Broadband Dielectric Spectroscopy as a Potential Label-Free Method to Rapidly Verify Ultraviolet-C Radiation Disinfection.

Microwave (MW) sensing offers noninvasive, real-time detection of the electromagnetic properties of biological materials via the highly concentrated electromagnetic fields, for which advantages include wide bandwidth, small size, and cost-effective fabrication. In this paper, we present the application of MW broadband dielectric spectroscopy (BDS) coupled to a fabricated biological thin film for evaluating ultraviolet-C (UV-C) exposure effects. The BDS thin film technique could be deployed as a biological indicator for assessing whole-room UV-C surface disinfection. The disinfection process is monitored by BDS as changes in the electrical properties of surface-confined biological thin films photodegraded with UV-C radiation. Fetal bovine serum (FBS, a surrogate for protein) and bacteriophage lambda double-stranded deoxyribonucleic acid (dsDNA) were continuously monitored with BDS during UV-C radiation exposure. The electrical resistance of FBS films yielded promising yet imprecise readings, whereas the resistance of dsDNA films discernibly decreased with UV-C exposure. The observations are consistent with the expected photo-oxidation and photodecomposition of protein and DNA. While further research is needed to characterize these measurements, this study presents the first application of BDS to evaluate the electrical properties of solid-state biological thin films. This technique shows promise toward the development of a test method and a standard biological test to determine the efficacy of UV-C disinfection. Such a test with biological indicators could easily be applied to hospital rooms between patient occupancy for a multipoint evaluation to determine if a room meets a disinfection threshold set for new patients.

Models for an Ultraviolet-C Research and Development Consortium.

The development of an international, precompetitive, collaborative, ultraviolet (UV) research consortium is discussed as an opportunity to lay the groundwork for a new UV commercial industry and the supply chain to support this industry. History has demonstrated that consortia can offer promising approaches to solve many common, current industry challenges, such as the paucity of data regarding the doses of ultraviolet-C (UV-C, 200 nm to 280 nm) radiation necessary to achieve the desired reductions in healthcare pathogens and the ability of mobile disinfection devices to deliver adequate doses to the different types of surfaces in a whole-room environment. Standard methods for testing are only in the initial stages of development, making it difficult to choose a specific UV-C device for a healthcare application. Currently, the public interest in UV-C disinfection applications is elevated due to the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes the respiratory coronavirus disease 19 (COVID-19). By channeling the expertise of different UV industry stakeholder sectors into a unified international consortium, innovation in UV measurements and data could be developed to support test methods and standards development for UV healthcare equipment. As discussed in this paper, several successful examples of consortia are applicable to the UV industry to help solve these types of common problems. It is anticipated that a consortium for the industry could lead to UV applications for disinfection becoming globally prolific and commonplace in residential, work, business, and school settings as well as in transportation (bus, rail, air, ship) environments. Aggressive elimination of infectious agents by UV-C technologies would also help to reduce the evolution of antibiotic-resistant bacteria.

Ultraviolet Radiation Technologies and Healthcare-Associated Infections: Standards and Metrology Needs.

