Organolead Research Articles

Aprotic Solvent Effect in Preparation of Organo Lead Iodide Perovskite Nanowires by Two-Step Spin-Coating Procedure

Lead-iodide perovskite (CH3NH3PbI3 ≡ MAPbI3) nanowires (NWs) were prepared by a two-step spin-coating technique by modifying one of the perovskite precursors with a small amount of aprotic solvent. In the two-step spin-coating technique, the perovskite precursors are MAI and PbI2. The first MAI powder is dissolved in isopropanol (IPA) to produce an isopropanol-MAI solution, while the second PbI2 is used in N, N-dimethylformamide (DMF) as an aprotic solvent. Here, a small amount of DMF was used with an IPA solution of MAI to grow 1D NWs based on MAPbI3 perovskite. Then, the film was formed directly from the MAPbI3 perovskite nanowires (PNWs) by coating the PbI2 layer with an IPA solution of MAI modified by DMF. The amount of DMF in the MAI/IPA solution was adjusted in the range between 0 and 50 μl. One-dimensional (1D) PNWs (∼100 nm diameter) and three-dimensional (3D) perovskite nanocrystals are compared. The structural and optical properties of the PNWs films are systematically investigated using X-ray diffraction patterns (XRD), scanning electron microscopy images (SEM), UV–vis absorption, and photoluminescence (PL). The result is that the presence of an additional solvent and its optimized amount in the MAI/IPA solution can increase the length and efficiency of charge transfer by facilitating perovskite transformation, as evidenced by the intensity of PL and the formation of a high-quality perovskite film. Compact, hole-free films with low trap states (crystal defects) were obtained. Further investigation of the lead iodide perovskite showed that reducing the dimensionality from 3D to 1D resulted in shorter wavelengths of the absorption edge and the PL peak in both the absorption and PL spectra. The shorter wavelengths indicate more localized exciton states in NWs. Finally, the amplified spontaneous emission (ASE) properties were obtained under picosecond laser excitation and a low ASE threshold was found at 10 and 53 μJ/cm2 for 1D and 3D, respectively, at about 300 nm film thickness.

PRODUCTION OF GASOLINE COMPONENTS IN ASEAN REFINERIES AND EFFECTS OF THE STRICTER FUEL QUALITY REQUIREMENT

Intensive implementation of the blue sky program in many countries imposed the use of reformulated gasoline with a very sophisticated specification. Motor gasoline is essentially a complex mixture of hydrocarbons distilled between 40 and 220 C, which consist of distillate fraction of crude oils and the conversion products of crude oil fractions. Small amounts of additives are also used to enhance various aspects of the performance of gasoline. In ASEAN refineries, over 740 MBPSD of feed- stock is processed which produce about 512 MBPSD of gasoline components. About 96 percent of the amount is processed in 39 units of the heterogeneous catalytic processes: i.e. cracking. reforming and isomerization, and the other 4 percent in 4 units of homogeneous catalytic processes: L.e. alkylation and polymerization. Volatility, octane number, hydroegtys4 com: position and impurity content are the most determinant criteria of the gasoline. In most spark-ignition internal combustion engines, the fuel is metered in liquid form through the carburettor or fuel injector, and is mixed with air and partially vaporized before entering the cylinders of the engine. Consequently. volatility, is and extremely important characteristic with respect to starting, driveability, vapor lock, dilution of engine oil fuel economy, and carburettor icing. To increase the octane level of gasoline an anti knock agent such as tetraethyl lead (TEL) or tetramethyl lead (TML) can also be used. Pres- sures to reduce atmospheric pollution are tending towards the reduction or elimination of lead from gasoline. Lead itself is known to be a poison and its presence in the exhaust gas is undesirable. Leudacts as a catalyst poison of catalytic converter installed to reduce carbon monaxide and hydrocarbon emission. Methyl tertiary butyl ether (MTBE) is one of the alternative to replace lead alkyls, and has been used as antiknock. Unleaded gasoline (ULG) has been introduced since 1990 in ASEAN Countries: The actual penetration of ULG utilization in the first half of 1998 are as follows : Brunei Darussalam 48.9 , Indonesia 0.6 %. Malaysia 80 %, Philippines 17.7 %, Singapore 81 %. and Thailand 100%. The passage of the Clean Air Act Amendment of 1990 in the USA has forced American refiners to install new facilities to comply with stricter specifications for fuels such as gasoline and diesel oil. Various terms in the models address quality of the gasoline blended, sulfur content, and total aromatics and olefins contents, RVP, the Tof distillation range, sulfur content, and oxygenated content. Specifications for the reformulated gasoline and the ASEAN commecial gasoline are presented. Driveability index (DI) has been standardized by ASTM D-4814-98a and in the near future this DI could be recommended in the specification for the reformulated gasoline. Reformu- lated gasoline can be blended from the high quality gasoline components. Volatitity (RVP. T T T and driveability index), octane number (RON, MON and octane distribution), and hydrocarbon compositions of the gasoline components, as well as the refinery configuration to improve the quality of the gasoline components, and the compositions of these improved gasoline components of reformulated gasoline production are briefly discussed in this paper.

