Hexane extract of Persea schiedeana Ness as green corrosion inhibitor for the brass immersed in 0.5 M HCl.

The hexane extract of Persea schiedeana Ness (PSN) was analyzed as corrosion inhibitor for the brass surface immersed in 0.5 M HCl. Fourier-transform infrared spectroscopy and a gas chromatographic (GC) and mass spectrometric (MS) were used to identify the PSN extract's functional groups and compound constituents. The functional groups identified were CH 3 and CH 2 functional alkyl groups, C=O stretching vibration of aldehydes, ketones, and carbonyl groups. The GC/MS determined the presence of fatty acids in the PSN extract, where palmitic acid, oleic acid, and ethyl oleate were the major constituents. Electrochemical characterizations were conducted to observe the effect of PSN as corrosion inhibitor on the brass surface. The Rp and Rn calculated from EIS and ENA give the same behavior. Based on the OCP behavior, it was determined that the PSN works as a mix inhibitor, affecting both anodic and cathodic reactions. The corrosion current density (Icorr) suggests that the extract of PSN reduces the corrosion rate of the brass with efficiencies above 90% for all concentrations. The efficiency obtained for each PSN concentration was attributed to forming a corrosion scale of CuO and Cu 2 O , which reacted with the carboxyl group to form copper carboxylates on the metal surface.

Comparison of the Analgesic Efficacy between Levobupivacaine 0.25% and Ropivacaine 0.375% for PENG (Pericapsular Nerve Group) Block in the Context of Hip Fracture Surgery of Elderly Patients: A Single-Center, Randomized, and Controlled Clinical Trial.

Previous studies have compared levobupivacaine versus ropivacaine in various peripheral nerve blocks in terms of block duration, quality of analgesia, and onset time, but this has not occurred in the PENG block. Here, a single-center, randomized, and controlled clinical trial is presented. One hundred and twenty patients older than 65 years suffering from hip fractures and surgically treated at our institution under spinal anesthesia were eligible for participation; of them, one hundred and eight were analyzed. Patients were randomized to receive ultrasound-guided PENG blocks using 20 mL of either 0.25% levobupivacaine or 0.375% ropivacaine (both of which are equipotent concentrations). The primary endpoint was to compare the analgesic duration (time to first rescue) and analgesic quality (pain scores using the VAS, PAINAD, and AlgoPlus scales) between the groups. Secondary endpoints included comparing the onset time, describing the need for and type of rescue analgesics, and possible associated adverse effects. There were no statistically significant differences in analgesic duration between levobupivacaine (median 861.0, IQR 960) and ropivacaine (median 1205.0, IQR 1379; p = 0.069). Likewise, the quality of analgesia and onset time were comparable among the groups. A small number of patients required opioids as rescue analgesics (4.6%). The possible associated adverse effects included postoperative infection (11.1%) and delirium (2.8%).

Non-invasive characterization of the elastic protein resilin in insects using Raman spectroscopy.

Resilin is an extremely efficient elastic protein found in the moving parts of insects. Despite many years of resilin research, we are still only just starting to understand its diversity, native structures, and functions. Understanding differences in resilin structure and diversity could lead to the development of bioinspired elastic polymers, with broad applications in materials science. Here, to better understand resilin structure, we offer a novel methodology for identifying resilin-rich regions of the insect cuticle using non-invasive Raman spectroscopy in a model species, the desert locust (Schistocerca gregaria). The Raman spectrum of the resilin-rich semilunar process of the hind leg was compared with that of nearby low-resilin cuticle, and reference spectra and peaks assigned for these two regions. The main peaks of resilin include two bands associated with tyrosine at 955-962 and 1141-1203 cm-1 and a strong peak at 1615 cm-1, attributed to the α-Amide I group associated with dityrosine. We also found the chitin skeletal modes at ~485-567 cm-1 to be significant contributors to spectra variance between the groups. Raman spectra were also compared to results obtained by fluorescence spectroscopy, as a control technique. Principal component analysis of these resulting spectra revealed differences in the light-scattering properties of resilin-rich and resilin-poor cuticular regions, which may relate to differences in native protein structure and relative abundance.