The National Institute of Standards and Technology (NIST) hosted an international workshop on ultraviolet-C (UV-C) disinfection technologies on January 14-15, 2020, in Gaithersburg, Maryland, in collaboration with the International Ultraviolet Association (IUVA). This successful public event, as evidenced by the participation of more than 150 attendees, with 65% from the ultraviolet technology industry, was part of an ongoing collaborative effort between NIST and the IUVA and its affiliates to examine the measurement and standards needs for pathogen abatement with UV-C in the healthcare whole-room environment. Prior to and since this event, stakeholders from industry, academia, government, and public health services have been collaboratively engaged with NIST to accelerate the development and use of accurate measurements and models for UV-C disinfection technologies and facilitate technology transfer. The workshop served as an open forum to continue this discussion with a technical focus centered on the effective design, use, and implementation of UV-C technologies for the prevention and treatment of healthcare-associated infections (HAIs) in complex hospital settings. These settings include patient rooms, operating rooms, common staging areas, ventilation systems, personal protective equipment, and tools for the reprocessing and disinfecting of instruments or devices used in medical procedures, such as catheters and ventilators. The critical need for UV-C technologies for disinfection has been amplified by the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), stimulating an even greater emphasis on identifying testing and performance metrology needs. This paper discusses these topics based on the international workshop and community activities since the workshop, including a public World-Wide-Web-based seminar with more than 500 registered attendees on September 30, 2020; an international conference on UV-C technologies for air and surface disinfection, December 8-9, 2020; and a webinar on returning to normalcy with the use of UV-C technologies, April 27 and 29, 2021. This article also serves as an introduction to a special section of the Journal of Research of the National Institute of Standards and Technology, where full papers address recent technical, noncommercial, UV-C technology and pathogen-abatement investigations. The set of papers provides keen insights from the vantage points of medicine and industry. Recent technical developments, successes, and needs in optics and photonics, radiation physics, biological efficacy, and the needs of future markets in UV-C technologies are described to provide a concise compilation of the community's efforts and the state of the field. Standards needs are identified and discussed throughout this special section. This article provides a summary of the essential role of standards for innovation and implementation of UV-C technology for improved patient care and public health.

A comparison of ion channel current blockades caused by individual poly(ethylene glycol) molecules and polyoxometalate nanoclusters.

Proteinaceous nanometer-scale pores have been used to detect and physically characterize many different types of analytes at the single-molecule limit. The method is based on the ability to measure the transient reduction in the ionic channel conductance caused by molecules that partition into the pore. The distribution of blockade depth amplitudes and residence times of the analytes in the pore are used to physically and chemically characterize them. Here we compare the current blockade events caused by flexible linear polymers of ethylene glycol (PEGs) and structurally well-defined tungsten polyoxymetallate nanoparticles in the nanopores formed by Staphylococcus aureusα-hemolysin and Aeromonas hydrophila aerolysin. Surprisingly, the variance in the ionic current blockade depth values for the relatively rigid metallic nanoparticles is much greater than that for the flexible PEGs, possibly because of multiple charged states of the polyoxymetallate clusters.

Ionizing radiation processing and its potential in advancing biorefining and nanocellulose composite materials manufacturing.

Nanocellulose is a high value material that has gained increasing attention because of its high strength, stiffness, unique photonic and piezoelectric properties, high stability and uniform structure. Through utilization of a biorefinery concept, nanocellulose can be produced in large volumes from wood at relatively low cost via ionizing radiation processing. Ionizing radiation causes significant break down of the polysaccharide and leads to the production of potentially useful gaseous products such as H2 and CO. The application of radiation processing to the production of nanocellulose from woody and non-wood sources, such as field grasses, bio-refining byproducts, industrial pulp waste, and agricultural surplus materials remains an open field, ripe for innovation and application. Elucidating the mechanisms of the radiolytic decomposition of cellulose and the mass generation of nanocellulose by radiation processing is key to tapping into this source of nanocelluose for the growth of nanocellulostic-product development. More importantly, understanding the structural break-up of the cell walls as a function of radiation exposure is a key goal and only through careful, detailed characterization and dimensional metrology can this be achieved at the level of detail that is needed to further the growth of large scale radiation processing of plant materials. This work is resulting from strong collaborations between NIST and its academic partners who are pursuing the unique demonstration of applied ionizing radiation processing to plant materials as well as the development of manufacturing metrology for novel nanomaterials.

Results of an interlaboratory study on the working curve in vat photopolymerization.

