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1.
ACS Nano ; 18(18): 11655-11664, 2024 May 07.
Article in English | MEDLINE | ID: mdl-38652866

ABSTRACT

Conjugated polymers have become materials of choice for applications ranging from flexible optoelectronics to neuromorphic computing, but their polydispersity and tendency to aggregate pose severe challenges to their precise characterization. Here, the combination of vacuum electrospray deposition (ESD) with scanning tunneling microscopy (STM) is used to acquire, within the same experiment, assembly patterns, full mass distributions, exact sequencing, and quantification of polymerization defects. In a first step, the ESD-STM results are successfully benchmarked against NMR for low molecular mass polymers, where this technique is still applicable. Then, it is shown that ESD-STM is capable of reaching beyond its limits by characterizing, with the same accuracy, samples that are inaccessible to NMR. Finally, a recalibration procedure is proposed for size exclusion chromatography (SEC) mass distributions, using ESD-STM results as a reference. The distinctiveness of the molecular-scale information obtained by ESD-STM highlights its role as a crucial technique for the characterization of conjugated polymers.

2.
Z Evid Fortbild Qual Gesundhwes ; 185: 54-63, 2024 Apr.
Article in German | MEDLINE | ID: mdl-38388279

ABSTRACT

BACKGROUND: Data collected by general practitioners (GPs) may provide potential for health services research. In this study, we investigated if clinical questions can be answered with GPs' electronic medical records (EMRs) by means of diagnosing community-acquired pneumonia (CAP). METHOD: Patients diagnosed with CAP, defined as ICD code J18.9, were identified in the fourth quarter of 2021. The data were derived from the EMR system (Medical Office®) of a central German association of 30 general practices, using three different approaches: 1. The integrated statistic tool was used to record whether patients were referred for radiological diagnostic confirmation. 2. Retrospectively, EMRs were evaluated manually by a doctor familiar with the EMR. 3. The raw data of the EMR system were extracted by automated export. The information obtained through the three types of access was compared. For each patient case, detailed comments on problems and specifics were documented and evaluated by qualitative content analysis (QCA) according to Mayring. RESULTS: In total, 164 patients diagnosed with CAP were identified. The numbers of documented radiological diagnostic confirmations varied between data approaches: While the manual evaluation of the EMRs revealed 60 referred patients, the statistics tool identified 38 of these cases. The export of the raw data identified 58 referrals to radiography after adjustment. According to QCA, there was a high variation in applied diagnostics and time of diagnosis. Referrals for radiography were made both before and after coding of the diagnosis. In case of hospitalization, X-rays were usually performed during the inpatient stay. Laboratory tests were performed as an alternative to radiography. There was also a high variation in the documentation of risk factors and diagnostic certainty. DISCUSSION: The statistics tool integrated into the EMR system is a quick way to perform simple queries but proved to be impracticable for complex questions. The EMRs provide detailed information but need to be evaluated manually. An automated data export from the raw data offers both detailed information and access to large volumes of data but requires complex preparation and appropriate IT expertise. CONCLUSION: Based on the example of diagnosed CAP in a GP setting, the use of data extracted from an EMR system seems to be feasible to answer simple clinical questions. However, it is necessary to adapt the data export, and a comparison with a small number of manually evaluated cases is useful to achieve valid results.


Subject(s)
Electronic Health Records , General Practitioners , Humans , Retrospective Studies , Feasibility Studies , Germany
3.
Chemphyschem ; 25(9): e202300971, 2024 May 02.
Article in English | MEDLINE | ID: mdl-38372667

ABSTRACT

Conjugated donor-acceptor copolymers hold great potential as materials for high-performance organic photovoltaics, organic transistors and organic thermoelectric devices. Their low optical bandgap is achieved by alternation of donor and acceptor moieties along the polymer chain, leading to a pronounced charge-transfer character of electronic excitations. However, the influence of appended side chains and of chemical defects of the backbone on their photophysical and conformational properties remains largely unexplored on the level of individual chains. Here, we employ room temperature single-molecule photoluminescence spectroscopy on four compounds based on the prototypical copolymer PCDTBT with systematically changed chemical structure. Our results show that an increasing density of statistically added hexyl chains to the TBT comonomer distorts the molecular conformation, likely through the increase of average dihedral angles along the backbone. We find that, although the conformation becomes more twisted with high hexyl density, the side chains appear to stabilize the backbone in this twisted conformation. In addition, we demonstrate that homocoupling defects along the backbone barely influence the PL spectra of single chains, and thus intra-chain electronic properties.

