The authors would like to acknowledge the support from the Department of Earth Sciences, Uppsala University for supporting part of this research.

1. La funcionalización de nanotubos de carbono de pared múltiple <ol><li> Realizar toda la etapa de funcionalización dentro de una campana de extracción, usando anteojos de seguridad, guantes y bata de laboratorio. Medir 24 ml de ácido sulfúrico y 8 ml de ácido nitrato usando un cilindro graduado, y luego transferirlos a un vaso de precipitados. Añadir 32 mg de MWCNTs sin tratar en un vaso de precipitados utilizando estaño envase del papel en una balanza analítica (concentración final debe ser de 1 mg / ml de mezcla de ácido). </li><li> En primer lugar, mantener el vaso de precipitados con MWCNT y la mezcla de ácido en el limpiador ultrasónico (baño) durante 2 horas a RT. Luego, el calor y revuelva la solución MWCNT-ácido durante 5 horas a 90 ° C utilizando una placa caliente. </li><li> Filtrar la suspensión CNT con una membrana de filtro de PTFE de 0,2 micras de diámetro de poro colocado en un soporte de filtro, y el uso de vacío para ayudar a la filtración. Realizar la porción de filtración por porción y utilizar varias membranas de filtro (aproximadamente 1/4 th de mezcla anterior por porción para un filtro). Añadir agua hirviendodurante el proceso de filtración para filtrar la solución de ácido hasta que el pH de la mezcla se hace mayor que 5. </li><li> Siempre romper el vacío antes de que se apaga y no introducir nada en el sistema de vacío. Utilice un vaso de precipitados cónico para recoger el líquido de residuos. </li><li> Verter ácido filtrada en un contenedor de residuos (enviar el contenedor de residuos a una instalación de tratamiento de residuos o diluir el líquido antes de volcar en el fregadero añadiendo al menos diez veces más de agua del grifo). </li><li> Transferir las membranas filtrantes con MWCNTs retenidas en evaporando platos y poner los platos en el desecador (contiene aproximadamente 100 g de gel de sílice) y crear un ambiente de vacío (dejar el vacío durante aproximadamente 1 hora) para CNT para completar el secado (aproximadamente 24 horas ). <ol><li> Raspe los CNTs de las membranas utilizando cuidadosamente espátula y transferir las partículas en un recipiente limpio. Pesar el polvo MWCNTs y etiquetar el recipiente para su uso futuro. </li></ol></li></ol> 2. Poronosotros Medios para experimentos Transporte <ol><li> Preparar una solución de HCl 0,1 M para el lavado ácido de arena de sílice. <ol><li> Realice todos los pasos dentro de una campana de humos con gafas de seguridad, guantes y bata de laboratorio. Añadir 1 L de agua desionizada a un matraz de 2 L. Mide 8 ml de HCl al 37% usando un cilindro graduado. </li><li> Añadir el HCl en el agua desionizada con cuidado. Agitar el matraz con cuidado para ayudar a la mezcla. </li></ol></li><li> Lave la arena con la solución de HCl preparado. <ol><li> Pesar aproximadamente 1.000 g de arena. Añadir 1/3 de arena en el matraz con la solución de HCl y agitar el matraz dos veces para ayudar a mezclar a continuación, añadir el resto de la arena (1/3 de la arena cada vez). </li><li> Agitar el matraz tres veces y dejar el ácido con arena durante 30 min. </li><li> Vierta el líquido del matraz a un contenedor de residuos de ácido y enjuagar la arena con agua desionizada al menos 8 veces. </li></ol></li><li> Lave la