Nitrogen Peak Research Articles

Functionalizing non-smectic clay via methoxy-modification for enhanced removal and recovery of oxytetracycline from aqueous media

Kaolinite and methoxy-modified kaolinite were used as novel adsorbents for oxytetracycline (OTC) removal and recovery from aqueous media. Batch adsorption experiments were performed to study the effect of pH, ionic strengths, initial concentration, and contact time on OTC adsorption. The adsorbents were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after adsorption. Adsorption of OTC reached its maximum when solution pH increased up to 6 for 0.001 M ionic strength, above which adsorption decreased further when solution pH increased. Freundlich and Langmuir’s models best fit the equilibrium data with a strong dependency on OTC adsorption capacity giving its maximum at 36 mg g−1. Binding is postulated for OTC adsorption on pristine kaolinite as a special case of Hill model with independent binding interaction of OTC adsorption onto the clay that affects the adjacent sites on the pristine kaolinite, in contrast with the adsorption of OTC on methoxy-modified kaolinite. Nitrogen peaks of the XPS spectra indicated changes in the oxidation states of C–N bonds in the N1s peaks by forming tertiary amide C–N and methoxy O–CH3 bonds which corroborated with the results from FTIR spectra. Removal efficiencies and spectroscopic results indicate that performance on methoxy-modified kaolinite is a promising modification on the clay for recovering antibiotics from wastewater.

Research On the Change of Rainwater Quality in the Early Stage of River Discharge

The primary rainwater non-point source pollution is one of the main pollution reasons affecting river water quality. Based on the comprehensive analysis of the rainfall data, initial rainwater quality data and catchment area data, this paper obtains the variation rules and pollution characteristics of the initial rainwater quality at different catchment ranges of river outfall, and provides suggestions for the control of primary rainwater non-point source pollution of the target river outfalls. In the target River outlet of this study, the commercial area is the first to reach the peak of COD and ammonia nitrogen in the initial rainwater quality, and the living area is the highest in the initial rainwater COD and ammonia nitrogen concentration. Thus the control measures can be taken for the initial rainwater in the commercial area, and the key prevention and control measures can be taken for the higher concentration initial rainwater in the living area.

527. Corona Virus Disease-19 (COVID-19) in a Veterans Affairs Hospital at Suffolk County, Long Island, New York

BackgroundThe area of New York was hit hard by the COVID 19 pandemic with Suffolk county in Long Island numbering >40 thousand cases and 1900 deaths by the end of May 2020. The Veterans Affairs Medical Center (VAMC) at Northport NY serves over 30000 Veterans. We report our institution’s experience during the COVID 19 outbreakMethodsRetrospective chart review of hospitalized Veterans (VETS) with COVID-19 from March 1st to May 31st 2020 at Northport VAMCResultsA total of 141 VETS had laboratory confirmed SARS-CoV-2 infection, 67 got hospitalized, and 20/67 died. The median age of the hospitalized cohort was 73 years (33 to 94). Figure 1 shows the dates of tests, Tables 1 &2 summarize the demographic characteristics, medical history and laboratory findings. No co-infection with influenza or other respiratory viruses were identified. The deceased group was older 77.5 vs 71 years P 0.007, had lower oxygen saturation and higher respiratory rate on presentation, had longer length of stay P 0.091, more likely to be in ICU and intubated, had lower bicarbonate levels, higher SAPS P < 0.001, higher lactate dehydrogenase, blood urea nitrogen, potassium levels, and higher peak procalcitonin, CRP, ferritin, ESR levels. There was no difference between recovered and deceased in terms of comorbidities except atrial fibrillation. Also, no difference in use of ACE inhibitors, statins, famotidine, hydroxychloroquine (HCQ), azithromycin, doxycycline, steroids. Beta lactam antibiotics and tocilizumab were given more in the deceased group. HCQ was stopped in 1 patient due to QTc prolongation. No bacteremia identified in the recovered group contrary to two occasions in the deceased, E. faecalis and S. mitis. Six pneumonias in intubated deceased patients were identified (3 had received steroids and one tocilizumab) and 4 in recovered (2 intubated/steroids and 1 tocilizumab). 12 recovered patients had persistent positive nasopharyngeal PCR for SARS-CoV-2 for average 29 days (14 to 79 days), and 4 of them were checked and had detectable IgG antibodyDates of Tests for Hospitalized Veterans with COVID-19 Comparison of Demographic Data and Comorbidities in Recovered vs Diseased Hospitalized Veterans with COVID - 19 Comparison of Laboratory Data in Recovered vs Diseased Hospitalized Veterans with COVID - 19 ConclusionThe inpatient mortality of hospitalized VETS with COVID-19 in our institution was 30%. Mortality was associated with older age. Ongoing monitoring of outcomes in hospitalized patients will be important to understand the evolving epidemiology of COVID-19 among US VETS.Disclosures All Authors: No reported disclosures

