplet interactions with soft surfaces.},

keywords = {Adsorption, lipids, Liquids, Nanoemulsions, nanoparticles, openQCM NEXT, QCM, QCM-D, Quartz Crystal Microbalance},

pubstate = {published},

tppubtype = {article}

}

@article{PRASETYA2024115713,

title = {Investigation of the free-base Zr-porphyrin MOFs as relative humidity sensors for an indoor setting},

author = {Nicholaus Prasetya and Salih Okur},

url = {https://www.sciencedirect.com/science/article/pii/S0924424724007076},

doi = {https://doi.org/10.1016/j.sna.2024.115713},

issn = {0924-4247},

year  = {2024},

date = {2024-10-16},

urldate = {2024-01-01},

journal = {Sensors and Actuators A: Physical},

volume = {377},

pages = {115713},

abstract = {Maintaining optimal relative humidity is paramount for human comfort. Therefore, the utilization of quartz crystal microbalance (QCM) as a relative humidity sensor platform holds significant promise due to its cost-effectiveness and high sensitivity. This study explores the efficacy of three free-base Zr porphyrin metal-organic frameworks (MOFs) - namely MOF-525, MOF-545, and NU-902 - as sensitive materials for QCM-based relative humidity sensors. Our extended experimental findings reveal that these materials exhibit notable sensitivity, particularly within relative humidity ranges of 40–100 %. However, we observe potential irreversible adsorption sites within the MOF-545 framework, hindering its ability to revert to its initial state after prolonged exposure. In light of this observation, we conduct periodic cycling experiments at relative humidity levels of 40–70 % to evaluate the measurement repeatability and feasibility of these sensors for indoor applications. Interestingly, the periodic cycling study demonstrates that MOF-545 shows promising repeatability, positioning it as a strong contender for indoor relative humidity sensing. In contrast, MOF-525 may necessitate extended desorption time, and NU-902 displays diminished sensitivity at low relative humidity levels. Nevertheless, a preliminary treatment of the MOF-545 QCM sensor may be necessary to address irreversible adsorption sites and uphold measurement repeatability, as only reversible adsorption sites are currently accessible. This study underscores the potential of MOF-based QCM sensors for effective relative humidity monitoring in indoor environments, thus facilitating improved comfort and environmental control.},

keywords = {Adsorption, QCM Sensor SiO2, QCM sensors, Relative humidity, SiO2, Zr-porphyrin metal-organic framework},

pubstate = {published},

tppubtype = {article}

}

@article{karchilakis2024capturing,

title = {Capturing Enzyme-Loaded Diblock Copolymer Vesicles Using an Aldehyde-Functionalized Hydrophilic Polymer Brush},

author = {Georgios Karchilakis and Spyridon Varlas and Edwin C Johnson and Oleta Norvilaite and Matthew AH Farmer and George Sanderson and Graham J Leggett and Steven P Armes},

url = {https://pubs.acs.org/doi/full/10.1021/acs.langmuir.4c01561},

doi = {https://doi.org/10.1021/acs.langmuir.4c01561},

year  = {2024},

date = {2024-06-27},

urldate = {2024-06-27},

journal = {Langmuir},

publisher = {ACS Publications},

abstract = {Compared to lipids, block copolymer vesicles are potentially robust nanocontainers for enzymes owing to their enhanced chemical stability, particularly in challenging environments. Herein we report that cis-diol-functional diblock copolymer vesicles can be chemically adsorbed onto a hydrophilic aldehyde-functional polymer brush via acetal bond formation under mild conditions (pH 5.5, 20 °C). Quartz crystal microbalance studies indicated an adsorbed amount, Γ, of 158 mg m–2 for vesicle adsorption onto such brushes, whereas negligible adsorption (Γ = 0.1 mg m–2) was observed for a control experiment conducted using a cis-diol-functionalized brush. Scanning electron microscopy and ellipsometry studies indicated a mean surface coverage of around 30% at the brush surface, which suggests reasonably efficient chemical adsorption. Importantly, such vesicles can be conveniently loaded with a model enzyme (horseradish peroxidase, HRP) using an aqueous polymerization-induced self-assembly formulation. Moreover, the immobilized vesicles remained permeable toward small molecules while retaining their enzyme payload. The enzymatic activity of such HRP-loaded vesicles was demonstrated using a well-established colorimetric assay. In principle, this efficient vesicle-on-brush strategy can be applied to a wide range of enzymes and functional proteins for the design of next-generation immobilized nanoreactors for enzyme-mediated catalysis.},

keywords = {Adsorption, openQCM NEXT, peptides, proteins, QCM-D, Quartz Crystal Microbalance, RAFT polymerization, Thickness, Vesicles},

pubstate = {published},

tppubtype = {article}

}

@article{prasetya2024investigation,

title = {Investigation of the Free-Base Zr-Porphyrin MOFs as Humidity Sensors for an Indoor Setting},

author = {Nicholaus Prasetya and Salih Okur},

url = {https://chemrxiv.org/engage/chemrxiv/article-details/6608e3c466c138172950e040},