Identifying and locating carotenoids in supra-orbital combs of male black grouse (Lyurus tetrix) using Raman and transmission electron microscopy: A histological study using rehydrated tissue samples.

Colourful signals have long been implicated as indicators of individual quality in animals. Bare-skin signals are an understudied aspect of avian colouration compared with plumage studies, despite displaying rapid changes in size and colour in response to different environmental or physiological stressors. Even fewer studies have focused on the underlying histology of these structures and the importance this plays in the resulting skin colour. Using the Black Grouse (Lyrurus tetrix), we identified the underlying structure of individual dermal spikes, which make up the red supra-orbital comb (a known integumentary signal of male quality), and highlight visual structural differences between combs of different sizes. In addition, we used Raman spectroscopy to indicate the presence of carotenoids within the tissue, something that had previously only been inferred through characteristic reflectance patterns. An increased understanding of the structural basis of colour of featherless parts of the skin opens up exciting new avenues for interpreting the information content of integumentary signals.

A smart chitosan-graphite molecular imprinted composite for the effective trapping and sensing of dimethyl methylphosphonate based on changes in resistance.

A molecular imprinted polymer (MIP) fabricated from a chitosan doped with graphite to create a conductive composite (CG-MIC) with the ability to trap and detect dimethyl methylphosphonate (DMMP) through a change in resistance of the material has been successfully manufactured. The GC-MIC presented a maximum trapping capacity of 96 ppm (0.096 mg g-1) of DMMP. A similar non-imprinted composite made of chitosan-graphite (CG-NIC) had a surface adsorption of 48 ppm (0.048 mg g-1) of DMMP. The manufacturing process was tested for consistency and there were no significant differences in resistance between batches of CG-MIC before (around 450 Ω) and after (around 70 Ω) DMMP extraction, representing a homogeneous manufacturing process. Although Atomic Force Microscopy studies revealed that the graphite was not homogenously distributed throughout the chitosan matrix, the response was consistent. The changes in the concentration of DMMP within the self-sensing material, being proportional to those in gas concentration, could be followed by the changes in resistance. The inclusion of common interferents: Acetic acid, acetone, ethanol, ammonium hydroxide and 2-propanol, equivalent in concentration to the DMMP, caused a change in the resistance of the material but did not substantially affect the specific resistance response of the composite material. Based on this data, the CG-MIC could be used as a smart material with sensing capabilities to monitor trapping levels of DMMP.

Mechanistic Study of Arsenate Adsorption onto Different Amorphous Grades of Titanium (Hydr)Oxides Impregnated into a Point-of-Use Activated Carbon Block.

Millions of households still rely on drinking water from private wells or municipal systems with arsenic levels approaching or exceeding regulatory limits. Arsenic is a potent carcinogen, and there is no safe level of it in drinking water. Point-of-use (POU) treatment systems are a promising option to mitigate arsenic exposure. However, the most commonly used POU technology, an activated carbon block filter, is ineffective at removing arsenic. Our study aimed to explore the potential of impregnating carbon blocks with amorphous titanium (hydr)oxide (THO) to improve arsenic removal without introducing titanium (Ti) into the treated water. Four synthesis methods achieved 8-16 wt.% Ti loading within the carbon block with 58-97% amorphous THO content. The THO-modified carbon block could adsorb both oxidation states of arsenic (arsenate and arsenite) in batch or column tests. Modified carbon block with higher Ti and amorphous content always led to better arsenate removal, achieving arsenic loadings up to 31 mg As/mg Ti after 70,000 bed volumes in continuous flow tests. Impregnating carbon block with amorphous THO consistently outperformed impregnation using crystalline TiO2. The best-performing system (TTIP-EtOH carbon block) was an amorphous THO derived using titanium isopropoxide, ethanol, and acetic acid via sol-gel technique, aged at 80° for 18 hours and dried overnight at 60°. Comparable pore size distribution and surface area of the impregnated carbon blocks suggested that chemical properties play a more crucial role than physical and textural properties in removing arsenate via amorphous Ti-impregnated carbon block. Freundlich isotherms indicated energetically favorable adsorption for amorphous chemically synthesized adsorbents. The mass transport coefficients for the amorphous TTIP-EtOH carbon block were fitted using a pore surface diffusion model, resulting in Dsurface = 3.1×10-12 cm2/s and Dpore = 3.2×10-6 cm2/s. Impregnating the carbon block with THO enabled effective arsenic removal from water without adversely affecting the pressure drop across the unit or the carbon block's ability to remove polar organic chemical pollutants efficiently.

