What is an "ArchintorTM?" A paradigm shift in teaching, facilitation, and learning: The impact of different types of coursework expectations on classroom network structures.

Hypothetically, a student could attend a class, listen to lectures, and pass the class without knowing or interacting with other students. What happens to the network when the classroom expectations change? For example, there is a coursework expectation that students exchange contact information, or the instructor uses collaborative learning practices. Or what if the principal investigator (PI) of a scientific team goes on a sabbatical? This study uses the framework of classrooms because of their relatability across science. We asked how do different instructor coursework expectations change network structures within a classroom or other learning environments? A social network survey was administered at the start and end of the semester (pre- and post-test) in six university sociology classrooms to explore how expectations impacted the communication and learning networks. We found practical changes in course expectations impact the communication and learning networks, suggesting that instructors, facilitators, and others could be the archintorTM (architect+instructor+facilitator) of the network. Understanding that expectations can impact a network's structure marks a paradigm shift in educational assessment approaches. If the archintorTM has identified the "optimal" network structure, then their task is to design expectations that result in specific interactions that ultimately improve student achievement and success. This work provides recommendations for classroom archintorsTM to create the most impactful classroom networks. Future research should extend beyond education and classroom networks and identify the best or desired networks in other areas like public policy, urban planning, and more. If these "optimal" networks were identified, an archintorTM could design a social network to solve wicked problems, manage a crisis, and create social change.

Perspectives on antibacterial performance of silver nanoparticle-loaded three-dimensional polymeric constructs.

Silver nanoparticle (AgNP)-loaded polymeric constructs are widely investigated for potential applications as drug delivery systems, wound dressings, and antibiofouling biomaterials. Herein, the authors present several methods for fabricating such materials and evaluate their efficacy against Escherichia coli. H2O(v) plasma surface modification is employed to enhance material surface wettability (explored by water contact angle goniometry) and nanoparticle incorporation. Compositional analyses reveal that incorporation of AgNPs on the surface and bulk of the materials strongly depends on the fabrication methodology. More importantly, the nature of AgNP incorporation into the polymer has direct implications on the biocidal performance resulting from the release of Ag+. The materials fabricated herein fell significantly short of healthcare standards with respect to antimicrobial behavior, and, in comparing their results to numerous literature studies, the authors identified a glaring disparity in the way such results are often described. Thus, this work also contains a critical evaluation of the literature, highlighting select poor-performing materials to demonstrate several shortcomings in the quantitative analysis and reporting of the antibacterial efficacy of AgNP-loaded materials. Ultimately, recommendations for best practices for better evaluation of these constructs toward improved antibacterial efficacy in medical settings are provided.

Time of flight secondary ion mass spectrometry-A method to evaluate plasma-modified three-dimensional scaffold chemistry.

Biopolymers are used extensively in the manufacture of porous scaffolds for a variety of biological applications. The surfaces of these scaffolds are often modified to encourage specific interactions such as surface modification of scaffolds to prevent fouling or to promote a cell supportive environment for tissue engineering implants. However, few techniques can effectively characterize the uniformity of surface modifications in a porous scaffold. By filling the scaffold pores through polymer embedding, followed by analysis with imaging time-of-flight secondary ion mass spectrometry (ToF-SIMS), the distribution and composition of surface chemical species though complex porous scaffolds can be characterized. This method is demonstrated on poly(caprolactone) scaffolds modified with a low-fouling plasma-deposited coating from octafluoropropane via plasma enhanced chemical vapor deposition. A gradient distribution of CF+/CF3+ is observed for scaffolds plasma treated for 5 min, whereas a 20 min treatment results in more uniform distribution of the surface modification throughout the entire scaffold. The authors expect this approach to be widely applicable for ToF-SIMS analysis of scaffolds modified by multiple plasma processing techniques as well as alternative surface modification approaches.

Investigation of Antibacterial 1,8-Cineole-Derived Thin Films Formed via Plasma-Enhanced Chemical Vapor Deposition.