The working curve informs resin properties and print parameters for stereolithography, digital light processing, and other photopolymer additive manufacturing (PAM) technologies. First demonstrated in 1992, the working curve measurement of cure depth vs radiant exposure of light is now a foundational measurement in the field of PAM. Despite its widespread use in industry and academia, there is no formal method or procedure for performing the working curve measurement, raising questions about the utility of reported working curve parameters. Here, an interlaboratory study (ILS) is described in which 24 individual laboratories performed a working curve measurement on an aliquot from a single batch of PAM resin. The ILS reveals that there is enormous scatter in the working curve data and the key fit parameters derived from it. The measured depth of light penetration Dp varied by as much as 7x between participants, while the critical radiant exposure for gelation Ec varied by as much as 70x. This significant scatter is attributed to a lack of common procedure, variation in light engines, epistemic uncertainties from the Jacobs equation, and the use of measurement tools with insufficient precision. The ILS findings highlight an urgent need for procedural standardization and better hardware characterization in this rapidly growing field.

Measurement, standards, and data needs for CO2 capture materials: a critical review.

The commercial deployment of cost-effective carbon capture technology is hindered partially by the lack of a proper suite of materials-related measurements, standards, and data, which would provide critical information for the systematic design, evaluation, and performance of CO2 separation materials. Based on a literature search and conversations with the carbon capture community, we review the current status of measurements, standards, and data for the three major carbon capture materials in use today: solvents, solid sorbents, and membranes. We highlight current measurement, standards and data activities aimed to advance the development and use of carbon capture materials and major research needs that are critical to meet if innovation in carbon capture materials is to be achieved. The review reveals that although adsorbents are considered to have great potential to reduce carbon capture cost, there is no consensus on the experimental parameters to be used for evaluating sorbent properties. Another important finding is the lack of in situ experimental tools for the structural characterization of solid porous materials during CO2 adsorption, and computational methods that would enable a materials-by-design approach for their development.

Characterizing light engine uniformity and its influence on liquid crystal display based vat photopolymerization printing.

Vat photopolymerization (VP) is a rapidly growing category of additive manufacturing. As VP methods mature the expectation is that the quality of printed parts will be highly reproducible. At present, detailed characterization of the light engines used in liquid crystal display (LCD)-based VP systems is lacking and so it is unclear if they are built to sufficiently tight tolerances to meet the current and/or future needs of additive manufacturing. Herein, we map the irradiance, spectral characteristics, and optical divergence of a nominally 405 nm LCD-based VP light engine. We find that there is notable variation in all of these properties as a function of position on the light engine that cause changes in extent of polymerization and surface texture. We further demonstrate through a derived photon absorption figure of merit and through printed test parts that the spatial heterogeneity observed in the light engine is significant enough to affect part fidelity. These findings help to explain several possible causes of variable part quality and also highlight the need for improved optical performance on LCD-based VP printers.

Polycyclic aromatic hydrocarbons (PAHs) in a coal tar standard reference material--SRM 1597a updated.

SRM 1597 Complex Mixture of Polycyclic Aromatic Hydrocarbons from Coal Tar, originally issued in 1987, was recently reanalyzed and reissued as SRM 1597a with 34 certified, 46 reference, and 12 information concentrations (as mass fractions) for polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic sulfur heterocycles (PASHs) including methyl-substituted PAHs and PASHs. The certified and reference concentrations (as mass fractions) were based on results of analyses of the coal tar material using multiple analytical techniques including gas chromatography/mass spectrometry on four different stationary phases and reversed-phase liquid chromatography. SRM 1597a is currently the most extensively characterized SRM for PAHs and PASHs.

Marine mammal blubber reference and control materials for use in the determination of halogenated organic compounds and fatty acids.

The National Institute of Standards and Technology (NIST) has a diverse collection of control materials derived from marine mammal blubber, fat, and serum. Standard Reference Material (SRM) 1945 Organics in Whale Blubber was recertified for polychlorinated biphenyl (PCB) congeners, organochlorine pesticides, and polybrominated diphenyl ether (PBDE) congeners. SRM 1945 has also been assigned mass fraction values for compounds not frequently determined in marine samples including toxaphene congeners, coplanar PCBs, and methoxylated PBDE congeners which are natural products. NIST also has assigned mass fraction values, as a result of interlaboratory comparison exercises, for PCB congeners, organochlorine pesticides, PBDE congeners, and fatty acids in six homogenate materials produced from marine mammal blubber or serum. The materials are available from NIST upon request; however, the supply is very limited for some of the materials. The materials include those obtained from pilot whale blubber (Homogenates III and IV), Blainville's beaked whale blubber (Homogenate VII), polar bear fat (Homogenate VI), and California sea lion serum (Marine Mammal Control Material-1 Serum) and blubber (Homogenate V).

