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- ItemLabel free sensing of creatinine using a 6 GHz CMOS near-field dielectric immunosensor(Cambridge : Royal Society of Chemistry, 2015) Guha, S.; Warsinke, A.; Tientcheu, Ch.M.; Schmalz, K.; Meliani, C.; Wenger, Ch.In this work we present a CMOS high frequency direct immunosensor operating at 6 GHz (C-band) for label free determination of creatinine. The sensor is fabricated in standard 0.13 μm SiGe:C BiCMOS process. The report also demonstrates the ability to immobilize creatinine molecules on a Si3N4 passivation layer of the standard BiCMOS/CMOS process, therefore, evading any further need of cumbersome post processing of the fabricated sensor chip. The sensor is based on capacitive detection of the amount of non-creatinine bound antibodies binding to an immobilized creatinine layer on the passivated sensor. The chip bound antibody amount in turn corresponds indirectly to the creatinine concentration used in the incubation phase. The determination of creatinine in the concentration range of 0.88–880 μM is successfully demonstrated in this work. A sensitivity of 35 MHz/10 fold increase in creatinine concentration (during incubation) at the centre frequency of 6 GHz is gained by the immunosensor. The results are compared with a standard optical measurement technique and the dynamic range and sensitivity is of the order of the established optical indication technique. The C-band immunosensor chip comprising an area of 0.3 mm2 reduces the sensing area considerably, therefore, requiring a sample volume as low as 2 μl. The small analyte sample volume and label free approach also reduce the experimental costs in addition to the low fabrication costs offered by the batch fabrication technique of CMOS/BiCMOS process.
- ItemAnalysis of fatty acids and triacylglycerides by Pd nanoparticle-assisted laser desorption/ionization mass spectrometry(Cambridge : Royal Society of Chemistry, 2015) Silina, Yuliya E.; Fink-Straube, Claudia; Hayen, Heiko; Volmer, Dietrich A.In this study, we propose a simple and rapid technique for characterization of free fatty acids and triacylglycerides (TAG) based on palladium nanoparticular (Pd-NP) surface-assisted laser desorption/ionization (SALDI) mass spectrometry (MS). The implemented Pd-NP material allowed detection of free fatty acids and TAGs exclusively as [M + K]+ ions in positive ion mode. Under negative ionization conditions, unusual trimetric structures were generated for free fatty acids, while TAGs underwent irreproducible degradation reactions. Importantly, the mass spectra obtained from Pd-NP targets in positive ion mode were very clean without interferences from matrix-derived ions in the low m/z range and readily enabled the detection of intact TAGs in vegetable oils without major fragmentation reactions as compared to conventional MALDI-MS, requiring only a minimal amount of sample preparation.
- ItemFast IR laser mapping ellipsometry for the study of functional organic thin films(Cambridge : Royal Society of Chemistry, 2015) Furchner, Andreas; Sun, Guoguang; Ketelsen, Helge; Rappich, Jörg; Hinrichs, KarstenFast infrared mapping with sub-millimeter lateral resolution as well as time-resolved infrared studies of kinetic processes of functional organic thin films require a new generation of infrared ellipsometers. We present a novel laboratory-based infrared (IR) laser mapping ellipsometer, in which a laser is coupled to a variable-angle rotating analyzer ellipsometer. Compared to conventional Fourier-transform infrared (FT-IR) ellipsometers, the IR laser ellipsometer provides ten- to hundredfold shorter measurement times down to 80 ms per measured spot, as well as about tenfold increased lateral resolution of 120 μm, thus enabling mapping of small sample areas with thin-film sensitivity. The ellipsometer, equipped with a HeNe laser emitting at about 2949 cm−1, was applied for the optical characterization of inhomogeneous poly(3-hexylthiophene) [P3HT] and poly(N-isopropylacrylamide) [PNIPAAm] organic thin films used for opto-electronics and bioapplications. With the constant development of tunable IR laser sources, laser-based infrared ellipsometry is a promising technique for fast in-depth mapping characterization of thin films and blends.
