Shell Samples Research Articles

Adsorption Ability for Toxic Chromium (VI) Ions in Aqueous Solution of Some Modified Oyster Shell Types

In this paper, the chromium, Cr (VI), ion adsorption ability of oyster shell samples collected from two sea regions in Vietnam (Phu Yen province and Quang Ninh province) was investigated and compared. The oyster shell samples were calcined at different temperatures and denatured by using ethylenediaminetetraacetic acid (EDTA). The Cr (VI) ion adsorption ability of the prismatic (PP) and nacreous (NP) shell layers of oysters was also evaluated. The characteristics of oyster shell samples before and after treatment were determined by using analysis methods including XRD, IR, BET, UV-Vis, and FESEM. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models and fit statistic equations were used to study the adsorption isotherms of Cr (VI) ion adsorption by oyster shells. The Cr (VI) ions adsorption kinetic has been set up using four reaction models consisting of first-order, pseudo-first-order, second-order, and pseudo-second-order reaction models. Effects of experimental factors on the Cr (VI) ion adsorption process using oyster shells were also investigated and discussed in this work.

Unique Post-telemetry Recapture Enables Development of Multi-Element Isoscapes From Barnacle Shell for Retracing Host Movement

Many ecological investigations rely on understanding the movement of animals through marine environments. Most available tracking techniques are invasive (e.g., tissue sampling) and require extensive effort and/or cost (e.g., capture-mark-recapture or satellite telemetry). The isotopic compositions of barnacle shells (delta C-13 and delta O-18) are known to record the ambient water temperature and salinity conditions in which they grew. Thus, isotopic analysis of barnacles on animals or objects has the potential to yield information about their movement between water bodies of varying isotopic properties. We present, for the first time, isotopic data for barnacle shell samples that grew on a satellite-tracked sea turtle host. The satellite telemetry record, together with documented barnacle growth rates, allowed for sequential samples from individual barnacle shells to be assigned a specific time and location for direct comparison of isotope values to environmental conditions. We developed models that allow barnacle shell delta C-13 and delta O-18 to be linked, with a high degree of predictability, to sea surface temperature (SST) and salinity (SSS). Our sea turtle case study demonstrated how these models can be used to create isoscapes, allowing hosts to be tracked in space and time at higher resolution than most attempts to use soft-tissue isotopes for a similar purpose, and at considerably lower cost than satellite telemetry. The conceptual advance presented here could be applied widely to understand the movement of any animal or object that carries hitchhiking barnacles.

Prism substructures in the shell of Pinna nobilis (Linnaeus, 1758), Mollusca – Evidence for a three-dimensional pulsed-growth model

In the shells of the Pelecypods belonging to the Pinnidae family, the calcareous prismatic units of the outer layer are long-standing references for biomineralization studies. To elucidate how the mechanism of prism formation enables both shell elongation and thickness increase, a top-down structural analysis of these classical “simple prisms” has been carried out, taking advantage of shell sampling on actively mineralizing animals. Particular attention was paid to the morphological and structural patterns of the calcareous units sequentially produced at the margins of the growth lamellae. This pre-prismatic part of the shell allows for studying the mineralizing stages not taken into account in prism reconstructions based on samples taken from older areas of the shell. Examination of the microstructural sequence shows that within the actively mineralizing area of the shell, a step-by-step structuring process is continuously running, providing a renewed view of prism formation as it makes obvious the progressive occurrence of their specific patterns. Given the critically endangered status of the species, a better knowledge of the mineralization process associated to shell growth may become handy for future studies aimed at understanding the health status of individuals based on their shell records.

