HBr Concentration Research Articles

Prediction, modeling, and optimization studies of eco-friendly gold extraction using alpha-cyclodextrin and the RSM and CCD methods

In the Democratic Republic of the Congo, gold extraction from ore in South Kivu utilized alpha-cyclodextrin (α-CD) as an eco-friendly method to replace harmful methods. Analysis of variance and response surface methodology were employed for prediction, modeling, and optimization studies. Atomic absorption spectroscopy revealed a 0.06% gold content in a randomly taken ore sample. Leaching with modified aqua regia was optimized with the following parameters: 7.27 h, 50 g/L HBr concentration, pH 1, and 200 rpm stirring speed, resulting in 98.5% removal. Neutralization tests with potassium hydroxide (KOH) followed leaching to prepare the solution medium with appropriate pH for extraction test, by varying parameters such as time, KOH concentration, and pH. Following neutralization, extraction tests with α-CD were carried out and optimized with the following parameters: 40 min, α-CD concentration of 11.6166 g/L, and a pH of 5, resulting in a percent removal of 98.9%. α-CD’s eco-friendly nature, cost-effectiveness, and high percent removal make it a promising and sustainable alternative for gold recovery, appealing to the mining industry.

Distinct Time-Resolved Brain-Wide Coactivations in Oxygenated and Deoxygenated Hemoglobin.

Human resting-state networks (RSNs) estimated from oxygenated (HbO) and deoxygenated hemoglobin (HbR) data exhibit strong similarities, while task-based studies show different dynamics in HbR and HbO responses. Such a discrepancy might be explained due to time-averaged estimations of RSNs. Our study investigated differences between HbO and HbR on time-resolved brain-wide coactivation patterns (CAPs). Diffuse optical tomography was reconstructed from resting-state whole-head functional near-infrared spectroscopy data of HbR and HbO in individual healthy participants. Time-averaged RSNs were obtained using the group-level independent component analysis. Time-resolved CAPs were estimated using a clustering approach on the time courses of all obtained RSNs. Characteristics of the RSNs and CAPs from HbR and HbO were compared. Spatial patterns of HbR and HbO RSNs exhibited significant similarities. Meanwhile, HbR CAPs revealed much more organized spatial and dynamic characteristics than HbO CAPs. The entire set of HbR CAPs suggests a superstructure resulted from brain-wide neuronal dynamics, which is less evident in the set of HbO CAPs. These differences between HbO and HbR CAPs were consistently replicated in individual session data. Our results suggest that human resting brain-wide neuronal activations are preserved better in time-resolved brain-wide patterns, i.e., CAPs, from HbR than those from HbO, while such a difference is lost between time-averaged HbR and HbO RSNs. Our results reveal, for the first time, HbR concentration fluctuations are more directly coupled with resting dynamics of brain-wide neuronal activations in human brains.

Mass transport limitations in concentrated aqueous electrolyte solutions: Theoretical and experimental study of the hydrogen–bromine flow battery electrolyte

Modelling and simulation is a powerful tool to support the development of novel flow cells such as electrolysers and flow batteries. Electrolytes employed in such cells often consist of aqueous solutions of highly concentrated solutes at elevated temperatures. Such conditions pose numerous challenges in conventional model parametrisation because of non-ideal behaviour of the electrolytes. The aim of this work is to study mass transport of electroactive species in highly-concentrated media.We selected the hydrogen–bromine flow battery posolyte, HBr (aq) and Br2, as an exemplary flow battery electrolyte and we leveraged chronoamperometric techniques involving ultramicroelectrodes to study diffusion and migration of bromide and bromine at high concentration and temperature. We successfully simulated the current densities of HBr/Br2 redox reactions in solutions up to 8 mol L–1 using advanced mass transport theory which agreed well with the results obtained with ultramicroelectrodes.While uncharged species transport (Br2) can be credibly modelled using conventional theories such as Fick’s law, charged species (Br–) require special treatment as the diffusion coefficient vary with concentration up to 50 % with respect to the limiting value at infinite dilution. The transport of charged species without added supporting electrolyte occurs via both migration and diffusion and the contribution of migration current may be up to 50 % of the total current. At HBr concentration > 0.6 mol L–1 migration appears to be suppressed due to the “self-screening” effect of the electrolyte.Proper experimental electrolyte characterisation under operating conditions similar to the actual flow cell applications is indispensable to establish predictive models and digital twins of electrochemical devices. Straightforward transfer of concepts known in electro-analytical chemistry to flow cells modelling may lead to erroneous simulations or model overfitting.