4.
Macromolecules ; 57(3): 1238-1247, 2024 Feb 13.
Article in English | MEDLINE | ID: mdl-38370913

ABSTRACT

This study demonstrates the use of 1,5-naphthalenedisulfonic acid as a suitable building block for the efficient and economic preparation of alternating sulfonated polyphenylenes with high ion-exchange capacity (IEC) via Suzuki polycondensation. Key to large molar masses is the use of an all-meta-terphenyl comonomer instead of m-phenyl, the latter giving low molar masses and brittle materials. A protection/deprotection strategy for base-stable neopentyl sulfonates is successfully implemented to improve the solubility and molar mass of the polymers. Solution-based deprotection of polyphenylene neopentyl sulfonates at 150 °C in dimethylacetamide eliminates isopentylene quantitatively, resulting in membranes with high IEC (2.93 mequiv/g) and high proton conductivity (σ = 138 mS/cm). Water solubility of these copolymers with high IEC requires thermal cross-linking to prevent their dissolution under operating conditions. By balancing the temperature and time of the cross-linking process, water uptake can be restricted to 50 wt %, retaining an IEC of 2.33 mequiv/g and a conductivity of 85 mS/cm. Chemical stability is addressed by treatment of the membranes under Fenton's conditions and by considering barrier heights for desulfonation using density functional theory (DFT) calculations. The DFT results suggest that 1,5-disulfonated naphthalenes are at least as stable as sulfonated polyphenylenes against desulfonation.

5.
ACS Appl Polym Mater ; 6(1): 457-465, 2024 Jan 12.
Article in English | MEDLINE | ID: mdl-38230364

ABSTRACT

Single-oxygen-containing branched side chains are designed and used to solubilize n-type copolymers consisting of BDF (benzodifuranone), isatin, and thiophene-based units. We present a simple synthetic approach to side chains with varying linker distances between the backbone and the branching point. The synthetic pathway is straightforward and modular and starts with commercially available reagents. The side chains give rise to excellent solubilities of BDF-thiophene copolymers of up to 90 mg/mL, while still being moderate in size (26-34 atoms large). The excellent solubility furthermore allows high molar mass materials. BDF-thiophene copolymers are characterized in terms of optoelectronic and thermoelectric properties. The electrical conductivity of chemically doped polymers is found to scale with molar mass, reaching ∼1 S/cm for the highest molar mass and longest backbone-branching point distance.

6.
ACS Appl Mater Interfaces ; 16(5): 6301-6314, 2024 Feb 07.
Article in English | MEDLINE | ID: mdl-38265883

ABSTRACT

Lithium-sulfur (Li-S) batteries hold a promising position as candidates for next-generation high-energy storage systems. Here, we combine inverse vulcanization of sulfur with multiwalled carbon nanotubes (MWCNTs) to increase the conductivity of cathode materials for Li-S batteries. The mixing process of inversely vulcanized sulfur copolymer networks with MWCNTs is aided by shear in a two-roll mill to take advantage of the soft nature of the copolymer. The high-throughput mixing method demands a source of conductive carbon that can be intimately mixed with the S copolymer, rendering MWCNTs an excellent choice for this purpose. The resulting sulfur copolymer network-MWCNTs composites were thoroughly characterized in terms of structure, chemical composition, thermal, and electronic transport properties, and finally evaluated by electrochemical benchmarking. These promising hybrids yielded electrodes with high sulfur content and demonstrate stable electrochemical performance exhibiting a specific capacity of ca. 550 mAh·gsulfur-1 (380 mAh·gelectrode-1) even after 500 charge-discharge cycles at specific current of 167 mA·g-1 (corresponds to 0.1C discharge rate), and thus are superior to melt-infiltrated reference samples.