Comparison of two extraction methods for the determination of organolead compounds using sodium tetrapropylborate as derivatization reagent

Two extraction methods of accelerate solvent extraction (ASE) and supercritical fluid extraction (SFE) were used to the extraction of trimethyl lead (TML) and triethyl lead (TEL), which were detected by gas chromatographer coupled with mass spectrometry. Sodium tetrapropylborate, as the derivatization reagent, was applied for the detection of gas chromatography. The recovery rate of ASE were about 88.2% (TML) and 86.4% (TEL) with 15 min consuming. The recovery rate of SFE were about 93.7% (TML) and 94.1% (TEL) with 40 min consuming. Two extraction methods of ASE and SFE were optimized, which were also analyzed in recovery, repeatability, accuracy, limit of detection (LOD) and other aspect. Both ASE and SFE exhibited rational recovery efficiency. The established methods were also applied to the real soil samples. SFE had better extraction effect according to time consumption, recovery rate, LOD and accuracy. However, ASE had more advantages in automated extraction, which could be applied to the pretreatment of large amounts of samples. • Trimethyl lead and triethyl lead of soil environment are extracted and measured. • ASE / SFE - GC system is established for the assessment of trimethyl lead and triethyl lead. • Experimental parameters of ASE and SFE are evaluated and optimized. • Difference and efficiency of ASE and SFE are analyzed for practical application.

INTRAMOLECULARLY HYPERCOORDINATED ORGANOLEAD COMPOUNDS: (o-MeOC6H4-CH2)PbPh2R, R = Ph, Cl, WITH Pb–O SECONDARY BONDING

Abstract The tetrahedral geometry of organolead(IV) compounds can be readily transformed by using an organic ligand containing a dangling-arm oxygen functionality. The acidity of the Pb center results in so-called secondary bonding between O and Pb thereby pushing the geometry at Pb toward a trigonal bipyramidal (tbp) structure. Replacing a phenyl group by a chlorine atom dramatically enhances this phenomenon. Thus for (o-methoxybenzyl) triphenyllead (4), and (o-methoxybenzyl)diphenyllead chloride (5), the Pb–O internuclear distances are 3.362(4) and 2.845(3) Å, respectively; 83% (4) and 70% (5) of the sum of the van der Waals Pb and O radii. Within the group 14 element congeners the structural analysis of the (o-methoxybenzyl)triphenylE compounds, E = Si, Ge, Sn, and now Pb, demonstrates the relative acidities of E are Si < Ge < Sn < Pb.

Rapid Speciation of Lead in Human Blood and Urine Samples Based on MWCNTs@DMP by Dispersive Ionic Liquid-Suspension-Micro-Solid Phase Extraction.

An efficient sorbent based on 2,3-dimercapto-1-propanol immobilized on multi-wall carbon nanotubes (MWCNTs@DMP) was developed for separation/speciation of organic and inorganic lead (alkyl-Pb, Pb2+) in human blood, urine, and water samples by dispersive ionic liquid-suspension-micro-solid phase extraction (DIL-S-μ-SPE). By procedure, the MWCNTs@DMP as solid phase, acetone, and ionic liquid (IL, [HMIM][PF6]) were mixed and injected to 10mL of the liquid phase at pH = 6.5. After shaking, the Pb(II) was extracted in MWCNTs@DMP and settled down in a conical tube with IL by centrifuging (Pb2+→: SH-SiO2@CNTs). The lead (Pb2+) was back-extracted from sorbent/IL in acidic pH and measured by atom trap atomic absorption spectrometry (AT-AAS). In addition, the organic lead (R-Pb, alkyl lead) converted to Pb(II) and total lead (T-Pb) was determined in the same conditions by UV radiation in 95°C. Under the optimal conditions, the linear range (9.5-480μgL-1), LOD (3.2μgL-1), and enrichment factor (10.4) were obtained (RSD < 5%). The adsorption capacity of the MWCNTs@DMP and MWCNTs was achieved as 191.6mgg-1 and 25.8mgg-1, respectively. The method was validated by standard reference materials (SRM 1643d, SRM 955, and SRM 2668), ET-AAS, and ICP-MS analysis in real samples. Graphical abstract.