The hemodynamic initial-dip consists of both volumetric and oxymetric changes reflecting localized spiking activity.

The initial-dip is a transient decrease frequently observed in functional neuroimaging signals, immediately after stimulus onset, believed to originate from a rise in deoxy-hemoglobin (HbR) caused by local neural activity. It has been shown to be more spatially specific than the hemodynamic response, and is believed to represent focal neuronal activity. However, despite being observed in various neuroimaging modalities (such as fMRI, fNIRS, etc), its origins are disputed, and its precise neuronal correlates are unknown. Here we show that the initial-dip is dominated by a decrease in total-hemoglobin (HbT). We also find a biphasic response in deoxy-Hb (HbR), with an early decrease and later rebound. Both the HbT-dip and HbR-rebound were strongly correlated to highly localized spiking activity. However, HbT decreases were always large enough to counter the spiking-induced increase in HbR. We find that the HbT-dip counters spiking induced HbR increases, imposing an upper-limit to HbR concentration in the capillaries. Building on our results, we explore the possibility of active venule dilation (purging) as a possible mechanism for the HbT dip.

AN ENVIRONMENTALLY BENIGN APPROACH FOR GOLD RECOVERY FROM GOLD-BEARING ORE: MODELING AND OPTIMIZATION

The current work focuses on the extraction of gold using alpha-cyclodextrin (α-CD) from the Kimpese quarry in the Democratic Republic of the Congo, through an environmentally friendly gold process as an alternative to the amalgamation process. The ore was sampled and characterized using atomic absorption spectroscopy (AAS) prior to the experiments, and the analysis revealed 0.08% of gold. The ore was then leached with modified aqua regia (MAR). Time, HBr concentration, pH, and stirring speed were all varied during leaching to highlight the parameters that influence the leaching yield. The optimum conditions were determined using analysis of variance (ANOVA) and response surface methodology (RSM), implying time, HBr concentration, pH, and stirring speed of 6 hours, 80g/l, 1, and 800rpm, respectively, and a leaching percentage of 98.6928%. Following leaching, neutralization tests with potassium hydroxide (KOH) were performed by varying the following parameters: time, KOH concentration, and pH. The following factors were varied in the extraction tests after neutralization: time, α-CD concentration, pH. The optimal parameters were as follows: time of 30 minutes, α-CD concentration of 8.8639g/l, and pH of 6, with yield of 89.7350%. This method of recovering gold from ore using α-CD is inexpensive and does not harm the environment.

Decreased Hemodynamic Responses in Left Parietal Lobule and Left Inferior Parietal Lobule in Older Adults with Mild Cognitive Impairment: A Near-Infrared Spectroscopy Study.

The brain activation patterns of mild cognitive impairment (MCI) are still unclear and they involve multiple brain regions. Most previous studies have focused on abnormal activation in the frontal and temporal lobes, with few investigating the entire brain. To identify and compare the changes in cerebral hemodynamics and abnormal activation patterns in the entire brain of MCI patients and healthy older adults. Patients with MCI (n = 22) and healthy controls (HC, n = 34) matched by age, education levels, sex, and mental state were enrolled. They performed the same letter and category verbal fluency test (VFT) tasks while their behavioral performance and global cerebral hemodynamics were analyzed. The performance during the category VFT task was significantly better than that during the letter VFT task across all participants (HC: correct: p < 0.001; intrusions: p < 0.001; MCI: correct: p < 0.001; intrusions: p < 0.001). The number of correct words during the letter and category VFT tasks was significantly higher in the HC group than in the MCI group (p < 0.001). The deoxygenated-hemoglobin (HbR) concentrations in the left parietal lobule (p = 0.022) and left inferior parietal lobule (p = 0.034) were significantly different during the category VFT task. The differences between HC and MCI groups were greater in the category task. The HbR concentration was more sensitive for the category VFT task and concentration changes in the left parietal lobule and left inferior parietal lobule may be useful for clinical screening and application; thus, they deserve more attention.

