12 research outputs found
Evaluating the Use of Alternatives Assessment To Compare Bulk Organic Chemical and Nanomaterial Alternatives to Brominated Flame Retardants
Alternatives assessment
(AA) provides a framework for selection
of safer substitutes for problematic chemicals. This study assesses
alternatives for flame retardants (FR) in electrical and electronic
equipment (EEE), including two common brominated FR, decabromodiphenyl
ether (deca-BDE) and tetrabromobisphenol A (TBBPA). Although deca-BDE
is restricted in the EU and undergoing phase-out in the US, TBBPA
is still widely used. However, concerns about potential hazards are
driving a search for halogen-free alternatives. Nonhalogenated organic
chemical alternatives (e.g., phosphorus-based FRs) as well as minerals
(e.g., montmorillonite) and nanomaterials (e.g., carbon nanotubes)
have been proposed, yet it is unclear whether current frameworks can
be used to systematically compare such heterogeneous alternatives.
This study aims to (i) identify technologically and economically viable
alternative FRs and (ii) evaluate each under the current AA frameworks,
to (iii) elucidate challenges and shortcomings to adopting proposed
alternatives. Uncertainties persist regarding the hazards of both
novel nanomaterials and traditional chemicals. Historically, problematic
chemicals undergoing restriction have been substituted with another
chemical providing, at best, marginally reduced hazard, a problem
that AA was, in part, developed to solve. Its successful implementation
will depend on our ability to reduce hazard during the design stage,
which is currently precluded by the “commercially available
and economically viable” emphasis of AA. Methods are needed
to bridge AA with sustainable chemical design to prevent it from becoming
a tool of only incremental improvement
Life Cycle Payback Estimates of Nanosilver Enabled Textiles under Different Silver Loading, Release, And Laundering Scenarios Informed by Literature Review
Silver
was utilized throughout history to prevent the growth of
bacteria in food and wounds. Recently, nanoscale silver has been applied
to consumer textiles (nAg-textiles) to eliminate the prevalence of
odor-causing bacteria. In turn, it is proposed that consumers will
launder these items less frequently thus, reducing the life cycle
impacts. While previous studies report that laundering processes are
associated with the greatest environmental impacts of these textiles,
there is no data available to support the proposed shift in consumer
laundering behavior. Here, the results from a comprehensive literature
review of nAg-textile life cycle studies are used to inform a cradle-to-grave
life cycle impact assessment. Rather than assuming shifts in consumer
behavior, the impact assessment is conducted in such a way that considers
all laundering scenarios to elucidate the potential for reduced laundering
to enable realization of a net life cycle benefit. In addition to
identifying the most impactful stages of the life cycle across nine-midpoint
categories, a payback period and uncertainty analysis quantifies the
reduction in lifetime launderings required to recover the impacts
associated with nanoenabling the textile. Reduction of nAg-textile
life cycle impacts is not straightforward and depends on the impact
category considered
Life Cycle Impacts and Benefits of a Carbon Nanotube-Enabled Chemical Gas Sensor
As
for any emerging technology, it is critical to assess potential
life cycle impacts prior to widespread adoption to prevent future
unintended consequences. The subject of this life cycle study is a
carbon nanotube-enabled chemical gas sensor, which is a highly complex,
low nanomaterial-concentration application with the potential to impart
significant human health benefits upon implementation. Thus, the net
lifecycle trade-offs are quantified using an impact-benefit ratio
(IBR) approach proposed herein, where an IBR < 1 indicates that
the downstream benefits outweigh the upstream impacts. The cradle-to-gate
assessment results indicate that the midpoint impacts associated with
producing CNTs are marginal compared with those associated with the
other manufacturing stages. The cumulative upstream impacts are further
aggregated to units of disability-adjusted life years (DALYs) using
ReCiPe end point analysis method and quantitatively compared with
the potential downstream DALY benefits, as lives saved, during the
use phase. The approach presented in this study provides a guiding
framework and quantitative method intended to encourage the development
of nanoenabled products that have the potential to realize a net environmental,
health, or societal benefit
Toward safer multi-walled carbon nanotube design: Establishing a statistical model that relates surface charge and embryonic zebrafish mortality
