The authors are indebted to Barry G. Dorman, Robert A. Icenogle, Juan Rodriguez, Morris G. Welch, and Marlin Siegford for technical assistance in experimental measurements, and to Jim Clark and Dexter LaGrand for assistance with computer simulations. We thank XIA LLC for allowing the use of their electronics and detectors in this project. This work was supported by NIFA ALA Research Contract No ALA061-4-15014 "Precision geospatial mapping of soil carbon content for agricultural productivity and lifecycle management".

1. Construction of the INS system
<ol>
	<li>Use the general INS system geometry shown in Figure 1.</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56270/56270fig1.jpg" /> 
Figure 1. INS System Geometry. <a href="//cloudfront-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56270/56270fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>Use the INS system design shown in Figure 2.10</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56270/56270fig2.jpg" /> 
Figure 2. Overview of the INS System. 
A) first block contains neutron generator, neutron detector, and power system; B) second block contains three NaI (Tl) detectors; C) third block contains equipment for system operation; D) general view of the first block showing individual components; and E) close up view of the gamma detectors.10 <a href="//cloudfront-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56270/56270fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="3">
	<li>Use three blocks in the INS system (see Appendix).
	<ol>
		<li>For the first block (A), use a neutron generator (NG) and power system (Figure 2A and 2D). Pulsed neutron output of this generator will be 107 - 108 n/s with neutron energy of 14 MeV. The power system will consist of four batteries (12 V, 105 Ah), a DC-AC Inverter, and a charger. This block will also contain iron (10 cm x 20 cm x 30 cm) and boric acid (5 cm x 20 cm x 30 cm) shielding to protect the gamma detector from neutron irradiation. 
		NOTE: A neutron detector is also included in this block for checking that the NG is functioning properly.</li>
		<li>For the second block (B), use gamma-ray measurement equipment (Figure 2B and 2E). This block will contain three 12.7 cm x 12.7 cm x 15.2 cm scintillation NaI(Tl) detectors with corresponding electronics. The exterior size of the detectors with electronics will measure 15.2 cm x 15.2 cm x 46 cm.</li>
		<li>For the third block (C), use a laptop computer that controls the neutron generator (with DNC software), detectors, and data acquisition system (Figure 2C).</li>
	</ol>
	</li>
</ol>
2. Caution and Personal Requirements
<ol>
	<li>Have each user of the INS system pass radiological training.</li>
	<li>Ensure that each person operating the NG carries a radiation monitoring badge. During measurements, the restricted area boundary (&#62;20 &#181;Sv/h) around the NG will have the radiation symbol with the words &#34;CAUTION, RADIATION AREA.&#34; All edges of the restricted area will be no less than 4 m from the NG.</li>
	<li>In an emergency, immediately push the &#34;Emergency Interrupt&#34; button on the NG, remove the key from the NG, and unplug the NG from the power source.</li>
</ol>
3. Preparation of the INS system for Measurement
<ol>
	<li>Check the power system. The power level indicator on the charger will be green, or more than 3 red lamps must illuminate. If not, connect the charger to a power outlet and wait until batteries become fully charged (green lamp will illuminate) or until an acceptable power level is reached (&#8805;3 red lamps will illuminate).</li>
	<li>Turn on the inverter (green lamp illuminates) and laptop.</li>
	<li>Run the data acquisition program on the laptop to operate the gamma detectors and check the required parameters for each detector. The values of these parameters will be defined and recorded previously at INS system testing.
	<ol>
		<li>Place a Cs-137 control source (any type) within 5 - 15 cm from the detectors.</li>
		<li>Start spectra acquisition for 1 - 3 min; check the centroids of the 662 keV Cs-137 peak for all detectors. They must be at the same channel. If not, use the Energy Coefficient Scale of thedata acquisition program by changing the value to adjust the 662 keV peak centroids.</li>
	</ol>
	</li>
	<li>Turn on the NG by using the special key. The indicator lamp on the NG will illuminate green and yellow.</li>
</ol>
4. Calibration of the INS System
<ol>
	<li>Prepare 4 pits sized 1.5 m x 1.5 m x 0.6 m with homogeneous sand-carbon mixtures (Figure 3). Carbon contents is 0, 2.5, 5 and 10 w%. 
	NOTE: A concrete mixer is used to make synthetic soil composed of construction sand and coconut shell (100% carbon content, average granular diameter &#60; 0.5 mm). Homogeneity of these mixtures is determined visually.</li>
</ol>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56270/56270fig3.jpg" /> 
Figure 3. View of Pit with Sand and Pit with 10 Cw% Sand-carbon Mixture. <a href="//cloudfront-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56270/56270fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>Take measurements over the pits using the following steps.
	<ol>
		<li>Position the INS system over the pit manually or by towing with a suitable vehicle. Position the INS system such that the projection of the neutron source is centered on the pit.</li>
		<li>Run the DNC software on the laptop that operates the NG generator. In the Faults column on the right side of the DNC program screen, all lamps will illuminate green; if not, click the Clear button. Insert the following parameters: for Pulse Parameters - frequency 5 kHz, duty cycle 25%, delay 0 &#181;s, extension 2 &#181;s; for Beam - high voltage 50 kV, beam current 50 &#181;A (note that these parameters can be different depending on the particular INS system setup and task).
		<ol>