Coagulant derived from waste biogenic material for sustainable algae biomass harvesting

Highly efficient and sustainable algae harvesting that produced biomass with enhanced characteristics and reusable culture medium were developed from the use of coagulant derived from the waste shell of Gastropod. Thermally treated Gastropod shell samples were screened for the algal cell harvesting efficiency (%) and the underlying mechanism was elucidated from the hydrodynamic equilibrium data and scanning electron microscopic analysis. The floc strength, settling rate parameters, settleability, and filterability were determined and compared with the flocs obtained from the pH induced autocoagulation system. The values of floc settling rate and the sludge volume index (mL/g) showed that the flocs obtained from the Gastropod shell system (rate constant = 1.945 L·mol−1·s−1) settled faster and more compacted than those from the pH induced system (rate constant = 0.2155 (L·mol−1·s−1). Both the growing and harvested flocs from the Gastropod shell system had better strength and breakage factors (>90%) than the pH induced system. The proximate and elemental compositions of the biomass from the Gastropod shell system were comparable with those from centrifugation and pH induced systems. Both the separated culture medium and the harvested algae biomass were successfully reused, in separate systems, to cultivate fresh algae. This indicated the non-toxic effects of the coagulants on both the culture medium and the algae harvested biomass.

Performance Analysis of Inactivated and Acid Activated Marine and Terrestrial Shells Based Adsorbent as an Alternative Bleaching Material for Palm Oil

The use of environmentally benign materials as adsorbent for bleaching palm oil has been revitalize due to loss of significant amount of oil associated with commercial bleaching earth. This paper examined the performance of inactivated shell samples from snail, mussel, periwinkle and the corresponding acid activated samples as an alternative bleaching material for palm oil. Effectiveness of the bleaching process was examined by determining critical process parameters such as degree of bleaching (%), adsorbent dosage (%), and oil retention capacity of the adsorbent. Maximum bleaching performance of 98.70%–96.60% for inactivated samples and 97.79%–95.52% for 0.5 M hydrochloric acid activated samples were obtained at low adsorbent dosage of 9.09 wt.%. The weight percentage of residual oil (1.38–20.08 wt.%) in the spent adsorbent was extremely low for all the samples. Inactivated samples could be a better alternative for commercial adsorbent.

Identification of flavonoid compounds and total flavonoid content from biowaste of local durian shell (Durio zibethinus)

Flavonoid compound from durian shell biowaste was identified by phytochemical assay and FTIR spectrophotometric methods. Total flavonoid content determined by the aluminum chloride (AlCl3) method using a UV-Vis spectrophotometer. Durian shells, which are a waste that causes the environmental problem, can be used as a source of potentially valuable flavonoid compounds. Flavonoid has antioxidants ability that is beneficial and useful. Durian shell used in this research consists of three types, namely Malika, Malon, and Monti, which are from local Indonesian durian. Based on the result, proximate test analysis showed that three local durian shell samples generally had a water content of 7%, a fat content of 0.9%, the protein content of 4.9%, an ash content of 8.5%, and a 78% carbohydrate content. The results of the analysis of the three durian shell samples did not show significantly different results. Then for the phytochemical assay, three local durian shell samples contained phenols, steroids, and terpenoids, the results of the phytochemical assay showed that there were more phenolic groups than the flavonoid group. The following analysis result is the functional group of three samples using Fourier Transform Infrared (FT-IR) spectrophotometer shows that the three types of durian shell samples have a band that is slightly different from the standard, but the number of waves in this band is similar to the standard quercetin. Then for total flavonoid levels in local durian shell using the aluminum chloride (AlCl3) method, the result is Monti durian shell having higher flavonoid levels, each 0.405 ± 0.002 mg QE/g, compared with each other shell type namely Malika and Malon of 0.321 ± 0.003 mg QE / g and 0.324 ± 0.002 mg QE/g, respectively. Thus in this study shows that Indonesian local durian shell contains significant total flavonoid content without the need for extraction. Samples were only dissolved with ethanol solvent, then a series of tests were carried out, then a series of tests were carried out, ranging from phytochemical assessment, FTIR spectrophotometer, and AlCl3 methods to determine the total flavonoid content through quantitative.