arena con una solución de H 2 O 2. <ol><li> Añadir 700 ml de agua desionizada enel matraz con arena y luego medir 40 ml de 30% H 2 O 2 solución usando un cilindro graduado. </li><li> Añadir el 2 O 2 H solución en el frasco con arena y agitar dos veces para ayudar a la mezcla. A continuación, añadir otros 40 ml de 30% de H 2 O 2 solución 3 veces hasta que haya 160 ml en total H 2 O 2 en el matraz. </li><li> Agitar y mezclar la solución y la arena cada vez y dejar la solución de H 2 O 2 con arena durante 40 minutos para permitir que la reacción se complete. Agitar el matraz y se agita la arena con una varilla de plástico cada 10 min. </li><li> Decantar el líquido hasta el fregadero y deje correr el agua del grifo durante 30 segundos. </li></ol></li><li> Enjuague y seque la arena. <ol><li> Enjuague la arena con agua desionizada al menos 8 veces para deshacerse de cualquier solución o sobrantes productos de reacción. Agite y revuelva bien cuando enjuague. </li><li> Ponga frasco con arena enjuagados en un horno (105 ° C) durante 24 horas para secar, luego tomar la arena fuera del horno usandohorno-manopla y dejar en el mostrador durante 2 horas para la arena se enfríe. </li><li> Transferir la arena limpia en un recipiente de plástico. Marque el recipiente y colocarlo en una plataforma adecuada para estar listo para su uso. </li></ol></li></ol> 3. Experimentos de columna <ol><li> Preparación de la solución de fondo. <ol><li> Preparar la química solución de fondo apropiado para el experimento columna. </li><li> Utilice 0,1 M HCl y 0.1 M de NaOH soluciones para ajustar el pH y la sal NaCl para alcanzar la fuerza iónica apropiada para el siguiente experimento. </li></ol></li><li> Selección de columnas. <ol><li> Elige una columna de vidrio de 2,5 cm de diámetro y longitud 15 cm para este experimento (pH: 5 y la fuerza iónica: 2 mM en el estudio actual). Utilice un filtro de malla de acero (0,2 mm) en ambos lados de la columna de vidrio. </li><li> Lavar los tubos conectados a la columna y llenar con la solución de fondo (o solución MWCNTs hasta que la válvula de 3 vías para controlar el tipo de flujo de líquido (MWCNTs solution o solución de fondo) como se muestra en la Figura 1. </li></ol></li><li> Wet-embalaje de la columna. <ol><li> Pese la arena limpia en una escala y tomar 124 g de arena limpia para el tamaño de la columna seleccionada. </li><li> Use una bomba peristáltica de alta precisión. Calibrar la bomba para lograr 2 ml / min de flujo de líquido. </li><li> Arrancar la bomba para llenar la columna desde la parte inferior hasta que el nivel de agua es de un par de centímetros por encima de la parte inferior de la columna. Ponga aproximadamente 1/10 de la arena medido a la vez en la columna, pero asegúrese de que el nivel de la arena no viene por encima del nivel del agua en la columna. Continuar el flujo de agua a la columna de forma continua para permanecer por encima del nivel de arena. </li><li> Cierre la tapa de la columna con una malla de filtro adecuado después de llenado completo. </li><li> Permitir la columna de relleno fluya durante al menos 1 hr. Los parámetros individuales de la columna se indican en la Tabla 1. </li></ol></li><li> Prueba Tracer. <ol><li> Starta el experimento columna con una prueba de trazador antes de los experimentos de solución MWCNT. </li><li> Cambie la válvula de 3 vías para la solución de trazador (el uso de alimentos de color trazador a 20 mg / L) para iniciar el experimento. </li><li> Recoger las muestras de salida de flujo de la columna en cada 2 min (es decir, 4 ml / muestras en cada tubo de muestreo) utilizando el colector de fracciones conectado como se muestra en la Figura 1. </li><li> Continuar para inyectar la solución de trazador para un volumen de poro 4,32 (es decir, la solución pasa a 4,32 veces del espacio total de poros vacío en la columna de relleno de arena), que también se llama la fase I del experimento. </li><li> Cambie la válvula de 3 vías para la solución del flujo de fondo (agua DI en el caso del experimento trazador) para otro volumen 4.32 poro. </li></ol></li><li> Preparación de la solución MWCNT. <ol><li> Hacer una solución dispersa, funcionalizado MWCNTs colocando 15 mg de MWCNTs funcionalizados en un vaso de precipitados de 300 ml que contiene 200 ml de solución acuosa (con solutio deseadon es decir, química, pH 5 y 2 mM fuerza iónica en la condición experimental actual) y usando una sonda de homogeneizador ultrasónico colocado en el vaso de precipitados (con potencia de salida 40% durante 15 min). Mezclar la solución MWCNTs dispersa con otros 800 ml de la misma solución acuosa para conseguir la concentración MWCNT de 15 mg / L. </li><li> Realizar microscopía electrónica de barrido (SEM) de análisis de imagen de la solución madre por su tamaño y la forma de la nanopartícula después de funcionalización. </li></ol></li><li> Experimento transporte MWCNT. <ol><li> Cambie la válvula de 3 vías de solución MWCNT para iniciar el experimento de la columna. </li><li> Recoger las muestras de salida de flujo de la columna en cada 2 min utilizando el colector de fracciones conectado. </li><li> Se inyecta la solución MWCNT para un volumen de 4,32 poro (fase I del experimento). </li><li> Cambie la válvula de 3 vías para la solución del flujo de fondo para otro volumen 4.32 poros, que se llama la fase II del experimento. </li><li> Cambie el tubo de inyección de background solución en la botella de agua DI (después de parar la bomba por un momento para evitar la entrada de aire desde el tubo) y continuar el flujo de otro volumen de poro 4,32, que se llama la fase III del experimento. </li></ol></li><li> Análisis de la muestra. <ol><li> Transfiera todas las muestras de tubos de colector de fracciones en un bastidor de tubo. </li><li> Preparar un espectrofotómetro UV / VIS para el análisis de la muestra, es decir, saber la longitud de onda de exploración apropiado para la cuantificación de las muestras recogidas. Utilice 400 nm para una solución MWCNT y una longitud de onda 333 nm para la solución del trazador. </li><li> Analiza todas las muestras recogidas de la columna durante las fases I, II y III en cubeta a 400 nm de longitud de onda (o una longitud de onda diferente, si se considera más apropiado en el paso anterior) y almacenar los datos. </li><li> Recoge los datos desde el espectrofotómetro y plotearlos vs tiempo o volumen de poro para obtener curvas de ruptura como se muestra en los resultados representativos (por ejemplo, la figura3). </li><li> Realizar análisis de tamaño (diámetro hidrodinámico) de muestras de entrada y salida medida del potencial zeta y realizar la visualización estudiado para ambas muestras de entrada y salida mediante microscopía electrónica de barrido. </li></ol></li></ol>