			<li>Activate the switch on the DNC program screen and wait for the NG to enter the working regime where the High voltage and Beam current will come to stable values corresponding to the entered values; Reservoir current also will come to a stable value.</li>
		</ol>
		</li>
		<li>Run the data acquisition software on the laptop to operate the gamma detectors. Start spectra acquisition by running the data acquisition program for 1 h. The two spectra acquisition processes (INS &#38; TNC and TNC) will appear on the screen.</li>
		<li>After 1 h, stop the spectra acquisition and save spectra to the hard drive (File | Save MCA Data | choose the folder and enter the file name. 
		NOTE: There will be two saved spectra (TNC and INS) with filename extensions .mca and _gated.mca, respectively).</li>
		<li>Select second detector (click the arrow in the top left corner) and save the spectra for this detector. Do the same for third detector.</li>
		<li>Click File | Exit to close the software.</li>
		<li>Turn off the DNC software by turning off the switch on the DNC program screen.</li>
		<li>Repeat steps 4.2.1 - 4.2.7 for the other pits.</li>
		<li>Turn off the NG by using the special key. The indicator lamp on the NG will dim.</li>
	</ol>
	</li>
	<li>Determine the INS system background spectra by elevating the whole INS system to a distance greater than 4 m above the ground surface and away from any large objects, and repeat data acquisition steps 4.2.2 - 4.2.9.</li>
	<li>Data processing
	<ol>
		<li>Use a spreadsheet program to open data files saved in step 4.2.4. Find values for output and input count rates (OCR and ICR) and real time (RT) in rows 28, 27, and 30, respectively.</li>
		<li>Calculate the life time (LT) for INS &#38; TNC and TNC spectra for all measurements as 
		LTi = OCRi/ICRi&#183;RTi (1), 
		where OCRi and ICRi are the output and input count rates for the i-th measurement and RTi is real time of the i-th measurement.</li>
		<li>Calculate the gamma spectra in counts per second (cps) by dividing the spectra (rows 33-2080 in the spreadsheet) by the corresponding LT.</li>
		<li>Calculate the net INS spectra from the corresponding measurements for each pit as 
		Net INS Spectrum = (INS&#38;TNC - TNC)Pit - (INS&#38;TNC - TNC)Bkg (2)</li>
		<li>Find the gamma peaks 1.78 MeV (28Si) and 4.44 MeV (12C) in the Net INS spectrum for each pit, and calculate the peak areas (4.44 MeV C peak area, 1.78 MeV Si peak area) using IGOR software.
		<ol>
			<li>Open the software by double clicking the icon. Insert first Net INS Spectrum into the Table.</li>
			<li>Click Windows | New Graph | From Target | &#34;FileName&#34; | Do It. The Spectrum appears in the Graph Window. Click Graph | Show Info. The windows with A and B markers appears under the graph window.</li>
			<li>Place mouse pointer on sign A, push the left mouse button, and drag the cursor to the spectrum on left side of the 1.78 MeV peak. Place mouse pointer on the sign B, push the left mouse button, and drag the cursor to the spectrum on right side of the 1.78 MeV peak.</li>
			<li>Click Analysis | Multi-peak Fit | Start New Multi-peak Fit | From Target | Continue. In the pop-up window marked Use Graph Cursor | Baseline Linear| Auto-locate Peaks Now | Do it | Peak Results. The area of the peak appears in the pop-up window.</li>
			<li>Repeat the same operations for 4.44 MeV peak.</li>
			<li>Repeat all previous operations with the remaining Net INS Spectra.</li>
		</ol>
		</li>
		<li>Find the Net carbon peak areas for each pit by the equation 
		Net C peak areai = 4.44 MeV C peak areai- 0.058 &#183; 1.78 MeV Si peak areai (3)</li>
		<li>Build the calibration line for the INS system as a direct proportional dependence of the Net carbon peak area vs. carbon concentration expressed in weight percent.
		<ol>
			<li>Open new Table in IGOR software: click Window | New Table. Enter pit carbon concentration values in the first column, and the corresponding Net C peak area in the second column.</li>
			<li>Plot the Net C peak area vs pit carbon concentration: click Windows | New Graph. Choose Net C peak area as YWave, and carbon concentrations as XWave. Click Do it. The points appear on the Graph.</li>
			<li>Build the calibration line: Click Analysis | Curve Fitting | Function - line | From Target | Do it. The calibration line and the calibration coefficient (k) will appear in the window.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
5. Conducting Field Soil Measurements in Static Mode
<ol>
	<li>Prepare the INS system for measurement according to step 3.</li>
	<li>Place the system over the site requiring soil carbon content analysis manually or by towing using suitable vehicle. Position the INS system such that the projection of the neutron source is centered over the site being measured.</li>
	<li>Implement actions following steps 4.2.2 - 4.2.9 and 4.4.1 - 4.4.6 for determining Net C peak areas for the study sites.</li>
	<li>Calculate the carbon concentration in weight % using the calibration coefficient as 
	<img alt="Equation 1" src="/files/ftp_upload/56270/56270eq1.jpg" /></li>
</ol>
6. Conducting Field Soil Measurements in the Scanning Mode
<ol>
	<li>Estimate the path that the INS system will travel over the field while accounting for travel speed (&#8804; 5 km/h), field size, INS system footprint (radius ~1 m), and measurement time (1 h) such that the moving trajectory eventually covers the whole field area. For convenience, place flags at turn points along the field perimeter.</li>
	<li>Prepare the INS system for measurement according to step 3.</li>
	<li>Implement actions following steps 4.2.2 - 4.2.3.</li>
	<li>Follow the predetermined travel path for 1 h.</li>
	<li>Implement actions following steps 4.2.4 - 4.2.9 and 4.4.1 - 4.4.6 for determining Net C peak areas for the studied field.</li>
	<li>Calculate the carbon concentration in weight % using the calibration coefficient by equation 4.</li>
</ol>