Gaseous Mixtures Separation via Chemically-Activated Nano Silica-Modified Carbon Molecular Sieves

The goal of this research was to study the efficiency of the silica-modified, highly selective synthesized carbon molecular sieves for nitrogen separation in the methane purification process. For this purpose, carbon molecular sieves obtained from pistachio and walnut shells were impregnated in their raw form by means of phosphoric acid as an activator agent, and then cured with nano silica with different percentages. Calculations pointed out that impregnation ratio of activator agent and SiO2 concentration were influential on the adsorption rate and obviously has prevented the methane to get adsorbed. Maximum nitrogen adsorption was 8.8093 mM.g−1 which was the value related to the walnut shell sample with an impregnation ratio of 2:1 and SiO2 concentration equal to 1 w/w%, while minimum methane adsorption was observed to be 2.0129 mM.g−1 which was the value related to the pistachio-walnut shells mixed sample with an impregnation ratio equal to 4:1 and SiO2 concentration equal to 4 w/w%. The void volume of the micropores obtained from nitrogen adsorption was more than from methane. The walnut shell sample with an impregnation ratio of 4:1 demonstrated the highest selectivity equal to 2.1030 and was reported as the most proper sample in this study.

Trace elements in green turtles (Chelonia mydas) from Rocas Atoll, NE Brazil: Baseline reference from a pristine nesting site

This study presents the first report on the concentration of trace elements (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn) in the blood and egg fractions of green turtles from Rocas Atoll, a pristine nesting site in NE Brazil. The highest concentrations of all elements were in the blood or shell samples. In order, iron, Zn, Cu, Al and As presented the highest concentrations in all tissues. The nonessential trace elements were below the limit of detection for more than 50% of the yolk (Al, Cd and Pb) and albumen samples (Al, As, Ba, Cd and Pb). This study will serve as a baseline reference for future monitoring of the ecotoxicology of breeding green turtles in the southwestern Atlantic Ocean.

Mimicking the effects of anthropogenic heating on amino acid racemisation dating of gastropod shells

Abstract Pre- or post-depositional heating of fossil biominerals will impact resulting amino acid dates, but the study on the effects on their amino acids of dry artificial heating of molluscs has not yet been fully tested. Here we report a study on three mollusc species to show how amino acid content can potentially be used to identify archaeological samples that have been subjected to artificial heating. The identification of markers of exposure to high temperature could be useful to reject compromised samples for amino acid racemisation dating. In order to identify markers of heat exposure, we artificially heated modern shell samples belonging to three marine molluscs found in abundance at archaeological sites, namely Patella vulgata, Phorcus lineatus and Littorina littorea. The markers found were compared with data from an archaeological dataset for these three species. Our results indicate that there is unlikely to be a single marker indicating artificial heating of a sample, especially for archaeological samples, which have been exposed to a wide variety of complex conditions that cannot be simulated in an isothermal experiment. However in general, we observed changes in shell composition which were indicative of heating: higher %Glx and %Ala and lower %Asx and %Ser for a given Asx D/L value. Moreover, samples heated at high temperatures showed higher than expected Glx and Ala D/L values for a given Asx D/L value. Likewise, the amino acid content of the shells decreased with heating time and temperature. Furthermore, shells artificially heated at > 300 °C had additional compounds evident in the chromatogram, and a poor baseline, thus causing a loss of resolution of late eluting amino acids. Of note, samples heated at 500 °C (5 min) and 400 °C (10–20 min) preserved negligible amino acid content. Archaeological samples that deviated from the expected unheated trend were therefore identified as having been heated.