The need for low-fouling coatings for biomedical devices has prompted considerable interest in antibacterial compounds from natural and sustainable sources, such as essential oils. Herein, a tea tree oil-based precursor, 1,8-cineole, is used to fabricate antimicrobial films (denoted ppCin) by plasma-enhanced chemical vapor deposition. Film properties were comprehensively characterized using a variety of surface and bulk analytical tools, and the plasma gas phase is assessed using optical emission spectroscopy, which can be correlated to ppCin film properties. Notably, film wettability increases linearly with plasma pressure, yielding water contact angles ranging from ∼50° to ∼90°. X-ray photoelectron spectroscopy reveals less oxygen is incorporated at higher pressures, likely arising from the lower density of OH(g) species. Further, we utilized H2O(v) plasma surface modification of the ppCin films to improve wettability and find this results in a substantial increase in surface oxygen content. To elucidate the role of film wettability and antibacterial properties, both as-deposited and H2O(v) plasma-modified films were exposed to Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus using glass slides and hydrocarbon films deposited from 1,7-octadiene as positive controls. Overall, bacteria attach to a similar extent on all films, including controls, yet only essential oil-based films significantly prevent biofilm formation (4-7% coverage compared to ∼40% for controls).

Using Fundamental Spectroscopy to Elucidate Kinetic and Energetic Mechanisms within Environmentally Relevant Inductively Coupled Plasma Systems.

Understanding energy distributions and kinetic processes in NxOy plasma systems is vital to realizing their potential in a range of applications, including pollution abatement. Energy partitioning between degrees of freedom and multiple molecules formed within NxOy plasma systems (N2, N2O, N2/O2) was investigated using both optical emission and broadband absorption spectroscopies. Specifically, we determined electron temperatures (Te) as well as rotational (TR) and vibrational (TV) temperatures for various N2 (B3Πg and C3Πu) and NO (X2Π and A2Σ+) states. TR and TV for both molecules (regardless of state) show a strong positive correlation with applied plasma power, as well as a negative correlation with system pressure. In all cases, TV values are significantly higher than TR for both species, suggesting vibrational modes are preferentially excited over rotational degrees of freedom. Time-resolved optical emission spectroscopy was utilized to determine rate constants, providing mechanistic insight and establishing the relationships between system parameters and plasma chemistry. Ultimately, the combination of these data allows us to glean information regarding both the kinetics and energetics of N2 and NO molecules formed within nitrogen- and oxygen-containing plasma systems for potential applications in gas remediation of pollutants.

The Effect of Ar/O2 and H2O Plasma Treatment of SnO2 Nanoparticles and Nanowires on Carbon Monoxide and Benzene Detection.

As the final piece of a broader study on structure-property performance of SnO2 sensors, this study examines the performance of sensors created from tin(IV) oxide (SnO2) nanowires and nanoparticles as a function of temperature for untreated (UT) devices as well as those treated using Ar/O2 and H2O plasmas. Nanoparticle and nanowire sensors were exposed to air, carbon monoxide (CO), or benzene (C6H6) to determine sensor response (Rair/Rgas) and sensitivity (Rair/Rgas > 1 or Rgas/Rair > 1). Although both Ar/O2 and H2O plasma modification minimally increase sensor sensitivity toward CO and C6H6 under most conditions, this study explores initial plasma parameters of a wide array of plasma precursors to better understand the materials properties and gas-phase species that lead to specific sensing capabilities. In particular, certain Ar/O2 and H2O plasma treatment conditions resulted in increased sensitivity over UT nanomaterials at 25 and 50 °C, but of greatest importance is the knowledge gained from the combined materials, gas-phase, and sensor performance analysis that provide greater insight for effectively selecting future materials and modification systems to achieve optimal gas sensor performance.

In-Depth View of the Structure and Growth of SnO2 Nanowires and Nanobrushes.

Strategic application of an array of complementary imaging and diffraction techniques is critical to determine accurate structural information on nanomaterials, especially when also seeking to elucidate structure-property relationships and their effects on gas sensors. In this work, SnO2 nanowires and nanobrushes grown via chemical vapor deposition (CVD) displayed the same tetragonal SnO2 structure as revealed via powder X-ray diffraction bulk crystallinity data. Additional characterization using a range of electron microscopy imaging and diffraction techniques, however, revealed important structure and morphology distinctions between the nanomaterials. Tailoring scanning transmission electron microscopy (STEM) modes combined with transmission electron backscatter diffraction (t-EBSD) techniques afforded a more detailed view of the SnO2 nanostructures. Indeed, upon deeper analysis of individual wires and brushes, we discovered that, despite a similar bulk structure, wires and brushes grew with different crystal faces and lattice spacings. Had we not utilized multiple STEM diffraction modes in conjunction with t-EBSD, differences in orientation related to bristle density would have been overlooked. Thus, it is only through a methodical combination of several structural analysis techniques that precise structural information can be reliably obtained.