<ol>
	<li>Potter, K. N., Daniel, J. A., Altom, W., Torbert, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stocking+rate+effect+on+soil+carbon+and+nitrogen+in+degraded+soils.">Stocking rate effect on soil carbon and nitrogen in degraded soils.</a> J. Soil Water Conserv. 56, 233-236 (2001).</li><li>Torbert, H. A., Prior, S. A., Runion, G. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+the+return+to+cultivation+on+carbon+(C)+sequestration.">Impact of the return to cultivation on carbon (C) sequestration.</a> J. Soil Water Conserv. 59 (1), 1-8 (2004).</li><li>Stolbovoy, V., Montanarella, L., Filippi, N., Jones, A., Gallego, J., Grassi, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Soil sampling protocol to certify the changes of organic carbon stock in mineral soil of the European Union. Version 2. , (2007).</li><li>Smith, K. E., Watts, D. B., Way, T. R., Torbert, H. A., Prior, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+tillage+and+fertilizer+application+method+on+gas+emissions+(CO2,+CH4,+N2O)+in+a+corn+cropping+system.">Impact of tillage and fertilizer application method on gas emissions (CO2, CH4, N2O) in a corn cropping system.</a> Pedosphere. 22 (5), 604-615 (2012).</li><li>Seybold, C. A., Mausbach, M. J., Karlen, D. L., Rogers, H. H., Lal, R., Kimble, J., Stewart, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+soil+quality.">Quantification of soil quality.</a> Soil processes and the carbon cycle. , 387-404 (1997).</li><li>Nelson, D. W., Sommers, L. E., Sparks, D. 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The authors have nothing to disclose.

