Publications by authors named "Maximilian Moser"

41 Publications

Regiochemistry-Driven Organic Electrochemical Transistor Performance Enhancement in Ethylene Glycol-Functionalized Polythiophenes.

J Am Chem Soc 2021 Jul 30;143(29):11007-11018. Epub 2021 Jun 30.

Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.

Novel p-type semiconducting polymers that can facilitate ion penetration, and operate in accumulation mode are much desired in bioelectronics. Glycol side chains have proven to be an efficient method to increase bulk electrochemical doping and optimize aqueous swelling. One early polymer which exemplifies these design approaches was p(g2T-TT), employing a bithiophene--thienothiophene backbone with glycol side chains in the 3,3' positions of the bithiophene repeat unit. In this paper, the analogous regioisomeric polymer, namely pgBTTT, was synthesized by relocating the glycol side chains position on the bithiophene unit of p(g2T-TT) from the 3,3' to the 4,4' positions and compared with the original p(g2T-TT). By changing the regio-positioning of the side chains, the planarizing effects of the S-O interactions were redistributed along the backbone, and the influence on the polymer's microstructure organization was investigated using grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements. The newly designed pgBTTT exhibited lower backbone disorder, closer π-stacking, and higher scattering intensity in both the in-plane and out-of-plane GIWAXS measurements. The effect of the improved planarity of pgBTTT manifested as higher hole mobility (μ) of 3.44 ± 0.13 cm V s. Scanning tunneling microscopy (STM) was in agreement with the GIWAXS measurements and demonstrated, for the first time, that glycol side chains can also facilitate intermolecular interdigitation analogous to that of pBTTT. Electrochemical quartz crystal microbalance with dissipation of energy (eQCM-D) measurements revealed that pgBTTT maintains a more rigid structure than p(g2T-TT) during doping, minimizing molecular packing disruption and maintaining higher hole mobility in operation mode.
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http://dx.doi.org/10.1021/jacs.1c03516DOI Listing
July 2021

Rapid single-molecule detection of COVID-19 and MERS antigens via nanobody-functionalized organic electrochemical transistors.

Nat Biomed Eng 2021 07 24;5(7):666-677. Epub 2021 May 24.

Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia.

The coronavirus disease 2019 (COVID-19) pandemic has highlighted the need for rapid and sensitive protein detection and quantification in simple and robust formats for widespread point-of-care applications. Here, we report on nanobody-functionalized organic electrochemical transistors with a modular architecture for the rapid quantification of single-molecule-to-nanomolar levels of specific antigens in complex bodily fluids. The sensors combine a solution-processable conjugated polymer in the transistor channel and high-density and orientation-controlled bioconjugation of nanobody-SpyCatcher fusion proteins on disposable gate electrodes. The devices provide results after 10 min of exposure to 5 μl of unprocessed samples, maintain high specificity and single-molecule sensitivity in human saliva and serum, and can be reprogrammed to detect any protein antigen if a corresponding specific nanobody is available. We used the sensors to detect green fluorescent protein, and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and Middle East respiratory syndrome coronavirus (MERS-CoV) spike proteins, and for the COVID-19 screening of unprocessed clinical nasopharyngeal swab and saliva samples with a wide range of viral loads.
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http://dx.doi.org/10.1038/s41551-021-00734-9DOI Listing
July 2021

Microfluidic Integrated Organic Electrochemical Transistor with a Nanoporous Membrane for Amyloid-β Detection.

ACS Nano 2021 05 30;15(5):8130-8141. Epub 2021 Mar 30.

Biological and Environmental Science and Engineering (BESE), Organic Bioelectronics Laboratory, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.

Alzheimer's disease (AD) is a neurodegenerative disorder associated with a severe loss in thinking, learning, and memory functions of the brain. To date, no specific treatment has been proven to cure AD, with the early diagnosis being vital for mitigating symptoms. A common pathological change found in AD-affected brains is the accumulation of a protein named amyloid-β (Aβ) into plaques. In this work, we developed a micron-scale organic electrochemical transistor (OECT) integrated with a microfluidic platform for the label-free detection of Aβ aggregates in human serum. The OECT channel-electrolyte interface was covered with a nanoporous membrane functionalized with Congo red (CR) molecules showing a strong affinity for Aβ aggregates. Each aggregate binding to the CR-membrane modulated the vertical ion flow toward the channel, changing the transistor characteristics. Thus, the device performance was not limited by the solution ionic strength nor did it rely on Faradaic reactions or conformational changes of bioreceptors. The high transconductance of the OECT, the precise porosity of the membrane, and the compactness endowed by the microfluidic enabled the Aβ aggregate detection over eight orders of magnitude wide concentration range (femtomolar-nanomolar) in 1 μL of human serum samples. We expanded the operation modes of our transistors using different channel materials and found that the accumulation-mode OECTs displayed the lowest power consumption and highest sensitivities. Ultimately, these robust, low-power, sensitive, and miniaturized microfluidic sensors helped to develop point-of-care tools for the early diagnosis of AD.
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http://dx.doi.org/10.1021/acsnano.0c09893DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8158856PMC
May 2021

Acene Ring Size Optimization in Fused Lactam Polymers Enabling High n-Type Organic Thermoelectric Performance.

J Am Chem Soc 2021 Jan 22;143(1):260-268. Epub 2020 Dec 22.

Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.