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.

Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper Aging.

The current analytical techniques for characterizing printing and graphic arts substrates, particularly those used to date and authenticate provenance, are destructive. This limits the amount of data that can be captured from an individual sample. For samples being evaluated in forensic and archeological investigations, any loss or degradation of the materials is undesirable. Furthermore, it is difficult to produce statistically relevant data for such analytes. We have shown elsewhere that a contactless microwave resonant cavity dielectric spectroscopy technique can discriminate between paper samples made from different plant fiber species based on their lignin content. In this publication, we demonstrate the utility of the contactless resonant cavity dielectric spectroscopy (RCDS) technique in the characterization of naturally and artificially aged paper samples. Based on our experimental results, we suggest that the technique could be used in forensic and archeological investigations of unique paper products.

Innovative Approaches to Combat Healthcare-Associated Infections Using Efficacy Standards Developed Through Industry and Federal Collaboration.

Nation-wide, healthcare-associated infections (HAIs) infect one in every 25 hospital patients, account for more than 100,000 deaths and increase medical costs by around $96-147B, each year. Ultraviolet-C (UV-C) antimicrobial devices are shown to reduce the incidence of many of these HAIs by 35% or more, through the deactivation of the pathogen's DNA chain following irradiation with a wavelength of ~254 nm. This irradiation does not kill the cells, per se but effectively prevents the cells from multiplying. Clinical case reductions of 30-70% in Clostridium difficile (C. diff.) have been reported with similar results for methicillin-resistant Staphylococcus aureus (MRSA), and others. The methodology works, but, the adoption of UV-C technology by the healthcare industry has been sporadic. This is largely due to the lack of definitive knowledge and uniform performance standards or measures for efficacy to help healthcare managers make informed, credible investment decisions. The leveling of the playing field with scientifically certifiable data of the efficacy of antimicrobial devices will enhance acceptance by the healthcare industry and public, at large, as well as facilitate science-based decision making. The National Institute of Standards and Technology (NIST) has engaged with the International Ultra Violet Association (IUVA) and its member companies and affiliates to explore ways to develop needed standards, determine appropriate testing protocols, and transfer the technology to help to reduce these inharmonious market conditions. Collaborative efforts are underway to develop science-based answers to the healthcare industry's questions surrounding standards and measures of device disinfection efficacy, as well as reliability, operations and durability. These issues were recently discussed at the IUVA 2018 America's Conference in Redondo Beach, CA in several panel sessions. A major output of the sessions was the formation of a formal IUVA Working Group for the development of antimicrobial standards and initiatives for the healthcare industry. The goal of this working group is to provide global guidance, with specific programs and deliverables, on the use of UV technologies and standards to combat HAIs and to further the stated aims of the IUVA on its outreach to the healthcare industry. This paper reviews the strong collaboration between NIST and its industry partners pursuing the development of standards, guidelines and guidance documents related to healthcare applications that include standard methods for validating performance of UV devices and test guidelines for efficacy measurements. In addition, an overview of the issues, problems, and a summary of the needs confronting future growth and success of the UV industry in the Nation's healthcare application space is provided.

Dielectric spectroscopic studies of biological material evolution and application to paper.