Building on the foundation established by previous researchers, the NSDL staff addressed questions critical to the practical and successful use of this technology in real world field settings. Initially, NSDL researchers demonstrated the necessity to account for the INS system background signal when determining net carbon peak areas.11 Another effort showed that the net carbon peak area characterizes the average carbon weight percent in the upper 10 cm soil layer (regardless of carbon depth distri...

Knowledge of soil carbon content is required for optimization of soil productivity and profitability, understanding the impact of agricultural land use practices on soil resources, and evaluating strategies for carbon sequestration1,2,3,4. Soil carbon is a universal indicator of soil quality5. Several methods have been developed for soil carbon measurements. Dry combustion (DC) has been the most widely used method for years6; this method is based on field sample collection and laboratory processing and measurement that is destructive, labor intensive, and time consuming. Two newer methods are laser-induced breakdown spectroscopy, and near and mid infrared spectroscopy7. These methods are also destructive and only analyze the very near-surface soil layer (0.1 - 1 cm soil depth). In addition, these methods only yield point measurements of carbon content for small sample volumes (~60 cm3 for DC method, and 0.01-10 cm3 for infrared spectroscopy methods). Such point measurements make it difficult to extrapolate results to field or landscape scales. Since these methods are destructive, recurring measurements are also impossible.
Previous researchers at Brookhaven National Laboratory suggested applying neutron technology for soil carbon analysis (INS method)7,8,9. This initial effort developed the theory and practice of using neutron gamma analysis for soil carbon measurement. Starting in 2013, this effort was continued at the USDA-ARS National Soil Dynamics Laboratory (NSDL). The expansion of this technological application over the last 10 years is due to two main factors: the availability of relatively inexpensive commercial neutron generators, gamma detectors, and corresponding electronics with software; and state of the art neutron-nuclei interaction reference databases. This method has several advantages over others. An INS system, placed on a platform, could be maneuvered over any type of field that requires measurement. This non-destructive in-situ method can analyze large soils volumes (~300 kg) that can be interpolated to a whole agricultural field using just a few measurements. This INS system is also capable of operating in a scanning mode that determines the average carbon content of an area based on scanning over a predetermine grid of the field or landscape.

<table border="0" cellpadding="0" cellspacing="0" width="717">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Neutron Generator</td>
			<td style="width:327px;">Thermo Fisher Scientific, Colorado Springs, CO 
			DNC software</td>
			<td style="width:125px;">MP320</td>
			<td style="width:72px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Gamma-detector:</td>
			<td></td>
			<td>na</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">- NaI(Tl) crystal</td>
			<td>Scionix USA, Orlando, FL</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">- Electronics</td>
			<td>XIA LLC, Hayward, CA</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">- Software</td>
			<td>ProSpect</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Battery</td>
			<td>Fullriver Battery USA, Camarillo, CA</td>
			<td>DC105-12</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Invertor</td>
			<td>Nova Electric, Bergenfield, NJ</td>
			<td>CGL 600W-series</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Charger</td>
			<td>PRO Charging Systems, LLC, LaVergne, TN</td>
			<td>PS4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Block of Iron</td>
			<td>Any</td>
			<td>na</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Boric Acid</td>
			<td>Any</td>
			<td>na</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Laptop</td>
			<td>Any</td>
			<td>na</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mu-metal</td>
			<td>Magnetic Shield Corp., Bensenville, IL</td>
			<td>&#160;MU010-12</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Construction sand</td>
			<td>Any</td>
			<td>na</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Coconut shell</td>
			<td>General Carbon Corp., Patterson, NJ</td>
			<td>GC 8 X 30S</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;">Reference Cs-137 source</td>
			<td>Any</td>
			<td>na</td>
			<td></td>
		</tr>
	</tbody>
</table>

measurements of soil carbon by neutron-gamma analysis in static and scanning modes