- ItemSurface-assisted laser desorption/ionization mass spectrometry using ordered silicon nanopillar arrays(Cambridge : Royal Society of Chemistry, 2014) Alhmoud, Hashim Z.; Guinan, Taryn M.; Elnathan, Roey; Kobus, Hilton; Voelcker, Nicolas H.Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) is ideally suited for the high-throughput analysis of small molecules in bodily fluids (e.g. saliva, urine, and blood plasma). A key application for this technique is the testing of drug consumption in the context of workplace, roadside, athlete sports and anti-addictive drug compliance. Here, we show that vertically-aligned ordered silicon nanopillar (SiNP) arrays fabricated using nanosphere lithography followed by metal-assisted chemical etching (MACE) are suitable substrates for the SALDI-MS detection of methadone and small peptides. Porosity, length and diameter are fabrication parameters that we have explored here in order to optimize analytical performance. We demonstrate the quantitative analysis of methadone in MilliQ water down to 32 ng mL-1. Finally, the capability of SiNP arrays to facilitate the detection of methadone in clinical samples is also demonstrated.
- ItemSelf-calibrating highly sensitive dynamic capacitance sensor: Towards rapid sensing and counting of particles in laminar flow systems(Cambridge : Royal Society of Chemistry, 2015) Guha, S.; Schmalz, K.; Wenger, Ch.; Herzel, F.In this report we propose a sensor architecture and a corresponding read-out technique on silicon for the detection of dynamic capacitance change. This approach can be applied to rapid particle counting and single particle sensing in a fluidic system. The sensing principle is based on capacitance variation of an interdigitated electrode (IDE) structure embedded in an oscillator circuit. The capacitance scaling of the IDE results in frequency modulation of the oscillator. A demodulator architecture is employed to provide a read-out of the frequency modulation caused by the capacitance change. A self-calibrating technique is employed at the read-out amplifier stage. The capacitance variation of the IDE due to particle flow causing frequency modulation and the corresponding demodulator read-out has been analytically modelled. Experimental verification of the established model and the functionality of the sensor chip were shown using a modulating capacitor independent of fluidic integration. The initial results show that the sensor is capable of detecting frequency changes of the order of 100 parts per million (PPM), which translates to a shift of 1.43 MHz at 14.3 GHz operating frequency. It is also shown that a capacitance change every 3 μs can be accurately detected.
- ItemMagnetic superexchange interactions: Trinuclear bis(oxamidato) versus bis(oxamato) type complexes(Cambridge : Royal Society of Chemistry, 2015) Abdulmalic, Mohammad A.; Aliabadi, Azar; Petr, Andreas; Krupskaya, Yulia; Kataev, Vladislav; Büchner, Bernd; Zaripov, Ruslan; Vavilova, Evgeniya; Voronkova, Violeta; Salikov, Kev; Hahn, Torsten; Kortus, Jens; Meva, Francois Eya’ane; Schaarschmidt, Dieter; Rüffer, TobiasThe diethyl ester of o-phenylenebis(oxamic acid) (opbaH2Et2) was treated with an excess of RNH2 in MeOH to cause the exclusive formation of the respective o-phenylenebis(N(R)-oxamides) (opboH4R2, R = Me 1, Et 2, nPr 3) in good yields. Treatment of 1–3 with half an equivalent of [Cu2(AcO)4(H2O)2] or one equivalent of [Ni(AcO)2(H2O)4] followed by the addition of four equivalents of [nBu4N]OH resulted in the formation of mononuclear bis(oxamidato) type complexes [nBu4N]2[M(opboR2)] (M = Ni, R = Me 4, Et 5, nPr 6; M = Cu, R = Me 7, Et 8, nPr 9). By addition of two equivalents of [Cu(pmdta)(NO3)2] to MeCN solutions of 7–9, novel trinuclear complexes [Cu3(opboR2)(L)2](NO3)2 (L = pmdta, R = Me 10, Et 11, nPr 12) could be obtained. Compounds 4–12 have been characterized by elemental analysis and NMR/IR spectroscopy. Furthermore, the solid state structures of 4–10 and 12 have been determined by single-crystal X-ray diffraction studies. By controlled cocrystallization, diamagnetically diluted 8 and 9 (1%) in the host lattice of 5 and 6 (99%) (8@5 and 9@6), respectively, in the form of single crystals have been made available, allowing single crystal ESR studies to extract all components of the g-factor and the tensors of onsite CuA and transferred NA hyperfine (HF) interaction. From these studies, the spin density distribution of the [Cu(opboEt2)]2− and [Cu(opbonPr2)]2− complex fragments of 8 and 9, respectively, could be determined. Additionally, as a single crystal ENDOR measurement of 8@5 revealed the individual HF tensors of the N donor atoms to be unequal, individual estimates of the spin densities on each N donor atom were made. The magnetic properties of 10–12 were studied by susceptibility measurements versus temperature to give J values varying from −96 cm−1 (10) over −104 cm−1 (11) to −132 cm−1 (12). These three trinuclear CuII-containing bis(oxamidato) type complexes exhibit J values which are comparable to and slightly larger in magnitude than those of related bis(oxamato) type complexes. In a summarizing discussion involving experimentally obtained ESR results (spin density distribution) of 8 and 9, the geometries of the terminal [Cu(pmdta)]2+ fragments of 12 determined by crystallographic studies, together with accompanying quantum chemical calculations, an approach is derived to explain these phenomena and to conclude if the spin density distribution of mononuclear bis(oxamato)/bis(oxamidato) type complexes could be a measure of the J couplings of corresponding trinuclear complexes.
