This work was supported by the National Science Foundation (NSF CHE-1847830).

1. Making polyvinyl alcohol (PVA) solution
<ol>
	<li>Measure water and PVA polymer pellets (see Table of Materials) to create a 10 mL solution at a 20% PVA to water ratio by weight.</li>
	<li>Heat the water in the glassware over a hot plate set to 100 &#176;C.</li>
	<li>Place the PVA polymer pellets into the heated water. Insert a magnetic stir bar.</li>
	<li>Reduce the heat to 80 &#176;C and stir until the PVA fully dissolves.</li>
	<li>Cover the top of the glassware to prevent contamination.</li>
	<li>Once fully dissolved, place the 20% PVA solution into an appropriate storage container for storage at room temperature.</li>
</ol>
2. Preparing PVA-coated silicon (Si) wafers
<ol>
	<li>Cut a silicon (Si) wafer (see Table of Materials) into ~10 x 10 mm2 squares.</li>
	<li>Clean the Si substrate using isopropyl alcohol and let it dry.</li>
	<li>Place the clean Si wafer on the chuck of the spin coater (see Table of Materials).
	<ol>
		<li>Drop cast approximately 10 &#181;L of PVA solution onto the center of the Si substrate. Try to avoid bubble formation.</li>
		<li>Coat the Si substrate with a uniform PVA film by spin coating for 30 s at 1,500 rotations per minute (rpm). 
		NOTE: The specified volume of liquid and spin coating parameters create a uniform layer of PVA across the surface of the substrate with sufficient thickness to prevent rapid drying between the spin coating and placing the PS beads onto the PVA surface in the next step.</li>
	</ol>
	</li>
	<li>Remove the sample from the spin coater and place it into a clean sample container to prevent contamination before transferring the PS beads.</li>
</ol>
3. Placing the PS beads onto the PVA-coated surface
<ol>
	<li>Clean a Si substrate using isopropyl alcohol and let it dry.</li>
	<li>Using a pipette, place 1 &#181;L of PS beads suspended in water onto the center of the substrate.</li>
	<li>Let the water evaporate by placing the sample in a storage compartment containing bentonite clay desiccant. 
	NOTE: This step preserves the sample by reducing exposure to humidity.</li>
	<li>Place the PVA-coated substrate (step 2.4) and the substrate with the dried PS beads (step 3.3) under an optical microscope. Depending on their size, a single bead will be visible using simple binoculars or will require higher optical magnification.</li>
	<li>Gently loosen the beads using ultrafine tweezers (see Table of Materials). Use a fine hair paintbrush to collect a few loose beads and lightly tap the hairs of the paintbrush over the freshly PVA-coated wafer. Multiple sweeps should allow the beads to accumulate within the hairs of the brush. Tap the top of the paintbrush hairs to disturb the PS bead powder to release beads onto the tacky PVA surface. 
	NOTE: It is important that the paintbrush is of high quality and clean to avoid releasing fibers and contaminants onto the PVA film&#39;s surface. Moving quickly during this step is essential so that the PVA does not completely dry.</li>
	<li>Repeat this step until it is confirmed by optical microscopy inspection that individual PS beads adhere to the PVA surface.</li>
	<li>Store the sample in a clean container. Allow the sample to dry fully. 
	NOTE: The sample should be allowed to cool and dry completely before further analysis attempts are performed. AFM height measurements or surface profiler measurements can assess the thickness of successive PVA films.</li>
</ol>
4. Loading the sample for AFM characterization
NOTE: The protocol described is based on standard operating procedures of a nanoIR2 (see Table of Materials) platform, but should be adapted according to the AFM model used for the measurement.
<ol>
	<li>Mount the PVA and PS bead sample onto the AFM stage using a metallic AFM disk and adhesive tabs, so that the sample is firmly attached to the sample holder.</li>
	<li>Mount a nanoIR probe (e.g., FORTGG) onto the AFM probe holder. 
	&#8203;NOTE: The AFM cantilever is 225 &#181;m long, 27 &#181;m wide, and 2.7 &#181;m thick, with a tip radius of less than 10 nm. The cantilever is coated with 45 nm thick gold film on both sides to limit its response to the top-side IR illumination of the sample (see Table of Materials). For nanoIR spectroscopy measurements, preferably use a cantilever that has been stored in a polydimethylsiloxane-free environment prior to use.</li>
	<li>Align the read-out laser at the free end of the cantilever beam by turning the laser alignment knobs (x and y adjustments of the laser position and vertical adjustment of the detector position).
	<ol>
		<li>Maximize the SUM signal of the detector.</li>
		<li>Adjust the position of the detector by turning the deflection knob so that the laser is aligned with the center of the position-sensitive detector of the AFM read-out system, corresponding to a vertical deflection signal of ~0 V.</li>
	</ol>
	</li>
	<li>Click on the Load icon in the AFM &#34;Probe&#34; control panel.
	<ol>
		<li>Follow the prompts within the wizard screen. Use the focus arrows to determine the focal plane of the nanoIR cantilever. Use the XY-displacement controls to position the cantilever in the center of the screen (aligned with the white cross).</li>
		<li>Next, click on the focus arrows to find the focal plane of the surface of the sample.</li>