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The authors declare that they have no competing financial interests.

Efecto de funcionalización MWCNT Como muestra la Figura 2 confirma la estabilidad de MWCNTs funcionalizados, la diferencia observada en el volumen eluido de MWCNT era debido a la funcionalización y, en particular debido a la adición de carboxilo (-COOH) grupos a la superficie de las MWCNTs (Figuras 3 y 4). En el proceso de funcionalización similares, la presencia de oxígeno fue confirmada por espectroscopia de rayos X d...

Con el reciente desarrollo en nanotecnología que utiliza diferentes tipos de nanopartículas para mejorar algunas de las tecnologías en industrias como la tecnología de la información, la energía, la ciencia del medio ambiente, la medicina, la seguridad nacional, la seguridad alimentaria, y el transporte; un conocimiento profundo del transporte y la retención de las nanopartículas en el suelo y las aguas subterráneas es fundamental para la evaluación de riesgos, así como aplicaciones ambientales de nanopartículas artificiales 1-3. Los nanotubos de carbono (CNTs) son una de las nanopartículas a base de carbono más producidas 2,4. CNTs son la forma larga y cilíndrica de grafeno con un diámetro típicamente por debajo de 100 nm y una longitud en el intervalo de 100 nm a 50 micras. Tienen propiedades únicas, que han acelerado su uso en muchas aplicaciones, tales como la electrónica, la óptica, cosméticos y tecnología biomédica (por ejemplo, materiales compuestos) 5. Con un mayor uso, también hay un mayor rISK a la exposición humana y el efecto sobre la salud, así como las consecuencias ecológicas adversas siguientes CNT y otra disposición nanomateriales de carbono basado en el medio ambiente 5-8. Sin modificaciones de superficie (no funcionalizados), CNTs son extremadamente hidrófobo y tienden a agregarse en una solución acuosa. CNT funcionalizados pueden, sin embargo, permanecen dispersos y estable en soluciones acuosas y se utilizan para fines biomédicos tales como la administración de fármacos 9. Aquí es esencial que los nanotubos de carbono permanecen dispersos y movilizaron, por lo que el fármaco puede ser entregado dentro del cuerpo humano 10. Por otra parte, para reducir los riesgos medioambientales, hay una necesidad de estudios centrados en cómo inmovilizar los CNTs con el fin de evitar su entrada en los acuíferos y los recursos de agua potable 11. Estudios recientes han reportado el efecto tóxico de la CNT en los organismos vivos y también riesgos para los ecosistemas en términos de CNT que entran y se acumulan en la cadena alimentaria, desdeCNT son difíciles de biodegradar 5,8. Incluso con sistemas de barrera en vertederos que contienen nanotubos de carbono, puede ser posible para CNTs pasen a través de las barreras. En tales casos CNT podían entrar en los depósitos de agua subterránea y los cuerpos de agua superficiales. Como las normas de eliminación de la CNT no están bien definidas y mecanismos de transporte, son poco conocidos, una mejor comprensión de la movilidad de los nanotubos de carbono es necesario formular y diseñar sistemas de eliminación adecuada 12. Por lo tanto, es importante para estudiar y comprender el destino y el transporte de los CNT en medios porosos y el efecto de factores físicos y químicos comúnmente presentes en el entorno del subsuelo en la superficie modificada de retención CNT. Un número de investigaciones se han llevado a cabo sobre el efecto de tamaño de grano colector 13-15, velocidad de flujo 16, y propiedades superficiales de los granos 17 en el transporte de nanopartículas en medios porosos. Sin embargo, investigaciones sistemáticas sobre el efecto de solutquímica de iones (tales como el pH y la fuerza iónica) sobre la posible deposición sobre las superficies de colector son todavía limitados 18-20. Además, el impacto combinado de los factores físicos, la solución química del medio, y propiedades de la superficie de los nanotubos de carbono no se entiende bien y varían en diferentes literatura. En este estudio, un método de preparación para la modificación de la superficie de MWCNTs se demostrará junto con una columna a escala de laboratorio sistemática lleno de arena de cuarzo-limpiarse con ácido se utiliza para investigar el transporte, la retención y la removilización de nanotubos de carbono de superficie modificada en medios porosos saturados .

