Ag Nanorod Arrays for SERS: Aspects of Spectral Reproducibility, Surface Contamination, and Spectral Sensitivity

Ag nanorod arrays prepared by oblique angle vapor deposition (OAD) represent regular, large area substrates for surface-enhanced Raman scattering (SERS) spectroscopy. We studied uniformity and spectral reproducibility of silver OAD-fabricated substrates (AgOADs) by spectral mapping of methylene blue. The results demonstrate good reproducibility apart from occasional “hot-spot” sites where the intensity is higher. The number of “hot-spots” represents 2%–6% of SERS-active sites of mapping substrate area. We were able to obtain good SERS spectra of testing amino acid tryptophan at 1 × 10−5 M concentration and three different free-base porphyrins down to ∼10−7 M concentration. We found out that keeping the AgOADs in a vacuum chamber overnight prevents the surface from binding any contaminants from the ambient atmosphere, without significant reduction in the SERS enhancement. Such substrates provide stable SERS enhancement even when stored for 1 year after preparation

Tropospheric and stratospheric smoke over Europe as observed within EARLINET/ACTRIS in summer 2017

For several weeks in summer 2017, strong smoke layers were observed over Europe at numerous EARLINET stations. EARLINET is the European research lidar network and part of ACTRIS and comprises more than 30 ground-based lidars. The smoke layers were observed in the troposphere as well as in the stratosphere up to 25 km from Northern Scandinavia over whole western and central Europe to the Mediterranean regions. Backward trajectory analysis among other tools revealed that these smoke layers originated from strong wild fires in western Canada in combination with pyrocumulus convection. An extraordinary fire event in the mid of August caused intense smoke layers that were observed across Europe for several weeks starting on 18 August 2017. Maximum aerosol optical depths up to 1.0 at 532 nm were observed at Leipzig, Germany, on 22 August 2017 during the peak of this event. The stratospheric smoke layers reached extinction coefficient values of more than 600 Mm−1 at 532 nm, a factor of 10 higher than observed for volcanic ash after the Pinatubo eruption in the 1990s. First analyses of the intensive optical properties revealed low particle depolarization values at 532 nm for the tropospheric smoke (spherical particles) and rather high values (up to 20%) in the stratosphere. However, a strong wavelength dependence of the depolarization ratio was measured for the stratospheric smoke. This indicates irregularly shaped stratospheric smoke particles in the size range of the accumulation mode. This unique depolarization feature makes it possible to distinguish clearly smoke aerosol from cirrus clouds or other aerosol types by polarization lidar measurements. Particle extinction-to-backscatter ratios were rather low in the order of 40 to 50 sr at 355 nm, while values between 70-90 sr were measured at higher wavelengths. In the western and central Mediterranean, stratospheric smoke layers were most prominent in the end of August at heights between 16 and 20 km. In contrast, stratospheric smoke started to occur in the eastern Mediterranean (Cyprus and Israel) in the beginning of September between 18 and 23 km. Stratospheric smoke was still visible in the beginning of October at certain locations (e.g. Evora, Portugal), while tropospheric smoke was mainly observed until the end of August within Europe. An overview of the smoke layers measured at several EARLINET sites will be given. The temporal development of these layers as well as their geometrical and optical properties will be presented

Equipment for continuous collection, correction, and distribution of air samples for evaluation of greenhouse gases at the Atmospheric Station Křešín u Pacova

The Atmospheric Station Křešín u Pacova is focused mainly on research and monitoring of greenhouse gases in the atmosphere. The station was built and equipped according to recommendations of international monitoring network ICOS. The concentration of greenhouse gases is measured continuously at 4 different heights of 250 m tall meteorological mast that is the main part of the station

RETRACTED: POSSIBILITY OF MONITORING OF PAHs DISTRIBUTION IN THE VERTICAL PROFILE AT THE BACKGROUND METEOROLOGICAL STATION KREŠÍN