Current product composition and quality test methods for the paper and pulp industry are mainly based on manual ex-situ wet-bench chemistry techniques. For example, the standard method for determining the furnish of paper, TAPPI T 401 "Fiber analysis of paper and paperboard," relies on the experience and visual acuity of a specially trained analyst to determine the individual plant species present and to quantify the amount of each constituent fiber type in a sheet of paper. Thus, there is a need for a fast, nondestructive analytical technique that leverages intrinsic attributes of the analytes. In this paper, we demonstrate an application of dielectric spectroscopy (DS) as a potential metrology to differentiate between nonwood pulp and wood pulp fibers. This in-situ, noncontact and nondestructive assessment method has inherent forensic capabilities and is also amiable to quality assurance techniques such as gauge capability studies and real-time statistical process control (SPC). APPLICATION: The dielectric spectroscopy results presented in this paper can nondestructively determine the amount of lignin in paper products and are in principle comparable to the performance specifications of the TAPPI Standard Test Method T 401 and should enable the sources of printing substrates to be both authenticated and validated in real time in a paper testing laboratory environment.

Mechanisms and Characterization of the Pulsed Electron-Induced Grafting of Styrene onto Poly(tetrafluoroethylene-co-hexafluoropropylene) to Prepare a Polymer Electrolyte Membrane.

During the pulsed-electron beam direct grafting of neat styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) substrate, the radiolytically-produced styryl and carbon-centered FEP radicals undergo various desired and undesired competing reactions. In this study, a high-dose rate is used to impede the undesired free radical homopolymerization of styrene and ensure uniform covalent grafting through 125-µm FEP films. This outweighs the enhancement of the undesired crosslinking reactions of carbon-centered FEP radicals and the dimerization of the styryl radicals. The degree of uniform grafting through 125-µm FEP films increases from ≈8%, immediately after pulsed electron irradiation to 33% with the subsequent thermal treatment exceeding the glass transition temperature of FEP of 39°C. On the contrary, steady-state radiolysis using 60Co gamma radiolysis, shows that the undesired homopolymerization of the styrene has become the predominant reaction with a negligible degree of grafting. Time-resolved fast kinetic measurements on pulsed neat styrene show that the styryl radicals undergo fast decays via propagation homopolymerization and termination reactions at an observed reaction rate constant of 5 × 108 l · mol-1 · s-1. The proton conductivity of 25-µm film at 80°C is 0.29 ± 0.01 s cm-1 and 0.007 s cm-1 at relative humidity of 92% and 28%, respectively. The aims of this work are: 1. electrolyte membranes are prepared via grafting initiated by a pulsed electron beam; 2. postirradiation heat-treated membranes are uniformly grafted, ideal for industry; 3. High dose rate is the primary parameter to promote the desired reactions; 4. measurement of kinetics of undesired radiation-induced styrene homopolymerization; and 5. The conductivity of prepared membranes is on par or higher than industry standards.

Update on Bio-Refining and Nanocellulose Composite Materials Manufacturing.

Nanocellulose is a high value material that has gained increasing attention because of its high strength, stiffness, unique photonic and piezoelectric properties, high stability and uniform structure. One of the factors limiting the potential of nanocellulose and the vast array of potential new products is the ability to produce high-volume quantities of this nano-material. However, recent research has demonstrated that nanocellulose can be efficently produced in large volumes from wood at relatively low cost by the incorporation of ionizing radiation in the process stream. Ionizing radiation causes significant break down of the polysaccharides and leads to the production of potentially useful gaseous products such as H2 and CO. Ionizing radiation processing remains an open field, ripe for innovation and application. This presentation will review the strong collaboration between the National Institute of Standards and Technology (NIST) and its academic partners pursuing the demonstration of applied ionizing radiation processing to plant materials for the manufacturing and characterization of novel nanomaterials.

Preparation of Reference Material 8504, Transformer Oil.

A new reference material (RM), RM 8504, has been prepared for use as a diluent oil with Aroclors in transformer oil Standard Reference Materials (SRMs) 3075 to 3080 and SRM 3090 when developing and validating methods for the determination of polychlorinated biphenyls (PCBs) as Aroclors in transformer oil or similar matrices. SRMs 3075-3080 and SRM 3090 consist of individual Aroclors in the same transformer oil that was used to prepare RM 8504. A unit of RM 8504 consists of one bottle containing approximately 100 mL of transformer oil. No additional constituents have been added to the oil.

Standard Reference Materials (SRMs) for the Calibration and Validation of Analytical Methods for PCBs (as Aroclor Mixtures).