Quantification of ultra-trace organolead species in environmental water by inductively coupled plasma mass spectrometry with online solid-phase extraction and high performance liquid chromatographic separation

Quantification of organolead compounds in environmental water is an essential task considering much higher toxicity and bioavailability of organolead species than inorganic plumbic ions. However, the speciation of ultra-trace organolead compounds at sub ng L−1 levels is challengeable for current instruments incorporating high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) and even offline enrichment that offer detection limits around several to tens of ng L−1. In this paper, an online solid-phase extraction (SPE) coupled HPLC-ICP-MS method was developed for speciation analysis of trace lead in water. Graphene oxide bounded silica particles (GO@SiO2) was utilized as the SPE adsorbent because of its superior performance over graphene bounded silica particles and commercial C18 packing particles. High enrichment factors (1603 for TML and 1376 for TEL) were obtained when lead species in 10 mL sample was adsorbed by 1 mM sodium dodecyl benzene sulfonate (SDBS) preconditioned GO@SiO2 at 10 mL min−1 and then eluted by 5 μL of 5 mM SDBS. Because of the highly efficient preconcentration, detection limits were downscaled to be 0.018 for TML and 0.023 ng L−1 for TEL with relative standard deviations below 5%. Additionally, the proposed method also yielded rapid separation of Pb(II), TML and TEL (8 min) by using green mobile phases (aqueous solutions of 5 mM sodium 1-pentanesulfonate at pH 2.5 with/without 4 mM tetrabutylammounium hydroxide). Upon successful application to fresh water, TML and TEL were only presented in the river water whereas Pb(II) was only existed in the tap water, along with accuracy validation by good spiked recoveries (93–106%).

Long range correlations of the ion current in SV channels. Met3PbCl influence study.

The long-range correlations within the current signal time series of the Beta vulgaris vacuolar membrane under the influence of organolead compound (Met3PbCl) are investigated. The current time series is transformed into a dwell time series. Then the rescaled range and detrended fluctuations analyses are used. It is shown that the presence of Met3PbCl in the solution decreases the mean value of the Hurst exponent and therefore influences the long-range correlations in ionic channel current. This observation is statistically significant. An ion channel model is built and the experimental results reconstructed and analysed.

A Facile Green Synthesis of Ultranarrow PbS Nanorods

Lead alkyl xanthate (alkyl = octyl, nonyl and dodecyl) complexes have been synthesized and characterized using micro-elemental analyses, infra-red and thermogravimetric analyses. The synthesized complexes were used as molecular precursors (SSP) for preparation of PbS nanowires using the hot injection technique in olive oil. The influence of the alkyl chain length on the structural and electronic properties on the PbS nanowires are reported. Powder X-ray diffraction (p-XRD) analyses of the as-synthesized nanowires show a face centred cubic rocksalt structure (halite). Transmission electron microscope (TEM) images of the as-synthesized PbS nanomaterials reveal 1-dimensional growth of nanowires. The estimated optical band gaps from the Tauc plots were 1.34, 1.41 and 1.45 eV for PbS nanowires obtained from the octyl, nonyl and dodecyl chain lengths respectively at 125 °C. The composition and purity of the as-synthesized PbS nanowires was observed by energy dispersive X-ray analysis (EDX) which showed an approximately 1:1 Pb to S ratios in all the as-synthesized nanowires.

Numerical modeling of exciton impact in two crystalographic phases of the organo-lead halide perovskite (CH3NH3PbI3) solar cell

To improve the power conversion efficiency of solar cells based on organo–lead halide perovskites, a detailed understanding of the device physics is fundamental. Here, a computational analysis of excitons impact is reported for these types of photocell. Numerical calculations based on the model, which take into account electronic charge carriers (electrons and holes), excitons and ions, have been carried out. The role of excitons in two crystallographic phases associated with different temperatures (80 K and 295 K) have been studied with the Saha relation, which clearly distinguishes a domination of free charge carriers or excitons. We have confirmed that excitons prevail in the orthorombic phase. Our work provides information about the photophysics of the lead halide perovskite, which allows for a better understanding of the operation of devices based on perovskite materials.

Fluorescence Blinking Beyond Nanoconfinement: Spatially Synchronous Intermittency of Entire Perovskite Microcrystals.

