TY - JOUR A1 - Poghossian, A. A1 - Weil, M. A1 - Cherstvy, Andrey G. A1 - Schöning, M. J. T1 - Electrical monitoring of polyelectrolyte multilayer formation by means of capacitive field-effect devices JF - Analytical & bioanalytical chemistry N2 - The semiconductor field-effect platform represents a powerful tool for detecting the adsorption and binding of charged macromolecules with direct electrical readout. In this work, a capacitive electrolyte-insulator-semiconductor (EIS) field-effect sensor consisting of an Al-p-Si-SiO2 structure has been applied for real-time in situ electrical monitoring of the layer-by-layer formation of polyelectrolyte (PE) multilayers (PEM). The PEMs were deposited directly onto the SiO2 surface without any precursor layer or drying procedures. Anionic poly(sodium 4-styrene sulfonate) and cationic weak polyelectrolyte poly(allylamine hydrochloride) have been chosen as a model system. The effect of the ionic strength of the solution, polyelectrolyte concentration, number and polarity of the PE layers on the characteristics of the PEM-modified EIS sensors have been studied by means of capacitance-voltage and constant-capacitance methods. In addition, the thickness, surface morphology, roughness and wettabilityof the PE mono- and multilayers have been characterised by ellipsometry, atomic force microscopy and water contact-angle methods, respectively. To explain potential oscillations on the gate surface and signal behaviour of the capacitive field-effect EIS sensor modified with a PEM, a simplified electrostatic model that takes into account the reduced electrostatic screening of PE charges by mobile ions within the PEM has been proposed and discussed. KW - Field-effect KW - Capacitive sensor KW - Polyelectrolyte multilayer KW - Electrical monitoring KW - ConCap Y1 - 2013 U6 - https://doi.org/10.1007/s00216-013-6951-9 SN - 1618-2642 VL - 405 IS - 20 SP - 6425 EP - 6436 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Abouzar, Maryam H. A1 - Poghossian, Arshak A1 - Cherstvy, Andrey G. A1 - Pedraza, Angela M. A1 - Ingebrandt, Sven A1 - Schöning, Michael J. T1 - Label-free electrical detection of DNA by means of field-effect nanoplate capacitors experiments and modeling JF - Physica status solidi : A, Applications and materials science N2 - Label-free electrical detection of consecutive deoxyribonucleic acid (DNA) hybridization/denaturation by means of an array of individually addressable field-effect-based nanoplate silicon-on-insulator (SOI) capacitors modified with gold nanoparticles (Au-NP) is investigated. The proposed device detects charge changes on Au-NP/DNA hybrids induced by the hybridization or denaturation event. DNA hybridization was performed in a high ionic-strength solution to provide a high hybridization efficiency. On the other hand, to reduce the screening of the DNA charge by counter ions and to achieve a high sensitivity, the sensor signal induced by the hybridization and denaturation events was measured in a low ionic-strength solution. High sensor signals of about 120, 90, and 80 mV were registered after the DNA hybridization, denaturation, and re-hybridization events, respectively. Fluorescence microscopy has been applied as reference method to verify the DNA immobilization, hybridization, and denaturation processes. An electrostatic charge-plane model for potential changes at the gate surface of a nanoplate field-effect sensor induced by the DNA hybridization has been developed taking into account both the Debye length and the distance of the DNA charge from the gate surface. KW - DNA KW - field-effect KW - gold nanoparticle KW - label-free detection KW - nanoplate capacitor Y1 - 2012 U6 - https://doi.org/10.1002/pssa.201100710 SN - 1862-6300 VL - 209 IS - 5 SP - 925 EP - 934 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Pfestorf, H. A1 - Weiss, L. A1 - Müller, J. A1 - Boch, Steffen A1 - Socher, S. A. A1 - Prati, Daniel A1 - Schöning, Ingo A1 - Weisser, W. A1 - Fischer, M. A1 - Jeltsch, Florian T1 - Community mean traits as additional indicators to monitor effects of land-use intensity On grassland plant diversity JF - Perspectives in plant ecology, evolution and systematics N2 - Semi-natural grasslands, biodiversity hotspots in Central-Europe, suffer from the cessation of traditional land-use. Amount and intensity of these changes challenge current monitoring frameworks typically based on classic indicators such as selected target species or diversity indices. Indicators based on plant functional traits provide an interesting extension since they