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Utilization of Au and nanocrystalline diamond (NCD) as interlayers noticeably modifies the microstructure and field electron emission (FEE) properties of hexagonal boron nitride nanowalls (hBNNWs) grown on Si substrates. The FEE properties of hBNNWs on Au could be turned on at a low turn-on field of 14.3 V μm−1, attaining FEE current density of 2.58 mA cm−2 and life-time stability of 105 min. Transmission electron microscopy reveals that the Au-interlayer nucleates the hBN directly, preventing the formation of amorphous boron nitride (aBN) in the interface, resulting in enhanced FEE properties. But Au forms as droplets on the Si substrate forming again aBN at the interface. Conversely, hBNNWs on NCD shows superior in life-time stability of 287 min although it possesses inferior FEE properties in terms of larger turn-on field and lower FEE current density as compared to that of hBNNWs-Au. The uniform and continuous NCD film on Si also circumvents the formation of aBN phases and allows hBN to grow directly on NCD. Incorporation of carbon in hBNNWs from the NCD-interlayer improves the conductivity of hBNNWs, which assists in transporting the electrons efficiently from NCD to hBNNWs that results in better field emission of electrons with high life-time stability. [ABSTRACT FROM AUTHOR]

We report on the use of the heat transfer method, a novel surface-sensitive technique based on heat transfer through solid-liquid interfaces, to detect phase transitions of model lipid membranes. We selected the lipid DPPC because of its rich phase behavior in an experimentally accessible temperature range. The vesicles were adsorbed on nanocrystalline diamond films, known as a versatile platform material for biosensing with outstanding heat-conduction properties. Complementary Peltier-element-based adiabatic scanning calorimetry (pASC) and quartz crystal microbalance with dissipation monitoring (QCM-D) measurements were carried out to monitor the phase transitions in multilamellar and small unilamellar vesicles, respectively. The heat-transfer measurements revealed reversible jumps upon heating and cooling in the thermal resistance in the vicinity of the expected transition temperature and they agree qualitatively with molecular simulations of the thermal conductivity across a lipid bilayer. The results show the capability of the heat transfer method to detect the main phase transition in DPPC, opening new perspectives for the study of more complex lipid systems and different solid platforms. This work confirms QCM-D as a useful tool for the assessment of the structural changes upon the phase conversion and shows the capability of pASC to provide high-resolution thermodynamic information on biophysical systems. Temperature profile of the heat transfer resistance Rth during the main phase transition of a DPPC supported vesicle layer adsorbed on a hydrogen-terminated nanocrystalline diamond substrate. The arrows indicate the sense of the run: heating (red solid line) and cooling (blue solid line). [ABSTRACT FROM AUTHOR]

Carrier dynamics under interband carrier injection conditions (213 nm) was studied in undoped and boron-doped microcrystalline diamond layers with different grain size. The grain size, determined by scanning electron microscopy and electron backscattered diffraction, varied from 130 μm on the growth side to ∼1-2 μm on the nucleation side of a 1.0 mm-thick undoped layer. Carrier lifetimes measured by differential transmittivity (DT) technique varied from 1 to 4 ns on the growth side to ∼220 ps on the nucleation side. Also the carrier diffusivity was found higher on the growth side. The B-doped layer with 40 μm grain size at the growth side exhibited 380 ps carrier lifetime, which decreased to 130 ps on the nucleation side. Even shorter lifetimes (∼100-200 ps and ∼10 ps, correspondingly) were revealed in this layer by differential reflectivity decay due to impact of subsurface defects. Therefore we conclude that the recombination rate in presence of large grains is dominated by bulk non-radiative traps, as diffusion time of carriers to reach grain boundaries is much longer (few μs). An impact of grain boundaries to recombination is expected in case of smaller grains. Thermal grating decay provided values of thermal diffusivity Dth in the range of 12-6 cm2 s−1, respectively, on the growth and nucleation side of the layers, and its decrease with reduction of grain size was attributed to phonon scattering on grain boundaries. [ABSTRACT FROM AUTHOR]

Probe DNA, consisting of a 36-mer fragment was covalently immobilized on nanocrystalline chemical vapour deposition (CVD) diamond electrodes and hybridized with a 29-mer target DNA. In this paper, we report on the label-free real-time electronic monitoring of DNA denaturation upon exposure to NaOH at different flow rates and molarities, using electrochemical impedance spectroscopy as readout technology. The impedance response was separated into a denaturation time constant and a medium exchange time constant by means of a double exponential fit. It was observed that the denaturation time is dependent on the flow rate as well as on the molarity of the NaOH. Surprisingly, it was observed that at low molarities (0.05 M) the DNA does not fully denature at low flow rates. Only after flushing the flow cell a second time with 0.05 M NaOH, complete denaturation was achieved. Confocal images were obtained and plotted in 3D graphs to confirm the results. This paper provides a systematic overview of measured denaturation times for different flow rates and at different molarities of NaOH. Optimization of these parameters can be a valuable asset in the field of mutation analysis. [ABSTRACT FROM AUTHOR]

We report investigation of carrier recombination and diffusivity in bulk diamonds of different crystalline structure - microcrystalline (MC) CVD-grown and single crystalline HPHT diamonds. Presence of neutral and positively charged nitrogen and hydrogen defects was determined from NIR and UV-IR absorption spectra. Carrier injection into 1-mm thick bulk layers was realized by two-photon absorption at 351 nm wavelength. Carrier lifetimes of 150-330 ns in IIa type HPHT crystals correlated with N density, while the lifetimes in CVD crystal exhibited very fast (80 ps), slower one (3-8 ns), and µs-duration thermally-activated (∼1.5 eV) decay components. The initial two components correlated with the grain size at the front and backsides of the MC diamond. Linearly increasing with injection carrier recombination rates were observed in both CVD and HPHT samples at 800 K, and fitted with effective recombination coefficient B = 3-4 × 10−9 cm3/s. Ambipolar mobility and thermal diffusivity parameters in CVD and HPHT bulk crystals were measured by light-induced free carrier and thermal grating techniques. [ABSTRACT FROM AUTHOR]

Objective: To determine the medium-term maternal impact of open fetal spina bifida repair., Design: Prospective cohort study., Setting: University Hospitals Leuven, Belgium., Population: Mothers who had open maternal-fetal spina bifida repair between March 2012 and December 2021., Methods: A patient-reported survey on subsequent fertility, pregnancy, and gynaecological and psychological outcomes., Main Outcome Measures: Complications during subsequent pregnancies, and gynaecological and psychological problems., Results: Seventy-two out of 100 invited women completed the questionnaire (72%). Despite being advised not to, seven of 13 women attempting to conceive became pregnant within 2 years after fetal surgery and one woman delivered vaginally. Two of the 16 subsequent pregnancies were complicated by an open neural tube defect. One pregnancy was complicated by a placenta accreta and one pregnancy was complicated by a uterine rupture, both with good neonatal outcomes. Nearly half of respondents who did not attempt to conceive reported that this was because of their experience of the index pregnancy and caring for the index child. Three out of four respondents reported medium-term psychological problems, mostly anxiety for the health of the index child, fear for recurrence in subsequent pregnancies and feelings of guilt., Conclusions: Open maternal-fetal surgery for spina bifida did not appear to affect fertility in our cohort. Half of the attempts to conceive took place within 2 years. One uterine rupture and one placenta accreta occurred in 16 subsequent pregnancies. Most respondents reported psychological problems linked to the index pregnancy, which reinforces the need for long-term psychological support., (© 2023 John Wiley & Sons Ltd.)