Abrupt fluorescence intermittency or blinking is long recognized to be characteristic of single nano-emitters. Extended quantum-confined nanostructures also undergo spatially heterogeneous blinking; however, there is no such precedent in dimensionally unconfined (bulk) materials. Herein, we report multi-level blinking of entire individual organo-lead bromide perovskite microcrystals (volume=0.1-3 μm3 ) under ambient conditions. Extremely high spatiotemporal correlation (>0.9) in intracrystal emission intensity fluctuations signifies effective communication amongst photogenerated carriers at distal locations (up to ca. 4 μm) within each crystal. Fused polycrystalline grains also exhibit this intriguing phenomenon, which is rationalized by correlated and efficient migration of carriers to a few transient nonradiative traps, the nature and population of which determine blinking propensity. Observation of spatiotemporally correlated emission intermittency in bulk semiconductor crystals opens the possibility of designing novel devices involving long-range (mesoscopic) electronic communication.

Fluorescence Blinking Beyond Nanoconfinement: Spatially Synchronous Intermittency of Entire Perovskite Microcrystals

AbstractAbrupt fluorescence intermittency or blinking is long recognized to be characteristic of single nano‐emitters. Extended quantum‐confined nanostructures also undergo spatially heterogeneous blinking; however, there is no such precedent in dimensionally unconfined (bulk) materials. Herein, we report multi‐level blinking of entire individual organo–lead bromide perovskite microcrystals (volume=0.1–3 μm3) under ambient conditions. Extremely high spatiotemporal correlation (&gt;0.9) in intracrystal emission intensity fluctuations signifies effective communication amongst photogenerated carriers at distal locations (up to ca. 4 μm) within each crystal. Fused polycrystalline grains also exhibit this intriguing phenomenon, which is rationalized by correlated and efficient migration of carriers to a few transient nonradiative traps, the nature and population of which determine blinking propensity. Observation of spatiotemporally correlated emission intermittency in bulk semiconductor crystals opens the possibility of designing novel devices involving long‐range (mesoscopic) electronic communication.

Between MOFs and molecules: organolead(IV) compounds with chain structures.

Organolead compounds are of interest mainly as catalysts and organolead halides have proved to be very efficient materials for solar cells. Two organolead(IV) dimethylarsinates, namely catena-poly[[triphenyllead(IV)]-μ-chlorido-[triphenyllead(IV)]-μ-dimethylarsinato-κ2O:O'], [Pb2(C6H5)6(C2H6AsO2)Cl]n or [(Ph3Pb)2Cl(O2AsMe2)], (1), and poly[chlorido(μ3-dimethylarsinato-κ3O:O,O':O')diphenyllead(IV)], [Pb(C6H5)2(C2H6AsO2)Cl]n or [(Ph2ClPb)(O2AsMe2)], (2), together with the triphenyllead(IV) diphenylphosphinate catena-poly[[triphenyllead(IV)]-μ-diphenylphosphinato-κ2O:O'], [Pb(C6H5)3(C12H10O2P)]n or [(Ph3Pb)(O2PPh2)], (3), have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy and mass spectrometry. In (1), a chain structure was found with alternating chloride and Pb-O-As-O-Pb arsinate bridges between five-coordinate PbIV atoms. In (2), bidentate and chelate-like bonded dimethylarsinate ligands form double chains with heptacoordinated PbIV atoms. In (3), a pentacoordinated PbIV atom is connected by Pb-O-P-O-Pb phosphinate bridges to form a linear chain. Obviously, the steric demand of the phenyl ligands at PbIV reduces the possibility of interconnections via polydentate ligands to one dimension only. Thus, no metal-organic frameworks (MOF) are formed but instead various chain structures are observed.

Highly Luminescent Phase-Stable CsPbI3 Perovskite Quantum Dots Achieving Near 100% Absolute Photoluminescence Quantum Yield.

Perovskite quantum dots (QDs) as a new type of colloidal nanocrystals have gained significant attention for both fundamental research and commercial applications owing to their appealing optoelectronic properties and excellent chemical processability. For their wide range of potential applications, synthesizing colloidal QDs with high crystal quality is of crucial importance. However, like most common QD systems such as CdSe and PbS, those reported perovskite QDs still suffer from a certain density of trapping defects, giving rise to detrimental nonradiative recombination centers and thus quenching luminescence. In this paper, we show that a high room-temperature photoluminescence quantum yield of up to 100% can be obtained in CsPbI3 perovskite QDs, signifying the achievement of almost complete elimination of the trapping defects. This is realized with our improved synthetic protocol that involves introducing organolead compound trioctylphosphine-PbI2 (TOP-PbI2) as the reactive precursor, which also leads to a significantly improved stability for the resulting CsPbI3 QD solutions. Ultrafast kinetic analysis with time-resolved transient absorption spectroscopy evidence the negligible electron or hole-trapping pathways in our QDs, which explains such a high quantum efficiency. We expect the successful synthesis of the "ideal" perovskite QDs will exert profound influence on their applications to both QD-based light-harvesting and -emitting devices.