Six Standard Reference Materials (SRMs®) have been prepared by the National Institute of Standards and Technology (NIST) for the determination of PCBs as different Aroclor mixtures in methanol. Six additional SRMs of the same Aroclors in transformer oil have also been prepared. Specifically, solutions of Aroclors 1016, 1232, 1242, 1254, and 1260 have been gravimetrically prepared (individually) in methanol and transformer oil, mixed, and transferred to amber glass ampoules in approximately 1.2 mL aliquots. Gas chromatography with electron capture detection (GC-ECD) has been used to verify the gravimetric data for each solution and transformer oil SRM. Liquid chromatography was used for the isolation of the Aroclors from the transformer oil SRMs prior to GC-ECD analysis. Separate calibration solutions and oils were prepared with Aroclor levels similar to those in each methanol solution and transformer oil SRM and were processed alongside the samples. The GC-ECD response of each Aroclor was monitored relative to internal standards that were added to the complex mixtures for quantification. The gravimetric concentrations of Aroclors 1242 and 1254 in methanol were also examined by the same method of analysis (GC-ECD) using several different sources of Aroclors and two different capillary GC columns: a 5 % phenyl methylpolysiloxane phase and a relatively non-polar phase. The preparation of the materials, the gas chromatographic results, and the certified concentration values for each Aroclor SRM are described in this paper.

Evidence for a pore-filling mechanism in the adsorption of aromatic hydrocarbons to a natural wood char.

Sorption isotherms for five aromatic hydrocarbons were obtained with a natural wood char (NC1) and its residue after solvent extraction (ENC1). Substantial isotherm nonlinearity was observed in all cases. ENC1 showed higher BET surface area, higher nitrogen-accessible micropore volume, and lower mass of extractable organic chemicals, including quantifiable polycyclic aromatic hydrocarbons (PAHs),while the two chars showed identical surface oxygen/ carbon (O/C) ratio. For two chlorinated benzenes that normally condense as liquids at the temperatures used, sorption isotherms with NC1 and ENC1 were found to be statistically identical. For the solid-phase compounds (1,4-dichlorobenzene (1,4-DCB) and two PAHs), sorption was statistically higher with ENC1, thus demonstrating sorption effects due to both (1) authigenic organic content in the sorbentand (2)the sorbate's condensed state. Polanyi-based isotherm modeling, pore size measurements, and comparisons with activated carbon showthe relative importance of adsorptive pore filling and help explain results. With both chars, maximum sorption increased in the order of decreasing molecular diameter: phenanthrene < naphthalene < 1,2-dichlorobenzene/1,2,4-trichlorobenzene < 1,4-DCB. Comparison of 1,4- and 1,2-DCB shows that the critical molecular diameter was apparently more important than the condensed state, suggesting that 1,4-DCB sorbed in the liquid state for ENC1.

Development of a house dust standard reference material for the determination of organic contaminants.

National-level health survey studies, such as the National Human Exposure Assessment Survey field program, have targeted the determination of organic contaminants in house dust in an effort to characterize human exposure in the domestic environment. As the effort to further understand human health effects in relation to organic contaminants associated with indoor dust accelerates, the need for an indoor dust Standard Reference Material (SRM) that is characterized for organic contaminants has become critical. To meet this need, a new organic contaminant house dust SRM has been developed. SRM 2585 Organic Contaminants in House Dust is intended for use in evaluating analytical methods for the determination of selected polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyl (PCB) congeners, chlorinated pesticides, and polybrominated diphenyl ether (PBDE) congeners in house dust and similar matrices. The material may also be useful for evaluation and comparison of methods or instruments used for sampling in the indoor environment. Moreover, because of the material's extensive characterization (140 organic contaminant concentrations), the material may be useful in toxicity studies related to indoor air (in vitro or in vivo). The determination of the concentrations of PAHs (including alkyl-PAHs and PAHs with molecular mass 300 and 302), PCBs, and chlorinated pesticides is reported here, and these results are compared to values reported in the literature for house dust.