United States Government Publishing Office and the National Institute of Standards and Technology.

1. Setup of materials
<ol>
	<li>Record all manufacturing information provided with the ream of paper (e.g., basis weight, manufacturer&#39;s advertised PCW content, and manufacturer&#8217;s advertised brightness).</li>
	<li>Take an average of ten thickness measurements along a sheet from the ream, using a caliper.</li>
	<li>Identify the machine and cross directions of the sheet (i.e., the machine direction is the long dimension).</li>
	<li>Using a protractor identify and cut the paper along the desired strip&#160;angle between the machine and cross directions.</li>
	<li>Using a rotary cutter, slice test strips 0.5 cm wide by 8 cm long in the target orientation for the sample.</li>
	<li>Label samples from one end and store between glass microscopy slides. Store until testing under nitrogen atmosphere. 
	NOTE: It is advisable to wear gloves and perform handling with tweezers to avoid creasing and / or contaminating the paper samples.</li>
</ol>
2. Accelerated paper fade testing
NOTE: Paper samples are aged under UV-light at elevated temperature at laboratory ambient humidity. The aging is performed using an accelerated weathering chamber equipped with 340 nm UVA bulbs, at an irradiance of 0.72 W/m2 at 50 &#176;C for 169 h, by following the following protocol.
<ol>
	<li>Calibrate the UV-sensors, by running the calibration radiometer routine pre-preprogrammed in the UV-based accelerated weathering chamber.</li>
	<li>Calibrate the temperature sensors by running the P4 calibrate panel temperature program pre-preprogrammed in the weathering chamber.</li>
	<li>Measure the pre-post-aging color of the paper samples using a portable spectrophotometer operating in the visible wave range from 400 nm to 800 nm.</li>
	<li>Select appropriate standard test cycles pre-preprogrammed in the weathering chamber.</li>
	<li>Mount whole sheets of test papers on the flat panel (optionally, mount one sheet of either side of the flat panel).</li>
	<li>Fasten the flat panels to the sample holders with snap rings, pushing the rings snugly against the panel.</li>
	<li>Install the panel holders with the stop pin down.</li>
	<li>Attach aluminum blanks to mount in the panel holders for condensation.</li>
	<li>For uniform exposure, reposition the test samples (at least five times) during the test cycle.</li>
	<li>Measure the post-aging color of the paper samples using a portable spectrophotometer.</li>
	<li>Cut sample strips out of the aged paper samples to fit the resonant cavity. The typical specimen area is 0.5 cm (width) x 8 cm (length). 
	NOTE: For these tests, we use commercially produced colored 90 g/m2 (gsm) (24 lb) office paper of two different compositions: virgin and 30% recycled fibers (i.e., 0% and 30% post-consumer waste [PCW] recycled fiber content, respectively).</li>
</ol>
3. Setup of equipment and taking resonant cavity measurements
NOTE: The resonant cavity testing fixture consists of an air-filled standard WR-90 rectangular waveguide. The cavity has a 10 mm x 1 mm slot machined in the center for specimen insertion. The waveguide is terminated on both ends by the WR-90 to coax adapters that connect the cavity with a microwave network analyzer via semi-rigid coaxial cables. The coupling adapters are nearly cross polarized with respect to the waveguide polarization angle, which creates sharp impedance discontinuities at both waveguide ends and consequently the cavity walls. The polarization angle is about 87&#176;, which is suf&#64257;cient to achieve optimal power loading into cavity while maximizing the quality factor. The quality factor, Q0, and the resonant frequency, f0, of the empty cavity at the third odd resonant mode TE103 at which we make the measurements are 3.200 and 7.435 GHz respectively. The measurements are performed in ambient laboratory conditions by following the protocol listed below.
<ol>
	<li>Record the temperature and relative humidity and take the initial reading of the quality factor Q0, and the resonant frequency f0 of the empty cavity.</li>
	<li>Position the specimen secured in the sample holder above the slot at the center of the cavity. During the measurements, the specimen is inserted into cavity through this slot in steps of increasing volume Vx= hx&#183;w&#183;t, where hx is the specimen length inserted into cavity, and w and t are the specimen width and thickness respectively.</li>
	<li>Using the Vernier caliper on the sample mount, insert the sample into the cavity by &#916;hx = 50 &#181;m increments and take readings of the quality factor and resonant frequency at each step until the sample has been lowered 10 mm (1 cm) into the cavity.</li>
	<li>Retract the sample from the interior at the same increments of 50 &#181;m and take readings of the quality factor and resonant frequency until the sample has been fully retracted.</li>
	<li>Store the sample between glass slides and return them to nitrogen atmosphere.</li>
	<li>The dielectric loss, &#949;&#34;, of the paper samples is obtained from the slop of the perturbation (Equation 1). Optionally, the dielectric constant, &#949;&#39;&#160;can be obtained from the measured Vx, and the resonant frequency fx by solving the perturbation equations for (&#949;&#39;&#160;&#8211; 1) as described in elsewhere18,19,20.</li>
</ol>