EKSTRAKSI KALIUM DARI LIMBAH KULIT BIJI KOPI (COFFEA SP) MENGGUNAKAN METODE REFLUX

Abstract. Coffee is a type of plantation that has long been cultivated and has a fairly high economic value. Coffee comes from Africa, which is a mountainous region in Europe. In general, after being harvested the skin and seeds are separated, the results of the processing turn out to produce 35% coffee skin and 65% coffee beans, generally the coffee skin is thrown away as fertilizer. It turns out that coffee bean skin contains potassium which can be used as an additional raw material for making soap. One method to obtain potassium from the skin of coffee beans is by extracting the potassium found in the skin of coffee beans. The purpose of this study was to determine the effect of variations in the extraction time of coffee bean shells by the volume of solvent on the levels of potassium produced. In this research, the process of extracting coffee bean skin ashes, by reacting coffee bean skin ashes with aquadest solvent at a temperature of 80oC. Where the weight of coffee bean shell samples 50 gr, and the volume of solvents varied 100 ml, 150 ml, and 200 ml, and extraction time 60 minutes, 90 minutes, 120 minutes, 150 minutes and 180 minutes. To find out the results of this study, pH levels were analyzed using a pH meter and potassium levels using Atomic Absorption Spectrometry (AAS). The results of this study indicate that the average pH value of the extraction result is 13, the greatest value of the analysis yield is 2.46% in the extraction time of 180 minutes with a solvent volume of 100 ml while the potassium content of the largest coffee bean shell ash is 9.524 × 105 mg / l at a volume of 100 ml solvent for 60 minutes.Keywords: Extraction, Potassium, Reflux, Rendemen, Coffee bean skin ashes

Evaluation of multi-shell diffusion MRI acquisition strategy on quantitative analysis using multi-compartment models.

Multi-compartment diffusion models such as Neurite Orientation Dispersion and Density Imaging (NODDI) have been increasingly used for diffusion MRI (dMRI) data processing in biomedical research. However, those models usually require multiple HARDI shells that may increase scanning duration substantially, and their application can be hindered in uncooperative patients (like infants) accordingly. Also, it is highly expected that the same dataset can be explored with multiple diffusion models for retrieving complementary information. Multiple gradient-encoding schemes which consisted of 4-6 shells, moderate b-values (bmax =1,500 or 2,000 s/mm2), and 32-80 gradient directions were explored. The corresponding time of acquisition (TA) for a single scan ranged from 3 to 8 minutes respectively. The dMRI protocols were tested on macaque monkeys using a 3T clinical setting. The data were analysed using both NODDI and diffusion basic spectrum imaging (DBSI) models. The maps of orientation dispersion index (ODI) and CSF were consistent across the 4-6 shell sampling schemes. However, the corresponding intra-cellular volume fraction (ICVF) maps showed reduced pixel counts [1,100±98 (80 directions) vs. 806±70 (32 directions), one slice] in white matter when fewer gradient directions or lower b-value was applied. The hindered diffusion and CSF ratio maps were comparable across these sampling schemes. The maps of restricted diffusion ratio varied across the schemes. However, its mean ratios (0.23±0.02 vs. 0.22±0.01) and pixel counts (1,540±70 vs. 1,510±38, one slice) between the schemes of 80 and 32 directions with b=2,000 s/mm2 were comparable. The present study reports a fast multi-shell dMRI data acquisition and processing strategy which allows for obtaining complementary information about microstructural alteration and inflammation from a single dMRI data set with both NODDI and DBSI models. The proposed approach may be particularly useful for characterizing the neurodegenerative disorders in uncooperative patients like children or acute stroke patients in which brain injury is associated with inflammation.

Improved room temperature magnetoelectric response in CoFe2O4-BaTiO3 core shell and bipolar magnetostrictive properties in CoFe2O4

A large Magnetoelectric (ME) response at room temperature in CoFe2O4 - BaTiO3 core shell composite is crucial for the biomedical application because of its biocompatibility. Good ME response of core–shell system is directly related to synthesis conditions as it determinesextent of coupling between core and shell structures. In this work, CoFe2O4 - BaTiO3 core shell structures with improved ME response were prepared through hydrothermal and citric gel synthesis. Reitveld refinement analysis and microscopic images confirmed the successful formation of CoFe2O4 - BaTiO3 core shell structure. The core shell sample is composed of tetragonal BaTiO3 and cubic spinel CoFe2O4 phases. CoFe2O4 was found to exhibit both positive and negative magnetostriction at room temperature. ME coefficient of 12.38 mV/cm Oe was observed at room temperature, which is quite high and can enhance the efficiency of targeted drug delivery.