Functional near-infrared spectroscopy measures of frontal hemodynamic responses in Parkinson's patients and controls performing the Timed-Up-and-Go test

Using functional near-infrared spectroscopy (fNIRS), hemodynamic responses (i.e., changes in oxygenated and deoxygenated hemoglobin) were measured while participants with Parkinson’s disease (PD) and healthy controls performed the Timed-Up-and-Go test (TUGT), and differences in cortical activity at baseline and three different intervals were examined between the two groups. Seventeen PD patients and twenty-two controls participated in the study, but two PD patients were excluded from statistical analysis due to the presence of freezing of gait and using walking aids during the TUGT. During the TUGT, activity in the front, left, right and total frontal cortices initially decreased significantly, then significantly increased in PD participants and low-risk faller PD participants, compared to when in a sitting position. ΔHbO (HbO change from baseline) over the front, left and total frontal cortices in the PD group was significantly lower than the control group in interval 1 (P = 0.019, P = 0.014 and P = 0.031, respectively), while significantly higher than the control group in interval 2 over the left frontal cortex (P = 0.010). No significant differences were observed between the high-risk faller and low-risk faller subgroups of PD participants in ΔHbO and ΔHbR in the three intervals (P > 0.05). In the high-risk faller subgroup, ΔHbO over the left frontal cortex was significantly higher than the right frontal cortex in interval 2 and interval 3 (P = 0.015, P = 0.030, respectively). There was a strong positive correlation between education and HbR concentration over the right frontal cortex in PD participants (rho = 0.557, P = 0.031), while there were strong negative correlations between PD duration and HbR concentration over the right and total frontal cortices in the high-risk faller subgroup of PD participants (rho = −0.854, P = 0.014 for the right; rho = −0.784, P = 0.037 for the total). The falls prediction cutoff TUGT time for PD participants was 14.2 s. These results suggest that frontal cognition training, along with exercise training, could be used as an effective training method to improve motor performance in PD patients, especially for those at high-risk for falls.

Investigating mental workload-induced changes in cortical oxygenation and frontal theta activity during simulated flights

Monitoring pilots’ cognitive states becomes increasingly important in aviation. Physiological measurement can detect increased mental workload (MWL) even before performance declines. Yet, changes in MWL are rarely varied systematically and few studies control for confounding effects of other cognitive states. The present study targets these shortcomings by analysing the effects of stepwise increased MWL on cortical activation, while controlling for mental fatigue (MF). 35 participants conducted a simulated flight with an incorporated adapted n-back and monitoring task. We recorded cortical activation with concurrent EEG and fNIRS measurement, performance, self-reported MWL and MF. Our results show the successful manipulation of MWL without confounding effects of MF. Higher task difficulty elicited higher subjective MWL ratings, performance decline, higher frontal theta activity and reduced frontal deoxyhaemoglobin (Hbr) concentration. Using both EEG and fNIRS, we could discriminate all induced MWL levels. fNIRS was more sensitive to tasks with low difficulty, and EEG to tasks with high difficulty. Our findings further suggest a plateau effect for high MWL that could present an upper boundary to individual cognitive capacity. Our results highlight the benefits of physiological measurement in aviation, both for assessment of cognitive states and as a data source for adaptive assistance systems.