The chemistry of an insect ear: ionic composition of a liquid-filled ear and haemolymphs of Neotropical katydids.

The purpose of this study is to examine and to compare the ionic composition of the haemolymph and the ear fluid of seven species of katydids (Orthoptera: Tettigoniidae) with the aim of providing from a biochemical perspective a preliminary assessment for an insect liquid contained in the auditory organ of katydids with a hearing mechanism reminiscent of that found in vertebrates. A multi-element trace analysis by inductively coupled plasma optical-emission spectrometry was run for 16 elements for the ear liquid of seven species and the haemolymph of six of them. Based on the obtained results, it can be recognized that the ionic composition is variable among the studied insects, but sodium (Na+), potassium (K+), calcium (Ca2+) and magnesium (Mg2+) are the most prominent of the dissolved inorganic cations. However, the ion concentrations between the two fluids are considerably different and the absence or low concentration of Ca2+ is a noticeable feature in the inner ear liquid. A potential relationship between the male courtship song peak frequency and the total ion (Na+, K+, Mg2+ and Ca2+) concentration of the inner ear liquid is also reported.

Brain Nocardiosis Defined by 18 F-Fluorocholine PET/CT.

ABSTRACT: Nocardia infection (nocardiosis) is usually acquired by inhalation; so pulmonary nocardiosis is the most common clinical presentation. Extrapulmonary localization occurs through hematogenous dissemination or contiguous spread. Nocardia can involve the central nervous system in a very reduced number of patients, mainly in immunocompromised. We present a case of a 56-year-old woman with a history of aggressive systemic mastocytosis, treated with chemotherapy 1 year ago. Patient reported intense headache, disorientation, and blurry vision without other symptoms being diagnosed with a rare brain nocardiosis by Nocardia cerradoensis . Neither bacteremia nor pulmonary involvement was detected. Brain PET/CT illustrated 18 F-fluorocholine avidity on brain abscesses.

Electropolymerization of Metallo-Octaethylporphyrins: A Study to Explore Their Sensing Capabilities.

The electropolymerization of metallo-octaethylporphyrins (OEP) containing copper, zinc or nickel metal were performed using cyclic voltammetry at three different potential ranges. The electropolymerized porphyrins were characterized by UV-Vis and Raman spectroscopies and the Soret band (393-445 nm) and Raman bands were used to assess the degree of electropolymerization obtained. The application for an analytical use of the modified electrodes to determine phenobarbital in aqueous solution was evaluated. The electropolymerized CuOEP produced at potentials ranging from 0.0 to 2.2 V was the best performer with a limit of detection (LoD) of 10 mg L-1 (43.07 µM), a linear range of 10-150 mg L-1 (43.07 to 646 µM), an average precision of 4.3% (%RSD) and an average % recovery of 101.34%. These results indicate that the CuOEP-modified electrode is suitable for the analysis of phenobarbital in human samples, as the concentration range varies from 10 to 40 mg L-1 (43.07 to 172.27 µM), typically found in antiepileptic treatments, to those at the toxic level (172-258 µM) or lethal levels (345-650 µM).

Behavior of Ni20Cr Alloy in Molten Nitrate Salts.