Effect of different itaconic acid contents of poly(acrylonitrile-co-itaconic acid)s on their carbonization behaviors at elevated temperatures

The carbonization procedure is a crucial step for polyacrylonitrile (PAN)-based precursors to be transformed into carbon materials. In this study, PAN and poly(acrylonitrile-co-itaconic acid)s (PAIs) with different contents of itaconic acid (IA) were prepared through free radical polymerization, and their carbonization behaviors were investigated at different thermal treatment temperatures. As confirmed by Fourier transform infrared spectroscopy analyses, functional groups containing heteroatoms practically disappeared above 600 °C, due to crosslinking, condensation, dehydrogenation, and gas-evolution reactions of the carbonization processes. Deconvolution of the carbon, oxygen and nitrogen peaks from X-ray photoelectron spectroscopy analyses revealed the development of ordered and doped graphitic carbons at elevated thermal treatment temperatures. The total yields of PAIs with excess amounts of IA (3 ~ 6 mol%) demonstrated a large carbon loss during the carbonization procedures. PAI with 1 ~ 2 mol% IA afforded carbon materials with a relatively high graphitic carbon content at 1200 °C, which is potentially important for electrical conductivity. Meanwhile, carbon materials prepared from PAI with 2 mol% IA at 1200 °C exhibited a relatively high content of pyridinic nitrogen, suggesting potentially superior catalytic activity. This study afforded technical guidelines on the structural elements of PAN-based precursors to prepare carbon materials with predesigned characteristics.

Online detection of halogen atoms in atmospheric VOCs by the LIBS-SPAMS technique.

Volatile organic compounds (VOCs) are one of the major pollutants in the atmospheric and indoor environment. The direct detection of halogen atoms in VOCs via laser induced breakdown spectroscopy (LIBS) is highly challenging work because of the high ionization energy of these halogen elements. In this paper, the LIBS system combined with a self-designed single particle aerosol mass spectrometry (SPAMS) system were applied to the direct online detection of VOCs in the atmosphere. The experimental parameters of LIBS experiment were optimized in the measurement of ambient air. Under the best experimental conditions, the characteristic peaks of nitrogen, hydrogen, oxygen, as well as argon, were observed in the LIBS spectra of air. Then, LIBS and SPAMS measurements were performed on Halon 2402, Freon R11 and iodomethane samples under the atmospheric pressure. The characteristic spectral lines of fluorine, chlorine, bromine and iodine were observed and recorded in LIBS spectra. The SPAMS measurements also provide the elemental compositional information of individual VOCs aerosol particles in real time, which is an effective supplement to LIBS analysis. In addition, the different isotopes of bromine and chlorine can be clearly distinguished at the same time. Finally, the home-built portable Raman spectrometer was utilized to analyze the vibrational modes and get the "spectral fingerprint" of VOCs. All the results indicate that the direct online detection performed by the LIBS and SPAMS techniques could provide elemental and isotopic information of halogen atoms in atmospheric VOCs.