<table border="0" cellpadding="0" cellspacing="0" width="750">
	<tbody>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">Name of Material/ Equipments</td>
			<td style="width:228px;">Company</td>
			<td style="width:169px;">Catalog Number</td>
			<td style="width:171px;">Comments/Description</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">MWCNT</td>
			<td style="width:228px;">Cheap Tubes Inc., USA</td>
			<td style="width:169px;">sku-03040304</td>
			<td style="width:171px;">Purchased as semi-functionlized powder</td>
		</tr>
		<tr height="148">
			<td height="148" style="height:148px;width:183px;">Quartz sand</td>
			<td style="width:228px;">Sibelco Nordic, Baskarp, Sweden</td>
			<td style="width:169px;">B44</td>
			<td style="width:171px;">Purchased with more than 91% silica sand</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">H2SO4</td>
			<td style="width:228px;">VWR</td>
			<td style="width:169px;">1.01833.2500</td>
			<td style="width:171px;">95-97% purity</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">HNO3</td>
			<td style="width:228px;">VWR</td>
			<td style="width:169px;">1.00441.1000</td>
			<td style="width:171px;">70% purity</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">HCl</td>
			<td style="width:228px;">VWR</td>
			<td style="width:169px;">1.00317.2500</td>
			<td style="width:171px;">37-38% purity</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">H2O2</td>
			<td style="width:228px;">VWR</td>
			<td style="width:169px;">23615.248</td>
			<td style="width:171px;">30% purity</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">NaCl</td>
			<td style="width:228px;">VWR</td>
			<td style="width:169px;">1.06404.0500</td>
			<td style="width:171px;">99.5% purity</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:183px;">NaOH</td>
			<td style="width:228px;">Sigma-Aldrich</td>
			<td style="width:169px;">S8045-500G</td>
			<td style="width:171px;">99.99% pur pellets&#160;</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">Ultrasonic Homogenizer</td>
			<td style="width:228px;">Biologics Inc. Manassas, Virginia</td>
			<td style="width:169px;">Model 3000, 0-127-0002</td>
			<td style="width:171px;">Operated for fix time interval</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:183px;">Sonicator (bath)</td>
			<td style="width:228px;">Kerry Ultrasonic Ltd</td>
			<td style="width:169px;">1808</td>
			<td style="width:171px;">Common bath sonicator</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">Peristaltic pump</td>
			<td style="width:228px;">Ismantec, Glattbrugg, Switzerland</td>
			<td style="width:169px;">ISM931</td>
			<td style="width:171px;">Work with tygon tubing in the pump</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:183px;">Spectrophotometer</td>
			<td style="width:228px;">Hach Lange</td>
			<td style="width:169px;">DR500, LPV408.99.0001</td>
			<td style="width:171px;">Operate with manual cuvette as well as automated sampling</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:183px;">pH meter</td>
			<td style="width:228px;">Metrohm</td>
			<td style="width:169px;">781</td>
			<td style="width:171px;">pH analysis</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">Glass column</td>
			<td style="width:228px;">Chromaflex</td>
			<td style="width:169px;">420830-1510</td>
			<td style="width:171px;">Column with adjustable cap</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:183px;">Fraction collector</td>
			<td style="width:228px;">Spectrum Labs Europe</td>
			<td style="width:169px;">CF-2, 124846</td>
			<td style="width:171px;">Fixed at regular interval of time</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:183px;">Fraction collector tubes</td>
			<td style="width:228px;">VWR</td>
			<td style="width:169px;">212-9599</td>
			<td style="width:171px;">6 ml volume glass tube</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:183px;">Hot plate stir</td>
			<td style="width:228px;">Thermo Scientific</td>
			<td style="width:169px;">SP131320-33</td>
			<td style="width:171px;">Adjustable tempurature</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:183px;">Oven</td>
			<td style="width:228px;">Elektro Helios</td>
			<td style="width:169px;">259</td>
			<td style="width:171px;">For oven dry of sand</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:183px;">Balance</td>
			<td style="width:228px;">Mettler Toledo</td>
			<td style="width:169px;">AE 160</td>
			<td style="width:171px;">For accurate weight</td>
		</tr>
	</tbody>
</table>

transport of surface-modified carbon nanotubes through a soil column

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, electronics and biomedical applications. Due to their accelerating production and use, CNTs constitute a potential environmental risk if they are released to soil and groundwater systems. It is therefore essential to improve the current understanding of environmental fate and transport of CNTs. The transport and retention of CNTs in both natural and artificial media have been reported in literature, but the findings widely vary and are thus not conclusive. There are a number of physical and chemical parameters responsible for variation in retention and transport. In this study, a complete procedure of selected multiwalled carbon nanotubes (MWCNTs) is presented starting from their surface modification to a complete set of laboratory column experiments at critical physical and chemical scenarios. Results indicate that the stability of the commercially available MWCNTs are critical with their attached surface functional group which can also influence the transport and retention of MWCNT through the surrounding medium.

Efecto de funcionalización MWCNT La solución MWCNT funcionalizado y dispersa se selló en el vaso de precipitados para permitir que la solución para alcanzar el equilibrio. No había ni sedimentación ni la agregación observada en la solución madre después de la sonicación, como el diámetro hidrodinámico de MWCNT (1619 ± 262 nm) en la solución sigue siendo el mismo durante seis meses de tratamiento con ultrasonidos (Figura 2). Para investigar el e...

Watch this Scientific Journal Video about Transport of Surface-modified Carbon Nanotubes through a Soil Column at JoVE.com

Transport of Surface-modified Carbon Nanotubes through a Soil Column

Surface properties of a nanoparticle are important for their interaction with the surrounding medium. Therefore the surface modification of carbon nanotubes can be critical for their transport and retention through porous media. Here, lab scale column experiments are used to understand the possible transport and retention of these nanoparticles.