doi = {https://doi.org/10.26434/chemrxiv-2024-1jwr7},

year  = {2024},

date = {2024-04-01},

urldate = {2024-04-01},

abstract = {Maintaining optimal relative humidity is paramount for human comfort. Therefore, the utilization of quartz crystal microbalance (QCM) as a humidity sensor platform holds significant promise due to its cost-effectiveness and high sensitivity. This study explores the efficacy of three free-base Zr porphyrin metal-organic frameworks (MOFs) - namely MOF-525, MOF-545, and NU-902 - as sensitive materials for QCM-based humidity sensors. Our extended experimental findings reveal that these materials exhibit notable sensitivity, particularly within relative humidity ranges of 40% to 100%. However, we observe potential irreversible adsorption sites within the MOF-545 framework, hindering its ability to revert to its initial state after prolonged exposure. In light of this observation, we conduct periodic cycling experiments at relative humidity levels of 40-70% to evaluate the measurement repeatability and feasibility of these sensors for indoor applications. Interestingly, the periodic cycling study demonstrates that MOF-545 shows promising repeatability, positioning it as a strong contender for indoor humidity sensing. In contrast, MOF-525 may necessitate extended desorption time, and NU-902 displays diminished sensitivity at low relative humidity levels. Nevertheless, a preliminary treatment of the MOF-545 QCM sensor may be necessary to address irreversible adsorption sites and uphold measurement repeatability, as only reversible adsorption sites are currently accessible. This study underscores the potential of MOF-based QCM sensors for effective humidity monitoring in indoor environments, thus facilitating improved comfort and environmental control.},

keywords = {Adsorption, humidity, openQCM, QCM, QCM sensor, Zr-porphyrin metal organic frameworks},

pubstate = {published},

tppubtype = {article}

}

@article{astier2024controlling,

title = {Controlling Adsorption of Diblock Copolymer Nanoparticles onto an Aldehyde-Functionalized Hydrophilic Polymer Brush via pH Modulation},

author = {Samuel Astier and Edwin C Johnson and Oleta Norvilaite and Spyridon Varlas and Emma E Brotherton and George Sanderson and Graham J Leggett and Steven P Armes},

url = {https://pubs.acs.org/doi/full/10.1021/acs.langmuir.3c03392},

doi = {https://doi.org/10.1021/acs.langmuir.3c03392},

year  = {2024},

date = {2024-02-06},

urldate = {2024-02-06},

journal = {Langmuir},

publisher = {ACS Publications},

abstract = {Sterically stabilized diblock copolymer nanoparticles with a well-defined spherical morphology and tunable diameter were prepared by RAFT aqueous emulsion polymerization of benzyl methacrylate at 70 °C. The steric stabilizer precursor used for these syntheses contained pendent cis-diol groups, which means that such nanoparticles can react with a suitable aldehyde-functional surface via acetal bond formation. This principle is examined herein by growing an aldehyde-functionalized polymer brush from a planar silicon wafer and studying the extent of nanoparticle adsorption onto this model substrate from aqueous solution at 25 °C using a quartz crystal microbalance (QCM). The adsorbed amount, Γ, depends on both the nanoparticle diameter and the solution pH, with minimal adsorption observed at pH 7 or 10 and substantial adsorption achieved at pH 4. Variable-temperature QCM studies provide strong evidence for chemical adsorption, while scanning electron microscopy images recorded for the nanoparticle-coated brush surface after drying indicate mean surface coverages of up to 62%. This fundamental study extends our understanding of the chemical adsorption of nanoparticles on soft substrates.},

keywords = {Adsorption, Copolymers, nanoparticles, openQCM NEXT, QCM-D, Silicon, Solution chemistry},

pubstate = {published},

tppubtype = {article}

}

@article{okur2024optimized,

title = {Optimized Detection of Volatile Organic Compounds Utilizing Durable and Selective Arrays of Tailored UiO-66-X SURMOF Sensors},

author = {Salih Okur and Tawheed Hashem and Evgenia Bogdanova and Patrick Hodapp and Lars Heinke and Stefan Bräse and Christof Wöll},

url = {https://pubs.acs.org/doi/abs/10.1021/acssensors.3c01575},

doi = {https://doi.org/10.1021/acssensors.3c01575},

year  = {2024},

date = {2024-02-06},

urldate = {2024-01-01},

journal = {ACS sensors},

publisher = {ACS Publications},

abstract = {Metal–organic frameworks (MOFs), with their well-defined and highly flexible nanoporous architectures, provide a material platform ideal for fabricating sensors. We demonstrate that the efficacy and specificity of detecting and differentiating volatile organic compounds (VOCs) can be significantly enhanced using a range of slightly varied MOFs. These variations are obtained via postsynthetic modification (PSM) of a primary framework. We alter the original MOF’s guest adsorption affinities by incorporating functional groups into the MOF linkers, which yields subtle changes in responses. These responses are subsequently evaluated by using machine learning (ML) techniques. Under severe conditions, such as high humidity and acidic environments, sensor stability and lifespan are of utmost importance. The UiO-66-X MOFs demonstrate the necessary durability in acidic, neutral, and basic environments with pH values ranging from 2 to 11, thus surpassing most other similar materials. The UiO-66-NH2 thin films were deposited on quartz-crystal microbalance (QCM) sensors in a high-temperature QCM liquid cell using a layer-by-layer pump method. Three different, highly stable surface-anchored MOFs (SURMOFs) of UiO-66-X obtained via the PSM approach (X: NH2, Cl, and N3) were employed to fabricate arrays suitable for electronic nose applications. These fabricated sensors were tested for their capability to distinguish between eight VOCs. Data from the sensor array were processed using three distinct ML techniques: linear discriminant (LDA), nearest neighbor (k-NN), and neural network analysis methods. The discrimination accuracies achieved were nearly 100% at high concentrations and over 95% at lower concentrations (50–100 ppm).},

keywords = {Adsorption, Liquids, Metal organic frameworks, openQCM Q-1, QCM-D, sensors, Volatile organic compounds},

pubstate = {published},

tppubtype = {article}

}