Behavior simulation of nitrogen compounds in rivers with uncertainty analysis

This study simulated nitrogen-compound concentration changes in rivers, taking into account uncertainty analysis carried out by the Monte Carlo Method. The study area is the final stretch of the Piracicaba River, located in Minas Gerais, Brazil, which is an important Doce River tributary. The uncertainty analysis took into account random generation of hydrodynamic variables, initial water quality conditions and kinetic constants. Different variation percentages for the organic nitrogen decay kinetic constants random generation did not influence considerably the ammonia or organic nitrogen maximum concentration extreme values. In the simulations, maximum organic nitrogen concentrations were most frequently between 0.20 mg.L-1 and 0.22 mg.L-1 (42%), maximum ammonia nitrogen between 0.28 mg.L-1 and 0.30 mg.L-1 (30%), maximum nitrite between 0.05 mg.L-1 and 0.07 mg.L-1 (49%) and maximum nitrate between 0.46 mg.L-1 and 0.50 mg.L-1 (37%). Estimated maximum concentrations for ammonia nitrogen, nitrite and nitrate did not exceed the environmental quality standards established by Brazilian CONAMA Resolution 357/2005 for Class 2 watercourses. Random generation of kinetic constants that regulate ammonia and nitrite decay produced significant ammonia nitrogen, nitrite, and nitrate peak concentrations value frequencies, histograms and forms changes, when considering variation percentages equal to or greater than 50%. Some simulation results showed more inhibition of oxidized nitrogen forms production.

Development of novel ion detector that combines a microchannel plate with an avalanche diode

Detector gain saturation is a well-known issue with the chevron microchannel plate (MCP) detector configured with two MCPs, which is widely used in the time-of-flight (TOF) mass spectrometer. In these detectors, high-intensity signals saturate the gain stages, thus reducing the magnitude of subsequent signals. To solve this issue, we developed a new detector that combines an MCP with an avalanche diode. Gain saturation was evaluated by measuring the percent of signal intensity loss of the second significant ion peak on the TOF spectrum using xenon isotopes, and then verified by argon spiked with nitrogen as a model sample.The signal intensity ratio of 132Xe/129Xe on the chevron MCP and the new detector named ‘MIGHTION’ was 0.31 and 0.94 using the ion counting result as the reference, which corresponds to 69 % signal suppression for the chevron MCP, but only an 8% difference for MIGHTION.By using trace-level argon spiked with nitrogen, the argon intensity change was monitored by alternately switching the nitrogen sample on and off with the ion gate. The intense nitrogen peak did not suppress the argon intensity peak, which appears 1.17μs later. The nitrogen peak intensity was about 240 times larger compared to argon, and the peak voltage was 3.25 V with a 50-Ω load.

Dynamic Covalent Synthesis of Crystalline Porous Graphitic Frameworks

Summary Porous graphitic framework (PGF) is a two-dimensional (2D) material that has emerging energy applications. An archetype contains stacked 2D layers, the structure of which features a fully annulated aromatic skeleton with embedded heteroatoms and periodic pores. Due to the lack of a rational approach in establishing in-plane order under mild synthetic conditions, the structural integrity of PGF has remained elusive and ultimately limited its material performance. Here, we report the discovery of the unusual dynamic character of the C=N bonds in the aromatic pyrazine ring system under basic aqueous conditions, which enables the successful synthesis of a crystalline porous nitrogenous graphitic framework with remarkable in-plane order, as evidenced by powder X-ray diffraction studies and direct visualization using high-resolution transmission electron microscopy. The crystalline framework displays superior performance as a cathode material for lithium-ion batteries, outperforming the amorphous counterparts in terms of capacity and cycle stability.