<p>Given the increased utility and lack of consensus regarding carbon nanotube (CNT) environmental and human health hazards, there is a growing demand for guidelines that inform safer CNT design. In this study, the zebrafish (<i>Danio rerio</i>) model is utilized as a stable, sensitive biological system to evaluate the bioactivity of systematically modified and comprehensively characterized multi-walled carbon nanotubes (MWNTs). MWNTs were treated with strong acid to introduce oxygen functional groups, which were then systematically thermally reduced and removed using an inert temperature treatment. While 25 phenotypic endpoints were evaluated at 24 and 120 hours post-fertilization (hpf), high mortality at 24 hpf prevented further resolution of the mode of toxicity leading to mortality. Advanced multivariate statistical methods are employed to establish a model that identifies those MWNT physicochemical properties that best estimate the probability of observing an adverse outcome. The physicochemical properties considered in this study include surface charge, percent surface oxygen, dispersed aggregate size and morphology and electrochemical activity. Of the five physicochemical properties, surface charge, quantified as the point of zero charge (PZC), was determined as the best predictor of mortality at 24 hpf. From a design perspective, the identification of this property–hazard relationship establishes a foundation for the development of design guidelines for MWNTs with reduced hazard.</p
Network Analysis for Prioritizing Biodegradation Metabolites of Polycyclic Aromatic Hydrocarbons
Toward safer multi-walled carbon nanotube design: Establishing a statistical model that relates surface charge and embryonic zebrafish mortality
Highly Conductive Single-Walled Carbon Nanotube Thin Film Preparation by Direct Alignment on Substrates from Water Dispersions
A safe,
scalable method for producing highly conductive aligned
films of single-walled carbon nanotubes (SWNTs) from water suspensions
is presented. While microfluidic assembly of SWNTs has received significant
attention, achieving desirable SWNT dispersion and morphology in fluids
without an insulating surfactant or toxic superacid is challenging.
We present a method that uniquely produces a noncorrosive ink that
can be directly applied to a device <i>in situ</i>, which
is different from previous fabrication techniques. Functionalized
SWNTs (f-SWNTs) are dispersed in an aqueous urea solution to leverage
binding between the amine group of urea and the carboxylic acid group
of f-SWNTs and obtain urea-SWNT. Compared with SWNTs dispersed using
conventional methods (e.g., superacid and surfactants), the dispersed
urea-SWNT aggregates have
a higher aspect ratio with a rodlike morphology as measured by light
scattering. The Mayer rod technique is used to prepare urea-SWNT,
highly aligned films (two-dimensional nematic order parameter of 0.6,
5 ÎĽm spot size, via polarized Raman) with resistance values
as low as 15–1700 Ω/sq in a transmittance range of 2–80%
at 550 nm. These values compete with the best literature values for
conductivity of SWNT-enabled thin films. The findings offer promising
opportunities for industrial applications relying on highly conductive
thin SWNT films
Shape-Dependent Surface Reactivity and Antimicrobial Activity of Nano-Cupric Oxide
Shape
of engineered nanomaterials (ENMs) can be used as a design
handle to achieve controlled manipulation of physicochemical properties.
This tailored material property approach necessitates the establishment
of relationships between specific ENM properties that result from
such manipulations (e.g., surface area, reactivity, or charge) and
the observed trend in behavior, from both a functional performance
and hazard perspective. In this study, these structure–property-function
(SPF) and structure–property-hazard (SPH) relationships are
established for nano-cupric oxide (n-CuO) as a function of shape,
including nanospheres and nanosheets. In addition to comparing these
shapes at the nanoscale, bulk CuO is studied to compare across length
scales. The results from comprehensive material characterization revealed
correlations between CuO surface reactivity and bacterial toxicity
with CuO nanosheets having the highest surface reactivity, electrochemical
activity, and antimicrobial activity. While less active than the nanosheets,
CuO nanoparticles (sphere-like shape) demonstrated enhanced reactivity
compared to the bulk CuO. This is in agreement with previous studies
investigating differences across length-scales. To elucidate the underlying
mechanisms of action to further explain the shape-dependent behavior,
kinetic models applied to the toxicity data. In addition to revealing
different CuO material kinetics, trends in observed response cannot
be explained by surface area alone. The compiled results contribute
to further elucidate pathways toward controlled design of ENMs