Estimation of Particulate Emission Generation in Palm Oil Mill Boiler

The palm oil industries in Malaysia has been positively growth throughout the year, for it sustainable approach in terms of production and environmental protection. However, this industry also producing considerable amount of particulate emission from the process of burning its biomass waste of palm fibre and shell in the boiler. This study present a method to estimate the particulate emission that are being generated from the boiler. The method were done by analyzing the proximate analysis value of the ash content of palm fibre and shell found in this study. The particulate emission were physically collected from five palm oil mill boilers with boiler capacity ranging from 18-45 tonne/hour. The particulate stack fly ash was collected from the stack gas downstream of a multi-cyclones particulate arrestor according to the USEPA Method 17- Determination of particulate matter emissions from stationary sources. Meanwhile the sample of palm fibre and shell were collected to determine the proximate value. The estimation were then being further analyzed according to the particulate emission that were obtained by the real-stack sampling. In summary, the average moisture content, ash content, volatile matter and fixed carbon for palm shell found in this study are 19.3 ± 5.7%, 2.79 ± 2.2%, 74.3 ± 3.0, and 11.3 ± 4.3, respectively.). The average particulate concentration for these five mills is 2.2±0.9g/Nm3 and the air pollution control requirement are between 64 and 96% with reference to Clean Air Regulations 2014 of 0.15g/Nm3 which is very high to be achieve. It also can be estimated that 26% of the ash generated from the combustion of palm fibre and shell in palm oil mill boiler are being released at the stack.

Quantification of Residual Perfume by Py-GC-MS in Fragrance Encapsulate Polymeric Materials Intended for Biodegradation Tests

Perfume encapsulates are widely used in commercial products to control the kinetic release of odorant molecules, increase storage stability and/or improve deposition on different substrates. In most of the cases, they consist of core-shell polymeric microcapsules that contain fragrance molecules. A current challenge is to design and produce polymeric materials for encapsulation that are both resistant and non-persistent. The selection of such eco-friendly formulations is linked to a deep understanding of the polymeric material used for encapsulation and its biodegradation profile. To collect this information, pure samples of capsule shells are needed. In this article we present an innovative quantification method for residual volatiles based on pyrolysis-GC-MS to enable validation of sample quality prior to further testing. The presented analytical method also led to the development of a robust and comprehensive purification protocol for polymers from commercial samples. Standard techniques are not suited for this kind of measurement due to the non-covalent embedding of volatiles in the 3D structure of the polymers. We demonstrated the confounding impact of residual volatiles on the estimated biodegradability of fragrance encapsulates.

Studying Structural and Optical Properties of TiO2–SnO2 Core–Shell Synthesized by Sol–Gel Route

AbstractHerein, the TiO2–SnO2 core–shell structures with the core‐to‐shell molar ratios of 5:0.5, 5:0.67, and 5:1 are synthesized by the sol–gel route, and then the structural and optical properties of the synthesized samples are investigated. In order to characterize the samples, the XRD, Raman, FESEM, and TEM techniques are used for their structural verification, while the UV–visible and photoluminescence spectra are used for their optical characterization. The XRD results obtained showed that the annealed TiO2 sample has an anatase tetragonal structure and that the core–shell samples contain the diffraction peaks of both the core TiO2 and the shell SnO2. The XRD results obtained are supported by Raman spectroscopy. The TEM images obtained show evidence of the formation of the composite (core–shell) nanostructure in the samples. The optical investigation shows that the band gaps of the core–shell samples are indirect, like the TiO2 core itself, and increase with an increase in the core‐to‐shell molar ratio. These results also show that the synthesized core–shell samples are suitable candidates for use in optoelectronic devices.

НОВЫЕ ДАННЫЕ ПО ПАЛЕОГЕОГРАФИИ ВОСТОЧНОГО ПОБЕРЕЖЬЯ ЗАЛИВА ГРЁН-ФЬОРД (ОСТРОВ ЗАПАДНЫЙ ШПИЦБЕРГЕН) НА ОСНОВАНИИ ИЗУЧЕНИЯ ГОЛОЦЕНОВЫХ ОТЛОЖЕНИЙ НА МЫСЕ ФИННИСЕТ С ПРИМЕНЕНИЕМ ИЗОТОПНО-ГЕОХИМИЧЕСКИХ МЕТОДОВ