Effect of nitrogen substitution and π-conjugation on photophysical properties and excited state intramolecular proton transfer reactions of methyl salicylate derivatives: Theoretical investigation

Effects of nitrogen substitution and π-conjugation on the strength of intramolecular hydrogen bond (H-bond), photophysical properties, and excited-state intramolecular proton transfer (ESIPT) reactions of MS derivatives have been systematically investigated using DFT and TD-DFT methods at the B3LYP/TZVP level. The H-bond strength of all studied compounds becomes stronger in the S1 than in the S0. This result is confirmed by vibrational IR spectra and topological analysis. The H-bond strength of nitrogen substituted compounds is lower than those of compounds with the π-extended conjugation. For photophysical properties, the HOMO-LUMO energy gaps in normal and tautomer forms of nitrogen substituted compounds are insignificantly increased, whereas those of compounds with the π-extended conjugation are notably decreased. The slight widening of the energy gaps results in the slight blue-shifts of the absorption and emission peaks of nitrogen substituted compounds compared to those of MS, whereas the significant narrowing of the energy gaps makes the incredible red-shifts of both electronic spectra of compounds with the π-extended conjugation. Thus, remarkably large Stokes shifts of about 1000 cm−1 are observed for compounds with the π-extended conjugation (M3HN, M2HQC, and M3HQC). In addition, potential energy curves along the PT reaction indicate that the ESIPT of all studied compounds should occurred due to low PT barriers in the exothermic reaction. Dynamic simulations reveal that the ESIPT reactions of studied compounds are observed in an ultrafast time scale (38–130 fs). Most of them have remarkably high PT probabilities (0.84–1.00) except M3HP (0.56), which are in good agreement with the results of H-bond strength. Therefore, the photophysical properties of studied compounds can be significantly tuned by controlling the effect of π-conjugation.

Measuring hydrogen with fast neutrons: Application to organic materials identification in cargo containers

To inspect cargo containers, X-ray imaging can be complemented by fast neutron interrogation to provide indication concerning the chemical nature of the transported goods through the detection of neutron-induced gamma rays. Organic goods are of special interest since they constitute a significant part of the merchandises. In addition, in the context of NRBC-E threats search in cargo containers, a nondestructive inspection system should also be able to detect explosives. Until now, fast neutron interrogation systems identify organic materials in cargo containers using characteristic neutron-induced gamma-ray peaks of carbon, oxygen and nitrogen. However, identifying organics in this way can lead to ambiguities, since no hydrogen gamma ray can be measured with fast neutrons. Nevertheless, it is known that hydrogen strongly modifies the neutron energy spectrum, which in turn affects the amplitudes of gamma-ray peaks. The link between the hydrogen fraction and the amplitude of gamma ray peaks being complex, no attempt has been made to inverse this link until now. Simulations show, however, that a neural network that takes as inputs the heights of carbon, oxygen and nitrogen gamma ray peaks can indeed determine the hydrogen fraction. Simulations of realistic cases show that the use of a neural network indeed allows identifying compounds having similar fractions of carbon, oxygen and nitrogen but different hydrogen fraction, thus opening the way to more accurate materials identification.

Adsorption Capability of Fe-HT3.0 for Nitrite and Nitrate Ions in a Binary Solution System.

In this study, the adsorption capability of Fe-HT3.0 for nitrite and nitrate ions in a binary solution system was evaluated. It was found that the amount of nitrite and nitrate ions adsorbed in a single solution (1.19 and 1.27 mmol/g, respectively) was higher than that in a binary solution (0.36 and 0.90 mmol/g, respectively). Equilibrium adsorption was attained within 6-24 h. The adsorption data were fitted to a pseudo-second-order model (correlation coefficient: 0.999), and indicated that the adsorption of both nitrite and nitrate ions is controlled by chemical sorption. Additionally, the binding energies before and after the adsorption of nitrite and nitrate ions in the binary solution system were measured. After adsorption, new nitrogen peaks (approx. 399 and 403 eV) were detected. The results of this study show the potential of Fe-HT3.0 for the removal of nitrite and nitrate ions from aqueous solution systems.