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of gamma rays created when neutrons interact with soil elements. The main parts of the INS system are a pulsed neutron generator, NaI(Tl) gamma detectors, split electronics to separate gamma spectra due to INS and thermo-neutron capture (TNC) processes, and software for gamma spectra acquisition and data processing. This method has several advantages over other methods in that it is a non-destructive in situ method that measures the average carbon content in large soil volumes, is negligibly impacted by local sharp changes in soil carbon, and can be used in stationary or scanning modes. The result of the INS method is the carbon content from a site with a footprint of ~2.5 - 3 m2 in the stationary regime, or the average carbon content of the traversed area in the scanning regime. The measurement range of the current INS system is &#62;1.5 carbon weight % (standard deviation &#177; 0.3 w%) in the upper 10 cm soil layer for a 1 hmeasurement.

Soil INS &#38; TNC and TNC gamma spectra
A general view of the measured soil gamma spectra is shown in Figure 4. The spectra consist of a set of peaks on a continuous background. The main peaks of interest have centroids at 4.44 MeV and 1.78 MeV in the INS &#38; TNC spectra. The second peak can be attributed to silicon nuclei contained in soil, and the first peak is an overlapping peak from carbon and silicon nucle...

Watch this Scientific Journal Video about Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes at JoVE.com

Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes

Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures.

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of ...

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7.2K Views.  Agricultural Research Service, United States Department of Agriculture. Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures.

Video: Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes

Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. 
Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3.

We present methods for fabrication of patterned microstructures of vertically aligned carbon nanotubes (CNTs), and their use as master molds for production of polymer microstructures with organized nanoscale surface texture. The CNT forests are densified by condensation of solvent onto the substrate, which significantly increases their packing density and enables self-directed formation of 3D shapes.

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip ...

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can potentially contribute to the exposure of biota and humans. The diffusive gradients in thin films technique is introduced here for in-situ measurements of Pu bioavailability and speciation. A diffusion cell constructed for laboratory experiments with Pu and the newly developed protocol make it possible to simulate the environmental behavior of Pu in model solutions of various chemical compositions. Adjustment of the oxidation states to Pu(IV) and Pu(V) described in this protocol is essential in order to investigate the complex redox chemistry of plutonium in the environment. The calibration of this technique and the results obtained in the laboratory experiments enable to develop a specific DGT device for in-situ Pu measurements in freshwaters. Accelerator-based mass-spectrometry measurements of Pu accumulated by DGTs in a karst spring allowed determining the bioavailability of Pu in a mineral freshwater environment. Application of this protocol for Pu measurements using DGT devices has a large potential to improve our understanding of the speciation and the biological transfer of Pu in aquatic ecosystems.

The technique of diffusive gradients in thin films (DGT) is proposed for speciation studies of plutonium. This protocol describes diffusion experiments probing the behavior of Pu(IV) and Pu(V) in presence of organic matter. DGTs deployed in a karstic spring allow assessment of the bioavailability of Pu.

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can ...