		<li>Use the optical view of the system and the XY-displacement controls to position the cantilever tip above the bead of interest and click on Next.</li>
		<li>On the engage screen, set the &#34;standoff&#34; to 50 &#181;m and click on Approach Only.</li>
	</ol>
	</li>
	<li>Initiate the Engage procedure to approach the tip for imaging.</li>
</ol>
5. Creating topographical and nanoIR images of the multipolymer sample
<ol>
	<li>Acquire topography images in standard &#34;Contact Mode&#34;. Once the position of the cantilever with respect to the PS bead is set, initiate the approach by clicking on the engage icon in the AFM &#34;Probe&#34; control panel. An engage setpoint of a deflection differential of 0.2 V is used for the entire study here, corresponding to a force of ~100 nN. 
	In the AFM &#34;Scan&#34; control panel, set the scan rate to 0.8 Hz, scan size (height and width), and the number of points per line and number of lines per image to use for imaging (512 x 512 was used here). Click on Scan to acquire the topography image. 
	NOTE: Calibration of the cantilever18 is done by determining the deflection sensitivity (in nm/V) from the slope of the deflection-distance curve obtained with the cantilever interacting with a sapphire substrate (Supplementary Figure 1A). The cantilever stiffness is determined from thermal tuning19 (Supplementary Figure 1B). The resonance of the cantilever is fitted using a Lorentzian function. The cantilever stiffness (in N/m) is determined using the equipartition theorem <img alt="Equation 1" src="/files/ftp_upload/65357/65357eq01.jpg" style="margin: auto;" />, where KB is the Boltzmann constant, T is the temperature (T = 295K), and P is the area of the power spectrum of the thermal fluctuations of the cantilever determined by integrating the Lorentzian fit of the thermal tuning data20.</li>
	<li>For nanoIR measurements, position the AFM tip on the feature of interest identified from the topography image.
	<ol>
		<li>Select the tuning fork icon in the nanoIR control panel to determine the contact resonance frequencies of the cantilever. Set an illumination wavenumber that will excite photothermal expansion in the material. Set a range of laser pulse frequency to sweep and set the duty cycle of the nanoIR laser. Select Acquire within the &#34;Laser Pulse Tune Window&#34;.</li>
		<li>Select the second contact resonance of the tip-sample system for nanoIR measurements by positioning the marker bar (green vertical line) at the peak of the second contact resonance. 
		NOTE: The selection of the contact resonance mode can vary depending on the type of cantilever and sample.</li>
		<li>Click on Optimize to align the center of the IR laser focal region with the position of the cantilever tip. Alignment is done at a selected IR illumination wavenumber, corresponding to an absorption band of the material probed. The cantilever is positioned at the center of the laser footprint (Supplementary Figure 2). 
		NOTE: Alignment can vary for different wavenumbers depending on the laser model.</li>
		<li>Acquire a background of the IR laser illumination. This consists of measuring the output of the IR quantum cascade laser (QCL) in the wavelength range of emission at the pulse frequency selected (Supplementary Figure 3). This is important for background correction of the nanoIR spectra.</li>
		<li>Acquire the nanoIR spectrum by selecting the wavenumber range (here, Start and Stop are set to 1,530 cm-1 and 1,800 cm-1, respectively), the step size (2 cm-1), and the number of averages used for the measurement. Perform background correction of the spectra displayed by dividing the photothermal amplitude measured by the attenuated background, which consists of multiplying the background collected in step 5.2.4 by the percentage of power selected for the measurement.</li>
	</ol>
	</li>
	<li>For nanoIR imaging, select the region of interest for imaging.
	<ol>
		<li>Enable phase-locked loop (PLL) auto-tune in the &#34;Laser Pulse Tune Window&#34; (accessed by the Tuning fork icon).</li>
		<li>Adjust the minimum and maximum frequency to create a sweep range centered at the second resonance mode in the general control panel.</li>
		<li>Zero the phase by clicking on zero in the PLL control panel and then click on OK in the &#34;Laser Pulse Tune window&#34;.</li>
		<li>Select IR Imaging Enabled by putting a checkmark in the box within the nanoIR control panel.</li>
		<li>In the &#34;Imaging View&#34; control panel, choose Height (Imaging View 1), Amplitude 2 (Imaging View 2), and Phase 2 (Imaging View 3) to acquire the topographical and chemical images of the sample. Set the acquisition direction to Trace (or Retrace). A line fit Line is often required to observe the topography image of the sample being acquired. Capture fit should be set to None. 
		NOTE: Scanning preferences, such as scan direction captured or color palette used, can be adjusted as needed.</li>
		<li>In the AFM &#34;Scan&#34; control panel, select the Scan icon.</li>
		<li>To save the image, select the Now or End of frame icon in the &#34;Capture&#34; control panel.</li>
	</ol>
	</li>
	<li>To export the data, right-click on the image or spectrum file names within the data lists. Select Export and choose the format of the file to export. Save the file in the desired computer folder location.</li>
</ol>