7.
Swiss Med Wkly ; 153: 40131, 2023 Dec 01.
Article in English | MEDLINE | ID: mdl-38037847

ABSTRACT

AIMS: Early diagnosis of autism spectrum disorders (ASD) offers the possibility of early intervention and, in turn, gains in adaptive behaviour, language and cognition. The aim of the present study was to analyse whether age at diagnosis of autism spectrum disorders decreased in two regions of Switzerland from 2006 to 2016 following the implementation of different screening and referral techniques. In southern Switzerland, systematic paediatric screening using the Modified Checklist for Autism (M-CHAT) in toddlers was implemented in 2013, whereas in northwestern Switzerland, periodic trainings were used to increase paediatrician awareness of ASD. We investigated which method was associated with a younger average age at diagnosis. METHODS: We conducted a retrospective, two-centre study searching clinical records of children and adolescents (aged 0-16 years) diagnosed with ASD in two neuropaediatric departments at Swiss hospitals between January 2006 and December 2016. All patients were diagnosed via a standardised evaluation based on two approved diagnostic tests: the Autism Diagnostic Observation Schedule-Second Edition (ADOS-2) and the Autism Diagnostic Interview-Revised (ADI-R). RESULTS: In southern Switzerland, training and subsequent widespread use of the M-CHAT among paediatricians appeared to contribute to a significantly younger age at diagnosis. Age at diagnosis did not significantly decrease during the same period in northwestern Switzerland. CONCLUSION: Our results point to the possibility of successfully reducing age at diagnosis in specific geographic areas through the implementation of screening questionnaires, such as the M-CHAT, at year 2 well-baby visits.


Subject(s)
Autism Spectrum Disorder , Infant , Humans , Child , Adolescent , Autism Spectrum Disorder/diagnosis , Switzerland , Sensitivity and Specificity , Retrospective Studies , Mass Screening/methods , Checklist
8.
Mater Horiz ; 10(12): 5538-5546, 2023 Nov 27.
Article in English | MEDLINE | ID: mdl-37853812

ABSTRACT

The optoelectronic performance of organic semiconductor devices is related to the static and dynamic disorder in the film. The disorder can be assessed by considering the linewidth of its optical spectra. We focus on identifying the effect of conjugation length distribution on the static energetic disorder. Hence, we disentangle the contributions of static and dynamic disorder to the absorption and emission spectra of poly(3-(2,5-dioctylphenyl)-thiophene) (PDOPT) by exploring how the linewidth and energy of the spectra evolve upon cooling the sample from 300 K to 5 K. PDOPT has sterically hindered side chains that arrange such as to cause a planarized polymer backbone. This makes it a suitable model for a quasi-one-dimensional molecular system. By modelling the conjugated segments as coupled oscillators we find that the linewidth contribution resulting from the variation of conjugation length decreases linearly with decreasing exciton energy and extrapolates to zero at the energy corresponding to an infinite chain. These results provide a new avenue to the design of low disorder and hence high mobility polymeric semiconductors.

9.
Phys Chem Chem Phys ; 25(30): 20395-20404, 2023 Aug 02.
Article in English | MEDLINE | ID: mdl-37465922

ABSTRACT

Inverse vulcanization is a promising route to stabilize sulfur in lithium-sulfur batteries, but the resulting sulfur strand lengths in the materials are elusive. We address the strand length by characterization via sulfur near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Theoretical predictions of NEXAFS spectra for model molecules containing strands with up to three sulfur atoms are verified by experiment. The near perfect agreement between simulation and experiment on the absolute energy scale allows for the predictions for larger chain lengths also. Inspection and interpretation of NEXAFS spectra from real battery materials on this basis reveals the appearance of single connecting sulfur atoms for very low sulfur content, and of longer strands when the sulfur fraction increases.