Three n-type fused lactam semiconducting polymers were synthesized for thermoelectric and transistor applications via a cheap, highly atom-efficient, and nontoxic transition-metal free aldol polycondensation. Energy level analysis of the three polymers demonstrated that reducing the central acene core size from two anthracenes (), to mixed naphthalene-anthracene (), and two naphthalene cores () resulted in progressively larger electron affinities, thereby suggesting an increasingly more favorable and efficient solution doping process when employing 4-(2,3-dihydro-1,3-dimethyl-1-benzimidazol-2-yl)-,-dimethylbenzenamine (N-DMBI) as the dopant. Meanwhile, organic field effect transistor (OFET) mobility data showed the and polymers to feature the highest charge carrier mobilities, further highlighting the benefits of aryl core contraction to the electronic performance of the materials. Ultimately, the combination of these two factors resulted in , , and to display power factors (PFs) of 3.2 μW m K, 1.6 μW m K, and 0.3 μW m K, respectively, when doped with N-DMBI, whereby the PFs recorded for and are among the highest reported in the literature for n-type polymers. Importantly, the results reported in this study highlight that modulating the size of the central acene ring is a highly effective molecular design strategy to optimize the thermoelectric performance of conjugated polymers, thus also providing new insights into the molecular design guidelines for the next generation of high-performance n-type materials for thermoelectric applications.
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http://dx.doi.org/10.1021/jacs.0c10365DOI Listing
January 2021

Polaron Delocalization in Donor-Acceptor Polymers and its Impact on Organic Electrochemical Transistor Performance.

Angew Chem Int Ed Engl 2021 Mar 26;60(14):7777-7785. Epub 2021 Feb 26.

University of Oxford, Department of Chemistry, Oxford, OX1 3TA, UK.

Donor-acceptor (D-A) polymers are promising materials for organic electrochemical transistors (OECTs), as they minimize detrimental faradaic side-reactions during OECT operation, yet their steady-state OECT performance still lags far behind their all-donor counterparts. We report three D-A polymers based on the diketopyrrolopyrrole unit that afford OECT performances similar to those of all-donor polymers, hence representing a significant improvement to the previously developed D-A copolymers. In addition to improved OECT performance, DFT simulations of the polymers and their respective hole polarons also reveal a positive correlation between hole polaron delocalization and steady-state OECT performance, providing new insights into the design of OECT materials. Importantly, we demonstrate how polaron delocalization can be tuned directly at the molecular level by selection of the building blocks comprising the polymers' conjugated backbone, thus paving the way for the development of even higher performing OECT polymers.
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http://dx.doi.org/10.1002/anie.202014078DOI Listing
March 2021

Falls Risk, Circadian Rhythms and Melatonin: Current Perspectives.

Clin Interv Aging 2020 11;15:2165-2174. Epub 2020 Nov 11.

Institute for Biomedical Research (BIOMED), Catholic University of Argentina (UCA) and National Scientific and Technical Research Council (CONICET), Autonomous City of Buenos Aires, Argentina.

Aging is associated with weakening of the circadian system. The circadian amplitude of most physiological variables is reduced, while the circadian phase becomes more labile and tends to occur earlier with advancing age. As the incidence of falls in older persons could follow circadian variations, a better understanding of conditions in which falls occur can lead to the implementation of countermeasures (such as adjusting the scheduling of hospital staff, or changing the timing of anti-hypertensive medication if falls are related to undesirable circadian patterns of blood pressure and/or heart rate). This includes knowing the times of the day, days of the week, and times of the year when falls are more likely to occur at home or in the hospital. Additionally, the links between aging processes and factors associated with an increased risk of developing autonomic dysfunction are well established. A strong association between heart rate variability indexes and aging has been shown. Circadian rhythms of autonomous nervous system activity may play important role for maintenance of orthostatic tolerance. Whether one is concerned with disease prediction and prevention or maintenance of healthy aging, the study of circadian rhythms and the broader time structure underlying physiopathology is helpful in terms of screening, early diagnosis and prognosis, as well as the timely institution of prophylactic and/or palliative/curative treatment. Timing the administration of such treatment as a function of circadian (and other) rhythms also could lead to reduction of falls in older persons. Finally, a prominent circadian rhythm characterizes melatonin, which peaks during the night. The circadian amplitude of melatonin decreases as a function of age, raising the questions whether such a decrease in the circadian amplitude of melatonin relates to a higher risk of falls and, if so, whether melatonin supplementation may be an effective countermeasure. This narrative review assesses the relationships between fall risk and the potential role circadian rhythms and melatonin play in mitigating this risk. We aim to provide healthcare workers adequate information about fall risk in older persons, including the potential role of the circadian rhythms and/or melatonin, as well as to lay foundations for future fall prevention interventional studies.
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http://dx.doi.org/10.2147/CIA.S283342DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7666981PMC
March 2021

Nonfullerene-Based Organic Photodetectors for Ultrahigh Sensitivity Visible Light Detection.

ACS Appl Mater Interfaces 2020 Oct 15;12(43):48836-48844. Epub 2020 Oct 15.

Department of Chemistry and Centre for Processable Electronics, Imperial College London, London SW72AZ, U.K.