Exploring Multiphase Polymeric Systems by Nanoscale Infrared Spectroscopy

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H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=34;May+the+force+be+with+you!&amp;#34;+Force-volume+mapping+with+atomic+force+microscopy.">34;May the force be with you!&amp;#34; Force-volume mapping with atomic force microscopy.</a> ACS Omega. 6 (40), 25860-25875 (2021).</li><li>Dokukin, M. 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The authors have nothing to disclose.

AFM combined with nanoIR spectroscopy can provide nanoscale chemical information using a cantilever in contact mode and a pulsed tunable IR light source. Model systems, such as embedding an absorber with finite dimensions in the volume of a polymeric material, are important to improve the understanding of image formation mechanisms and to determine the performance of the tool. In the case of the PS/PVA configuration presented here, optimization was carried out to obtain a stable PS bead positioned above or below the surf...

Atomic force microscopy (AFM) has become essential to image and characterize the morphology of a wide variety of samples with nanoscale resolution1,2,3. By measuring the deflection of an AFM cantilever resulting from the interaction of the sharp tip with the sample surface, nanoscale functional imaging protocols for local stiffness measurements and tip-sample adhesion have been developed4,5. For soft condensed matter and polymer analysis, AFM measurements exploring the nanomechanical and nanochemical properties of local domains are highly sought after6,7,8. Before the emergence of nanoscale infrared (nanoIR) spectroscopy, AFM tips were chemically modified to assess the presence of different domains from the AFM force curve and deduct the nature of the tip-sample interaction. For instance, this approach was used to unveil the transformation of microdomains of poly(tert-butyl acrylate) at the surface of cyclohexane-treated polystyrene-block-poly(tert-butyl acrylate)block copolymer thin films at the sub 50 nm level9.
The combination of infrared (IR) light with AFM has had a significant impact on the field of polymer science6. Conventional IR spectroscopy is a widely used technique for studying the chemical structure of polymeric materials10,11, but it fails to provide information on individual phases and interphase behavior, as the regions are too small compared to the size of the IR beam used to probe the sample. The problem holds with IR microspectroscopy, as it is restricted by the optical diffraction limit6. Such measurements average the contributions of the entire region excited by the IR light; the signals resulting from the presence of nanoscale phases inside the probed region either exhibit complex fingerprints that should be deconvoluted during post-processing or are lost due to a signal level below the detectable level. Hence, it is essential to develop tools capable of nanoscale spatial resolution and high IR sensitivity to explore nanoscale chemical features in complex media.
Schemes to achieve nanoIR spectroscopy have been developed, first using a metallic AFM tip as a nanoantenna12,13, and more recently exploiting the AFM cantilever&#39;s ability to monitor changes in the photothermal expansion incurred during IR illumination of the sample12,14,15. The latter uses a pulsed, tunable IR light source tuned to an absorption band of the material probed, which causes the sample to absorb radiation and undergo photothermal expansion. This approach is well-suited for organic and polymeric materials. The pulsed excitation makes the effect detectable by the AFM cantilever in contact with the sample surface in the form of an oscillation. The amplitude of one of the contact resonances of the system observed in the frequency spectrum is then monitored as a function of