This study reports the behavior of the Ni20Cr alloy in molten nitrate salts. Its behavior was evaluated in the eutectic mixture called Solar Salt (binary salt) and in a ternary mixture (90% Solar Salt and 10% lanthanum nitrate). The addition of lanthanum nitrate was performed to determine if the presence of the La3+ cation could act as a corrosion inhibitor. Through mass loss and potentiodynamic polarization studies, the effects of both electrolytes on the corrosion resistance of the alloy at 300, 400, and 500 °C and at exposure times of 250, 500, 750, and 1000 h were determined. The results showed an increase in the corrosivity of the ternary salt, due to a decrease in its melting point and an increase in the concentration of nitrate ions. However, it was observed that the La3+ cations formed a protective layer (La2O3) on the alloy surface. In both corrosive media, the Ni20Cr alloy showed excellent corrosion resistance, due to its ability to form protective layers of Cr2O3, NiO, and NiCr2O4, in addition to the presence of a layer of La2O3 in the case of the ternary salt.

The Production and Evaluation of an Electrochemical Sensors for Strychnine and Its Main Metabolite Strychnine N-Oxide for Their Use in Biological Samples.

Strychnine (STN) and its major metabolite Strychnine N-Oxide (SNO) were examined electrochemically. Both parent compounds and its major metabolite showed electroactivity on glassy carbon electrodes using CV and DPV techniques. One oxidation peak at 1008 mV was observed for STN with the optimum peak intensity at pH 7. SNO produced two oxidation peaks, at 617 mV and 797 mV, at pH 5. The peaks demonstrated irreversible behaviour and the irreversibility of the system was confirmed at different scan rates. A calibration curve was produced for both CV and DPV measurements and the sensitivity of the proposed EC method was good compared with previous electrochemical and non-electrochemical methods. The precision of oxidation peak of STN using the STN-MIP method produced a maximum value of 11.5% and 2.32% for inter-day and intraday %RSD, respectively. The average% recovery was around 92%. The electrochemical method has been successfully applied to the determination of STN in spiked plasma and urine samples. For SNO, both anodic peaks of SNO demonstrated irreversible behaviour. A different sweep rate was used for calculating the number of 'transfer electrons' in the system; based on this, the mechanism of oxidation reaction was proposed. Calibration curves for both oxidative peaks were produced using DPV measurements. The second anodic peak demonstrated high linearity and precision with %RSD < 1.96%.

Factores relacionados con histoplasmosis diseminada en los pacientes admitidos con VIH-SIDA y fiebre, CHDrAAM, 2017 - 2019

Introducción: el diagnóstico de histoplasmosis diseminada (HD) es un desafío debido a la similitud del cuadro clínico con otras enfermedades infecciosas y no infecciosas. Confirmar un caso de HD requiere realizar procedimientos poco sensibles como hemocultivos, mielocultivos y biopsias de tejidos, o costosos como el antígeno urinario de Histoplasma capsulatum. Conocer los factores clínicos y de laboratorios relacionados con el diagnóstico de HD es de vital importancia en especial en sitios con recursos limitados. Metodología: se realizó un estudio de cohorte retrospectivo donde los expedientes clínicos de los pacientes con fiebre y VIH-SIDA, admitidos con sospecha de histoplasmosis diseminada del 1 de enero de 2017 al 31 de diciembre de 2019 en el Complejo Hospitalario Dr. Arnulfo Arias Madrid (CHDrAAM) de Panamá, fueron evaluados por características demográficas, clínicas y de laboratorio relacionadas con el diagnóstico de HD. Resultados: 63 pacientes cumplieron los criterios de inclusión, 14 con diagnóstico confirmado de HD y 49 con diagnóstico no confirmado de HD. Los niveles de lactato deshidrogenasa (LDH) y aspartato transaminasa (AST) se relacionaron con el diagnóstico de HD en el análisis univariado. Luego de realizar regresión logística ni AST ni LDH fueron estadísticamente significativas. (p= 0.22 y P = 0.92). Conclusión: Ninguna característica clínica ni de laboratorio se relacionó de forma independiente con el diagnóstico de HD, en pacientes con VIH-SIDA admitidos con sospecha de histoplasmosis diseminada. (provisto por Infomedic International)