It is well established that for organic photodetectors (OPDs) to compete with their inorganic counterparts, low dark currents at reverse bias must be achieved. Here, two rhodanine-terminated nonfullerene acceptors O-FBR and O-IDTBR are shown to deliver low dark currents at -2 V of 0.17 and 0.84 nA cm, respectively, when combined with the synthetically scalable polymer PTQ10 in OPD. These low dark currents contribute to the excellent sensitivity to low light of the detectors, reaching values of 0.57 μW cm for PTQ10:O-FBR-based OPD and 2.12 μW cm for PTQ10:O-IDTBR-based OPD. In both cases, this sensitivity exceeds that of a commercially available silicon photodiode. The responsivity of the PTQ10:O-FBR-based OPD of 0.34 AW under a reverse bias of -2 V also exceeds that of a silicon photodiode. Meanwhile, the responsivity of the PTQ10:O-IDTBR of 0.03 AW is limited by the energetic offset of the blend. The OPDs deliver high specific detectivities of 9.6 × 10 Jones and 3.3 × 10 Jones for O-FBR- and O-IDTBR-based blends, respectively. Both active layers are blade-coated in air, making them suitable for high-throughput methods. Finally, all three of the materials can be synthesized at low cost and on a large scale, making these blends good candidates for commercial OPD applications.
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http://dx.doi.org/10.1021/acsami.0c14016DOI Listing
October 2020

Side Chain Redistribution as a Strategy to Boost Organic Electrochemical Transistor Performance and Stability.

Adv Mater 2020 Sep 5;32(37):e2002748. Epub 2020 Aug 5.

Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia.

A series of glycolated polythiophenes for use in organic electrochemical transistors (OECTs) is designed and synthesized, differing in the distribution of their ethylene glycol chains that are tethered to the conjugated backbone. While side chain redistribution does not have a significant impact on the optoelectronic properties of the polymers, this molecular engineering strategy strongly impacts the water uptake achieved in the polymers. By careful optimization of the water uptake in the polymer films, OECTs with unprecedented steady-state performances in terms of [μC ] and current retentions up to 98% over 700 electrochemical switching cycles are developed.
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http://dx.doi.org/10.1002/adma.202002748DOI Listing
September 2020

General and Disease-Specific Health Indicator Changes Associated with Inpatient Rehabilitation.

J Am Med Dir Assoc 2020 12 28;21(12):2017.e10-2017.e27. Epub 2020 Jul 28.

Division of Physiology, Otto Loewi Research Center, Medical University of Graz, Graz, Austria; Human Research Institute, Weiz, Austria.

Objectives: Rehabilitation plays a vital role in the mitigation and improvement of functional limitations associated with aging and chronic conditions. Moderating factors such as sex, age, the medical diagnosis, and rehabilitation timing for admission status, as well as the expected change related to inpatient rehabilitation, are examined to provide a valid basis for the routine assessment of the quality of medical outcomes.

Design: An observational study was carried out, placing a focus on general and disease-specific health measurements, to assess representative results of multidisciplinary inpatient rehabilitation. Aspects that were possibly confounding and introduced bias were controlled based on data from a quasi-experimental (waiting) control group.

Measures: Existing data or general health indicators were extracted from medical records. The indicators included blood pressure, resting heart rate, self-assessed health, and pain, as well as more disease-specific indicators of physical function and performance (eg, activities of daily living, walking tests, blood lipids). These are used to identify moderating factors related to health outcomes.

Setting And Participants: A standardized collection of routine data from 16,966 patients [61.5 ± 12.5 years; 7871 (46%) women, 9095 (54%) men] with different medical diagnoses before and after rehabilitation were summarized using a descriptive evaluation in terms of a content and factor analysis.

Results: Without rehabilitation, general health indicators did not improve independently and remained stable at best [odds ratio (OR) = 0.74], whereas disease-specific indicators improved noticeably after surgery (OR = 3.20). Inpatient rehabilitation was shown to reduce the risk factors associated with certain lifestyles, optimize organ function, and improve well-being in most patients (>70%; cutoff: z-difference >0.20), with a standardized mean difference (SMD) seen in overall medical quality outcome of -0.48 ± 0.37 [pre- vs post-rehabilitation: η = 0.622; d = -1.22; 95% confidence interval (95% CI) -1.24 to -1.19]. The baseline medical values obtained at the beginning of rehabilitation were influenced by indication, age, and sex (all P < .001); however, these factors have less significant effects on improvements in general health indicators (η < 0.01). According to the disease-specific results, the greatest improvements were found in older patients (SMD for patients >60 vs ≤60 years: 95% CI 0.08-0.11) and during the early rehabilitation stage (η = 0.063).

Conclusions And Implications: Compared with those who received no inpatient rehabilitation, patients who received rehabilitation showed greater improvements in 2 independent areas, general and disease-specific health measures, regardless of their diagnosis, age, and sex. Due to the study design and the use of a nonrandomized waiting group, causal conclusions must be drawn with caution. However, the comparability and stability of the presented results strongly support the validity of the observed improvements associated with inpatient rehabilitation.
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http://dx.doi.org/10.1016/j.jamda.2020.05.034DOI Listing
December 2020

Thermally Induced Formation of HFTCNQ in FTCNQ-Doped Regioregular P3HT.

J Phys Chem Lett 2020 Aug 3;11(16):6586-6592. Epub 2020 Aug 3.

Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London, U.K.

The prototypical system for understanding doping in solution-processed organic electronics has been poly(3-hexylthiophene) (P3HT) p-doped with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (FTCNQ). Multiple charge-transfer states, defined by the fraction of electron transfer to FTCNQ, are known to coexist and are dependent on polymer molecular weight, crystallinity, and processing. Less well-understood is the loss of conductivity after thermal annealing of these materials. Specifically, in thermoelectrics, FTCNQ-doped regioregular (rr) P3HT exhibits significant conductivity losses at temperatures lower than other thiophene-based polymers. Through detailed spectroscopic investigation of progressively heated P3HT films coprocessed with FTCNQ, we demonstrate that this diminished conductivity is due to formation of the nonchromophoric, weak dopant HFTCNQ. This species is likely formed through hydrogen abstraction from the α aliphatic carbon of the hexyl chain at the 3-position of thiophene rings of rr-P3HT. This reaction is eliminated for polymers with ethylene glycol-containing side chains, which retain conductivity at higher operating temperatures. In total, these results provide a critical materials design guideline for organic electronics.
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http://dx.doi.org/10.1021/acs.jpclett.0c01673DOI Listing
August 2020

Universal Spray-Deposition Process for Scalable, High-Performance, and Stable Organic Electrochemical Transistors.