Актуальность исследования заключается в определении возраста моллюсков в заливе Грен-фьорд на архипелаге Шпицберген и физико-химических параметров среды их обитания в условиях угрозы разрушения геологических обнажений с находящимися в них моллюсками и костным материалом птиц и рыб в результате активно развивающихся процессов береговой термоабразии и техногенной нагрузки комбината «Арктикуголь». Цель: реконструкция основных физико-химических параметров среды обитания моллюсков в голоцене на основе определения видовой принадлежности моллюсков и изучения изотопно-геохимического состава раковин и вмещающих их горных пород. Методы: определение видовой принадлежности раковин моллюсков с использованием морфологического метода; разложение образцов раковин путем кислотного вскрытия; определение содержания макро- и микроэлементов на масс-спектрометре с индуктивно связанной плазмой Aurora Elite фирмы Bruker (Германия) и на волнодисперсном рентгенфлуоресцентном спектрометре LabCenter XRF-1800; определение отношений стабильных изотопов на масс-спектрометре Finningan МАТ253; определение возраста раковин моллюсков на жидкостном низкофоновом сцинтилляционном счетчике. Объекты: четвертичные отложения берегового клифа мыса Финнисет (залив Грён-фьорд, арх. Западный Шпицберген), раковины двустворчатых моллюсков и их фрагменты. Результаты. Определены обнаруженные комплексы макрофауны, представленные двустворчатыми моллюсками (Hiatella arctica, Mytilus edulis, Tridonta borealis, Mya truncata). Впервые для мыса Финнисет установлен возраст ископаемых раковин морских моллюсков, который составляет от 7970 до 8050 кал. лет. Установлено, что моллюски, найденные в нижних слоях, обитали в более теплой среде чем те, что обнаружены в вышележащих. Реконструированы редокс-условия с помощью соотношения Ni/Co в пределах от 1,5 до 9 единиц и V/Cr менее 2 единиц. Определено содержание U, которое изменяется в диапазоне от 0,2 мг до 4 мг. Анализ отношения Сu/Cr в разрезе показал, что расстояние от области сноса до области осадконакопления изменялось незначительно. Содержания Zn в горной породе свидетельствует о временной регрессии моря и преобладании континентального режима осадконакопления над морским. Определение концентраций Mn в раковинах моллюсков показало, что они обитали в прибрежно-морской зоне с высоким содержанием кислорода.

PENGUJIAN ANTI AGING SEDIAAN KRIM CANGKANG BEKICOT (ACHATINA FUNICA) PADA KELINCI (ORYCTOLAGUS CUNICULUS) YANG DIPAPAR SINAR UV

Snail shells is one of the mollusk phyla that contains protein and chitin function as protector from wind. The protector of wind is a process to prevent premature of the skin. This research aimed to find the formulation and efficacy test of snail shel cream (Achatina fulica) on rabbits (Oryctolagus cuniculus) as protector from the wind .The type of this research used experimental method with UV exposure method using Philips light intensity 10 Mw/cm2 where the back skin of animals try to be wrinkled. The samples of snail shells (Achatina fulica) used the powdered shell is then used as the active compound in the cream dosage formulation. Cracked cream shell powder formulas are formulated in four formulas with concentration 0% (without cracked cream shell powder) 5%, 10%, 15%, and testing the skin of the rabbit’s back (Oryctolagus cuniculus). Treatment is divided into 5 treatments namely treatment 1 as positive control used cream without active compound, treatment 2 concentration cream 5%, treatment 3 concentration cream 10%, treatment 4 concentration cream 15%, and treatment 5 as negative control used cream patent as the protector of x wind. The result of this research showed the effectivitas of concentration cream 5% which had 16,4 mm, and the positive control had 5,7 mm. It can conclude that with concentration 5% had the most powerful effectiveness than variation in the concentration of other creamsKeywords : Snail shells (Achatina fulica), Formulation, The protector of wind