Introduction: The diagnosis of disseminated histoplasmosis (HD) is a challenge due to the similarity of the clinical picture with other infectious and non-infectious diseases. Confirming a case of HD requires performing insensitive procedures such as blood cultures, myelocultures and tissue biopsies, or expensive procedures such as urinary Histoplasma capsulatum antigen. Knowing the clinical and laboratory factors related to the diagnosis of HD is of vital importance, especially in places with limited resources. Methodology: a retrospective cohort study was conducted where clinical records of patients with fever and HIV-AIDS, admitted with suspected disseminated histoplasmosis from January 1, 2017, to December 31, 2019, at the Complejo Hospitalario Dr. Arnulfo Arias Madrid (CHDrAAM) in Panama, were evaluated for demographic, clinical and laboratory characteristics related to the diagnosis of HD. Results: 63 patients met the inclusion criteria, 14 with confirmed diagnosis of HD and 49 with unconfirmed diagnosis of HD. Lactate dehydrogenase (LDH) and aspartate transaminase (AST) levels were related to HD diagnosis in univariate analysis. After logistic regression neither AST nor LDH were statistically significant. (p= 0.22 and P = 0.92). Conclusion: No clinical or laboratory characteristics were independently related to the diagnosis of HD in HIV-AIDS patients admitted with suspected disseminated histoplasmosis. (provided by Infomedic International)

Application of LC-QTOF/MS for the validation and determination of organic explosive residues on Ionscan® swabs.

The identification and confirmation of trace explosive residues along with potential precursors and degradation products require a comprehensive laboratory analysis procedure. This study presents the determination of organic explosives consisting of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2,4,6-trinitrotoluene (TNT), 2,4,6,N-tetranitro-N-methylaniline (Tetryl), 1,3,5-trinitrobenzene (1,3,5-TNB) and pentaerythritol tetranitrate (PETN) by a high-resolution liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF/MS). The qualitative information including retention time, collision energy, precursor ions, and characteristic fragmentation pattern of each explosive were collected using an atmospheric pressure chemical ionization (APCI) in negative ion mode. The separation efficiency among five compounds was greatly achieved in this study. Four real explosive samples consisting of TNT, RDX, PETN and Tetryl and 12 Ionscan® quality control swabs from the Royal Thai Army were also tested to validate and verify the viability of the GC-MS method used to validate results from an Ionscan® system. The results showed that LC-QTOF/MS is a powerful technique for the identification and confirmation of thermally unstable organic explosives on Ionscan® swabs compared to a conventional GC-MS technique.

Intervenciones en infecciones del tracto urinario, neumonías, COVID-19 y bacteriemias por programas de uso optimizado de antimicrobianos (PROA): enfoque síndrome específico

Introducción: El uso de los antibióticos ha logrado curar infecciones anteriormente letales. Como profilaxis ha mejorado el pronóstico de pacientes en múltiples escenarios; sin embargo, estos fármacos tienen efectos adversos los cuales pueden ocurrir en 1 de cada 5 pacientes hospitalizados que los reciben, algunos de estos eventos son potencialmente mortales. Los programas de Antimicrobial Stewardship (ASP), conocidos en español como Programas de Uso Optimizado de Antibióticos (PROA), son intervenciones coordinadas, diseñadas para mejorar y medir el uso apropiado de antibióticos, promoviendo la selección del régimen óptimo, incluyendo dosis, duración de la terapia y su ruta de administración. Objetivo: describir el beneficio de las intervenciones síndrome específico en infecciones del tracto urinario, neumonías, bacteriemias y COVID-19, realizadas por programas de uso optimizado de antimicrobianos (PROA). Metodología: se realizó una búsqueda en PubMed y se seleccionó aquellos artículos donde se realizaron intervenciones que mostraron beneficios clínicos en infecciones del tracto urinario, neumonías, bacteriemias y COVID-19 por parte de programas de uso optimizado de antimicrobianos. Síntesis de los datos: se seleccionaron 18 estudios, de los cuales 3 mostraron intervenciones con beneficios en el tratamiento de Infecciones del tracto urinario, 9 en neumonías, 1 en COVID-19 y 5 en bacteriemias. Conclusión: Las intervenciones síndrome específicas, en Infecciones del tracto urinario (ITU), neumonías COVID-19 y bacteriemias, de los programas de uso optimizado de antibióticos (PROA) se han asociado con disminución de los costos de atención y mejores resultados clínicos. (provisto por Infomedic International)

Computational Design of a Molecularly Imprinted Polymer for the Biomonitoring of the Organophosphorous Metabolite Chlorferron.