illumination wavelength, which constitutes the nanoIR absorption spectrum of the material beneath the AFM tip15. The spatial resolution of nanoIR imaging and spectroscopy is limited by various effects of the photothermal expansion of the material. It has been evaluated that photothermal nanoIR spectroscopy using contact mode AFM can acquire the vibrational absorption spectra properties of materials with sub 50 nm scale spatial resolution14, with recent work demonstrating the detection of monomers and dimers of &#945;-synuclein16,17. However, quantitative studies of the performance of nanoIR measurements on heterogeneous polymeric materials assembled in various configurations, such as the case of absorbers of finite dimensions embedded in the volume of various polymeric films, remain limited.
This article aims to create a polymeric assembly with an embedded feature of a known dimension to evaluate the sensitivity of photothermal expansion and spatial resolution of nanoIR during surface analysis. The protocol covers the preparation of a polyvinyl alcohol (PVA) polymer thin film on a silicon substrate and the placement of a three-dimensional polystyrene (PS) bead onto or embedded in the PVA film, which constitutes the formation of the model system. NanoIR imaging and spectroscopy measurements are described in the context of evaluating the signals generated by the same PS bead positioned on or beneath the PVA film. The influence of the bead position on the nanoIR signals is evaluated. Methods to assess the spatial footprint of the bead in the nanoIR map are discussed, and the effects of several parameters are considered.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>10|0 2200 Golden Taklon Round</td>
			<td>Zem</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>5357-8NM Tweezers</td>
			<td>Pelco</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Adhesive Tabs</td>
			<td>Ted Pella</td>
			<td>16079</td>
			<td></td>
		</tr>
		<tr>
			<td>AFM metal specimen disks</td>
			<td>Ted Pella</td>
			<td>16208</td>
			<td></td>
		</tr>
		<tr>
			<td>Binocular</td>
			<td>AmScope</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cantilever for nanoIR measurements</td>
			<td>AppNano</td>
			<td></td>
			<td>FORTGG</td>
		</tr>
		<tr>
			<td>Cell culture dishes</td>
			<td>Greiner bio-one GmbH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Desiccator</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Floating optical table</td>
			<td>Newport</td>
			<td>RS 4000</td>
			<td></td>
		</tr>
		<tr>
			<td>Hotplate</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropanol&#160;</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Kimwipes</td>
			<td>KIMTECH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic stir bar</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microparticles based on polystyrene size: 5 &#181;m</td>
			<td>SIGMA-ALDRICH</td>
			<td>79633</td>
			<td></td>
		</tr>
		<tr>
			<td>nanoIR2 microscope</td>
			<td>Bruker</td>
			<td></td>
			<td>Contact mode NanoIR2</td>
		</tr>
		<tr>
			<td>Nitrogen Tank</td>
			<td>Airgas</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dishes</td>
			<td>Greiner bio-one GmbH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Polyvinyl Alcohol</td>
			<td>SIGMA-ALDRICH</td>
			<td>363170</td>
			<td>this polymer was only 87%-89% hydrolyzed, which explains the presence of residual C=O at 1730 cm-1</td>
		</tr>
		<tr>
			<td>Quantum Cascade Laser</td>
			<td>Daylight Solutions</td>
			<td></td>
			<td>1550-1800 cm-1 range</td>
		</tr>
		<tr>
			<td>Silicon wafer</td>
			<td>MEMC St. Peters</td>
			<td>#901319343000</td>
			<td></td>
		</tr>
		<tr>
			<td>Spin coater</td>
			<td>Oscilla</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

advances in nanoscale infrared spectroscopy to explore multiphase polymeric systems