PRE-NURSERY OF SHRIMP POST-LARVAE REARED IN BIOFLOC SYSTEM UNDER DIFFERENT STOCKING DENSITIES

This study evaluated different stocking densities during pre-nursery of Pacific white shrimp postâ€"˜larvae (PL) reared in a biofloc system. The tanks (60 L) were stocked with PL stage 5 (PL 5) under five densities (80, 100, 120, 140 and 160 PLs L-1), in triplicate, resulting in 15 experimental units. PLs were fed nine times a day using commercial feed. Molasses was added in all treatments four times a day at an average carbon: nitrogen ratio of 14.7: 1. The experiment was carried out until the PLs reached PL 20 stage, and during this time, water quality variables, survival, weight gain and survival to salinity stress were all evaluated. For treatments above 100 PLs L-1, total suspended solids were higher than recommended (700 mg L-1). Also, the treatment with 160 PL L-1 had higher total ammonia nitrogen peaks (&gt;10 mg L-1), resulting in lower survival in this treatment. No differences were observed between treatments in the other performance parameters evaluated (final weight and survival to salinity stress). It was concluded that pre-nursery of Pacific white shrimp can be performed using densities up to 140 post-larvae L-1 in a biofloc system without compromising shrimp growth performance.&#x0D;

Nitrogen moieties -dominated Co–N-doped nanoparticle-modified cathodes in heterogeneous-electro-Fenton-like system for catalytic decontamination of EDTA-Ni(II)

Ethylenediaminetetraacetic acid (EDTA) could form stable complexes with toxic metals such as nickel due to its strong chelation. In this study, with the same doping level of Co and N, MoO2 and ZIF-67 were used as precursors to prepare MoO2@Co/N and FeC@Co/N electrocatalysts for the modified graphite felt cathodes in heterogeneous-electro-Fenton-like reaction (HEFL) system. The X-ray diffraction and X-ray photoelectron spectroscopy results indicated that both of the catalysts are dominated with pyridinic N (2.42% and 2.82%) upon co-doping Co/N, and FeC@Co/N exhibited an obviously higher additional sp-hybridized nitrogen (sp-N) peak. The co-doping of Co/N induced the lattice modifications to produce more lattice defects, where pyridinic N and sp-N, related with the active sites (C–N, Co-Nx), were formed at near-ring defects along sheet edges through the nitrogen replacement of CC groups. FeC@Co/N demonstrated superior oxygen reduction reaction catalytic activity in terms of Cyclic Voltammetry and Rotating Ring-disk Electrode, and exhibited the remarkably higher current density (30 mA) and lower onset potential (−0.208 V) in Linear Sweep Voltammetry analysis. In the FeC@Co/N/CF modified HEFL system, despite the generated H2O2 concentrations (62.5 mg L−1) is not very high, the reducing reaction of ≡Fe(III)/Co(III)–OH could get the electron directly from the cathode, which would greatly reduce the consumption of H2O2, high utilization efficiency of H2O2 (η: 87.63%) could greatly improve the EDTA-Ni removal (97.5%) and TOC (92.6%). This work demonstrates the feasibility of utilizing FeC@Co/N/CF as a cathode for breaking metal-complex in HEFL process.

Antibacterial Properties of Charged TiN Surfaces for Dental Implant Application.

The formation and characterization of positively surface charged TiN surfaces were investigated for improving dental implant survival. Surface nitrogen atoms of a traditional TiN implant were converted to a positive charge by a quaternization reaction which greatly increased the antibacterial efficiency. Ti, TiN, and quaternized TiN samples were incubated with human patient subgingival bacteria for 4 hours at 37°C in an anaerobic environment with an approximate 40% reduction in counts on the quaternized surface over traditional Ti and TiN. The samples were challenged with Streptococcus Mutans and fluorescent imaging confirmed significant reduction in the quaternized TiN over the traditional Ti and TiN. Contact angle measurement and X-Ray Photoelectron Spectroscopy (XPS) were utilized to confirm the surface chemistry changes. The XPS results found the charged quaternized nitrogen peak at 399.75 eV that is unique to the quaternized sample.