10.
Sci Total Environ ; 887: 163986, 2023 Aug 20.
Article in English | MEDLINE | ID: mdl-37150465

ABSTRACT

Increased crop production is a main goal to feed the predicted human population in future. The current management practice is, however, not sustainable as it depends on high amounts of fertilizer application and is highly vulnerable to decreased soil water availability. At the same time it becomes more and more crucial to reduce or even mitigate anthropogenic greenhouse gas (GHG) emissions. A possible way to enable this, might be the increase of the soil C sequestration and thus the C sink function of arable lands. A recent and potentially more sustainable idea is the single time fertilization with amorphous silicon (ASi) which is known to increase both nutrient and water availability. Here we show for the first time on the basis of a field plot experiment how a fertilization with ASi is affecting both, crop yield and the C sequestration of the soils in an agricultural system cultivating wheat. We found a strong increase in wheat yield and biomass production after ASi fertilization by increasing soil moisture during the whole growing season. Additionally, despite a relatively short growing season, Si fertilization increased the net C uptake by soils, i.e., C sequestration with both Si fertilized treatments showing a negative net ecosystem C balance (soil C gain) during the measurement period, while the control showed a small positive net ecosystem C balance (soil C loss). To our best knowledge, this is the first time such effect has ever been observed. In summary, our study demonstrates a new management strategy for crop production increasing yield and biomass production as well as soil C uptake on a more sustainable basis, by a single time fertilization with ASi.

11.
J Am Chem Soc ; 2023 Apr 06.
Article in English | MEDLINE | ID: mdl-37022930

ABSTRACT

Efficient organic electronic devices are fabricated from both small molecules and disperse polymers, but materials with characteristics in between remain largely unexplored. Here, we present a gram-scale synthesis for a series of discrete n-type oligomers comprising alternating naphthalene diimide (NDI) and bithiophene (T2). Using C-H activation, discrete oligomers of type T2-(NDI-T2)n (n ≤ 7) and persistence lengths up to ∼10 nm are made. The absence of protection/deprotection reactions and the mechanistic nature of Pd-catalyzed C-H activation allow one to produce symmetrically terminated species almost exclusively, which is key to the fast preparation, high yields, and the general success of the reaction pathway. The reaction scope includes different thiophene-based monomers, end-capping to yield NDI-(T2-NDI)n (n ≤ 8), and branching at T2 units by nonselective C-H activation under certain conditions. We show how the optical, electronic, thermal, and structural properties depend on oligomer length along with a comparison to the disperse, polymeric analogue PNDIT2. From theory and experiments, we find that the molecular energy levels are not affected by chain length resulting from the strong donor-acceptor system. Absorption maxima saturate for n = 4 in vacuum and for n = 8 in solution. Linear oligomers T2-(NDI-T2)n are highly crystalline with large melting enthalpies up to 33 J/g; NDI-terminated oligomers show reduced crystallinity, stronger supercooling, and more phase transitions. Branched oligomers and those with bulky thiophene comonomers are amorphous. Large oligomers exhibit similar packing characteristics compared to PNDIT2, making these oligomers ideal models to study length-structure-function relationships at constant energy levels.

12.
Retina ; 43(3): 531-532, 2023 03 01.
Article in English | MEDLINE | ID: mdl-32404845

ABSTRACT

PURPOSE: To develop a quick and cost-effective alternative to a chandelier light for vitrectomy. METHODS: The surgical material available in an ophthalmologic operating room was used to create a sleeve for the vitrectomy light probe and tested on 30 consecutive retinal detachment cases for feasibility. RESULTS: A 64 × 5-mm cotton swab stick was cut into the length of the light probe minus the length of the trocar and subsequently pierced by a blunt needle. With this sleeve, the light probe could be safely handled similar to a chandelier light during surgery. CONCLUSION: A sleeve for the light probe can serve as a substitute for a chandelier light during scleral depression in retinal detachment surgery.