ACS Appl Mater Interfaces 2020 May 23;12(18):20757-20764. Epub 2020 Apr 23.

School of Electrical Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.

Organic electrochemical transistors (OECTs) with high transconductance and good operating stability in an aqueous environment are receiving substantial attention as promising ion-to-electron transducers for bioelectronics. However, to date, in most of the reported OECTs, the fabrication procedures have been devoted to spin-coating processes that may nullify the advantages of large-area and scalable manufacturing. In addition, conventional microfabrication and photolithography techniques are complicated or incompatible with various nonplanar flexible and curved substrates. Herein, we demonstrate a facile patterning method via spray deposition to fabricate ionic-liquid-doped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based OECTs, with a high peak transconductance of 12.9 mS and high device stability over 4000 switching cycles. More importantly, this facile technique makes it possible to fabricate high-performance OECTs on versatile substrates with different textures and form factors such as thin permeable membranes, flexible plastic sheets, hydrophobic elastomers, and rough textiles. Overall, the results highlight the spray-deposition technique as a convenient route to prepare high-performing OECTs and will contribute to the translation of OECTs into real-world applications.
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http://dx.doi.org/10.1021/acsami.0c04776DOI Listing
May 2020

Energetic Control of Redox-Active Polymers toward Safe Organic Bioelectronic Materials.

Adv Mater 2020 Apr 3;32(16):e1908047. Epub 2020 Mar 3.

Simpson Querrey Institute, Northwestern University, Chicago, IL, 60611, USA.

Avoiding faradaic side reactions during the operation of electrochemical devices is important to enhance the device stability, to achieve low power consumption, and to prevent the formation of reactive side-products. This is particularly important for bioelectronic devices, which are designed to operate in biological systems. While redox-active materials based on conducting and semiconducting polymers represent an exciting class of materials for bioelectronic devices, they are susceptible to electrochemical side-reactions with molecular oxygen during device operation. Here, electrochemical side reactions with molecular oxygen are shown to occur during organic electrochemical transistor (OECT) operation using high-performance, state-of-the-art OECT materials. Depending on the choice of the active material, such reactions yield hydrogen peroxide (H O ), a reactive side-product, which may be harmful to the local biological environment and may also accelerate device degradation. A design strategy is reported for the development of redox-active organic semiconductors based on donor-acceptor copolymers that prevents the formation of H O during device operation. This study elucidates the previously overlooked side-reactions between redox-active conjugated polymers and molecular oxygen in electrochemical devices for bioelectronics, which is critical for the operation of electrolyte-gated devices in application-relevant environments.
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http://dx.doi.org/10.1002/adma.201908047DOI Listing
April 2020

Heart Rhythm Analyzed via Shapelets Distinguishes Sleep From Awake.

Front Physiol 2019 17;10:1554. Epub 2020 Jan 17.

Complex Systems and Data Science Lab, Faculty of Information Studies in Novo Mesto, Novo Mesto, Slovenia.

Automatically determining when a person falls asleep from easily available vital signals is important, not just for medical applications but also for practical ones, such as traffic safety or smart homes. Heart dynamics and respiration cycle couple differently during sleep and awake. Specifically, respiratory modulation of heart rhythm or (RSA) is more prominent during sleep, as both sleep and RSA are connected to strong vagal activity. The onset of sleep can be recognized or even predicted as the increase of cardio-respiratory coupling. Here, we employ this empirical fact to design a method for detecting the change of consciousness status (sleep/awake) based only on heart rate variability (HRV) data. Our method relies on quantifying the (self)similarity among - short chunks of HRV time series - whose "shapes" are related to the respiration cycle. To test our method, we examine the HRV data of 75 healthy individuals recorded with microsecond precision. We find distinctive patterns stable across age and sex, that are not only indicative of sleep and awake, but allow to pinpoint the change from awake to sleep almost immediately. More systematic analysis along these lines could lead to a reliable prediction of sleep.
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http://dx.doi.org/10.3389/fphys.2019.01554DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6978775PMC
January 2020

Reversible Electronic Solid-Gel Switching of a Conjugated Polymer.

Adv Sci (Weinh) 2020 Jan 28;7(2):1901144. Epub 2019 Oct 28.

Laboratory of Organic Electronics Department of Science and Technology Linköping University SE-60174 Norrköping Sweden.

Conjugated polymers exhibit electrically driven volume changes when included in electrochemical devices via the exchange of ions and solvent. So far, this volumetric change is limited to 40% and 100% for reversible and irreversible systems, respectively, thus restricting potential applications of this technology. A conjugated polymer that reversibly expands by about 300% upon addressing, relative to its previous contracted state, while the first irreversible actuation can achieve values ranging from 1000-10 000%, depending on the voltage applied is reported. From experimental and theoretical studies, it is found that this large and reversible volumetric switching is due to reorganization of the polymer during swelling as it transforms between a solid-state phase and a gel, while maintaining percolation for conductivity. The polymer is utilized as an electroactive cladding to reduce the void sizes of a porous carbon filter electrode by 85%.
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http://dx.doi.org/10.1002/advs.201901144DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6974956PMC
January 2020

Modification of Indacenodithiophene-Based Polymers and Its Impact on Charge Carrier Mobility in Organic Thin-Film Transistors.