<ol>
	<li>Marinissen, E. J., Zorian, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Test Conference, 2009. ITC 2009. International. , 1-11 (2009).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> TAPPI/ANSI Method T 401 om-15, Fiber analysis of paper and paperboard. , (2015).</li><li>Jablonsky, M., 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=Cellulose+Fibre+Identification+through+Color+Vectors+of+Stained+Fibre.">Cellulose Fibre Identification through Color Vectors of Stained Fibre.</a> BioResources. 10 (3), 5845-5862 (2015).</li><li>El Omari, H., Zyane, A., Belfkira, A., Taourirte, M., Brouillette, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dielectric+Properties+of+Paper+Made+from+Pulps+Loaded+with+Ferroelectric+Particles.">Dielectric Properties of Paper Made from Pulps Loaded with Ferroelectric Particles.</a> Journal of Nanomaterials. 2016, 1-10 (2016).</li><li>Sahin, H. 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This is a contribution of the National Institute of Standards and Technology, and not subject to copyright. Certain commercial equipment, instruments, or materials are identified in this report to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology or the United States Government Publishing Office, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose. The authors have nothing to disclose.

We have shown elsewhere that the presence of lignin content of fibers does significantly alter the dielectric behavior of manufactured papers15. Speciation is not only important in the QA/QC testing of modern papers but of great interest in the study of historical papers which were predominantly manufactured from non-wood plant sources, such as bamboo, hemp, flax, and papyrus. As shown in Figure 7, our technique can distinguish between non-wood plant sources (100% cot...