Transporte de nanotubos de carbono modificado en la superficie a través de una columna de suelo

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, ...

transport-of-surface-modified-carbon-nanotubes-through-a-soil-column

Research

JoVE Journal

Chemistry

9.4K vistas.  Nalanda University. Surface properties of a nanoparticle are important for their interaction with the surrounding medium. Therefore the surface modification of carbon nanotubes can be critical for their transport and retention through porous media. Here, lab scale column experiments are used to understand the possible transport and retention of these nanoparticles. 

Video: Transport of Surface-modified Carbon Nanotubes through a Soil Column

Template Directed Synthesis of Plasmonic Gold Nanotubes with Tunable IR Absorbance

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) membranes have been under development since the 1990's and have become a common method to template the synthesis of high aspect ratio nanostructures, mostly by electrochemical growth or pore-wetting. Recently, these membranes have become commercially available in a wide range of pore sizes and densities, leading to an extensive library of functional nanostructures being synthesized from AAO membranes. These include composite nanorods, nanowires and nanotubes made of metals, inorganic materials or polymers 3-10. Nanoporous membranes have been used to synthesize nanoparticle and nanotube arrays that perform well as refractive index sensors, plasmonic biosensors, or surface enhanced Raman spectroscopy (SERS) substrates 11-16, as well as a wide range of other fields such as photo-thermal heating 17, permselective transport 18, 19, catalysis 20, microfluidics 21, and electrochemical sensing 22, 23. Here, we report a novel procedure to prepare gold nanotubes in AAO membranes. Hollow nanostructures have potential application in plasmonic and SERS sensing, and we anticipate these gold nanotubes will allow for high sensitivity and strong plasmon signals, arising from decreased material dampening 15.

Solution-suspendable gold nanotubes with controlled dimensions can be synthesized by electrochemical deposition in porous anodic aluminum oxide (AAO) membranes using a hydrophobic polymer core. Gold nanotubes and nanotube arrays hold promise for applications in plasmonic biosensing, surface-enhanced Raman spectroscopy, photo-thermal heating, ionic and molecular transport, microfluidics, catalysis and electrochemical sensing.

Plantilla Dirigida Síntesis de nanotubos de oro plasmónicos con Tunable absorbancia IR

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) ...

Investigación

Química

Dependence of Laser-induced Breakdown Spectroscopy Results on Pulse Energies and Timing Parameters Using Soil Simulants

The dependence of some LIBS detection capabilities on lower pulse energies (&lt;100 mJ) and timing parameters were examined using synthetic silicate samples. These samples were used as simulants for soil and contained minor and trace elements commonly found in soil at a wide range of concentrations. For this study, over 100 calibration curves were prepared using different pulse energies and timing parameters; detection limits and sensitivities were determined from the calibration curves. Plasma temperatures were also measured using Boltzmann plots for the various energies and the timing parameters tested. The electron density of the plasma was calculated using the full-width half maximum (FWHM) of the hydrogen line at 656.5 nm over the energies tested. Overall, the results indicate that the use of lower pulse energies and non-gated detection do not seriously compromise the analytical results. These results are very relevant to the design of field- and person-portable LIBS instruments.

LIBS detection capabilities on soil simulants were tested using a range of pulse energies and timing parameters. Calibration curves were used to determine detection limits and sensitivities for different parameters. Generally, the results showed that there was not a significant reduction in detection capabilities using lower pulse energies and non-gated detection.

Dependencia de la inducida por láser Desglose Espectroscopia Resultados sobre Energías pulso y parámetros de temporización utilizando simulantes de suelo

The  dependence of some LIBS detection capabilities on lower pulse energies (&lt;100  mJ) and timing parameters were examined using synthetic silicate ...

An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX.

In this paper, a procedure for quantifying the mass transport parameters of chemicals in various materials is presented. This process involves employing an inverse-analysis based diffusion model to vapor emission profiles recorded by real-time, mass spectrometry in high vacuum.

Un enfoque de análisis inverso a la caracterización de Transporte de Productos Químicos en Pinturas

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in ...