Subject(s)
Retinal Detachment , Humans , Retinal Detachment/surgery , Visual Acuity , Retina/surgery , Vitrectomy , Scleral Buckling , Treatment Outcome
13.
J Cataract Refract Surg ; 49(2): 154-158, 2023 02 01.
Article in English | MEDLINE | ID: mdl-36100162

ABSTRACT

PURPOSE: To assess the influence of capsular tension ring (CTR) implantation on the development of in-the-bag (ITB) dislocations after cataract surgery. SETTING: Department of Ophthalmology Graz, Graz, Austria. DESIGN: Single-center, retrospective cohort study. METHODS: The medical records of patients who underwent cataract operation between 1996 and 2017 were analyzed. Cox proportional hazards regression analysis was used to assess the influence of CTR implantation and other predisposing factors (pseudoexfoliation [PEX], age, retinitis pigmentosa, sex, zonular weakness, uveitis, high myopia, and intraocular lens design and material) on ITB dislocations. RESULTS: ITB dislocations were found in 111 (0.16%) of 68199 eyes (46 632 patients). In the multivariate analysis adjusted for other predisposing risk factors, a CTR implantation was associated with a lower risk of an ITB dislocation (hazard ratio [HR], 0.29; 95% CI, 0.11-0.80; P = .017). In eyes with PEX, a CTR implantation was associated with an HR of 0.16 (95% CI, 0.04-0.70; P = .015), whereas eyes without PEX had an HR of 0.80 (95% CI, 0.14-4.41; P = .793). A CTR implantation in eyes with zonular weakness resulted in a potentially lower risk (HR, 0.37; 95% CI, 0.12-1.12; P = .078). CONCLUSIONS: According to the dataset, implantation of a CTR was a protective measure against an ITB dislocation. Especially in patients with zonular weakness and PEX, the CTR implantation was association with a lower risk of ITB dislocations. In patients without PEX, no association was established.


Subject(s)
Cataract , Lens Capsule, Crystalline , Lenses, Intraocular , Phacoemulsification , Humans , Lens Implantation, Intraocular/methods , Phacoemulsification/methods , Retrospective Studies , Cataract/complications , Lens Capsule, Crystalline/surgery
14.
J Am Chem Soc ; 144(48): 21897-21907, 2022 12 07.
Article in English | MEDLINE | ID: mdl-36414534

ABSTRACT

Mechanochromophores based on conformational changes of donor-acceptor-donor (DAD) springs allow sensing of forces acting on polymer chains by monotonic changes of absorbance or photoluminescence (PL) wavelength. Here, we identify a series of thiophene (D)-flanked quinoxalines (A) as molecular torsional springs for force sensing in bulk polymers at room temperature. The mode of DAD linkage to the polymer matrix and linker rigidity are key parameters that influence the efficacy of force transduction to the DAD spring and thus mechanochromic response, as probed by in situ PL spectroscopy of bulk films during stress-strain experiments. The largest shift of the PL maximum, and thus the highest sensitivity, is obtained from an ansa-DAD spring exhibiting bridged D units and a stiff A linker. Using detailed spectroscopy and density functional theory calculations, we reveal conformer redistribution in the form of a thiophene ring flip as the major part of the overall mechanochromic response. At forces as low as 27 pN at early stages of deformation, the ring flip precedes mechanically induced planarization of the ansa-DAD spring, the latter process producing a PL shift of 21 nm nN-1. Within the stress-strain diagram, the thiophene ring flip and DAD planarization are thus two separated processes that also cause irreversible and reversible mechanochromic responses, respectively, upon sample failure. As the thiophene ring flip requires much smaller forces than planarization of the DAD spring, such micromechanical motion gives access to sensing of tiny forces and expands both sensitivity and the force range of conformational mechanochromophores.