This article has been retracted by Editorial Office, upon an approval of all authors. The Publisher apologized for any inconvenience this may cause. The contaminants present in the atmosphere have a substantial impact on public health. Among contaminants, the most important are polycyclic aromatic hydrocarbons (PAHs). This paper is focused on the possibility of continuous PAHs monitoring and the description of their vertical distribution using filters, which serve to purify the air before the determination of the greenhouse gases (CO2, CH4, N2O, CO, ozone) and Hg in air, continuously sampled at 8, 50 and 230m at the atmospheric station Krešín near Pacov and elaboration of a simple and economical method of extraction of these filters. The station serves as a point for monitoring the occurrence and remote transport of greenhouse gases and selected atmospheric pollutants and for the measurements of basic meteorological characteristics. In December, 17, 2014, a sampling of 16 priority PAHs started and lasted until December, 9, 2015. Samples were taken approximately once a month. The maximum concentration of ΣPAHs was 15.905 ng/m3, measured at the height of 8 meters in the period of 11. 2. 2015–11. 3. 2015, the concentration of benzo[a]pyrene exceeded the immission limit in the period by more than 50%. By the sampling, the hypothesis about decreasing concentration of PAHs with increasing height was confirmed, especially the decrease of heavier PAHs. The sampling has shown that it is highly desirable to use the meteorological tower for sampling of PAHs using PTFE filters either by including the active sampler itself, or by using pre-filters for tropospheric ozone and gaseous elemental mercury analysers

Atmosférická stanice Křešín u Pacova, Česká republika - středoevropská výzkumná infrastruktura pro studium skleníkových plynů, aerosolů a kvality ovzduší

Long-lasting research infrastructures covering the research areas of atmospheric chemistry, meteorology and climatology are of highest importance. The Atmospheric station Křešín u Pacova, central Czech Republic, is focused on monitoring of the occurence and long-range transport of greenhouse gases, atmospheric aerosols, selected gaseous atmospheric pollutants and basic meteorological characteristics. The atmospheric station and its 250 m tall tower was built according to the recommendations of the Integrated Carbon Observation System (ICOS) and cooperates with numerous national and international projects and monitoring programmes. First measurements conducted at ground started in 2012, vertical profile measurements were added in 2013. A seasonal variability with slightly higher autumn and winter concentrations of elemental and organic carbon was revealed. The suitability of the doubly left-censored Weibull distribution for modelling and interpretation of elemental carbon concentrations, which are often lower than instrumental quantification limits, was verified. Initial data analysis also suggests that in summer, the tower top at 250 m is frequently above the nocturnal surface inversions, thus being decoupled from local influences.Dlouhotrvající výzkumné infrastruktury pokrývající oblasti výzkumu atmosférické chemie, meteorologie a klimatologie jsou velmi důležité. Atmosférická stanice Křešín u Pacova, Česká republika, je zaměřena na monitorování výskytu a dálkového přenosu skleníkových plynů, atmosférických aerosolů, vybraných plynných látek znečišťujících ovzduší a základních meteorologických charakteristiky. Atmosférická stanice a její 250 m vysoká věž byla postavena v souladu s doporučeními Integrated Carbon Observation System (ICOS) a spolupracuje s řadou národních a mezinárodních projektů a monitorovacích programů. První měření prováděná u země začala v roce 2012, měření vertikálního profilu byla přidána v roce 2013. Byla odhalena sezónní variabilita koncentrací elementárního a organického uhlíku s mírně zvýšenými hodnotami na podzim a v zimě. Dále byla ověřena vhodnost dvojnásobně zleva cenzorovaného Weibullova rozdělení pro modelování a interpretaci koncentrací elementárního uhlíku, které jsou často nižší než kvantifikační limity měřicích zařízení. Počáteční analýza dat ukazuje, že v létě je vrchol věže často nad noční povrchovou inverzí, a tedy oddělen od lokálních vlivů