J Am Chem Soc 2020 01 7;142(2):652-664. Epub 2020 Jan 7.

Department of Chemistry and Centre for Plastic Electronics , Imperial College London , Exhibition Road , London SW7 2AZ , United Kingdom.

The polymer indacenodithiophene--benzothiadiazole (IDT-BT) has been thoroughly studied for its use in p-type organic thin-film transistors over the course of the past decade. While a variety of modifications have been made to its structure, few analogues have been able to match or surpass the hole mobility that can be obtained by IDT-BT. Here, we discuss the rationale behind the chemical modifications that have been utilized and suggest design principles toward high-mobility indacenodithiophene-based polymers. It is clear that planarizing intramolecular interactions, which exist between the peripheral thiophene of the IDT unit and the benzothiadiazole, are imperative for achieving high hole mobilities in this relatively amorphous polymer. Moreover, despite the less ordered backbones of the extended fused-ring cores that have recently been utilized (TIF-BT and TBIDT-BT), high mobilities were still attained in these polymers owing to additional interchain charge transfer. Thus, maintaining the beneficial thiophene-benzothiadiazole intramolecular interactions, while further extending the IDT core to promote interchain charge transfer, is a logical strategy toward high-mobility p-type polymers.
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http://dx.doi.org/10.1021/jacs.9b09374DOI Listing
January 2020

Dynamics of Vagal Activity Due to Surgery and Subsequent Rehabilitation.

Front Neurosci 2019 5;13:1116. Epub 2019 Nov 5.

Human Research Institute, Weiz, Austria.

Background: Vagal activity is critical for maintaining key body functions, including the stability of inflammatory control. Its weakening, such as in the aftermatch of a surgery, leaves the body vulnerable to diverse inflammatory conditions, including sepsis.

Methods: Vagal activity can be measured by the cardiorespiratory interaction known as respiratory sinus arrhythmia or high-frequency heart-rate variability (HRV). We examined the vagal dynamics before, during and after an orthopedic surgery. 39 patients had their HRV measured around the period of operation and during subsequent rehabilitation. Measurements were done during 24 h circadian cycles on ten specific days. For each patient, the circadian vagal activity was calculated from HRV data.

Results: Our results confirm the deteriorating effect of surgery on vagal activity. Patients with stronger pre-operative vagal activity suffer greater vagal withdrawal during the peri-operative phase, but benefit from stronger improvements during post-operative period, especially during the night. Rehabilitation seems not only to efficiently restore the vagal activity to pre-operative level, but in some cases to actually improve it.

Discussion: Our findings indicate that orthopedic rehabilitation has the potential to strengthen the vagal activity and hence boost inflammatory control. We conclude that providing a patient with a vagal reinforcement procedure to the surgery ("pre-habilitation") might be a beneficial strategy against post-operative complications. The study also shows the clinical usefulness of quantifying the cardiorespiratory interactions.
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http://dx.doi.org/10.3389/fnins.2019.01116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6849369PMC
November 2019

Low-Temperature Cross-Linking Benzocyclobutene Based Polymer Dielectric for Organic Thin Film Transistors on Plastic Substrates.

J Org Chem 2020 Jan 12;85(1):277-283. Epub 2019 Dec 12.

King Abdullah University of Science and Technology (KAUST), KAUST Solar Center (KSC) , Thuwal 23955-6900 , Saudi Arabia.

The synthesis of a new benzocyclobutene based polymer, , designed as a dielectric material for use in organic thin film transistors was reported. Compared to conventional benzocyclobutene-based materials, the introduction of a butoxide substituent at the 7-position of the benzocyclobutene pendant unit on the polymer allowed to be cross-linked at temperatures of 120 °C, thus rendering it compatible with the processing requirements of flexible plastic substrates. The cross-linking behavior of was investigated by Fourier transform infrared spectroscopy and differential scanning calorimetry, demonstrating cross-linking of the polymer after curing at 120 °C. Bottom-gate bottom-contact organic thin film transistors were fabricated using as dielectric, affording a performance comparable to that of other dielectric polymeric materials.
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http://dx.doi.org/10.1021/acs.joc.9b02981DOI Listing
January 2020

Novel approaches for the assessment of relative body weight and body fat in diagnosis and treatment of anorexia nervosa: A cross-sectional study.

Clin Nutr 2019 12 10;38(6):2913-2921. Epub 2019 Jan 10.

Department of Immunology and Pathophysiology, Medical University of Graz, Otto Loewi Research Center, Heinrichstraße, Graz, Austria.

Background & Aims: Anorexia nervosa (AN) is a severe psychosomatic disease that seriously affects nutritional status. Therapeutic approaches primarily aim for rapid weight restoration by high caloric diets and activity restriction. This often promotes abdominal body fat gain, which potentially negatively influences the patient's compliance and increases the risk of relapse. This study focused on the evaluation of body weight and subcutaneous adipose tissue (SAT) in AN patients by novel approaches.

Methods: The SAT of AN patients (n = 18, body mass index (BMI) 15.3 ± 1.3 kg/m) was determined by a highly accurate and reliable ultrasound method. The sum of SAT thicknesses of eight sites (D) was calculated. Individual metabolic profiles were analyzed. The mass index (MI), which considers body proportions, was used in addition to BMI. Additional to the standard laboratory diagnostics, dermal carotenoids measured by resonance Raman spectroscopy, leptin, and oxidative stress indicators were determined.