Paper is a sheeted, heterogenous, manufactured product comprised of cellulosic fibers, sizing agents, inorganic fillers, colorants, and water. The cellulose fibers may originate from a variety of plant sources; the raw material is then broken down through a combination of physical and/or chemical treatments to produce a workable pulp consisting primarily of cellulose fibers. The cellulose in the paper product may also be recovered secondary, or recycled fiber1. The TAPPI Method T 401, &#34;Fiber analysis of paper and paperboard,&#34;&#160;is currently the state of the art method for identifying fiber types and their ratios present within a paper sample and is utilized by many communities2. It is a manual, colorimetric technique reliant on the visual acuity of a specially trained human analyst to discern the constituent fiber types of a paper sample. Furthermore, sample preparation for the TAPPI 401 method is laborious and time consuming, requiring physical destruction and chemical degradation of the paper sample. Staining with specially prescribed reagents renders fiber samples subject to the effects of oxidation, making it difficult to archive samples for preservation or specimen banking. Thus, the results from TAPPI Method T 401 are subject to human interpretation and are directly dependent upon the visual discernment of an individual analyst, which varies based upon that individual&#8217;s level of experience and training, leading to inherent errors when comparing results between and within sample sets. Multiple sources of imprecision and inaccuracy are present as well3. Additionally, the TAPPI method is incapable of determining the quantity of secondary fiber or the relative age of paper samples4,5.
In contrast, the resonant cavity dielectric spectroscopy (RCDS) technique we describe in this article offers analytical capabilities that are well-suited for paper examinations. Dielectric spectroscopy probes the relaxation dynamics of dipoles and mobile charge carriers within a matrix in response to rapidly changing electromagnetic fields, such as microwaves. This involves molecular rotational reorientation, making RCDS particularly well-suited to examine the dynamics of molecules in confined spaces, such as the water adsorbed on the cellulose fibers imbedded within a sheet of paper. By using water as a probe molecule, RCDS simultaneously can extract information on the chemical environment and physical conformation of the cellulose polymer.
The chemical environment of the cellulose fibers influences the extent of hydrogen bonding with water molecules, hence the ease of motion in response to the fluctuating electromagnetic fields. The cellulosic environment is determined, in part, by the concentrations of hemicellulose and lignin in the paper analyte. Hemicellulose is a hydrophilic branched polymer of pentoses, while lignin is a hydrophobic, cross-linked, phenolic polymer. The amounts of hemicellulose and lignin in a paper fiber are a consequence of the paper-making process. Adsorbed water in paper partitions between the hydrophilic sites, and the hydrogen bonding within the cellulose polymer, especially with the adsorbed water molecules, influences the level of cross-linking within the cellulose structure, the level of polarizability, and the architecture of pores within the cellulose polymer5. The total dielectric response of a material is a vector sum of all the dipole moments within the system and can be distinguished via dielectric spectroscopy through the use of effective medium theories6,7. Similarly, the capacitance of a dielectric material is inversely proportional to its thickness; hence, resonant cavity dielectric spectroscopy is ideal to study sample-to-sample thickness reproducibility of ultra-thin films materials such as paper8,9,10. While there is a significant body of work pertaining to the use of dielectric spectroscopy techniques to study wood and cellulose products, the scope of those studies has been limited to paper manufacturability issues11,12,13. We have taken advantage of the anisotropic nature of paper to demonstrate the application of RCDS to testing paper beyond moisture and mechanical properties14,15,16 and to show that it yields numerical data that can be used in quality assurance techniques such as gauge capability studies and real-time statistical process control (SPC). The method also has inherent forensic capabilities and can be used to quantitatively confront environmental sustainability concerns, support economic interests, and detect altered and counterfeit documents.
Resonant cavity dielectric spectroscopy (RCDS) theory and technique 
RCDS is one of several dielectric spectroscopy techniques available17; it was chosen specifically because it is non-contact, non-destructive, and experimentally simple in comparison to other methods of dielectric spectroscopy. In contrast to other analytical techniques used to study the properties of paper, RCDS eliminates the need for duplicate sets of measurements to account for the two sides of a sample sheet18. The resonant microwave cavity technique has the advantage of being sensitive to both the surface and bulk conductivity. For example, the surface conductance of a sample material is determined by tracking a change in the quality factor (Q-Factor) of the cavity as a specimen is progressively inserted into the cavity in quantitative correlation with the specimen&#8217;s volume18,19,20. Conductivity can be obtained by simply dividing surface conductance by the specimen thickness. The surface conductance of a thin, sheeted material like paper functions as a proxy for the dielectric profile of a material under test (MUT), as it is directly proportional to the dielectric loss, &#949;&#34;, of the MUT18,19,20. Dielectric loss is an indication of how much heat is dissipated by a dielectric material when an electric field is applied across it; materials with greater conductance will have a higher dielectric loss value than less conductive materials.
Experimentally, the dielectric loss, &#949;&#34;, associated with the specimen&#39;s surface is extracted from the rate of decrease of cavity resonance quality factor (Q) (i.e., energy loss), with increasing volume of specimen19. The Q is determined at the resonant frequency f from the 3 dB width, &#916;f, of the resonant peak at the resonant frequency f, Q = &#916;f /f. This relation is quantitatively correlated with the slope of the line given by Equation 1 below, <img alt="Equation 1" src="/files/ftp_upload/59991/59991eq1.jpg" /> where &#160;represents the difference of the reciprocal of the Q-factor of the specimen from the Q-factor of the empty cavity, <img alt="Equation 2" src="/files/ftp_upload/59991/59991eq2.jpg" /> is the ratio of the volume of the inserted specimen to the volume of the empty cavity, and the line intercept, b&#34;, accounts for the non-uniform field in the specimen, as shown in Figure 119.
<img alt="Equation 3" src="/files/ftp_upload/59991/59991eq3.jpg" />&#160; &#160; (Equation 1)
In this article, we illustrate the broad utility of this technique by determining the ratios of fiber species (speciation), determining the relative age of naturally and artificially aged papers, and quantifying the recycled fiber content of white office copier paper analytes. Whereas the RCDS technique may be suitable for studying other topics, such as aging issues in paper insulation in electric power apparatus, such studies are outside the scope of the current work but would be interesting to pursue in the future.

