In Situ Plasmon-Heating-Induced Generation of Au/TiO2“Hot Spots” on Colloidal Crystals

ChemPhysChem ◽  
2009 ◽  
Vol 10 (7) ◽  
pp. 1017-1022 ◽  
Author(s):  
Ivano Alessandri ◽  
Matteo Ferroni ◽  
Laura E. Depero
Keyword(s):  
Hot Spots ◽  
Colloidal Crystals

Capturing Spatial and Temporal Patterns of NO2 in Cities using mobile and stationary DOAS measurements

2021 ◽  
Author(s):  
Mark Wenig ◽  
Sheng Ye ◽  
Ying Zhu ◽  
Hanlin Zhang
Keyword(s):  
Air Quality ◽  
Hot Spots ◽  
Temporal Patterns ◽  
Optical Absorption Spectroscopy ◽  
Spatial And Temporal Patterns ◽  
The Public ◽  
Measurement Height ◽  
Weekly Cycles

<p>The problem of elevated NO<sub>2</sub> levels in cities has gained some attention in the public in recent years and has given rise to questions about the plausibility of banning diesel engines in cities, the meaning of exceedances of air quality limits and the effects of corona lock-downs on air quality to name a few. Urban air quality is typically monitored using a relatively small number of monitoring stations. Those in-situ measurements follow certain guidelines in terms of inlet height and location relative to streets, but the question remains how a limited number of point measurements can capture the spatial variability in cities. In this talk we present two measurement campaigns in Hong Kong and Munich where we utilized a combination of mobile in-situ and stationary remote sensing differential optical absorption spectroscopy (DOAS) instruments. We developed an algorithm to separate spatial and temporal patterns in order to generate pollution maps that represent average NO<sub>2</sub> exposure. </p> <p>We use those maps to identify pollution hot spots and capture the weekly cycles of on-road NO2 levels and spatial dependency of long-term changes and we analyze how on-road measurements compare to monitoring station data and how the measurement height and distance to traffic emissions have to be considered when interpreting observed concentration patterns.</p>

scholarly journals Prolific Lightning and Thunderstorm Initiation over the Lake Victoria Basin in East Africa

2020 ◽  
Vol 148 (5) ◽  
pp. 1971-1985 ◽  
Author(s):  
Katrina S. Virts ◽  
Steven J. Goodman
Keyword(s):  
East Africa ◽  
Hot Spots ◽  
Seasonal Cycle ◽  
Lake Victoria ◽  
Intertropical Convergence Zone ◽  
Lake Victoria Basin ◽  
The Earth ◽  
Total Lightning ◽  
Average Cluster

Abstract The Lake Victoria basin of East Africa is home to over 30 million people, over 200 000 of whom are employed in fishing or transportation on the lake. Approximately 3000–5000 individuals are killed by thunderstorms yearly, primarily by outflow winds and resulting large waves. Prolific lightning activity and thunderstorm initiation in the basin are examined using continuous total lightning observations from the Earth Networks Global Lightning Network (ENGLN) for September 2014–August 2018. Seasonal shifts in the intertropical convergence zone produce semiannual lightning maxima over the lake. Diurnally, solar heating and lake and valley breezes produce daytime lightning maxima north and east of the lake, while at night the peak lightning density propagates southwestward across the lake. Cluster analysis reveals terrain-related thunderstorm initiation hot spots northeast of the lake; clusters also initiate over the lake and northern lowlands. The most prolific clusters initiate between 1100 and 1400 LT, about 1–2 h earlier than the average cluster. Most daytime thunderstorms dissipate without reaching Lake Victoria, and annually 85% of clusters producing over 1000 flashes over Lake Victoria initiate in situ. Initiation times of prolific Lake Victoria clusters exhibit a bimodal seasonal cycle: equinox-season thunderstorms initiate most frequently between 2200 and 0400 LT, while solstice-season thunderstorms initiate most frequently from 0500 to 0800 LT, more than 12 h after the afternoon convective peak over land. More extreme clusters are more likely to have formed over land and propagated over the lake, including 36 of the 100 most extreme Lake Victoria thunderstorms. These mesoscale clusters are most common during February–April and October–November.

scholarly journals Highly ordered arrays of hat-shaped hierarchical nanostructures with different curvatures for sensitive SERS and plasmon-driven catalysis