Changes in cortical hemodynamics with the emergence of skilled motor ability in infants: An fNIRS study

The brain activity changes during infancy that underpin the emergence of functional motor skills, such as reaching and stepping, are not well understood. The current study used functional near-infrared spectroscopy (fNIRS) to examine the hemodynamic response across the frontal, mid-coronal plane (sensorimotor cortex) and external occipital protuberance (cerebellar cortex) regions of typically developing infants (5 to 13 months) during reach-to-grasp or supported treadmill stepping behaviour. Motor ability was assessed using the third edition of the Motor Subscale of the Bayley Scales of Infant Development (BSID-III). Infants with enhanced motor ability demonstrated greater oxy-hemoglobin (HbO) concentration in the contralateral anterior mid-coronal and frontal-dorsal areas during right-handed reach-to-grasp. During bilateral reaching behavior, infants with enhanced motor ability showed greater HbO increases in right frontal-dorsal regions and lower HbO increases in left anterior mid-coronal areas. In contrast, infants' motor ability was associated with changes in de-oxyhemoglobin (HbR) concentration in the ipsilateral anterior mid-coronal, contralateral frontal and left external occipital protuberance regions during left-handed reaching behavior. These relationships between upper limb hemodynamics and infant motor ability are consistent with increased lateralization and cognitive-motor coupling as motor skills emerge. During stepping behavior, infants with enhanced motor ability demonstrated smaller increases in HbR concentration in the bilateral external occipital protuberance region consistent with an emerging efficiency as cruising and independent stepping behavior is still nascent. Together, the current results identify several distinct neural markers of functional motor ability during infancy that may be relevant to diagnostic testing and rehabilitation of developmental movement disorders.

Reversible Emission Tunability from 2D‐Layered Perovskites with Conjugated Organic Cations

The structural flexibility of 2D‐layered halide perovskites provides unprecedented opportunities for tuning their optical properties. For example, lattice distortions facilitate white emission that stems from self‐trapped excitons or defects, and organic cations and halides determine structural stability and emission range. Herein, the optical properties of a set of single‐layer thiophene‐based 2D lead bromide platelets are investigated. Blue‐ and white‐emitting materials based on the choice of thiophene cation and HBr concentration in the synthesis and reversible white to blue color switching by sequential washing and precursor exposure of the fabricated samples are obtained. The photophysical and structural studies indicate that the key to color switching is the formation and suppression of self‐trapped excitons by the supply and removal of cations and halides in acetone. The range of emission color from these materials is extended to red by efficient Mn doping that leads to an additional strong emission peak centered at 620 nm. The findings stimulate the development of color‐tunable and switchable light emitters based on a single material.

Research on blood oxygen activity in cerebral cortical motor function areas with adjustment intention during gait.

The study of the neural mechanism of human gait control can provide a theoretical basis for the treatment of walking disorders or the improvement of rehabilitation strategies, and further promote the functional rehabilitation of patients with movement disorders. However, the performance and changes of cerebral cortex activity corresponding to gait adjustment intentions are still not clear. The purpose of this study was to detect the blood oxygen activation characterization of the cerebral cortex motor function area when people have the intention to adjust gait during walking. Thirty young volunteers (21 ± 1 years old) performed normal walking, speed increase, speed reduction, step increase, and step reduction, during which oxygenated hemoglobin (HbO), deoxygenated hemoglobin (HbR), and total oxyhemoglobin (HbT) information in the prefrontal cortex (PFC), premotor cortex (PMC), supplementary motor area (SMA) was continuous monitored using near-infrared brain functional imaging. (1) With the intention to adjust gait, the HbO concentration in the SMA increased significantly, while the HbT concentration in the medial-PFC decreased significantly. (2) In the HbO concentration, step reduction is more activated than the step increase in the left-PMC (p= 0.0130); step adjustment is more activated than speed adjustment in the right-PMC (p= 0.0067). In the HbR concentration, the speed reduction is more activated than the speed increase in the left-PFC (p= 0.0103). When the intention of gait adjustment occurs, the increase of HbO concentration in the SMA indicates the initial stage of gait adjustment will increase the cognitive-locomotor demand of the brain. The left brain area meets the additional nerve needs of speed adjustment. The preliminary findings of this study can lay an important theoretical foundation for the realization of gait control based on fNIRS-BCI technology.