Multiphase polymeric systems encompass local domains with dimensions that can vary from a few tens of nanometers to several micrometers. Their composition is commonly assessed using infrared spectroscopy, which provides an average fingerprint of the various materials contained in the volume probed. However, this approach does not offer any details on the arrangement of the phases in the material. Interfacial regions between two polymeric phases, often in the nanoscale range, are also challenging to access. Photothermal nanoscale infrared spectroscopy monitors the local response of materials excited by infrared light with the sensitive probe of an atomic force microscope (AFM). While the technique is suitable for interrogating small features, such as individual proteins on pristine gold surfaces, the characterization of three-dimensional multicomponent materials is more elusive. This is due to a relatively large volume of material undergoing photothermal expansion, defined by the laser focalization onto the sample and by the thermal properties of the polymeric constituents, compared to the nanoscale region probed by the AFM tip. Using a polystyrene (PS) bead and a polyvinyl alcohol (PVA) film, we evaluate the spatial footprint of photothermal nanoscale infrared spectroscopy for surface analysis as a function of the position of PS in the PVA film. The effect of the feature position on the nanoscale infrared images is investigated, and spectra are acquired. Some perspectives on the future advances in the field of photothermal nanoscale infrared spectroscopy are provided, considering the characterization of complex systems with embedded polymeric structures.

PS ((C8H8)n) beads were deposited on a clean Si substrate (Figure 1A) and on PVA ((CH2CHOH)n) (Figure 1B,C). Due to the poor adhesion of the bead on Si, nanoIR imaging in contact mode could not be acquired for this sample. Instead, using the optical view of the sample on nanoIR, the gold-coated AFM probe was engaged on top of the PS bead in contact mode, with an estimated force of about 100 ...

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Author Spotlight: Advances in Nanoscale Infrared Spectroscopy to Explore Multiphase Polymeric Systems  

This protocol describes the application of atomic force microscopy and nanoscale infrared spectroscopy to evaluate the performance of photothermal nanoscale infrared spectroscopy in the characterization of three-dimensional multi-polymeric samples.

Advances in Nanoscale Infrared Spectroscopy to Explore Multiphase Polymeric Systems

Multiphase polymeric systems encompass local domains with dimensions that can vary from a few tens of nanometers to several micrometers. Their composition ...

advances-nanoscale-infrared-spectroscopy-to-explore-multiphase

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Engineering

732 Views.  University of Central Florida. This protocol describes the application of atomic force microscopy and nanoscale infrared spectroscopy to evaluate the performance of photothermal nanoscale infrared spectroscopy in the characterization of three-dimensional multi-polymeric samples. 

Video: Author Spotlight: Advances in Nanoscale Infrared Spectroscopy to Explore Multiphase Polymeric Systems  

Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. Thus, understanding of spatial variations in composition as well as electrical properties of OPV materials is of paramount importance for moving PV technology forward.1,2 In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution. Currently, materials properties measurements performed using commercially available AFM-based techniques (PeakForce, conductive AFM) generally provide only qualitative information. The values for resistance as well as Young's modulus measured using our method on the prototypical ITO/PEDOT:PSS/P3HT:PC61BM system correspond well with literature data. The P3HT:PC61BM blend separates onto PC61BM-rich and P3HT-rich domains. Mechanical properties of PC61BM-rich and P3HT-rich domains are different, which allows for domain attribution on the surface of the film. Importantly, combining mechanical and electrical data allows for correlation of the domain structure on the surface of the film with electrical properties variation measured through the thickness of the film.

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution.

Organic photovoltaic  (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale  inhomogeneity of OPV materials affects performance ...