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Chao Zhang ◽  
Zhaoxiang Li ◽  
Si Qiu ◽  
Weixi Lu ◽  
Mingrui Shao ◽  
...  
Keyword(s):  
Hot Spots ◽  
Hybrid Structure ◽  
Sers Substrate ◽  
Polystyrene Spheres ◽  
Hierarchical Nanostructures ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering ◽  
Narrow Gaps

Abstract Regulation of hot spots exhibits excellent potential in many applications including nanolasers, energy harvesting, sensing, and subwavelength imaging. Here, hat-shaped hierarchical nanostructures with different space curvatures have been proposed to enhance hot spots for facilitating surface-enhanced Raman scattering (SERS) and plasmon-driven catalysis applications. These novel nanostructures comprise two layers of metal nanoparticles separated by hat-shaped MoS2 films. The fabrication of this hybrid structure is based on the thermal annealing and thermal evaporation of self-assembled polystyrene spheres, which are convenient to control the metal particle size and the curvature of hat-shaped nanostructures. Based on the narrow gaps produced by the MoS2 films and the curvature of space, the constructed platform exhibits superior SERS capability and achieves ultrasensitive detection for toxic molecules. Furthermore, the surface catalytic conversion of p-nitrothiophenol (PNTP) to p, p′-dimercaptobenzene (DMAB) was in situ monitored by the SERS substrate. The mechanism governing this regulation of hot spots is also investigated via theoretical simulations.

Debris cover and the thinning of Kennicott Glacier, Alaska

2021 ◽  
Author(s):  
Leif S. Anderson ◽  
William H. Armstrong ◽  
Robert S. Anderson ◽  
Dirk Scherler
Keyword(s):  
Satellite Imagery ◽  
Hot Spots ◽  
High Mountain ◽  
Threshold Method ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Debris Cover ◽  
A Chain ◽  
The Relationship

<p>Many glaciers in High Mountain Asia are experiencing the debris-cover anomaly. The Kennicott Glacier, a large Alaskan Glacier, is also thinning most rapidly under debris cover. This contradiction has been explained by melt hotspots, such as ice cliffs, streams, or ponds scattered within the debris cover or by declining ice flow in time. We collected abundant in situ measurements of debris thickness, sub-debris melt, and ice cliff backwasting, allowing for extrapolation across the debris-covered tongue. A newly developed automatic ice cliff delineation method is the first to use only optical satellite imagery. The adaptive binary threshold method accurately estimates ice cliff coverage even where ice cliffs are small and debris color varies. We also develop additional remotely-sensed datasets of ice dynamical variables, other melt hot spots, and glacier thinning.</p><p>Kennicott Glacier exhibits the highest fractional area of ice cliffs (11.7 %) documented to date. Ice cliffs contribute 26 % of total melt across the glacier tongue. Although the <em>relative</em> importance of ice cliffs to area-average melt is significant, the<em> absolute</em> area-averaged melt is dominated by debris. At Kennicott Glacier, glacier-wide melt rates are not maximized in the zone of maximum thinning. Declining ice discharge through time therefore explains the rapid thinning. Through this study, Kennicott Glacier is the first glacier in Alaska, and the largest glacier globally, where melt across its debris-covered tongue has been rigorously quantified.</p><p>We also carefully explore the relationship between debris, melt hotspots, ice dynamics, and thinning across the debris-covered tongue. In doing so we reveal a chain of linked processes that can explain the striking patterns expressed on the debris-covered tongue of Kennicott Glacier.</p>

In Situ Visualization of Layer Transitions during Convective Self-Assembly in a Sessile Drop

2007 ◽  
Vol 31 ◽  
pp. 117-119
Author(s):  
Li Gao ◽  
Qing Feng Yan ◽  
C.C. Wong ◽  
Yet Ming Chiang
Keyword(s):  
Self Assembly ◽  
Sessile Drop ◽  
Three Dimensional ◽  
Colloidal Crystals ◽  
Layer Transition ◽  
Simple Method ◽  
Colloidal Spheres ◽  
In Situ Visualization ◽  
Set Up

Convective self-assembly of colloidal spheres provides a simple method for fabricating two and three dimensional colloidal crystals. In this work, we investigated the layer transitions phenomena during colloidal self-assembly in a sessile drop by using an in-situ videoscopic set-up. The effects of surface charge, colloidal concentration, and surfactant additions were examined. The results show that the chemical environment plays an important role in colloidal self-assembly. In the case of ordered growth, different layer transition phenomena were observed when the colloidal concentration is different.

scholarly journals Ag Nanostructures with Spikes on Adhesive Tape as a Flexible Sers-Active Substrate for In Situ Trace Detection of Pesticides on Fruit Skin