Coumaphos is an organophosphorus compound used as insecticide and frequently used by beekeepers for the management of parasitic mites. The most important metabolite, chlorferron (CFN), has been identified in biological samples and foodstuff. The need to quickly identify the presence of typical metabolites, as an indication of interaction with coumaphos has driven the need to produce a highly sensitive electrochemical method for chlorferron analysis, based on molecularly imprinting polymers (MIP) technology. It showed irreversible behaviour with mixed diffusion/adsorption-controlled reactions at the electrode surface. A monoelectronic mechanism of reaction for oxidation has also been suggested. The linear range observed was from 0.158 to 75 µM. Median precision in terms of %RSD around 3% was also observed. For DPV, the limit of detection (LOD) and the limit of quantitation (LOQ) for the CFN-MIP were 0.158 µM and 0.48 µM, respectively. The obtained median % recovery was around 98%. The results were also validated to reference values obtained using GC-MS. Urine and human synthetic plasma spiked with CFN were used to demonstrate the usability of the method in biological samples, showing the potential for biomonitoring. The developed imprinted sensor showed maximum signal change less than 16.8% when related metabolites or pesticide were added to the mix, suggesting high selectivity of the MIP sensor toward CFN molecules. The results from in vitro metabolism of CMP analysed also demonstrates the potential for detection and quantification of CFN in environmental samples. The newly developed CFN-MIP sensor offers similar LoDs than chromatographic methods with shorter analysis time.

Evaluating residual compressive strength of post-fire concrete using Raman Spectroscopy.

Cement and water within the concrete mass create a hydrated phase which acts as the glue for holding the sand and coarse aggregates in place to develop a strong construction material. The most important phase within the cement matrix is that of calcium silicate hydrate (CSH), which is largely responsible for the concrete strength. Decomposition of the CSH phase due to high temperatures will affect compressive strength of the concrete. Raman bands at 1083, 709 and 276 cm-1, which are representative of the CaCO3 and CSH presence in the concrete matrix phases can be used to assess changes in compressive strength as a result of thermal decomposition. The ratio between 1083/709 cm-1 bands was calculated and correlated to the compression strength of the concrete. The results show there is a rapid decline in strength around a critical peak ratio of 8.78 and a residual compressive strength of 0.62, closely following a polynomial curve. The tool developed here allows an indirect evaluation of the temperature the concrete has been exposed to by studying the band. A case study from a fire scene taken from a warehouse in Kingston (Jamaica) is also presented with the conclusion and results compared. The study showed that Raman spectroscopy has the potential to provide in-situ non-destructive testing of fire damaged concrete rapidly and accurately.

Three-dimensional voltammetry: Use of chronoamperometric E-t-i data to achieve second-order advantage.

This work studied the use of three-dimensional voltammetry, particularly potential-time-current (E-t-i) data, on the development of electroanalytical methods. E-t-i data was obtained by taking chronoamperograms at potentials applied as pulses on a staircase waveform. By using this three-way kind of data and appropriate calibration algorithms, the possibility of achieving the second-order advantage was evaluated in the determination of ferrocyanide in the presence of the uncalibrated interference hydroquinone as a model system. The determination of acetaminophen in urine samples, where ascorbic acid and uric acid play the major roles as interferents was also studied. Parallel factor analysis (PARAFAC) and multivariate curve resolution alternating least-squares (MCR-ALS) were the algorithms employed in this work. Both algorithms successfully achieved the second-order advantage by correctly predicting the concentrations of the validation synthetic samples. Excellent predictions were obtained in the direct analysis of acetaminophen-spiked urine samples by E-t-i data and MCR-ALS.

Challenges in the identification of new thermolabile psychoactive substances: The 25I-NBOH case.