Hg0 catalytic oxidation by HBr over Ce-modified regenerated selective catalytic reduction catalyst

A method of spent catalyst (V-Mo/TiO2) regeneration with simultaneous Ce-modification was designed in this research. The physical and chemical properties, denitrification activity and elemental mercury (Hg0) oxidation ability were studied to select the most effective procedure and Ce content (1 wt%). Compared to the ordinarily regenerated selective catalytic reduction (SCR) catalyst, the Ce-modified regenerated SCR catalyst showed higher catalytic activity for Hg0 oxidation. As for the influence of the flue gas conditions, HBr showed a strong promotion for the Hg0 oxidation on Ce-modified regenerated catalyst, and with the increase of HBr concentration, the catalytic oxidation abilities of both catalysts exhibited an increasing trend. In contrast, NH3 suppressed the catalytic oxidation abilities of both catalysts, particularly the Ce-modified catalyst.

Mixed 2D/3D perovskite with fine phase control modulated by a novel cyclopentanamine hydrobromide for better stability in light-emitting diodes

Abstract The mixed 2D/3D perovskite has been proved to be a promising candidate to increase the exciton binding energy in perovskite light-emitting diodes (PeLEDs). However, the complex phase distribution and impurity (usually referring to ligands) limit the stability of the corresponding PeLEDs. Here, a novel molecule, cyclopentanamine hydrobromide (CyPA·HBr), is adopted to construct a mixed 2D/3D perovskite by partial substitution of FA with CyPA, realizing fine phase control for improved device stability. The adoption of CyPA·HBr helps to tune perovskite grain growth and passivate the defect, resulting in high coverage and smooth thin film with improved photoluminescence property. The PeLEDs with an optimized CyPA·HBr concentration of a molar ratio of 40% exhibit a pure green emission with a full width at half maximum of 22 nm, an external quantum efficiency of 6.55%, and a maximum brightness of 9408 cd m−2 simultaneously. Interestingly, the CyPA·HBr-based device shows a half-lifetime two times longer than the one based on the most commonly used ligand of phenethylammonium bromide (PEA·HBr), assigned to the better phase control ability of CyPA·HBr in 2D/3D perovskite. Those results testify the importance of ligands to modulate perovskite phase along with efficient passivation defects for better stability of PeLEDs.

Effect of Hydrobromic Acid Concentration on the Chemical Etching Behavior of PbTe and Pb1 –xSnxTe Single Crystals in Aqueous H2O2–HBr–Ethylene Glycol Solutions

We have studied the effect of HBr concentration in (H2O2–HBr–EG)/EG etching mixtures on chemical–mechanical polishing (CMP) and dynamic chemical polishing (DCP) of single-crystal PbTe and Pb1 –xSnxTe solid solutions. The CMP and DCP rates have been measured as functions of solution composition, and the effect of initial HBr concentration on the composition range of polishing etchants, surface quality, and surface condition after polishing has been assessed by measuring surface roughness. We have optimized the composition of polishing mixtures and processing conditions for obtaining high-quality polished surfaces.

Influence of plant growth regulators on sex differentiation and floral characteristics of pomegranate flowers: a case of brassinosteroids

The objective of the present study was to determine the effects of brassinosteroid application on the sex determination and floral growth of pomegranate flowers. Whole tress of &lt;em&gt;Punica granatum&lt;/em&gt; ‘Mayhoş-8’ were sprayed with 0.001, 0.01, and 0.1 mg L&lt;sup&gt;−1&lt;/sup&gt; 28-homobrassinolide (Hbr) at bud break. The selection of flowers was based on the appearance of a visible pistil/stigma and shape of the ovary of intact flowers. Grouping of bisexual flowers was based on their flower position, i.e., single, terminal, and lateral flowers, during the first flush of flowering in mid-June. Approximately 20 days and 40 days after spraying, 100 randomly chosen bisexual flowers per collection time were collected and measurements of floral parts were immediately taken. The differences between bisexual and functional male flowers were not distinct enough to assert any significant effects from the different Hbr treatments. Irrespective of treatments, the percentage of male flowers was higher than that of bisexual flowers. Hbr treatments applied at the bud break period had significant effects only on bisexual flowers that developed as single flowers. Applying 0.01 mg L&lt;sup&gt;−1&lt;/sup&gt; Hbr produced comparably lower percentages of single bisexual flowers (53.4%). Although the 0.1 and 0.001 mg L&lt;sup&gt;−1&lt;/sup&gt; Hbr treatments resulted in increased percentages of bisexual flowers, the difference was not significant. For the first collection time (mid-June), the effects of Hbr concentration on the size of the floral parts for bisexual flowers were only significant in ovary width and stigma diameter. As the concentration decreased, smaller ovaries were obtained. During the second flowering, application of 0.01 mg L&lt;sup&gt;−1&lt;/sup&gt; Hbr considerably increased the overall sizes of floral parts in bisexual flowers. Hbr might affect the ratio of flower formation in certain positions on a branch and could influence the growth of floral parts in bisexual flowers. Further elucidation of these effects would help to better understand floral organ development in plants.