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Monitoring the dynamics of protonation and protein backbone conformation changes during the function of a protein is an essential step towards understanding its mechanism. Protonation and conformational changes affect the vibration pattern of amino acid side chains and of the peptide bond, respectively, both of which can be probed by infrared (IR) difference spectroscopy. For proteins whose function can be repetitively and reproducibly triggered by light, it is possible to obtain infrared difference spectra with (sub)microsecond resolution over a broad spectral range using the step-scan Fourier transform infrared technique. With ~102-103 repetitions of the photoreaction, the minimum number to complete a scan at reasonable spectral resolution and bandwidth, the noise level in the absorption difference spectra can be as low as ~10-4, sufficient to follow the kinetics of protonation changes from a single amino acid. Lower noise levels can be accomplished by more data averaging and/or mathematical processing. The amount of protein required for optimal results is between 5-100 &#181;g, depending on the sampling technique used. Regarding additional requirements, the protein needs to be first concentrated in a low ionic strength buffer and then dried to form a film. The protein film is hydrated prior to the experiment, either with little droplets of water or under controlled atmospheric humidity. The attained hydration level (g of water / g of protein) is gauged from an IR absorption spectrum. To showcase the technique, we studied the photocycle of the light-driven proton-pump bacteriorhodopsin in its native purple membrane environment, and of the light-gated ion channel channelrhodopsin-2 solubilized in detergent.

Key steps of protein function, in particular backbone conformational changes and proton transfer reactions, often take place in the microsecond to millisecond time scale. These dynamical processes can be studied by time-resolved step-scan Fourier-transform infrared spectroscopy, in particular for proteins whose function is triggered by light.

Monitoring the dynamics of protonation and protein backbone conformation changes during the function of a protein is an essential step towards ...

Thermal Measurement Techniques in Analytical Microfluidic Devices

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. Micromachining techniques allow reduction of the thermal mass of fabricated structures and introduce the possibility to perform high sensitivity thermal measurements in the micro-scale and nano-scale devices. Combining thermal measurement techniques with microfluidic devices allows performing different analytical measurements with low sample consumption and reduced measurement time by integrating the miniaturized system on a single chip. The procedures of thermal measurement techniques for particle detection, material characterization, and chemical detection are introduced in this paper.

Here, we present three protocols for thermal measurements in microfluidic devices.

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems

This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the presence of carbon nanotubes. These nanowires are extreme in the sense that they are the limit of miniaturization of nanowires and their behavior is not always a simple extrapolation of the behavior of larger nanowires as their diameter decreases. The paper then describes the methods required to obtain Raman spectra from extreme nanowires and the fact that due to the van Hove singularities that 1D systems exhibit in their optical density of states, that determining the correct choice of photon excitation energy is critical. It describes the techniques required to determine the photon energy dependence of the resonances observed in Raman spectroscopy of 1D systems and in particular how to obtain measurements of Raman cross-sections with better than 8% noise and measure the variation in the resonance as a function of sample temperature. The paper describes the importance of ensuring that the Raman scattering is linearly proportional to the intensity of the laser excitation intensity. It also describes how to use the polarization dependence of the Raman scattering to separate Raman scattering of the encapsulated 1D systems from those of other extraneous components in any sample.

The paper describes a method for producing extreme nanowires by melt infiltration into carbon nanotubes and how 1D systems may be characterized and investigated using Resonance Raman Spectroscopy to determine vibrational and optical excitation energies.

This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the ...

Free-form Light Actuators &#8212; Fabrication and Control of Actuation in Microscopic Scale

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted researchers&#39; attention in many fields. Most of the studies focused on macroscopic LCE structures (films, fibers) and their miniaturization is still in its infancy. Recently developed lithography techniques, e.g., mask exposure and replica molding, only allow for creating 2D structures on LCE thin films. Direct laser writing (DLW) opens access to truly 3D fabrication in the microscopic scale. However, controlling the actuation topology and dynamics at the same length scale remains a challenge.
In this paper we report on a method to control the liquid crystal (LC) molecular alignment in the LCE microstructures of arbitrary three-dimensional shape. This was made possible by a combination of direct laser writing for both the LCE structures as well as for micrograting patterns inducing local LC alignment. Several types of grating patterns were used to introduce different LC alignments, which can be subsequently patterned into the LCE structures. This protocol allows one to obtain LCE microstructures with engineered alignments able to perform multiple opto-mechanical actuation, thus being capable of multiple functionalities. Applications can be foreseen in the fields of tunable photonics, micro-robotics, lab-on-chip technology and others.

Here, we fabricate 3D polymeric micro/nano structures in which both the shape and the molecular alignment can be engineered with nanometer scale accuracy by the use of direct laser writing. Light induced deformation of several types of liquid crystalline elastomer microstructures can be controlled in the microscopic scale.