Subject(s)
Thiophenes
15.
Front Med (Lausanne) ; 9: 968318, 2022.
Article in English | MEDLINE | ID: mdl-36203753

ABSTRACT

Purpose: There exists remarkable variation in definitions for the location of the center of a keratoconus. The objective of this study was to analyze deviations between locations obtained by different tomographic maps for that purpose. Furthermore, it was investigated whether these deviations are influenced by disease severity. Methods: In 162 eyes with keratoconus, corneal tomographic maps derived by Scheimpflug technology were retrospectively analyzed to determine the cone location with 5 different methods: maximum axial curvature of the front surface (Kmax), maximum tangential curvature of the front surface (tKmax), minimum pachymetry (Pachymin), maximum elevation of the front surface (ELEF), and maximum elevation of the back surface (ELEB). Distances between the locations were calculated and tested for a correlation with keratoconus severity and distance between cone and corneal vertex. Results: Cone locations derived from the curvature maps (Kmax, tKmax) showed the lowest agreement with the locations determined by pachymetry or elevation maps. The largest distances were found between Kmax and Pachymin [Median and Interquartile range: 1.19 mm (0.87, 1.60)], Kmax and ELEB [1.12 mm (0.79, 1.41)], and Kmax and ELEF [0.97 mm (0.64, 1.27)]. Low distances (<0.5 mm) were calculated between ELEB and ELEF, and ELEB and Pachymin. All of the calculated distances between the locations showed a significant negative correlation with keratoconus severity and most of them increased significantly with a more peripheral position of the cone (p < 0.05). Conclusions: There was low consistency between different methods for describing the location of a keratoconus. Curvature-based determinations of the cone center (Kmax, tKmax) showed the highest deviations and should not be used for that purpose. However, the discrepancies between different cone location methods diminished with increasing disease severity and more central position of the cone.

16.
ACS Appl Mater Interfaces ; 14(39): 44772-44781, 2022 Oct 05.
Article in English | MEDLINE | ID: mdl-36153978

ABSTRACT

We designed high-volumetric-energy-density supercapacitors from monolithic composites composed of self-standing carbon foam (CF) as the conducting matrix and embedded hierarchically organized porous carbon (PICK) as the active material. Using multiprobe scanning tunneling microscopy at selected areas, we were able to disentangle morphology-dependent contributions of the heterogeneous composite to the overall conductivity. Adding PICK is found to enhance the conductivity of the monoliths by providing additional links for the CF network, enabling high and stable performance. The resulting all-carbon CF-PICK composites were used as self-standing electrodes for symmetric supercapacitors without the need for a binder, additional conducting additive, metals as a current collector, or casting/drying steps. Supercapacitors achieved a capacitance of 181 F g-1 based on the entire mass of the monolithic electrode as well as an outstanding rate capability. Our symmetrical supercapacitors also delivered a record volumetric energy density of 19.4 mW h cm-3 when using aqueous electrolytes. Excellent cycling stability with almost quantitative retention of capacitance was found after 10,000 cycles in 6.0 M KOH as the electrolyte. Furthermore, charge-discharge testing at different currents demonstrated the fast charge-discharge capability of this material system that meets the requirements for practical applications.

17.
ACS Macro Lett ; 11(6): 760-765, 2022 06 21.
Article in English | MEDLINE | ID: mdl-35612497

ABSTRACT

Molecular force transduction in tough and glassy poly(meta,meta,para-phenylene) (PmmpP) was investigated as a function of Mn using covalently incorporated mechanochromic donor-acceptor torsional springs based on an ortho-substituted diphenyldiketopyrrolopyrrole (oDPP). Blending oDPP-PmmpP probe chains with long PmmpP matrix chains allowed us to investigate molar-mass-dependent mechanochromic properties for a series of specimens having mechanically identical properties. In the strain-hardening regime, the mechanochromic response (Δλmax,em) was found to be a linear function of the acting stress and fully reversible, making oDPP-PmmpP a real-time and quantitative stress sensor. For entangled and nonentangled probe chains, distinctly different values of Δλmax,em were observed, yielding a critical molar mass of Mc ≈ 11 kg mol-1 for PmmpP. Once physical cross-linking of oDPP in the network of PmmpP was ensured, Δλmax,em was found to be independent of Mn. The resulting value of Mc is in very good agreement with results from rheology.