Nanomaterials ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1750 ◽  
Author(s):  
Jaya Sitjar ◽  
Jiunn-Der Liao ◽  
Han Lee ◽  
Li Peng Pan ◽  
Bernard Haochih Liu ◽  
...  
Keyword(s):  
Hot Spots ◽  
Flexible Substrate ◽  
Signal Enhancement ◽  
Raman Signal ◽  
Adhesive Tape ◽  
Trace Detection ◽  
Fruit Skin ◽  
Active Substrate ◽  
Sers Active Substrate

Nanostructures with spikes (NSPs) have been a subject of several surface-enhanced Raman scattering (SERS) applications owing to their significant Raman signal enhancement brought about by the combined effects of interspike coupling and the accumulated induction on the tips of spikes. Thus, NSPs offer great potential as a SERS-active substrate for relevant applications that require a high density of enhanced “hot spots”. In this study, Ag NSPs were synthesized in varying degrees of agglomeration and were thereafter deposited onto a transparent adhesive tape as a flexible substrate for SERS applications, specifically, in the detection of trace amounts of pesticides. These flexible substrates were referred to as Ag NSPs/tape and optimized with an enhancement factor (EF) of ca. 1.7 × 107. A strong resulting signal enhancement could be attributed to an optimal degree of agglomeration and, consequently, the distances among/between spikes. Long spikes on the synthesized core of Ag NSPs tend to be loosely spaced, which are suitable in detecting relatively large molecules that could access the spaces among the spikes where “hot spots” are generally formed. Since one side of the transparent tape is adhesive, the paste-and-peel off method was successful in obtaining phosmet and carbaryl residues from apple peels as reflected in the acquired SERS spectra. In situ trace detection of the pesticides at low concentrations down to 10−7 M could be demonstrated. In situ trace detection of mixed pesticides was possible as the characteristic peaks of both pesticides were observed in equimolar mixtures of the analytes at 10−2 to 10−4 M. This study is, thus, premised upon applying for in situ trace detection on e.g., fruit skin.

scholarly journals An On-Line Multiway Approach to In-Situ NDI Looking at the PZL-130TCII

2014 ◽  
Vol 2013 (5) ◽  
pp. 5-11 ◽  
Author(s):  
Krzysztof Dragan ◽  
Michał Dziendzikowski ◽  
Artur Kurnyta ◽  
Adam Latoszek ◽  
Andrzej Leski ◽  
...  
Keyword(s):  
Damage Detection ◽  
Hot Spots ◽  
Lamb Waves ◽  
Holistic Approach ◽  
Growth Monitoring ◽  
Damage Growth ◽  
On Line ◽  
Detection Capabilities ◽  
Main Component

Abstract Providing a reliable and universal Structural Health Monitoring (SHM) system allowing for remote aircraft inspections and a reduction of maintenance costs is a major challenge confronting the aerospace industry today. SHM based on guided Lamb waves is one of the approaches capable of addressing the issue while satisfying all the associated requirements. This paper presents a holistic approach to the continuous real time damage growth monitoring and early damage detection in aircraft structure. The main component of the system is a piezoelectric transducers (PZT) network. It is complemented by other SHM methods: Comparative Vacuum Monitoring (CVMTM) and Resistance Gauges at selected aircraft hot spots. The paper offers the description of damage detection capabilities including the analysis of data collected from the PZL-130 Orlik aircraft full-scale fatigue test.

scholarly journals Interfacial and volumetric sensitivity of the dry sintering process of polymer colloidal crystals: a thermal transport and photonic bandgap study

2017 ◽  
Vol 19 (24) ◽  
pp. 16124-16130 ◽  
Author(s):  
Fabian A. Nutz ◽  
Markus Retsch
Keyword(s):  
Optical Spectroscopy ◽  
Thermal Transport ◽  
Photonic Bandgap ◽  
Colloidal Crystals ◽  
Sintering Process

In situ thermal transport and optical spectroscopy characterization reveal an interfacial and volumetric contribution during the dry sintering of colloidal crystals.

Creating SERS Hot Spots on MoS2 Nanosheets with in Situ Grown Gold Nanoparticles

2014 ◽  
Vol 6 (21) ◽  
pp. 18735-18741 ◽  
Author(s):  
Shao Su ◽  
Chi Zhang ◽  
Lihui Yuwen ◽  
Jie Chao ◽  
Xiaolei Zuo ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Hot Spots ◽  
Mos2 Nanosheets
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