Plasma-modified nitric oxide-releasing polymer films exhibit time-delayed 8-log reduction in growth of bacteria.

Tygon(®) and other poly(vinyl chloride)-derived polymers are frequently used for tubing in blood transfusions, hemodialysis, and other extracorporeal circuit applications. These materials, however, tend to promote bacterial proliferation which contributes to the high risk of infection associated with device use. Antibacterial agents, such as nitric oxide donors, can be incorporated into these materials to eliminate bacteria before they can proliferate. The release of the antimicrobial agent from the device, however, is challenging to control and sustain on timescales relevant to blood transport procedures. Surface modification techniques can be employed to address challenges with controlled drug release. Here, surface modification using H2O (v) plasma is explored as a potential method to improve the biocompatibility of biomedical polymers, namely, to tune the nitric oxide-releasing capabilities from Tygon films. Film properties are evaluated pre- and post-treatment by contact angle goniometry, x-ray photoelectron spectroscopy, and optical profilometry. H2O (v) plasma treatment significantly enhances the wettability of the nitric-oxide releasing films, doubles film oxygen content, and maintains surface roughness. Using the kill rate method, the authors determine both treated and untreated films cause an 8 log reduction in the population of both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Notably, however, H2O (v) plasma treatment delays the kill rate of treated films by 24 h, yet antibacterial efficacy is not diminished. Results of nitric oxide release, measured via chemiluminescent detection, are also reported and correlated to the observed kill rate behavior. Overall, the observed delay in biocidal agent release caused by our treatment indicates that plasma surface modification is an important route toward achieving controlled drug release from polymeric biomedical devices.

Modification of a commercial thromboelastography instrument to measure coagulation dynamics with three-dimensional biomaterials.

Three-dimensional synthetic constructs with complex geometries have immense potential for use in a multitude of blood-contacting applications. Understanding coagulation phenomena is arguably the most critical aspect for applications involving synthetic biomaterials; however, real-time evaluation of the clot formation while interfacing with these materials is difficult to achieve in a reproducible and robust manner. Here, work representing first steps toward addressing this deficit is presented, wherein modified consumables for a clinical instrument (a Thromboelastograph(®)) have been fabricated. Thromboelastography (TEG) measures viscoelastic properties throughout clot formation and therefore provides clinically relevant coagulation measurements in real time (i.e., kinetics and strength of clot formation). Through our modification, TEG consumables can readily accommodate three-dimensional materials (e.g., those for regenerative tissue applications). The authors performed proof-of-concept experiments using polymer scaffolds with a range of surface properties and demonstrated that variations in surface properties resulted in differences in blood plasma coagulation dynamics. For example, the maximum rate of thrombus generation ranged from 22.2 ± 2.2 (dyn/cm(2))/s for fluorocarbon coated scaffolds to 8.7 ± 1.0 (dyn/cm(2))/s for nitrogen-containing scaffolds. Through this work, the ability to make real-time coagulation activity measurements during constant coagulation factor interface with biomedically relevant materials is demonstrated.

Conformal encapsulation of three-dimensional, bioresorbable polymeric scaffolds using plasma-enhanced chemical vapor deposition.

Bioresorbable polymers such as poly(ε-caprolactone) (PCL) have a multitude of potential biomaterial applications such as controlled-release drug delivery and regenerative tissue engineering. For such biological applications, the fabrication of porous three-dimensional bioresorbable materials with tunable surface chemistry is critical to maximize their surface-to-volume ratio, mimic the extracellular matrix, and increase drug-loading capacity. Here, two different fluorocarbon (FC) precursors (octofluoropropane (C3F8) and hexafluoropropylene oxide (HFPO)) were used to deposit FC films on PCL scaffolds using plasma-enhanced chemical vapor deposition (PECVD). These two coating systems were chosen with the intent of modifying the scaffold surfaces to be bio-nonreactive while maintaining desirable bulk properties of the scaffold. X-ray photoelectron spectroscopy showed high-CF2 content films were deposited on both the exterior and interior of PCL scaffolds and that deposition behavior is PECVD system specific. Scanning electron microscopy data confirmed that FC film deposition yielded conformal rather than blanket coatings as the porous scaffold structure was maintained after plasma treatment. Treated scaffolds seeded with human dermal fibroblasts (HDF) demonstrate that the cells do not attach after 72 h and that the scaffolds are noncytotoxic to HDF. This work demonstrates conformal FC coatings can be deposited on 3D polymeric scaffolds using PECVD to fabricate 3D bio-nonreactive materials.