Kinetic Study on Mercury Sorption from Fuel Gas

In this paper, the adsorption performance of modified fly ash was evaluated using a fixed-bed adsorption device. The influence of different inlet concentrations of mercury in simulated flue gas and different concentrations of HBr solution on the mercury absorption process was studied. The results showed that, with the increase of the inlet mercury concentration in the simulated flue gas, the adsorption capacity and adsorption rate of the modified fly ash increased. With the increase of the HBr concentration, the adsorption amount and adsorption rate of mercury in simulated fly ash also increased. It was also found that the adsorption process follows the pseudo-first-order adsorption kinetic model.

Simultaneous EEG-fNIRS reveals how age and feedback affect motor imagery signatures

Stroke frequently results in motor impairment. Motor imagery (MI), the mental practice of movements, has been suggested as a promising complement to other therapeutic approaches facilitating motor rehabilitation. Of particular potential is the combination of MI with neurofeedback (NF). However, MI NF protocols have been largely optimized only in younger healthy adults, although strokes occur more frequently in older adults. The present study examined the influence of age on the neural correlates of MI supported by electroencephalogram (EEG)-based NF and on the neural correlates of motor execution. We adopted a multimodal neuroimaging framework focusing on EEG-derived event-related desynchronization (ERD%) and oxygenated (HbO) and deoxygenated hemoglobin (HbR) concentrations simultaneously acquired using functional near-infrared spectroscopy (fNIRS). ERD%, HbO concentration and HbR concentration were compared between younger (mean age: 24.4 years) and older healthy adults (mean age: 62.6 years). During MI, ERD% and HbR concentration were less lateralized in older adults than in younger adults. The lateralization-by-age interaction was not significant for movement execution. Moreover, EEG-based NF was related to an increase in task-specific activity when compared to the absence of feedback in both older and younger adults. Finally, significant modulation correlations were found between ERD% and hemodynamic measures despite the absence of significant amplitude correlations. Overall, the findings suggest a complex relationship between age and movement-related activity in electrophysiological and hemodynamic measures. Our results emphasize that the age of the actual end-user should be taken into account when designing neurorehabilitation protocols.

The Comprehension of the Interfacial Chemistry during Etching Process onto SC: A Way to Understand the Mechanism