The continuous emergence of NPS over the last years poses a series of novel challenges for forensic analysts. Most of those new compounds are synthesized with minimal chemical modifications to the structure of already known chemicals in order to avoid regulations. Some of these new compounds may undergo chemical changes during analysis leading to misidentification and detrimental legal consequences. GC-MS is one of the most widely used analytical techniques employed by forensic laboratories all over the world for drug analysis. Nevertheless, thermolabile NPS, such as 25I-NBOH can generate artefacts in the traditional GC-MS analysis. In this paper, we describe the fragmentation mechanism of the 25I-NBOH into a major peak corresponding to 2C-I and a minor one corresponding to the associated ortho-phenolic benzyl ether (o-PBE), which exact identity is directly linked with the solvent used for the analysis. Also, a series of method adjustments is displayed, encompassing variation on the injector temperature, split ratio and flow ratio, although with no success to prevent 25I-NBOH thermo degradation in the GC injector. Furthermore, differential scanning calorimetry and thermogravimetric analysis demonstrated that 25I-NBOH's thermal stability is due to a smaller temperature window between fusion and decomposition points. Finally, we perform derivatization experiments and demonstrate how to overcome 25I-NBOH degradation in the GC/MS analysis.

Effective replacement of cetyltrimethylammonium bromide (CTAB) by mercaptoalkanoic acids on gold nanorod (AuNR) surfaces in aqueous solutions.

The highly packed cetyltrimethylammonium bromide (CTAB) bilayer built up on the surface of gold nanorods (AuNRs) when synthesized by the seed-mediated procedure hampers the complete ligand exchange under experimental conditions that preserves the stability of the dispersions. In the present work, a ligand exchange protocol by using carboxy-terminated alkanethiols of different chain lengths by means of a green approach that uses only aqueous solutions is presented. The protocol is based on the knowledge of the stability in the aqueous solution of both the starting CTAB-AuNRs and the final products that help in the choice of the experimental conditions used for ligand exchange. The characterization of the CTAB protective layer as well as the study of its colloidal stability in solution has helped us to design an appropriate methodology. Cyclic voltammetry of CTAB-AuNRs demonstrates the high stability of the bilayer showing the existence of a two-dimensional phase transition from a highly ordered to a less organized phase. Other techniques such as XPS, FT-IR and Raman spectroscopy provide information about the structure of the layer and UV-visible-NIR spectroscopy establishes the stability conditions in aqueous solution. We have chosen an exchange procedure for 11-mercaptoundecanoic acid (MUA) and 16-mercaptohexadecanoic acid (MHDA) based on a one-pot methodology under conditions where all the species involved are stable. The protocol, however, can be extended to different chemical functionalities that are considered useful to be applied in living systems. Under these conditions the complete exchange of CTAB by the mercaptoderivatives was successful as demonstrated by the different characterization techniques used: UV-visible-NIR, FT-IR, Raman, XPS spectroscopy, cyclic voltammetry and transmission electron microscopy (TEM).

Classification of ANFO samples based on their fuel composition by GC-MS and FTIR combined with chemometrics.

Ammonium nitrate fuel oil (ANFO) is one of the most favorite explosives used in terrorist attacks. This explosive is a complex mixture of 95-96% ammonium nitrate (AN) and 4-5% liquid hydrocarbons (fuel oil). In this study, we analyze a variety of ANFO explosive mixtures in order to classify their different sources of origin by observing the difference in fuel components. The study was performed by mixing ammonium nitrate with eight different diesel brands collected in Lincoln, UK in two seasons (winter and summer). The samples were extracted using appropriate solvent and extracts were subsequently analyzed in sextuplicate by gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FTIR). A classification model was performed using principal component analysis (PCA) and Lineal Discriminant Analysis (LDA). In this study, four fatty acid methyl ester (FAME) contents were observed by GC-MS in all summer samples but found lack in some winter sample resulting in seasonal variation effect. The classification of pre-blast ANFO samples was achieved using GC-MS and FTIR in a combination with PCA/LDA. The results significantly showed the variation of specific diesel components and providing different classification performance among ANFO samples with high classification performance. Therefore, this study can be beneficial in forensic investigation that the use of diesel components are able to classify among different ANFO samples.