Application of Neutron-Gamma Analysis for Determining Compost C/N Ratio

The possible application of Pulsed Fast/Thermal Neutron Analysis (PFTNA) for determining the carbon-to-nitrogen ratio (C/N) of compost will be discussed. This analysis method has several advantages over traditional chemical analysis, including that it is a nondestructive in situ method that does not require extensive sample collection and it analyzes much larger volumes of material (∼1 m3) than traditional chemical analysis (∼1 cm3). The amount of carbon can be determined by irradiating compost with neutrons and measuring the gamma ray peak at an energy of 4.44 MeV that appears due to inelastic scattering. Nitrogen can be determined by measuring the gamma ray peak at 10.83 MeV that appears due to thermal neutron capture. For C/N measurements, a calibration line that relates the C/N mass ratio to the carbon/nitrogen gamma peak ratio should first be constructed; our calibration line was constructed using carbon–ammonium nitrate mixtures. PFTNA measurements were then used to determine carbon and nitrogen peak values in order to utilize the calibration line for calculating the C/N mass ratio. The workability of this methodology has been demonstrated in laboratory experiments. The applicability of PFTNA for compost C/N ratio determinations was evaluated with Monte Carlo computer simulations of neutron propagation in large compost volumes (Geant4 toolkit) and experimental measurements of real compost (volume 1.3 m3). Data from computer simulations and experiments demonstrated that the PFTNA method is fully applicable for determining the C/N ratio in compost material up to values of 25 and even greater.

Characteristics of Nitrogen and Phosphorus Concentration Dynamics in Natural Ditches Under an Irrigation-Drainage Unit in the Jianghan Plain

The paddy field in Jianghan Plain usually exists in the form of an irrigation-drainage unit, and the natural ditch is the main part of the unit. A continuous in situ monitoring of the natural ditch water level and water quality through the entire rice growing season in 2015 was conducted to investigate the dynamics of ditch water level and nitrogen and phosphorus concentration in the ditch. Another objective was to determine the effect of these factors. Results showed that during the entire rice growing season, the ditch water depth was maintained between 30 to 70 cm, and the water depth was higher during irrigation events than during rainfall events. Fertilization was the main factor affecting the nitrogen concentration in the ditch water. Two peaks of total nitrogen (TN) concentration appeared on June 18 and July 30 because of topdressing. In the early stage of rice growing, ammonia nitrogen (NH4+-N) concentration was higher than that of nitrate nitrogen (NO3--N). External disturbances (such as rainfall and irrigation events) were the main factors affecting the total phosphorus (TP) concentration in the ditch water. The dynamic of TP concentration in the ditch water was large, and it was consistent with that of the particulate phosphorus (PP) concentration. Drainage of the irrigation-drainage was mainly controlled artificially. The period from rice transplanting to 3 days after the first top dressing was critical in preventing the outflow of ditch water. During the rice harvest stage, the TN and TP concentration were 0.22 and 0.06 mg·L-1, and the water quality reached theⅡclass standard for surface water quality. This reduced the risk from drainage from the irrigation-drainage unit to the surrounding water environment.

In Situ XPS Reveals Voltage Driven Asymmetric Ion Movement of an Ionic Liquid through the Pores of a Multilayer Graphene Electrode

Under application of a voltage bias, asymmetric ion movement of an ionic liquid (IL) through a multilayered graphene (MLG) electrode has been detected by X-ray photoelectron spectroscopy, via recording the intensity of the two nitrogen peaks. Accordingly, we observe that upon increasing the bias, the two peaks representing the cationic and anionic fragments of the IL start appearing with increasing intensity, together with an asymmetry in their ratio, differing from unity by about 10%. Bias-dependent binding energy shifts followed through atomic features of the IL (F 1s, N 1s, and C 1s) and the graphene electrode (C 1s) indicate that a distinct solid–liquid interface develops throughout the entire intercalation process with an additional and pertinent evidence for finite potential drops across the two electrical double layers. This evidence is bolstered by the fact that the measured binding energy difference between the F 1s of the liquid and C 1s peak of the semisolid MLG electrode is only about half of ...