- ItemA novel precursor system and its application to produce tin doped indium oxide(Cambridge : Royal Society of Chemistry, 2011) Veith, Michael; Bubel, Carsten; Zimmer, MichaelA new type of precursor has been developed by molecular design and synthesised to produce tin doped indium oxide (ITO). The precursor consists of a newly developed bimetallic indium tin alkoxide, Me2In(OtBu)3Sn (Me = CH3, OtBu = OC(CH3)3), which is in equilibrium with an excess of Me2In(OtBu). This quasi single-source precursor is applied in a sol–gel process to produce powders and coatings of ITO using a one-step heat treatment process under an inert atmosphere. The main advantage of this system is the simple heat treatment that leads to the disproportionation of the bivalent Sn(II) precursor into Sn(IV) and metallic tin, resulting in an overall reduced state of the metal in the final tin doped indium oxide (ITO) material, hence avoiding the usually necessary reduction step. Solid state 119Sn-NMR measurements of powder samples confirm the appearance of Sn(II) in an amorphous gel state and of metallic tin after annealing under nitrogen. The corresponding preparation of ITO coatings by spin coating on glass leads to transparent conductive layers with a high transmittance of visible light and a low electrical resistivity without the necessity of a reduction step.
- ItemNovel single-source precursors for the fabrication of PbTiO3, PbZrO3 and Pb(Zr1-x Tix)O3 thin-films by chemical vapor deposition(Cambridge : Royal Society of Chemistry, 2011) Veith, Michael; Bender, Michael; Lehnert, Tobias; Zimmer, Michael; Jakob, AnetteLead titanate, lead zirconate, and lead zirconate titanate (PZT) films in the sub-μm-range were produced at temperatures around 400 °C using novel single-source precursors in a classical thermal CVD process. The design of two bimetallic alkoxide compounds, a lead titanate and a lead zirconate source with almost identical physical properties and complement miscibility, resulted in a new quasi-single-source PZT precursor, an azeotropic mixture that evaporates at 30 °C and at a pressure of 4 × 10−1 mbar. After thermal treatment at 650 °C, transparent (100)-oriented PZT films with remnant polarization of 20 μC cm−2 and a coercive field strength of 20 V μm−1 were achieved. An additional lead source is not required.
- ItemComment on "Synthesis, characterization and growth mechanism of flower-like vanadium carbide hierarchical nanocrystals"(Cambridge : Royal Society of Chemistry, 2012) Presser, Volker; Vakifahmetoglu, CekdarThis Letter is in response to a recent paper by Ma et al. (CrystEngComm, 2010, 12, 750-754) which arguably studied vanadium carbide nanostructures whereas all available evidence indicates the study of vanadium oxide. We feel that it is important to communicate to the community several inconsistencies so that the interesting material reported can be seen in the right light, especially with several groups nowadays having reported similar structures from vanadium oxide synthesis.
- ItemSwitching adhesion and friction by light using photosensitive guest - host interactions(Cambridge : Royal Society of Chemistry, 2015) Blass, Johanna; Bozna, Bianca; Albrecht, Marcel; Krings, Jennifer A.; Ravoo, Bart Jan; Wenz, Gerhard; Bennewitz, RolandFriction and adhesion between two β-cyclodextrin functionalized surfaces can be switched reversibly by external light stimuli. The interaction between the cyclodextrin molecules attached to the tip of an atomic force microscope and a silicon wafer surface is mediated by complexation of ditopic azobenzene guest molecules. At the single molecule level, the rupture force of an individual complex is 61 ± 10 pN.