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and non-destructively reveals the hydrogen density distribution at surfaces, at interfaces, and in the volume of solid materials with high depth resolution. The technique applies a 15N ion beam of 6.385 MeV provided by an electrostatic accelerator and specifically detects the 1H isotope in depths up to about 2 &#956;m from the target surface. Surface H coverages are measured with a sensitivity in the order of ~1013 cm-2 (~1% of a typical atomic monolayer density) and H volume concentrations with a detection limit of ~1018 cm-3 (~100 at. ppm). The near-surface depth resolution is 2-5 nm for surface-normal 15N ion incidence onto the target and can be enhanced to values below 1 nm for very flat targets by adopting a surface-grazing incidence geometry. The method is versatile and readily applied to any high vacuum compatible homogeneous material with a smooth surface (no pores). Electrically conductive targets usually tolerate the ion beam irradiation with negligible degradation. Hydrogen quantitation and correct depth analysis require knowledge of the elementary composition (besides hydrogen) and mass density of the target material. Especially in combination with ultra-high vacuum methods for in-situ target preparation and characterization, 1H(15N,&#945;&#947;)12C NRA is ideally suited for hydrogen analysis at atomically controlled surfaces and nanostructured interfaces. We exemplarily demonstrate here the application of 15N NRA at the MALT Tandem accelerator facility of the University of Tokyo to (1) quantitatively measure the surface coverage and the bulk concentration of hydrogen in the near-surface region of a H2 exposed Pd(110) single crystal, and (2) to determine the depth location and layer density of hydrogen near the interfaces of thin SiO2 films on Si(100).

We illustrate the application of 1H(15N,&#945;&#947;)12C resonant nuclear reaction analysis (NRA) to quantitatively evaluate the density of hydrogen atoms on the surface, in the volume, and at an interfacial layer of solid materials. The near-surface hydrogen depth profiling of a Pd(110) single crystal and of SiO2/Si(100) stacks is described.

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

The optical, electrical, and structural properties of dislocations and of grain boundaries in semiconductor materials can be determined by experiments performed in a scanning electron microscope. Electron microscopy has been used to investigate cathodoluminescence, electron beam induced current, and diffraction of backscattered electrons.

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications ...

Scanning SQUID Study of Vortex Manipulation by Local Contact

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual vortices is necessary in order to study how vortices interact with each other, with the lattice, and with other magnetic objects. Here, we present a protocol for vortex manipulation in thin superconducting films by local contact, without applying current or magnetic field. Vortices are imaged using a scanning superconducting quantum interference device (SQUID), and vertical stress is applied to the sample by pushing the tip of a silicon chip into the sample, using a piezoelectric element. Vortices are moved by tapping the sample or sweeping it with the silicon tip. Our method allows for effective manipulation of individual vortices, without damaging the film or affecting its topography. We demonstrate how vortices were relocated to distances of up to 0.8 mm. The vortices remained stable at their new location up to five days. With this method, we can control vortices and move them to form complex configurations. This technique for vortex manipulation could also be implemented in applications such as vortex based logic devices.

We present a protocol for manipulation of individual vortices in thin superconducting films, using local mechanical contact. The method does not include applying current, magnetic field or additional fabrication steps.

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual ...

Two-way Valorization of Blast Furnace Slag: Synthesis of Precipitated Calcium Carbonate and Zeolitic Heavy Metal Adsorbent

The aim of this work is to present a zero-waste process for storing CO2 in a stable and benign mineral form while producing zeolitic minerals with sufficient heavy metal adsorption capacity. To this end, blast furnace slag, a residue from iron-making, is utilized as the starting material. Calcium is selectively extracted from the slag by leaching with acetic acid (2 M CH3COOH) as the extraction agent. The filtered leachate is subsequently physico-chemically purified and then carbonated to form precipitated calcium carbonate (PCC) of high purity (&lt;2 wt% non-calcium impurities, according to ICP-MS analysis). Sodium hydroxide is added to neutralize the regenerated acetate. The morphological properties of the resulting calcitic PCC are tuned for its potential application as a filler in papermaking. In parallel, the residual solids from the extraction stage are subjected to hydrothermal conversion in a caustic solution (2 M NaOH) that leads to the predominant formation of a particular zeolitic mineral phase (detected by XRD), namely analcime (NaAlSi2O6&#8729;H2O). Based on its ability to adsorb Ni2+, as reported from batch adsorption experiments and ICP-OES analysis, this product can potentially be used in wastewater treatment or for environmental remediation applications.

A protocol for the parallel production of precipitated calcium carbonate and zeolitic material from blast furnace slag via mineral carbonation and alkaline hydrothermal conversion, respectively, is presented. The performance of the zeolitic material towards nickel adsorption is tested.