<table><tbody><tr><td>commercially produced colored office paper&amp;nbsp;</td><td>Neenah Paper</td><td></td><td>Purchased from Staples</td></tr><tr><td>Q-Lab QUV accelerated weathering chamber</td><td>Q-Lab Corporation, Westlake, OH</td><td></td><td></td></tr><tr><td>X-Rite eXact&amp;nbsp;</td><td>X-Rite, Inc., Grand Rapids, MI</td><td></td><td></td></tr><tr><td>Agilent N5225A network analyzer&amp;nbsp;</td><td>Agilent Technologies, Santa Rosa, CA</td><td></td><td></td></tr><tr><td>WR90 rectangular waveguide&amp;nbsp;</td><td>Agilent Technologies, Santa Rosa, CA</td><td></td><td>R 100 (a = 10.16 mm, b = 22.86 mm, l&lt;sub&gt;z&lt;/sub&gt; =127.0mm)&amp;nbsp;</td></tr><tr><td>JMP data analysis software</td><td>SAS, Cary, NC</td><td></td><td></td></tr></tbody></table>

method development for contactless resonant cavity dielectric spectroscopic studies of cellulosic paper

The current analytical techniques for characterizing printing and graphic arts substrates are largely ex situ and destructive. This limits the amount of data that can be obtained from an individual sample and renders it difficult to produce statistically relevant data for unique and rare materials. Resonant cavity dielectric spectroscopy is a non-destructive, contactless technique which can simultaneously interrogate both sides of a sheeted material and provide measurements which are suitable for statistical interpretations. This offers analysts the ability to quickly discriminate between sheeted materials based on composition and storage history. In this methodology article, we demonstrate how contactless resonant cavity dielectric spectroscopy may be used to differentiate between paper analytes of varying fiber species compositions, to determine the relative age of the paper, and to detect and quantify the amount of post-consumer waste (PCW) recycled fiber content in manufactured office paper.

Rationale for choosing the 60&#176; strip angle 
The cut orientation of the test sample influences the magnitude of the dielectric response, as shown in the graph in Figure 2. In initial experiments, test strips were cut from the orthogonal angles of the sheet, as is standard practice for measuring physical properties in paper science; however, strips cut from non-orthogonal angles along the paper sheet have provided the greatest resolution between paper types, particul...

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Method Development for Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper

A protocol for the non-destructive analysis of the fiber content and relative age of paper.

The current analytical techniques for characterizing printing and graphic arts substrates are largely ex situ and destructive. This limits the amount of ...

method-development-for-contactless-resonant-cavity-dielectric

Universidad de Cartagena UDEC

Research

JoVE Journal

Engineering

6.0K Views.  United States Government Publishing Office. A protocol for the non-destructive analysis of the fiber content and relative age of paper.

Video: Method Development for Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper

Covalent Binding of Antibodies to Cellulose Paper Discs and Their Applications in Naked-eye Colorimetric Immunoassays

This report presents two methods for the covalent immobilization of capture antibodies on cellulose filter paper grade No. 1 (medium-flow filter paper) discs and grade No. 113 (fast-flow filter paper) discs. These cellulose paper discs were grafted with amine functional groups through a silane coupling technique before the antibodies were immobilized on them. Periodate oxidation and glutaraldehyde cross-linking methods were used to graft capture antibodies on the cellulose paper discs. In order to ensure the maximum binding capacity of the capture antibodies to their targets after immobilization, the effects of various concentrations of sodium periodate, glutaraldehyde, and capture antibodies on the surface of the paper discs were investigated. The antibodies that were coated on the amine-functionalized cellulose paper discs through a glutaraldehyde cross-linking agent showed enhanced binding activity to the target when compared to the periodate oxidation method. IgG (in mouse reference serum) was used as a reference target in this study to test the application of covalently immobilized antibodies through glutaraldehyde. A new paper-based, enzyme-linked immunosorbent assay (ELISA) was successfully developed and validated for the detection of IgG. This method does not require equipment, and it can detect 100 ng/ml of IgG. The fast-flow filter paper was more sensitive than the medium-flow filter paper. The incubation period of this assay was short and required small sample volumes. This naked-eye, colorimetric immunoassay can be extended to detect other targets that are identified with conventional ELISA.

In this manuscript, periodate oxidation and glutaraldehyde cross-linking methods for covalent immobilization of antibodies on paper discs are presented. The binding activity of immobilized antibodies was evaluated. Based on these results, a glutaraldehyde cross-linking method was used to develop a novel paper-based immunoassay for immunoglobulin G (IgG) detection.

This report presents two methods for the covalent immobilization of capture antibodies on cellulose filter paper grade No. 1 (medium-flow filter paper) ...

Biochemistry

Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall.

The objective of this research was to form synthetic plant cell wall tissue using layer-by-layer assembly of nanocellulose fibrils and isolated lignin assembled from dilute aqueous suspensions.&#160; Surface measurement techniques of quartz crystal microbalance and atomic force microscopy were used to monitor the formation of the polymer-polymer nanocomposite material.