reflect ecological strategies at individual and ecological processes at community levels. They typically show convergent responses to gradients of land-use intensity over scales and regions, are more directly related to environmental drivers than diversity components themselves and enable detecting directional changes in whole community dynamics. However, probably due to their labor- and cost intensive assessment in the field, they have been rarely applied as indicators so far. Here we suggest overcoming these limitations by calculating indicators with plant traits derived from online accessible databases. Aiming to provide a minimal trait set to monitor effects of land-use intensification on plant diversity we investigated relationships between 12 community mean traits, 2 diversity indices and 6 predictors of land-use intensity within grassland communities of 3 different regions in Germany (part of the German 'Biodiversity Exploratory' research network). By standardization of traits and diversity measures, use of null models and linear mixed models we confirmed (i) strong links between functional community composition and plant diversity, (ii) that traits are closely related to land-use intensity, and (iii) that functional indicators are equally, or even more sensitive to land-use intensity than traditional diversity indices. The deduced trait set consisted of 5 traits, i.e., specific leaf area (SLA), leaf dry matter content (LDMC), seed release height, leaf distribution, and onset of flowering. These database derived traits enable the early detection of changes in community structure indicative for future diversity loss. As an addition to current monitoring measures they allow to better link environmental drivers to processes controlling community dynamics. KW - Biodiversity Exploratories KW - Biological conservation KW - (Semi-natural) Grasslands KW - Plant functional traits KW - Indicators KW - Land-use intensity Y1 - 2013 U6 - https://doi.org/10.1016/j.ppees.2012.10.003 SN - 1433-8319 VL - 15 IS - 1 SP - 1 EP - 11 PB - Elsevier CY - Jena ER - TY - JOUR A1 - Solly, Emily A1 - Schöning, Ingo A1 - Boch, Steffen A1 - Mueller, J. A1 - Socher, S. A. A1 - Trumbore, S. E. A1 - Schrumpf, M. T1 - Mean age of carbon in fine roots from temperate forests and grasslands with different management JF - Biogeosciences N2 - Fine roots are the most dynamic portion of a plant's root system and a major source of soil organic matter. By altering plant species diversity and composition, soil conditions and nutrient availability, and consequently belowground allocation and dynamics of root carbon (C) inputs, land-use and management changes may influence organic C storage in terrestrial ecosystems. In three German regions, we measured fine root radiocarbon (C-14) content to estimate the mean time since C in root tissues was fixed from the atmosphere in 54 grassland and forest plots with different management and soil conditions. Although root biomass was on average greater in grasslands 5.1 +/- 0.8 g (mean +/- SE, n = 27) than in forests 3.1 +/- 0.5 g (n = 27) (p < 0.05), the mean age of C in fine roots in forests averaged 11.3 +/- 1.8 yr and was older and more variable compared to grasslands 1.7 +/- 0.4 yr (p < 0.001). We further found that management affects the mean age of fine root C in temperate grasslands mediated by changes in plant species diversity and composition. Fine root mean C age is positively correlated with plant diversity (r = 0.65) and with the number of perennial species (r = 0.77). Fine root mean C age in grasslands was also affected by study region with averages of 0.7 +/- 0.1 yr (n= 9) on mostly organic soils in northern Germany and of 1.8 +/- 0.3 yr (n = 9) and 2.6 +/- 0.3 (n = 9) in central and southern Germany (p < 0.05). This was probably due to differences in soil nutrient contents and soil moisture conditions between study regions, which affected plant species diversity and the presence of perennial species. Our results indicate more long-lived roots or internal redistribution of C in perennial species and suggest linkages between fine root C age and management in grasslands. These findings improve our ability to predict and model belowground C fluxes across broader spatial scales. Y1 - 2013 U6 - https://doi.org/10.5194/bg-10-4833-2013 SN - 1726-4170 VL - 10 IS - 7 SP - 4833 EP - 4843 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Ge, Bixia A1 - Meyer, T. A1 - Schöning, M. J. A1 - Wollenberger, Ursula A1 - Lisdat, Fred T1 - Cytochrome c from chromatium vinosum on gold electrodes Y1 - 2000 ER -