The aim of this work is to present a zero-waste process for storing CO2 in a stable and benign mineral form while producing zeolitic minerals with ...

Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning electron microscope (ESEM) operating with a low pressure water vapor ambient. In this technique, a portion of the electron beam interacts with the water vapor in the vicinity of the CNT sample, dissociating the water molecules into hydroxyl radicals and other species by radiolysis. The remainder of the electron beam interacts with the CNT forest sample, making it susceptible to oxidation from the chemical products of radiolysis. This technique may be used to trim a selected region of an individual CNT, or it may be used to remove hundreds of cubic microns of material by adjusting ESEM parameters. The machining resolution is similar to the imaging resolution of the ESEM itself. The technique produces only small quantities of carbon residue along the boundaries of the cutting zone, with minimal effect on the native structural morphology of the CNT forest.

Low pressure scanning electron microscopy in a water vapor ambient is used to machine nanoscale to microscale features in carbon nanotube forests.

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Fabrication of 3D Carbon Microelectromechanical Systems (C-MEMS)

A wide range of carbon sources are available in nature, with a variety of micro-/nanostructure configurations. Here, a novel technique to fabricate long and hollow glassy carbon microfibers derived from human hairs is introduced. The long and hollow carbon structures were made by the pyrolysis of human hair at 900 &#176;C in a N2 atmosphere. The morphology and chemical composition of natural and pyrolyzed human hairs were investigated using scanning electron microscopy (SEM) and electron-dispersive X-ray spectroscopy (EDX), respectively, to estimate the physical and chemical changes due to pyrolysis. Raman spectroscopy was used to confirm the glassy nature of the carbon microstructures. Pyrolyzed hair carbon was introduced to modify screen-printed carbon electrodes ; the modified electrodes were then applied to the electrochemical sensing of dopamine and ascorbic acid. Sensing performance of the modified sensors was improved as compared to the unmodified sensors. To obtain the desired carbon structure design, carbon micro-/nanoelectromechanical system (C-MEMS/C-NEMS) technology was developed. The most common C-MEMS/C-NEMS fabrication process consists of two steps: (i) the patterning of a carbon-rich base material, such as a photosensitive polymer, using photolithography; and (ii) carbonization through the pyrolysis of the patterned polymer in an oxygen-free environment. The C-MEMS/NEMS process has been widely used to develop microelectronic devices for various applications, including in micro-batteries, supercapacitors, glucose sensors, gas sensors, fuel cells, and triboelectric nanogenerators. Here, recent developments of a high-aspect ratio solid and hollow carbon microstructures with SU8 photoresists are discussed. The structural shrinkage during pyrolysis was investigated using confocal microscopy and SEM. Raman spectroscopy was used to confirm the crystallinity of the structure, and the atomic percentage of the elements present in the material before and after pyrolysis was measured using EDX.

Fabrication of 3D Carbon Microelectromechanical Systems C-MEMS

Long and hollow glassy carbon microfibers were fabricated based on the pyrolysis of a natural product, human hair. The two fabrication steps of carbon microelectromechanical and carbon nanoelectromechanical systems, or C-MEMS and C-NEMS, are: (i) photolithography of a carbon-rich polymer precursor and (ii) pyrolysis of the patterned polymer precursor.

A wide range of carbon sources are available in nature, with a variety of micro-/nanostructure configurations. Here, a novel technique to fabricate long ...

Production and Characterization of Vacuum Deposited Organic Light Emitting Diodes

A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex donor-acceptor emitters is presented. With a step-by-step procedure, readers will be able to repeat and produce OLED devices based on simple organic emitters. A patterning procedure allowing the creation of personalized indium tin oxide (ITO) shape is shown. This is followed by the evaporation of all layers, encapsulation and characterization of each individual device. The end goal is to present a procedure that will give the opportunity to repeat the information presented in cited publication but also using different compounds and structures in order to prepare efficient OLEDs.

A protocol for the production of simple structured organic light-emitting diodes (OLEDs) is presented.

A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex ...