SearcharxivSearch

arXiv subjects

Howard E. Katz

Publications and source records attributed to Howard E. Katz.

3 recordsLinked to original sources

Interfacial Potential Transduction for Diagnostics

A major barrier to decentralized, near-patient diagnostics is the lack of a signal transduction modality that is both analytically precise and accessible at the point of care. Optical readouts remain instrument-dependent and difficult to miniaturize, while compact electrochemical readouts are prone to matrix-derived signal distortion, limiting their biomarker coverage in real clinical settings. Here, we define interfacial potential transduction as a standardized electrical modality for portable, clinical-grade diagnostics across diverse assay formats. A mechanistic framework identifying key sample matrix parameters within the interfacial potentials transduction system enables control of biofluid-derived interference, and is demonstrated in a widely accessible lateral flow immunoassay format through quantitative detection of estradiol, progesterone, and luteinizing hormone in human plasma with high correlation (r2 > 0.97) to clinical analyzers. Broader applicability across representative diagnostic sectors is further demonstrated through exceptional performance including glucose quantification for biochemical analysis with limit of detection (LOD) of 0.92 ug/dL, HIV p24 capsid protein under an immunomagnetic separation workflow (LOD = 44.8 fg/mL), and hepatitis B virus detection within 5 min via loop-mediated isothermal amplification for molecular diagnostics. Together, these results establish interfacial potentials transduction as a unified diagnostic paradigm for near-patient deployment beyond optical and electrochemical approaches.

q-bio.BM

Effects of carrier mobility and morphology in organic semiconductor spin valves

We studied spin transport in four organic semiconductors (OSCs) with different electronic properties, with Fe and Co as the top and bottom ferromagnetic (FM) contacts, respectively. Magnetoresistance (MR) effects were observed up to room temperature in junctions based on an electron-carrying OSC, tris(8-hyroxyquinoline) aluminum (Alq$_3$) and a hole-carrying OSC, copper phthalocyanine (CuPc). The MR shows similar temperature dependence for these two OSCs, which suggests that the FM leads rather than the OSCs play a dominant role on the spin-transport degradation with increasing temperature. We also investigated junctions based on two high lateral mobility electron-carrying OSCs, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and N, N'-bis(4-trifluoromethylbenzyl)-1,4,5,8-naphthalenetetracarboxylic diimide (CF$_3$-NTCDI). However, these junctions showed much weaker spin transport effects. Morphological studies suggest that these high mobility OSC films have much rougher surfaces than either Alq$_3$ or CuPc, therefore the degradation of spin transport may originate from enhanced scattering due to the rougher FM/OSC interfaces. Our study shows that FM/OSC interfaces play an important role for spin transport in organic devices and need further exploration.

cond-mat.mtrl-sci

Correlation between microstructure and magnetotransport in organic semiconductor spin valve structures

We have studied magnetotransport in organic-inorganic hybrid multilayer junctions. In these devices, the organic semiconductor (OSC) Alq$_3$ (tris(8-hydroxyquinoline) aluminum) formed a spacer layer between ferromagnetic (FM) Co and Fe layers. The thickness of the Alq$_3$ layer was in the range of 50-150 nm. Positive magnetoresistance (MR) was observed at 4.2 K in a current perpendicular to plane geometry, and these effects persisted up to room temperature. The devices' microstructure was studied by X-ray reflectometry, Auger electron spectroscopy and polarized neutron reflectometry (PNR). The films show well-defined layers with modest average chemical roughness (3-5 nm) at the interface between the Alq$_3$ and the surrounding FM layers. Reflectometry shows that larger MR effects are associated with smaller FM/Alq$_3$ interface width (both chemical and magnetic) and a magnetically dead layer at the Alq$_3$/Fe interface. The PNR data also show that the Co layer, which was deposited on top of the Alq$_3$, adopts a multi-domain magnetic structure at low field and a perfect anti-parallel state is not obtained. The origins of the observed MR are discussed and attributed to spin coherent transport. A lower bound for the spin diffusion length in Alq$_3$ was estimated as $43 \pm 5$ nm at 80 K. However, the subtle correlations between microstructure and magnetotransport indicate the importance of interfacial effects in these systems.

cond-mat.mtrl-sci