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and ...

Chemistry

Development of a 3D Graphene Electrode Dielectrophoretic Device

The design and fabrication of a novel 3D electrode microdevice using 50 &#181;m thick graphene paper and 100 &#181;m double sided tape is described. The protocol details the procedures to construct a versatile, reusable, multiple layer, laminated dielectrophoresis chamber. Specifically, six layers of 50 &#181;m x&#160;0.7 cm x&#160;2 cm graphene paper and five layers of double sided tape were alternately stacked together, then clamped to a glass slide. Then a 700 &#956;m diameter micro-well was drilled through the laminated structure using a computer-controlled micro drilling machine. Insulating properties of the tape layer between adjacent graphene layers were assured by resistance tests. Silver conductive epoxy connected alternate layers of graphene paper and formed stable connections between the graphene paper and external copper wire electrodes. The finished device was then clamped and sealed to a glass slide. The electric field gradient was modeled within the multi-layer device. Dielectrophoretic behaviors of 6 &#956;m polystyrene beads were demonstrated in the 1 mm deep micro-well, with medium conductivities ranging from 0.0001 S/m to 1.3 S/m, and applied signal frequencies from 100 Hz to 10 MHz. Negative dielectrophoretic responses were observed in three dimensions over most of the conductivity-frequency space and cross-over frequency values are consistent with previously reported literature values. The device did not prevent AC electroosmosis and electrothermal flows, which occurred in the low and high frequency regions, respectively. The graphene paper utilized in this device is versatile and could subsequently function as a biosensor after dielectrophoretic characterizations are complete.

A microdevice with high throughput potential is used to demonstrate three-dimensional (3D) dielectrophoresis (DEP) with novel materials. Graphene nanoplatelet paper and double sided tape were alternately stacked; a 700 &#956;m micro-well was drilled transverse to the layers. DEP behavior of polystyrene beads was demonstrated in the micro-well.

The design and fabrication of a novel 3D electrode microdevice using 50 &#181;m thick graphene paper and 100 &#181;m double sided tape is described. The ...

Combining Raman Imaging and Multivariate Analysis to Visualize Lignin, Cellulose, and Hemicellulose in the Plant Cell Wall

The application of Raman imaging to plant biomass is increasing because it can offer spatial and compositional information on aqueous solutions. The analysis does not usually require extensive sample preparation; structural and chemical information can be obtained without labeling. However, each Raman image contains thousands of spectra; this raises difficulties when extracting hidden information, especially for components with similar chemical structures. This work introduces a multivariate analysis to address this issue. The protocol establishes a general method to visualize the main components, including lignin, cellulose, and hemicellulose within the plant cell wall. In this protocol, procedures for sample preparation, spectral acquisition, and data processing are described. It is highly dependent upon operator skill at sample preparation and data analysis. By using this approach, a Raman investigation can be performed by a non-specialist user to acquire high-quality data and meaningful results for plant cell wall analysis.

This protocol aims to present a general method to visualize lignin, cellulose, and hemicellulose in plant cell walls using Raman imaging and multivariate analysis.

The application of Raman imaging to plant biomass is increasing because it can offer spatial and compositional information on aqueous solutions. The ...

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. ...

Non-contact, Label-free Monitoring of Cells and Extracellular Matrix using Raman Spectroscopy

Non-destructive, non-contact and label-free technologies to monitor cell and tissue cultures are needed in the field of biomedical research.1-5 However, currently available routine methods require processing steps and alter sample integrity. Raman spectroscopy is a fast method that enables the measurement of biological samples without the need for further processing steps. This laser-based technology detects the inelastic scattering of monochromatic light.6 As every chemical vibration is assigned to a specific Raman band (wavenumber in cm-1), each biological sample features a typical spectral pattern due to their inherent biochemical composition.7-9 Within Raman spectra, the peak intensities correlate with the amount of the present molecular bonds.1 Similarities and differences of the spectral data sets can be detected by employing a multivariate analysis (e.g. principal component analysis (PCA)).10
Here, we perform Raman spectroscopy of living cells and native tissues. Cells are either seeded on glass bottom dishes or kept in suspension under normal cell culture conditions (37 &deg;C, 5% CO2) before measurement. Native tissues are dissected and stored in phosphate buffered saline (PBS) at 4 &deg;C prior measurements. Depending on our experimental set up, we then either focused on the cell nucleus or extracellular matrix (ECM) proteins such as elastin and collagen. For all studies, a minimum of 30 cells or 30 random points of interest within the ECM are measured. Data processing steps included background subtraction and normalization.