Biomass energy potential of coconut varieties in Guyana

Guyana’s growing coconut industry has great potential for the generation of renewable energy using its waste materials currently discarded unsustainably. This study sought to investigate the energy potential of husks and shells of three common coconut varieties grown in Guyana. In this experiment, samples of coconut husks and shells were subjected to proximate, ultimate and calorific analyses. These analyses indicated that the energy value of the husks and shells of tall and dwarf coconuts were high, confirming the findings presented in previous studies. It was found that coconut shells have a higher energy content as opposed to the husk, mainly due to the presence of lignin and cellulose and a lower moisture content. The shell of one of the dwarf varieties (firmer and thinner) produced the greatest energy output. The coconut husks, however, followed closely where the tall variety reported the greatest energy value. Based on the energy output of the waste materials, possible energy, power, carbon, diesel and price savings were determined, if energy conversion is to be implemented. The analyses show substantial benefits for the country with respect to waste management, carbon emissions and costs, indicating the need for energy generation from coconut waste. A proposed gasification-pyrolysis system was developed and provided a baseline for the use of coconut biomass for energy generation in Guyana.

Photophysical and electronic properties of bismuth-perovskite shelled lead sulfide quantum dots.

Metal halide perovskite shelled quantum dot solids have recently emerged as an interesting class of solution-processable materials that possess the desirable electronic properties of both quantum dots and perovskites. Recent reports have shown that lead sulfide quantum dots (PbS QDs) with perovskite ligand-shells can be successfully utilized in (opto)electronic devices such as solar cells, photoconductors, and field-effect transistors (FETs), a development attributed to the compatibility of lattice parameters between PbS and certain metal halide perovskites that results in the growth of the perovskite shell on the PbS QDs. Of several possible perovskite combinations used with PbS QDs, bismuth-based variants have been shown to have the lowest lattice mismatch and to display excellent performance in photoconductors. However, they also display photoluminescence (PL), which is highly sensitive to surface defects. In this work, we present an investigation of the transport and optical properties of two types of bismuth-based perovskite (MA3BiI6 and MA3Bi2I9) shelled PbS QDs. Our photophysical study using temperature-dependent PL spectroscopy between 5 and 290 K indicates that the PL efficiency of the reference oleic acid (OA) capped samples is much higher than that of the Bi-shelled ones, which suffer from traps, most likely formed at their surfaces during the phase-transfer ligand exchange process. Nevertheless, the results from electrical measurements on FETs show the successful removal of the native-OA ligands, displaying electron dominated transport with modest mobilities of around 10-3 cm2 [V s]-1 - comparable to the reported values for epitaxial Pb-based shelled samples. These findings advance our understanding of perovskite shelled QD-solids and point to the utility of these Bi-based variants as contenders for photovoltaic and other optoelectronic applications.

Global oxygen isoscapes for barnacle shells: Application for tracing movement in oceans

It is helpful to understand the movement of animals and objects to inform species conservation and broader environmental management (e.g. by identifying the origin of marine debris). Tagging techniques are limited to investigations of future movement (e.g. after a tag has been applied), with no ability to understand where an animal or object has come from prior to encounter. However, studies that apply chemical techniques are able to address questions about historical movement prior to encounter, particularly through the analysis of stable isotopes from the tissues of migrating animals, or from barnacle shells that attach to migrating hosts. Barnacle shell isotope analysis is a promising technique that could provide a new understanding of the ecology of migrating marine fauna, or additionally the origin of marine debris. Here we use global datasets to assess the applicability of barnacle shell isotope techniques for identifying the origin and travel pathways of animals and objects that carry hitchhiking barnacles. We present the first global isoscapes for barnacle shell calcite, using these to identify areas that are likely to offer the finest spatial resolution for this application. We further demonstrate how isoscapes can be applied to back-trace animal migrations using real-world migration case studies of sea turtles and whales. We demonstrate that coastal areas and mid-latitude oceanic regions are likely to offer the best spatial resolution, and that migration pathways are able to be identified from successive barnacle shell samples. We expect that this work will allow for more efficient and precise future applications of barnacle shell isotope analyses to trace the movement and origin of barnacle hosts through marine waters.