Tuning a Parallel Segmented Flow Column and Enabling Multiplexed Detection

Active flow technology (AFT) is new form of column technology that was designed to overcome flow heterogeneity to increase separation performance in terms of efficiency and sensitivity and to enable multiplexed detection. This form of AFT uses a parallel segmented flow (PSF) column. A PSF column outlet end-fitting consists of 2 or 4 ports, which can be multiplexed to connect up to 4 detectors. The PSF column not only allows a platform for multiplexed detection but also the combination of both destructive and non-destructive detectors, without additional dead volume tubing, simultaneously. The amount of flow through each port can also be adjusted through pressure management to suit the requirements of a specific detector(s). To achieve multiplexed detection using a PSF column there are a number of parameters which can be controlled to ensure optimal separation performance and quality of results; that is tube dimensions for each port, choice of port for each type of detector and flow adjustment. This protocol is intended to show how to use and tune a PSF column functioning in a multiplexed mode of detection.

Here, we present a protocol for the operation and tuning of parallel segmented flow chromatography columns to enable multiplexed detection.

Puesta a punto del paralelo Columna de flujo segmentado y habilitación de detección de multiplexado

Active flow technology (AFT) is new form of column technology that was designed to overcome flow heterogeneity to increase separation performance in terms ...

Curtain Flow Column: Optimization of Efficiency and Sensitivity

Active Flow Technology (AFT) is a form of column technology that increases the separation performance of a HPLC column through the use of a specially purpose built multiport end-fitting(s). Curtain Flow (CF) columns belong to the AFT suite of columns, specifically the CF column is designed so that the sample is injected into the radial central region of the bed and a curtain flow of mobile phase surrounding the injection of solute prevents the radial dispersion of the sample to the wall. The column functions as an 'infinite diameter' column. The purpose of the design is to overcome the radial heterogeneity of the column bed, and at the same time maximize the sample load into the radial central region of the column bed, which serves to increase detection sensitivity. The protocol described herein outlines the system and CF column set up and the tuning process for an optimized infinite diameter 'virtual' column.

Here, we present a protocol for the operation and optimization of Active Flow Technology (AFT) column in Curtain flow (CF) mode for enhanced separation performance.

Cortina Columna de flujo: optimización de la eficiencia y sensibilidad

Active Flow Technology (AFT) is a form of column technology that increases the separation performance of a HPLC column through the use of a specially ...

Facile Preparation of Internally Self-assembled Lipid Particles Stabilized by Carbon Nanotubes

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled (functionalized) CNTs are used as stabilizers to produce Pickering type oil-in-water (O/W) emulsions. Lipids namely, Dimodan U and Phytantriol are used as emulsifiers, which in excess water self-assemble into the bicontinuous cubic Pn3m phase. This highly viscous phase is fragmented into smaller particles using a probe ultrasonicator in presence of conventional surfactant stabilizers or CNTs as done here. Initially, the CNTs (powder form) are dispersed in water followed by further ultrasonication with the molten lipid to form the final emulsion. During this process the CNTs get coated with lipid molecules, which in turn are presumed to surround the lipid droplets to form a particulate emulsion that is stable for months. The average size of CNT-stabilized nanostructured lipid particles is in the submicron range, which compares well with the particles stabilized using conventional surfactants. Small angle X-ray scattering data confirms the retention of the original Pn3m cubic phase in the CNT-stabilized lipid dispersions as compared to the pure lipid phase (bulk state). Blue shift and lowering of the intensities in characteristic G and G&#39; bands of CNTs observed in Raman spectroscopy characterize the interaction between CNT surface and lipid molecules. These results suggest that the interactions between the CNTs and lipids are responsible for their mutual stabilization in aqueous solutions. As the concentrations of CNTs employed for stabilization are very low and lipid molecules are able to functionalize the CNTs, the toxicity of CNTs is expected to be insignificant while their biocompatibility is greatly enhanced. Hence the present approach finds a great potential in various biomedical applications, for instance, for developing hybrid nanocarrier systems for the delivery of multiple functional molecules as in combination therapy or polytherapy.

We report on a smart application of carbon nanotubes for kinetic stabilization of lipid particles that contain self-assembled nanostructures in their cores. The preparation of lipid particles requires rather low concentrations of carbon nanotubes permitting their use in biomedical applications such as drug delivery.

Preparación fácil del ensamblado autónomos Internamente Lípidos Las partículas estabilizadas por nanotubos de carbono

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled ...