Raman spectroscopy is a suitable technique for the non-contact, label-free analysis of living cells, tissue-engineered constructs and native tissues. Source-specific spectral fingerprints can be generated and analyzed using multivariate analysis.

Non-destructive, non-contact and label-free technologies to monitor cell and tissue cultures are needed in the field of biomedical research.1-5 However, ...

Bioengineering

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail. A protocol for performing Flash-photolysis Time Resolved Microwave Conductivity (TRMC) experiments, a non-contact method of determining the conductivity of a material, is presented. A process for identifying the real and imaginary components of the complex conductivity by performing TRMC as a function of microwave frequency is given. Charge carrier dynamics are determined under different excitation regimes (including both power and wavelength). Techniques for distinguishing between direct and trap-mediated decay processes are presented and discussed. Results are modelled and interpreted with reference to a general kinetic model of photoinduced charge carriers in a semiconductor. The techniques described are applicable to a wide range of optoelectronic materials, including organic and inorganic photovoltaic materials, nanoparticles, and conducting/semiconducting thin films.

A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials ...

Raman and IR Spectroelectrochemical Methods as Tools to Analyze Conjugated Organic Compounds

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule on the vibrational level of energy. Raman and IR spectroelectrochemistry can be used for advanced characterization of the structural changes in the organic electroactive compounds. Here, the step-by-step analysis by means of Raman and IR spectroelectrochemistry is shown. Raman and IR spectroelectrochemical techniques provide complementary information about structural changes occurring during an electrochemical process, i.e. allows for the investigation of redox processes and their products. The examples of IR and Raman spectroelectrochemical analysis are presented, in which the products of the redox reactions, both in solution and solid state, are identified.

A protocol of step-by-step Raman and IR spectroelectrochemical analysis is presented.

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule ...

Fabrication of an Optical Cell Dryer for the Spectroscopic Analysis Cells

Optical cells, which are experimental instruments, are small, square tubes sealed on one side. A sample is placed in this tube, and a measurement is performed with a spectroscope. The materials used for optical cells generally include quartz glass or plastic, but expensive quartz glass is reused by removing substances, other than liquids, to be analyzed that adhere to the interior of the container. In such a case, the optical cells are washed with water or ethanol and dried. Then, the next sample is added and measured. Optical cells are dried naturally or with a manual hairdryer. However, drying takes time, which makes it one of the factors that increase the experiment time. In this study, the objective is to drastically reduce the drying time with a dedicated automatic dryer that can dry multiple optical cells at once. To realize this, a circuit was designed for a microcomputer, and the hardware using it was independently designed and manufactured.

A protocol for fabricating a device for simultaneously drying multiple optical cells is presented.

Optical cells, which are experimental instruments, are small, square tubes sealed on one side. A sample is placed in this tube, and a measurement is ...

Synthesis Method for Cellulose Nanofiber Biotemplated Palladium Composite Aerogels

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often result in fragile aerogels with poor shape control. The use of carboxymethylated cellulose nanofibers (CNFs) to form a covalently bonded hydrogel allows for the reduction of metal ions such as palladium on the CNFs with control over both nanostructure and macroscopic aerogel monolith shape after supercritical drying. Crosslinking the carboxymethylated cellulose nanofibers is achieved using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in the presence of ethylenediamine. The CNF hydrogels maintain their shape throughout synthesis steps including covalent crosslinking, equilibration with precursor ions, metal reduction with high concentration reducing agent, rinsing in water, ethanol solvent exchange, and CO2 supercritical drying. Varying the precursor palladium ion concentration allows for control over the metal content in the final aerogel composite through a direct ion chemical reduction rather than relying on the relatively slow coalescence of pre-formed nanoparticles used in other sol-gel techniques. With diffusion as the basis to introduce and remove chemical species into and out of the hydrogel, this method is suitable for smaller bulk geometries and thin films. Characterization of the cellulose nanofiber-palladium composite aerogels with scanning electron microscopy, X-ray diffractometry, thermal gravimetric analysis, nitrogen gas adsorption, electrochemical impedance spectroscopy, and cyclic voltammetry indicates a high surface area, metallized palladium porous structure.

A synthesis method for cellulose nanofiber biotemplated palladium composite aerogels is presented.The resulting composite aerogel materials offer potential for catalysis, sensing, and hydrogen gas storage applications.

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often ...