The understanding of the charge transfer at SC Electrolyte interfaces is one of the fundamentals of semiconductor electrochemistry. A lot of examples in literature show that this interfacial process can be governed by the presence of interfacial films. So it is interesting to explore how chemical interface modifications, modulate the chemical and electrochemical behavior of the SC electrodes and more interesting how its knowledge helps to its diagnostic. In this topic a very attractive SC to study this kind of phenomenon is InP. Indeed, among the semiconductors studied for their interfacial electrochemical behaviors, InP is probably one of the more interesting. This is due to its very particular anodic or cathodic responses that are governed partly by the pH of the solution. Very different surface chemistry are reachable which set the nature of the chemical status of the interface whose the surface oxide stability are probably the more important parameter for setting the charge transfer as the energy diagram of the liquid junction. A very interesting case is when oxidizing species are present in solution. It is interesting to relate the electrochemical responses of the interface (current vs potential or capacitance vs potential) to the interfacial chemistry of the interface undergoing an electrochemical transfer which is generally related to an etching process, an oxide growth or a passivation phenomenon [1]. Moreover on the same system it is opportune to dispose of accurate information about the chemical stability or instability of the interface which can be under a dissolution or a passivation regime. This regime can be discriminated by detection of anions or cations species coming from the sample interaction with the solution containing the oxidizing species. The more difficult information, to extract is the nature of the chemical transformation induced in situ during the interaction. Depending in its nature and its stability toward emerging from solution external chemical analysis can be provided as for example by XPS. All these general considerations can be attentively discussed on reference system as for example on InP/HBr:Br2 aqueous solutions system for which the etching properties of acidic bromide solutions have been investigated [2] indicating a strong impact of HBr concentration on etching process as on the related interface chemistry which governs the rate. In this contribution we add to the experimental procedure, electrochemical measurement performed on n-type or p-types samples as tool for investigating the interface evolution as for the modulation of the etching rate. As example are given in figure 1 the I(V) responses of an p-InP electrode submitted to the solution interaction. In the case of p-type there are no reduction current in the dark associated to Br2 reduction but this reduction current appears as soon as the surface is illuminated. In the dark the etching rate is important, constant whatever the polarization, governed by the rotation speed of the sample. Under illumination the etching rate decays as the photoréduction of Br2increases. At a given rotation speed for a sufficient incident flux the photocurrent saturates and at the same time the etching rate vanishes as shown in the fig1. A very different observation is obtained for n-type for which a spontaneous reduction is observed with also a typical modulation of the etching rate which depends on the éelctrode polarization. These opposite behaviors have been previously observed on GaAs for n&p type and have given rise to the well known “Unified Model” for describing on III-V the etching mechanisms induced by hydrogen peroxide or halogen in solution. It is clear that the combined study: species dosages in solution, electrochemical modulation, XPS of resulting surface performed for this work open opportunities to discuss this model and introduce possible electrochemical anodic step which have been neglected on the basis of the GaAs data. The origin of the proposed discussion is related to the observation performed ex situ by XPS which agrees with an anodic oxidation step until no mentioned. All this results demonstrate the strong correlation between the nature of the interfacial chemistry and the resulting electrochemical behaviors. This main point will be the purpose of our contribution. [1] P.H.L. Notten, J.E.A.M. Van den Meerakker, J.J. Kelly in Etching of III-V Semiconductors: An Electrochemical ApproachElsevier Oxford (1991) [2] A. Causier, M. Bouttemy, I. Gérard, D. Aureau, J. Vigneron, and A. Etcheberry ; Phys. Status Solidi C 9, No. 6, 1408–1410 (2012) Figure 1

Process intensification-assisted conversion of α,ω-alkanediols to dibromides

The increasingly widespread applications of α,ω-dibromides motivated development of a scalable, inexpensive process to rapidly convert selected α,ω-alkanediols to the corresponding dibromides. Diols were heated with only 48% aq HBr and an organic solvent, using a Dean–Stark apparatus modified to fractionate the azeotropic distillate, thereby maintaining a higher HBr concentration and reaction rate in the pot. Intensified distillation also increased the reaction rate. Various other substrate, solvent, and parameter effects have been discovered and rationalized.

Inductive couple plasma reactive ion etching characteristics of TiO2 thin films

Changes in the inductively coupled plasma reactive ion etching characteristics of TiO2 thin films in response to the addition of HBr, Cl2 and C2F6 to Ar gas were investigated. As the HBr, Cl2 and C2F6 concentration increased, the etch rate increased; however, the etch profile degree of anisotropy followed a different trend. As HBr concentration increased, the greatest anisotropic etch profile was obtained at 100% HBr, while the greatest anisotropic etch profile was obtained at concentrations of 25% when etching was conducted under C2F6 and Cl2. Field emission scanning electron microscopy revealed that 25% C2F6 generated the greatest vertical etch profile; hence, etch parameters were varied at this concentration. The effects of rf power, dc-bias voltage and gas pressure on the etch rate and etch profile were also investigated. The etch rate and degree of anisotropy in the etch profile increased with increasing rf power and dc-bias voltage and decreasing gas pressure. X-ray photoelectron spectroscopy analysis of the films etched under a C2F6/Ar gas mixture revealed the existence of etch byproducts containing F (i.e. TiFx) over the film. CxFy compounds were not detected on the film surface, probably due to contamination with atmospheric carbon.