Challenges in the characterization of plasma-processed three-dimensional polymeric scaffolds for biomedical applications.

Low-temperature plasmas offer a versatile method for delivering tailored functionality to a range of materials. Despite the vast array of choices offered by plasma processing techniques, there remain a significant number of hurdles that must be overcome to allow this methodology to realize its full potential in the area of biocompatible materials. Challenges include issues associated with analytical characterization, material structure, plasma processing, and uniform composition following treatment. Specific examples and solutions are presented utilizing results from analyses of three-dimensional (3D) poly(ε-caprolactone) scaffolds treated with different plasma surface modification strategies that illustrate these challenges well. Notably, many of these strategies result in 3D scaffolds that are extremely hydrophilic and that enhance human Saos-2 osteoblast cell growth and proliferation, which are promising results for applications including tissue engineering and advanced biomedical devices.

Design and operation of a rotating drum radio frequency plasma reactor for the modification of free nanoparticles.

A rotating drum rf plasma reactor was designed to functionalize the surface of nanoparticles and other unusually shaped substrates through plasma polymerization and surface modification. This proof-of-concept reactor design utilizes plasma polymerized allyl alcohol to add OH functionality to Fe2O3 nanoparticles. The reactor design is adaptable to current plasma hardware, eliminating the need for an independent reactor setup. Plasma polymerization performed on Si wafers, Fe2O3 nanoparticles supported on Si wafers, and freely rotating Fe2O3 nanoparticles demonstrated the utility of the reactor for a multitude of processes. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to characterize the surface of the substrates prior to and after plasma deposition, and scanning electron microscopy was used to verify that no extensive change in the size or shape of the nanoparticles occurred because of the rotating motion of the reactor. The reactor design was also extended to a non-depositing NH3 plasma modification system to demonstrate the reactor design is effective for multiple plasma processes.

Effect of ion energies on the surface interactions of NO formed in nitrogen oxide plasma systems.

The contributions of various gas-phase species in surface reactions are of significant value to assess and improve catalytic substrates for abatement of vehicular emissions. The impact of ions on surface scatter of NO radicals is investigated with an aim toward improving and tailoring surfaces for the reduction or removal of nitrogen oxide (N(x)O(y)) species via inductively coupled plasmas (ICPs). Nascent ions are monitored via mass spectrometry and energy analysis for a variety of N(x)O(y) precursor gases. The total average ion energy ((total)) determined for all ions within each respective plasma system shows a strong positive correlation with applied rf power and a negative correlation with system pressure. The imaging of radicals interacting with surfaces (IRIS) technique was used to determine the role ions play in the surface scatter of NO radicals. The net effect of ions on substrate processing is largely dependent upon (total). Scatter coefficients (S), determined for ion-limited and ion-rich plasma systems were used to correlate (total) and scatter. The resultant effect is that ions play a substantial role in scatter of NO only when (total) > ~50 eV. The majority of systems studied contained ions below this energy threshold, suggesting knowledge of ion energies is integral to appropriately controlling the chemistry occurring between the gas-phase and surface.

Fast one-step method to synthesize TiO2 nanoparticle clusters for dye sensitized solar cells.

We have successfully designed a rapid method for producing dye sensitized solar cells (DSSC) using TiO2 films prepared by a modified dielectric barrier discharge jet (m-DBD jet) method which uses a DBD jet with elevated substrate temperatures from room temperature (RT) to 500 degrees C for approximately 10 min. This facile process has several advantages over other methods such as (1) eliminating additional coating and annealing steps, (2) creating films with high speed electron mobility via hierarchical pore clusters, and (3) allowing controlled TiO2 bandgap by N doping using atmospheric nitrogen instead of supplying N2 gas. Depending on reaction conditions, the resulting nanostructured materials have various sizes and shapes, with those deposited at the highest substrate temperatures displaying hierarchical walnut-shaped morphology as revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A possible growth mechanism of TiO2 nanoparticle clusters (TNC) is presented and discussed. Finally, this m-DBD jet method produces TNC films that exhibit approximately 4 times higher photo-conversion efficiency than the nanoparticle films by the unmodified DBD jet method.