Results: The mean MI was 15.7 ± 1.4 kg/m. The D considerably differed between individuals with the same BMI. Half of the patients (Group 1) had low D: 1.3-28.4 mm, and Group 2 showed values up to 58.2 mm (corresponding to approximately 6 kg SAT mass). The two group means differed by more than 300% (P < 0.001). Accordingly, leptin levels significantly differed (P < 0.001). Mean SAT thicknesses were significantly higher in Group 2 at all eight sites. The groups also significantly differed in two oxidative stress parameters: total antioxidative capacity, malondialdehyde-modified low density lipoprotein immunoglobulin M (MDA-LDL IgM), and in the carotenoid level.

Conclusion: Half of the patients had sufficiently high fat mass, despite very low BMI. Consequently, their muscle (and other organ) masses must have been extremely low. Diagnostic criteria and treatment protocols for AN should consider each patient's body composition. In addition to dietary treatments, muscle training at low energy turnover rates may be essential for avoiding unnecessary body fat gain, better treatment results, and long-term recovery.
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http://dx.doi.org/10.1016/j.clnu.2018.12.031DOI Listing
December 2019

Critical review of the molecular design progress in non-fullerene electron acceptors towards commercially viable organic solar cells.

Chem Soc Rev 2019 Mar;48(6):1596-1625

Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London, SW7 2AZ, UK.

Fullerenes have formed an integral part of high performance organic solar cells over the last 20 years, however their inherent limitations in terms of synthetic flexibility, cost and stability have acted as a motivation to develop replacements; the so-called non-fullerene electron acceptors. A rapid evolution of such materials has taken place over the last few years, yielding a number of promising candidates that can exceed the device performance of fullerenes and provide opportunities to improve upon the stability and processability of organic solar cells. In this review we explore the structure-property relationships of a library of non-fullerene acceptors, highlighting the important chemical modifications that have led to progress in the field and provide an outlook for future innovations in electron acceptors for use in organic photovoltaics.
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http://dx.doi.org/10.1039/c7cs00892aDOI Listing
March 2019

Disentangling respiratory sinus arrhythmia in heart rate variability records.

Physiol Meas 2018 05 16;39(5):054002. Epub 2018 May 16.

Physiology, Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz, Neue Stiftingtalstr. 6/D05, A-8010 Graz, Austria. Department of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam-Golm, Germany.

Objective: Several different measures of heart rate variability, and particularly of respiratory sinus arrhythmia, are widely used in research and clinical applications. For many purposes it is important to know which features of heart rate variability are directly related to respiration and which are caused by other aspects of cardiac dynamics.

Approach: Inspired by ideas from the theory of coupled oscillators, we use simultaneous measurements of respiratory and cardiac activity to perform a nonlinear disentanglement of the heart rate variability into the respiratory-related component and the rest.

Main Results: The theoretical consideration is illustrated by the analysis of 25 data sets from healthy subjects. In all cases we show how the disentanglement is manifested in the different measures of heart rate variability.

Significance: The suggested technique can be exploited as a universal preprocessing tool, both for the analysis of respiratory influence on the heart rate and in cases when effects of other factors on the heart rate variability are in focus.
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http://dx.doi.org/10.1088/1361-6579/aabea4DOI Listing
May 2018

Investigation of a Micro-test for Circulatory Autonomic Nervous System Responses.

Front Physiol 2017 21;8:448. Epub 2017 Jul 21.

German Academy for AcupunctureMunich, Germany.

The autonomic nervous system plays an important role in homeostasis and organismic recreation, control of immune function, inflammation, and bone growth. It also regulates blood pressure and orthostasis via vagal and sympathetic pathways. Besides recording of heart rate variability (HRV), which characterizes medium (1-5 min) and long term (circadian) autonomic tone or modulation, no gentle tests of short-term autonomic reactivity and control are available. In 1976 Nogier described a short time cardiovascular response ("Réflexe Auriculo Cardiaque", RAC) which could be used to investigate short term autonomic reactions without changing system characteristics and thus being repeatable in short intervals. In this paper, we investigated the possible application of the Nogier reaction as a micro-test for the identification of a disturbed sensitivity or reactivity of the autonomic nervous system. We statistically analyzed cardiovascular signals derived during the application of small repeated stimuli utilizing methods of signal averaging to characterize the physiological background. Specifically, the Nogier reaction was investigated using simultaneous recordings of ECG, pulse waves, and respiration. Significant fast (delay 1-5 s) and slower (delay 6-12 s) cardio-autonomic responses to different stimuli which characterize short term were observed. From time characteristics and type of signals where they occur we deduce that fast changes observed in heart rate are vagal reactions to the small stimuli whereas slower changes observed in pulse waves stem from sympathetic nervous system responses. The investigated autonomic micro-test opens the possibility to differentially investigate both limbs of the autonomic nervous system with minimal stimuli. It can be performed within seconds and does not change the set point of the system in opposition to less subtle tests such as Valsalva maneuver. Therefore, it is well-suited for quick, repeated measurements of autonomic nervous system reactivity.
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http://dx.doi.org/10.3389/fphys.2017.00448DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5519958PMC
July 2017

Catalyst design for natural-gas upgrading through oxybromination chemistry.

Nat Chem 2016 08 23;8(8):803-9. Epub 2016 May 23.