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted ...

The Evolution of Silica Nanoparticle-polyester Coatings on Surfaces Exposed to Sunlight

Corrosion of metallic surfaces is prevalent in the environment and is of great concern in many areas, including the military, transport, aviation, building and food industries, amongst others. Polyester and coatings containing both polyester and silica nanoparticles (SiO2NPs) have been widely used to protect steel substrata from corrosion. In this study, we utilized X-ray photoelectron spectroscopy, attenuated total reflection infrared micro-spectroscopy, water contact angle measurements, optical profiling and atomic force microscopy to provide an insight into how exposure to sunlight can cause changes in the micro- and nanoscale integrity of the coatings. No significant change in surface micro-topography was detected using optical profilometry, however, statistically significant nanoscale changes to the surface were detected using atomic force microscopy. Analysis of the X-ray photoelectron spectroscopy and attenuated total reflection infrared micro-spectroscopy data revealed that degradation of the ester groups had occurred through exposure to ultraviolet light to form COO&#903;, -H2C&#903;, -O&#903;, -CO&#903; radicals. During the degradation process, CO and CO2 were also produced.

Two types of surfaces, polyester-coated steel and polyester coated with a layer of silica nanoparticles, were studied. Both surfaces were exposed to sunlight, which was found to cause substantial changes in the chemistry and nanoscale topography of the surface.

Corrosion of metallic surfaces is prevalent in the environment and is of great concern in many areas, including the military, transport, aviation, ...

High-speed Continuous-wave Stimulated Brillouin Scattering Spectrometer for Material Analysis

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as aqueous solutions and biomaterials, with fast acquisition times. Here, we discuss the assembly and operation of a Brillouin spectrometer that uses stimulated Brillouin scattering (SBS) to measure stimulated Brillouin gain (SBG) spectra of water and lipid emulsion-based tissue-like samples in transmission mode with &lt;10 MHz spectral-resolution and &lt;35 MHz Brillouin-shift measurement precision at &lt;100 ms. The spectrometer consists of two nearly counter-propagating continuous-wave (CW) narrow-linewidth lasers at 780 nm whose frequency detuning is scanned through the material Brillouin shift. By using an ultra-narrowband hot rubidium-85 vapor notch filter and a phase-sensitive detector, the signal-to-noise-ratio of the SBG signal is significantly enhanced compared to that obtained with existing CW-SBS spectrometers. This improvement enables measurement of SBG spectra with up to 100-fold faster acquisition times, thereby facilitating high spectral-resolution and high-precision Brillouin analysis of soft materials at high speed.

We describe the construction of a rapid continuous-wave-stimulated-Brillouin-scattering (CW-SBS) spectrometer. The spectrometer employs single-frequency diode-lasers and an atomic vapor notch-filter to acquire transmission spectra of turbid/non-turbid samples with high spectral-resolution at speeds up to 100-fold faster than those of existing CW-SBS spectrometers. This improvement enables high-speed Brillouin material analysis.

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

O-cresol Concentration Online Measurement Based On Near Infrared Spectroscopy Via Partial Least Square Regression

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the prediction of the components in industrial processes. The ability to record spectra for solid and liquid samples without any pretreatment is advantageous and the method is widely used. However, the disadvantages of analyzing high-dimensional near-infrared spectral data include information redundancy and multicollinearity of the spectral data. Thus, we propose to use partial least squares regression method, which has traditionally been used to reduce the data dimensionality and eliminate the collinearity between the original features. We implement the method for predicting the o-cresol concentration during the production of polyphenylene ether. The proposed approach offers the following advantages over component regression prediction methods: 1) partial least squares regression solves the multicollinearity problem of the independent variables and effectively avoids overfitting, which occurs in a regression analysis due to the high correlation between the independent variables; 2) the use of the near-infrared spectra results in high accuracy because it is a non-destructive and non-polluting method to obtain information at microscopic and molecular scales.

The protocol describes a method of predicting o-cresol concentration during the production of polyphenylene ether using near-infrared spectroscopy and partial least squares regression. To describe the process more clearly and completely, an example of predicting the o-cresol concentration during the production of polyphenylene is used to clarify the steps.

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the ...