Contributions of CF and CF2 Species to fluorocarbon film composition and properties for C(x)F(y) plasma-enhanced chemical vapor deposition.

Inductively-coupled C(x)F(y) (y/x = 2.0-4.0) plasma systems were investigated to determine relationships between precursor chemistry, CF(n) radical-surface reactivities, and surface properties of deposited films. The contributions of CF(n) (n = 1, 2) radicals to film properties were probed via gas-phase diagnostics and the imaging of radicals interacting with surfaces (IRIS) technique. Time-resolved radical emission data elucidate CF(g) and CF(2)(g) production kinetics from the C(x)F(y) source gases and demonstrate that CF(4) plasmas inherently lag in efficacy of film formation when compared to C(2)F(6), C(3)F(8), and C(3)F(6) systems. IRIS data show that as the precursor y/x ratio decreases, the propensity for CF(n) scatter concomitantly declines. Analyses of the composition and characteristics of fluorocarbon films deposited on Si wafers demonstrate that surface energies of the films decrease markedly with increasing film fluorine content. In turn, increased surface energies correspond with significant decreases in the observed scatter coefficients for both CF and CF(2). These data improve our molecular-level understanding of CF(n) contributions to fluorocarbon film deposition, which promises advancements in the ability to tailor FC films to specific applications.

Deposition of amorphous CN(x) materials in BrCN plasmas: exploring adhesion behavior as an indicator of film properties.

Adhesion and delamination behavior of amorphous carbon nitride (a-CN(x)) is critical to development of wear resistant materials and protective coatings. Here, the composition and delamination behavior of a-CN(x) films was explored utilizing BrCN, CH3CN, and CH4 as film precursors, either alone or in combination with one another. Film delamination depends on film thickness and plasma composition as well as post deposition treatment conditions. Delamination is not observed with films deposited from 100% CH3CN discharges, whereas films of similar thickness deposited from 100% BrCN plasmas delaminate almost immediately upon exposure to atmosphere. Exploration of these differences in delamination behavior is discussed relative to contributions of humidity, hydrocarbon species, and ion bombardment during deposition in conjunction with compositional studies using X-ray photoelectron spectroscopy (XPS).

Controlled nitrogen doping and film colorimetrics in porous TiO2 materials using plasma processing.

Nitrogen doping of TiO(2) films (N:TiO(2)) has been shown to improve the visible-light sensitivity of TiO(2), thereby increasing the performance of both photovoltaic and photocatalytic devices. Inductively coupled rf plasmas containing a wide range of nitrogen precursors were used to create nitrogen-doped TiO(2) films. These treatments resulted in anatase-phased materials with as high as 34% nitrogen content. As monitored with high-resolution X-ray photoelectron spectroscopy spectra, the nitrogen binding environments within the films were controlled by varying the plasma processing conditions. XPS peak assignments for multiple N 1s binding environments were made based on high resolution Ti 2p and O 1s XPS spectra, Fourier transform infrared spectroscopy (FTIR) data, and literature N 1s XPS peak assignments. The N:TiO(2) films produced via plasma treatments displayed colors ranging from gray to brown to blue to black, paralleling the N/Ti ratios of the films. Three possible mechanisms to explain the color changes in these materials are presented.

Gas phase energetics of CN radicals in radio frequency discharges: influence on surface reaction probability during deposition of carbon nitride films.

The CN radical has been implicated as an important contributor to the plasma deposition of amorphous carbon nitride. Here, laser-induced fluorescence and optical emission spectroscopy were used to explore in greater detail the gas phase energetics of CN in CH(3)CN, BrCN, and CH(4)/N(2) plasmas. Measurements of CN internal temperatures from these systems yield rotational temperatures well above 300 K, with notably higher ones for CN formed in BrCN plasmas, and vibrational temperatures of 4500-6000 K in all three systems. The data agree with the results of literature photodissociation experiments, and extension of those results to the plasma systems studied here provides insight into both the mechanisms for CN formation as well as the disposal of energy during fragmentation of the parent molecules. The internal energies of these species may influence their surface behavior; this issue is discussed in the context of previous work from our lab as well as others. The apparent trends not only offer a valuable perspective on the chemical dynamics of CN during the plasma deposition of a-CN(x) films but are also suggestive of a more general relationship between the energetics of plasma species and their behavior at surfaces.