Department of Chemistry and Applied Biosciences, Institute for Chemical and Bioengineering, ETH Zurich, Vladimir-Prelog-Weg 1, CH-8093 Zurich, Switzerland.

Natural gas contains large volumes of light alkanes, and its abundant reserves make it an appealing feedstock for value-added chemicals and fuels. However, selectively activating the C-H bonds in these useful hydrocarbons is one of the greatest challenges in catalysis. Here we report an attractive oxybromination method for the one-step functionalization of methane under mild conditions that integrates gas-phase alkane bromination with heterogeneously catalysed HBr oxidation, a step that is usually executed separately. Catalyst-design strategies to provide optimal synergy between these two processes are discussed. Among many investigated material families, vanadium phosphate (VPO) is identified as the best oxybromination catalyst, as it provides selectivity for CH3Br up to 95% and stable operation for over 100 hours on stream. The outstanding performance of VPO is rationalized by its high activity in HBr oxidation and low propensity for methane and bromomethane oxidation. Data on the oxybromination of ethane and propane over VPO suggest that the reaction network for higher alkanes is more complex.
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http://dx.doi.org/10.1038/nchem.2522DOI Listing
August 2016

Halogen Chemistry on Catalytic Surfaces.

Chimia (Aarau) 2016 ;70(4):274-8

Institute for Chemical and Bioengineering, Department of Chemical and Applied Biosciences, ETH Zurich Vladimir-Prelog-Weg 1 CH-8093 Zurich, Switzerland.

Halogens are key building blocks for the manufacture of high-value products such as chemicals, plastics, and pharmaceuticals. The catalytic oxidation of HCl and HBr is an attractive route to recover chlorine and bromine in order to ensure the sustainability of the production processes. Very few materials withstand the high corrosiveness and the strong exothermicity of the reactions and among them RuO2 and CeO2-based catalysts have been successfully applied in HCl oxidation. The search for efficient systems for HBr oxidation was initiated by extrapolating the results of HCl oxidation based on the chemical similarity of these reactions. Interestingly, despite its inactivity in HCl oxidation, TiO2 was found to be an outstanding HBr oxidation catalyst, which highlighted that the latter reaction is more complex than previously assumed. Herein, we discuss the results of recent comparative studies of HCl and HBr oxidation on both rutile-type (RuO2, IrO2, and TiO2) and ceria-based catalysts using a combination of advanced experimental and theoretical methods to provide deeper molecular-level understanding of the reactions. This knowledge aids the design of the next-generation catalysts for halogen recycling.
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http://dx.doi.org/10.2533/chimia.2016.274DOI Listing
June 2016

Interplay between surface chemistry and performance of rutile-type catalysts for halogen production.

Chem Sci 2016 May 27;7(5):2996-3005. Epub 2016 Jan 27.

Institute for Chemical and Bioengineering , Department of Chemistry and Applied Biosciences , ETH Zurich , Vladimir-Prelog-Weg 1 , 8093 Zurich , Switzerland . Email:

Catalytic HBr oxidation is an integral step in the bromine-mediated functionalisation of alkanes to valuable chemicals. This study establishes the relationships between the mechanism of HBr oxidation over rutile-type oxides (RuO, IrO, TiO) and their apparent catalytic performance. Comparison with the well-studied HCl oxidation revealed distinct differences in surface chemistry between HBr and HCl oxidation that impact the stability and activity of the catalysts. The kinetic fingerprints of both oxidation reactions over the three rutile-type oxides investigated are compared using temporal analysis of products, which substantiates the energy profiles derived from density functional theory. The quantitative determination of the halogen uptake under conditions using prompt gamma activation analysis demonstrates that RuO suffers from extensive subsurface bromination upon contact with hydrogen bromide, particularly at low temperature and low O : HBr ratios, which negatively affects the stability of the catalyst. TiO exhibits intrinsically low halogen coverage (30-50%) under all the conditions investigated, due to its unique defect-driven mechanism that renders it active and stable for Br production. On the contrary, for HCl oxidation TiO is inactive, and the chlorination of the highly active RuO is limited to the surface. Differences in the extent of surface halogenation of the materials were also confirmed by high-resolution transmission electron microscopy and explained by the DFT calculations. These insights into the molecular-level processes taking place under working conditions pave the way for the design of the next generation catalysts for bromine production.
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http://dx.doi.org/10.1039/c5sc04247jDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6004776PMC
May 2016

Oxychlorination-Dehydrochlorination Chemistry on Bifunctional Ceria Catalysts for Intensified Vinyl Chloride Production.

Angew Chem Int Ed Engl 2016 Feb 28;55(9):3068-72. Epub 2016 Jan 28.

Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 1, 8093, Zurich, Switzerland.

Ceria catalyzes the one-step production of the vinyl chloride monomer (VCM) from ethylene with a high yield because of its bifunctional character: redox centers oxychlorinate ethylene to ethylene dichloride (EDC), which is subsequently dehydrochlorinated to VCM over strong acid sites generated in situ. Nanocrystalline CeO2 and CeO2-ZrO2 lead to a VCM yield of 25 % in a single pass, outperforming the best reported systems and reaching industrially attractive levels. The use of CeO2 intensifies the current two-step process within PVC production encompassing CuCl2 -catalyzed oxychlorination and thermal cracking. In addition, ceria-based materials offer stability advantages with respect to the archetypical CuCl2 -based catalysts.
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http://dx.doi.org/10.1002/anie.201510903DOI Listing
February 2016

The virtue of defects: stable bromine production by catalytic oxidation of hydrogen bromide on titanium oxide.