Rapid and Quantitative Determination of Soil Water-Soluble Nitrogen Based on Surface-Enhanced Raman Spectroscopy Analysis

An accurate and rapid determination of soil water-soluble nitrogen is conducive to scientific fertilization in precision agriculture. Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive fingerprint with the advantages of simple operation and high detection efficiency. In this paper, partial least squares (PLS), principal components analysis (PCA), and least squares supports vector machine (LS-SVM) were applied to analyze the relationship between soil water-soluble nitrogen concentration and SERS. The results showed that the SERS-enhancing effect based on Opto Trace Raman 202 (OTR 202) was better than that of silver nanosubstrate and gold nanosubstrate. In addition, the prediction accuracy of soil water-soluble nitrogen in PLS was the highest ( R p 2 = 0.91 , RMSE p = 8.76 mg / L , R P D = 3.00 ) when the original spectra were preprocessed with first-derivative. Moreover, 1028, 1370, 1436, and 1636 cm−1 could be determined as characteristic peaks of soil water-soluble nitrogen, the association between soil water-soluble nitrogen concentration and a SERS intensity of 1370 cm−1 was the highest ( R p 2 = 0.94 ) , and the regression equation was y = 93.491x + 1771.5. Beyond that, the prediction accuracy of distinguishing between a low soil water-soluble nitrogen concentration (22.7–63.7 mg/L) and a high soil water-soluble nitrogen concentration (70.5–118.3 mg/L) based on PCA and LS-LVM was 86.67%. In conclusion, soil water-soluble nitrogen could be detected rapidly and quantitatively using SERS, which was beneficial to provide a rapid, accurate, and reliable scheme for scientific and precise fertilization.

Effect of ammonia plasma treatment on the luminescence and stability of porous silicon

Effect of ammonia plasma on the luminescence and stability of the porous silicon (PS) has been studied. Samples were cut into different parts to compare the as-deposited sample with the low (5 W) and high RF power (75 W) treated parts. Scanning electron microscopy (SEM) shown that the samples treated at 5 W did not demonstrate a change in the structural aspects, whereas, samples treated at 75 W shown some modifications in the final structure. Photoluminescence (PL) spectroscopy revealed strong diminishment in the luminescence as an outcome of plasma treatment for both samples. In comparison to sample treated at 5 W, high RF power treated sample did not show recovery in the PL with the course of time. Fourier transform infrared (FTIR) analysis shown the alterations in the hydrogen and oxygen bonding with time for the sample treated at 5 W. On the other hand, the appearance of stable nitrogen peaks (Si-N, N-H) were found for the other sample. PL quenching could be due to the appearance of plasma-induced defects and/or hydrogen-related dangling bonds and further shown the stability of the sample treated at 75 W (no recovery in PL) for optoelectronic applications.

Effect of concentration of hyaluronic acid and NaCl on corrosion behavior of 316L austenitic stainless steel

Due to low cost and easily available material, 316L stainless steel (SS) is used for biomedical implants. The electrochemical corrosion behavior of 316L (SS) was studied as a function of the concentration of simulated biological fluid (hyaluronic acid), the influence of Cl− and the combined effect of NaCl and hyaluronic acid (HA). For the electrochemical tests, potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) were undertaken. With the increase in HA concentration, corrosion rate increases. Whereas, with the addition of NaCl to HA the solution, the corrosion resistance of the sample was enhanced. Also, in pure NaCl solution, the corrosion current density (icorr) increased as compared to bare HA and HA + NaCl. This is due to the adhesion property of the HA on the sample surface. EIS result agrees with the findings of potentiodynamic polarization tests. X-ray photoelectron spectroscopy (XPS) was executed to analyze the passive film formed in the solution of HA and NaCl on 316L SS. XPS spectra confirms the formation of the passive film containing chromium oxide and hydroxides. Also, the formation of MoO2 helps in improving better corrosion resistance. The peak of nitrogen was observed in the sample immersed in HA solution. Scanning electron microscope (SEM) was carried out to analyze the surface morphology.