Preparation of Carbon Nanosheets at Room Temperature

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into defined aggregates in aqueous media and at the air-water interface. In the aggregated state, the oligoynes can then be carbonized under mild conditions while preserving the morphology and the embedded chemical functionalization. This novel approach provides direct access to functionalized carbon nanomaterials. In this article, we present a synthetic approach that allows us to prepare hexayne carboxylate amphiphiles as carbon-rich siblings of typical fatty acid esters through a series of repeated bromination and Negishi-type cross-coupling reactions. The obtained compounds are designed to self-assemble into monolayers at the air-water interface, and we show how this can be achieved in a Langmuir trough. Thus, compression of the molecules at the air-water interface triggers the film formation and leads to a densely packed layer of the molecules. The complete carbonization of the films at the air-water interface is then accomplished by cross-linking of the hexayne layer at room temperature, using UV irradiation as a mild external stimulus. The changes in the layer during this process can be monitored with the help of infrared reflection-absorption spectroscopy and Brewster angle microscopy. Moreover, a transfer of the carbonized films onto solid substrates by the Langmuir-Blodgett technique has enabled us to prove that they were carbon nanosheets with lateral dimensions on the order of centimeters.

We present the synthesis of an amphiphilic hexayne and its use in the preparation of carbon nanosheets at the air-water interface from a self-assembled monolayer of these reactive, carbon-rich molecular precursors.

Preparación de nanoláminas de carbono a temperatura ambiente

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into ...

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous solution. In a carbon nanotube/PEO105-PPO70-PEO105 (poloxamer 407) aqueous solution, the amphiphilic poloxamer 407 adsorbs onto the carbon nanotube surfaces and self-assembles into continuous layers, driven by intermolecular interactions between constituent molecules. The addition of 5-methylsalicylic acid changes the self-assembled structure from spherical-micellar to a cylindrical morphology. The fabricated poloxamer 407/carbon nanotube hybrid particles exhibit thermo-responsive structural features so that the density and thickness of poloxamer 407 layers are also reversibly controllable by varying temperature. The detailed structural properties of the poloxamer 407/carbon nanotube particles in suspension can be characterized by small-angle neutron scattering experiments and model fit analyses. The distinct curve shapes of the scattering intensities depending on temperature control or addition of aromatic additives are well described by a modified core-shell cylinder model consisting of a carbon nanotube core cylinder, a hydrophobic shell, and a hydrated polymer layer. This method can provide a simple but efficient way for the fabrication and in-situ characterization of carbon nanotube-based nano particles with a structure-tunable encapsulation.

A method for the functionalization of carbon nanotubes with structure-tunable polymeric encapsulation layers and structural characterization using small-angle neutron scattering is presented.

Funcionalización de pared simple nanotubos de carbono con Thermo-reversibles copolímeros de bloque y Caracterización de ángulo pequeño dispersión de neutrones

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous ...

Characterizing Electron Transport through Living Biofilms

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under physiologically relevant conditions.1 These measurements are performed on living biofilms in aqueous medium using source and drain electrodes patterned on a glass surface in a specialized configuration referred to as an interdigitated electrode (IDA) array. A biofilm is grown that extends across the gap connecting the source and drain. Potentials are applied to the electrodes (ES and ED) generating a source-drain current (ISD) through the biofilm between the electrodes. The dependency of electrical conductivity on gate potential (the average of the source and drain potentials, EG = [ED + ES]/2) is determined by systematically changing the gate potential and measuring the resulting source-drain current. The dependency of conductivity on gate potential provides mechanistic information about the extracellular electron transport process underlying the electrical conductivity of the specific biofilm under investigation. The electrochemical gating measurement method described here is based directly on that used by M. S. Wrighton2,3 and colleagues and R. W. Murray4,5,6 and colleagues in the 1980&#39;s to investigate thin film conductive polymers.

A protocol for measuring electrical conductivity of living microbial biofilms under physiologically relevant conditions is presented.

Caracterizar el transporte de electrones a través de Biofilms de vida

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

Injerto de nanotubos de carbono pirólisis con poliestireno para permitir uno mismo-Asamblea y pliegues anisotrópico

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...