Angew Chem Int Ed Engl 2014 Aug 2;53(33):8628-33. Epub 2014 Jun 2.

Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 1, 8093 Zurich (Switzerland).

Rutile TiO2 is a heavily investigated oxide with, to date, scarce applications in industrial catalysis. The inactivity of this material in oxidations has been related to its inability to dissociate molecular oxygen. Herein we show how rutile catalyzes the oxidation of HBr to Br2 through defect states that are introduced during the reaction. The identification of active, stable, and abundant materials for bromine production is key to the future implementation of Br2-mediated alkane functionalization processes. The catalytic properties of TiO2 are discussed in comparison to expensive rutile-type oxides, such as RuO2 and IrO2, on the basis of surface characterization and molecular modeling.
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http://dx.doi.org/10.1002/anie.201404022DOI Listing
August 2014

In vivo cardiac phase response curve elucidates human respiratory heart rate variability.

Nat Commun 2013 ;4:2418

Institut für Pädagogik, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 75, 24118 Kiel, Germany.

Recovering interaction of endogenous rhythms from observations is challenging, especially if a mathematical model explaining the behaviour of the system is unknown. The decisive information for successful reconstruction of the dynamics is the sensitivity of an oscillator to external influences, which is quantified by its phase response curve. Here we present a technique that allows the extraction of the phase response curve from a non-invasive observation of a system consisting of two interacting oscillators--in this case heartbeat and respiration--in its natural environment and under free-running conditions. We use this method to obtain the phase-coupling functions describing cardiorespiratory interactions and the phase response curve of 17 healthy humans. We show for the first time the phase at which the cardiac beat is susceptible to respiratory drive and extract the respiratory-related component of heart rate variability. This non-invasive method for the determination of phase response curves of coupled oscillators may find application in many scientific disciplines.
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http://dx.doi.org/10.1038/ncomms3418DOI Listing
April 2014

Detecting body fat-A weighty problem BMI versus subcutaneous fat patterns in athletes and non-athletes.

PLoS One 2013 26;8(8):e72002. Epub 2013 Aug 26.

Medical University Vienna, Clinic for Internal Medicine III, Department of Endocrinology and Metabolism, Vienna, Austria ; Medical University Graz, Inst. of Pathophysiology and Immunology, Graz, Austria ; SIPCAN Special Institute for Preventive Cardiology and Nutrition, Salzburg, Austria ; Medical University Graz, Inst. of Physiological Chemistry, Graz, Austria.

We aimed to describe the relationship between BMI and the subcutaneous adipose tissue topography within young athletes and non-athletic controls, to comparatively evaluate the diagnostic powers of subcutaneous adipose tissue thicknesses at different body sites, furthermore to explore appropriate cut-offs to discriminate between athletes and controls. Measurements were determined in 64 males and 42 females, who were subsequently separated into two even groups (athletes and non-athletes). The optical device LIPOMETER was applied at standardised body sites to measure the thickness of subcutaneous adipose tissue layers. To calculate the power of the different body sites and the BMI to discriminate between athletes and non-athletes, receiver operating characteristic curve analysis was performed. In men, the neck (optimal cut-off value 2.3 mm) and trunk (optimal cut-off value 15.5 mm) provided the strongest discrimination power: with 90.6% (58 of 64) of the subjects being correctly classified into athletes or non-athletes. Discrimination power of the BMI values was 64.1% (41 of 64 were correctly classified). In women, the upper back (optimal cut-off value 3.3 mm) and arms (optimal cut-off value 15.9 mm) provided the strongest discrimination power with 88.1% (37 of 42 being correctly classified). When using BMI to discriminate between athletes and non-athletes only 52.4% (22 of 42) were correctly classified. These results suggest that compared to BMI levels, subcutaneous fat patterns are a more accurate way of discriminating between athletes and non-athletes. In particular the neck and the trunk compartment in men and the upper back and arms compartment in women, were the best sites to discriminate between young athletes and non-athletes on the basis of their fat patterns.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0072002PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3753354PMC
April 2014

A measure of obesity: BMI versus subcutaneous fat patterns in young athletes and nonathletes.

Coll Antropol 2013 Jun;37(2):351-7

Medical University Graz, Institute of Pathophysiology and Immunology, Graz, Austria

Although the body mass index (BMI, kg/m2) is widely used as a surrogate measure of adiposity, it is a measure of excess weight, rather than excess body fat, relative to height. The BMI classification system is derived from cut points obtained from the general population. The influence of large muscle mass on BMI in athletes and young adults may misclassify these individuals as overweight and obese. Therefore, the use of subcutaneous adipose tissue topography (SAT-Top) may be more effective than BMI in assessing obesity in physically active people and young adults. The purposes of this study were 1) to describe the relationship between the BMI and SAT-Top of young athletes and nonathletes, and 2) to determine the accuracy of the BMI as a measure of overweight. Height, weight, BMI and SAT-Top were determined in 64 males (25.0 +/- 6.7) and 42 females (24.8 +/- 7.0), who were subsequently separated into two even groups (athletes and non-athletes). The optical Lipometer device was applied to measure the thickness of subcutaneous adipose tissue (SAT). While BMI was similar, male athletes showed a 50.3% lower total SAT thickness compared to their male nonathlete controls. Even though female athletes had significantly higher BMI and weight scores, their total SAT thickness was 34.9% lower than their nonathlete controls. These results suggest subcutaneous fat patterns are a better screening tool to characterize fatness in physically active young people.
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June 2013
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