Subject(s)
Polymers , Molecular Weight , Rheology
18.
J Environ Manage ; 317: 115383, 2022 Sep 01.
Article in English | MEDLINE | ID: mdl-35636114

ABSTRACT

Peatlands ecosystem is one of the largest global terrestrial carbon pools. However, there is a shortness of its characterisation and information through new proximal sensing approaches. The visible and near-infrared spectroscopy is an inexpensive, quick, non-evasive, proximal sensing and low-cost analysis employed in field and/or laboratory. Despite that, there is another current issue in using this tool for creating global models, which is how it can retrieve local characteristics such as soil organic carbon (SOC) and total nitrogen (TN) in peatlands ecosystems. The aims in this study were to: (i) create a local model for quantifying SOC and TN finding the best pre-processing and machine learning methods in peatlands ecosystem, and (ii) evaluate the contribution of SOC and TN data collected in that ecosystem to global models in European Union. The hypothesis was that the SOC and TN data sampled in peatlands ecosystem can improve analytical quantification of those soil properties. The soil and spectral datasets were retrieved from the Land Use/Cover Area frame Statistical Survey with 21,771 observations at 0-20 cm depth and 63 soil cores in a degraded peatland in Germany with 262 observations up to 2 m depth. We evaluated three spectral pre-processing techniques with the Partial Least Square Regression (PLSR), Random Forest (RF), and Cubist machine learning algorithms. The best pre-processing technique was achieved applying Savitzky-Golay smoothing with a window size of 71 points, 2nd order polynomial, and zero derivative with Cubist algorithm for both SOC and TN predictions. Furthermore, merging the local with global data for global modelling demonstrated to improve SOC and TN predictions because of the local data representativeness and quality. Therefore, the SOC and TN data sampled in peatlands ecosystem can improve quantification of those soil properties in field and laboratory, which are crucial proxies for GHG emissions and climate change.


Subject(s)
Carbon , Soil , Carbon/chemistry , Ecosystem , Nitrogen/analysis , Soil/chemistry , Spectroscopy, Near-Infrared/methods
19.
ACS Cent Sci ; 8(2): 268-274, 2022 Feb 23.
Article in English | MEDLINE | ID: mdl-35233458

ABSTRACT

The relationship between Kuhn length l k , Kuhn monomer volume v 0, and plateau modulus G N 0, initially proposed by Graessley and Edwards for flexible polymers, and extended by Everaers, has a large gap in experimental data between the flexible and stiff regimes. This gap prevents the prediction of mechanical properties from the chain structure for any polymer in this region. Given the chain architecture, including a semiflexible backbone and side chains, conjugated polymers are an ideal class of material to study this crossover region. Using small angle neutron scattering, oscillatory shear rheology, and the freely rotating chain model, we have shown that 12 polymers with aromatic backbones populate a large part of this gap. We also have shown that a few of these polymers exhibit nematic ordering, which lowers G N 0. When fully isotropic, these polymers follow a relationship between l k , v 0, and G N 0, with a simple crossover proposed in terms of the number of Kuhn segments in an entanglement strand N e.

20.
ACS Appl Mater Interfaces ; 13(49): 58486-58497, 2021 Dec 15.
Article in English | MEDLINE | ID: mdl-34866388

ABSTRACT

High mass loading asymmetric micro-supercapacitors (MSCs) are key components for the development of high-performance energy and power supply systems. Here, a concept for achieving high mass loading electrodes is presented and applied to high mass loading micro-supercapacitors with ultrahigh areal energy and power density. The positive electrode is made from porous carbon with birnessite coverage and multiwalled carbon nanotubes (CNTs) as conducting additives (PIC-CNTs-MnO2). The negative electrode is prepared from hierarchically porous active carbon mixed with CNTs (PICK-CNTs). Both positive and negative electrode materials are tailored to ensure a high content of macro- and mesopores. MSCs with an optimized mass loading of 13.9 mg·cm-2 (maximum: 23.6 mg·cm-2) provide an ultrahigh areal capacitance of 1.13 F·cm-2 (volumetric capacitance: 22.6 F·cm-3), an outstanding energy of 627.8 µWh·cm-2, and a maximum power density of 64 mW·cm-2. About 85% of the initial capacitance remained after 5000 cycles. Moreover, shunt and tandem device testing confirmed a high uniformity of these MSCs, meeting the requirements of adjustable output currents and voltages in microchips.

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