Speciation of organometallic compounds of Hg, Sn, and Pb in the market garden soil in Ngaoundéré (Cameroon)

The objective of this work is to study the contamination of market garden soils by organomercury compounds (OMC), organotin compounds (OTC), and organolead compounds (OLC) using combustion debris (CD) as fertilizers. Therefore, two parcels of land used for gardening are rented on two sites. Soils were plowed and amended with CD. Samples of non-amended and amended soils were treated and then organometallic compounds of Hg, Sn, and Pb were analyzed by GC–ICP–MS. The results obtained revealed the presence of methyl-mercury (MeHg) in the soil at concentrations varying from non-detected in non-amended soil to 171.6 µg/kg in amended soil. Among the OLC identified, tetra-ethyl-lead (TEtPb) is the most represented in the soil with concentrations ranging from 18.45 to 44,612 µg/kg. OTC has also been identified with a predominance of mono-butyl-tin (MBT) followed by tri-methyl-tin (TMT) and di-methyl-tin (DMT). Soil treatments to CD have a significant influence on soil contamination to OMC, OTC, and OLC. This means that a significant amount of organometallic compounds found in amended soils would come from either direct or indirect CD.

Environmental Impact of Alkyl Lead(IV) Derivatives: Perspective after Their Phase-out.

The use of alkyl lead derivatives as antiknock agents in gasoline can be considered as one of the main pollution disasters of the 20th century because of both the global character of the pollution emitted and the seriousness of the impact on human health. Alkyl lead derivatives in themselves cannot be considered to be persistent pollutants because they readily degrade either before being released from the tailpipes or soon afterwards in the atmosphere. However, the inorganic lead they produced has been deposited in soils all over the planet, largely, but not exclusively in urban areas and along motorways, since the direct emission of lead into the atmosphere favored its dispersal over great distances: The signal of the massive use of alkyl lead derivatives has been found all over the world, including in remote sites such as polar areas. The short residence time of lead in the atmosphere implies that this compartment is highly responsive to changes in emissions. This was demonstrated when leaded gasoline was phased-out and is in striking contrast to the very long permanence of inorganic lead in soils, where resuspension is a permanent source of toxic lead.

Structural and Biochemical Characterization of Organotin and Organolead Compounds Binding to the Organomercurial Lyase MerB Provide New Insights into Its Mechanism of Carbon-Metal Bond Cleavage.

The organomercurial lyase MerB has the unique ability to cleave carbon-Hg bonds, and structural studies indicate that three residues in the active site (C96, D99, and C159 in E. coli MerB) play important roles in the carbon-Hg bond cleavage. However, the role of each residue in carbon-metal bond cleavage has not been well-defined. To do so, we have structurally and biophysically characterized the interaction of MerB with a series of organotin and organolead compounds. Studies with two known inhibitors of MerB, dimethyltin (DMT) and triethyltin (TET), reveal that they inhibit by different mechanisms. In both cases the initial binding is to D99, but DMT subsequently binds to C96, which induces a conformation change in the active site. In contrast, diethyltin (DET) is a substrate for MerB and the SnIV product remains bound in the active site in a coordination similar to that of HgII following cleavage of organomercurial compounds. The results with analogous organolead compounds are similar in that trimethyllead (TML) is not cleaved and binds only to D99, whereas diethyllead (DEL) is a substrate and the PbIV product remains bound in the active site. Binding and cleavage is an exothermic reaction, while binding to D99 has negligible net heat flow. These results show that initial binding of organometallic compounds to MerB occurs at D99 followed, in some cases, by cleavage and loss of the organic moieties and binding of the metal ion product to C96, D99, and C159. The N-terminus of MerA is able to extract the bound PbVI but not the bound SnIV. These results suggest that MerB could be utilized for bioremediation applications, but certain organolead and organotin compounds may present an obstacle by inhibiting the enzyme.

Lead Poisoning – The Roman Scenario and Today’s World

Lead Poisoning is unfamiliar to most of the people although it is still a potent industrial disease. A new explanation for the fall of Rome, based on evidences such as the study of old bones, old Roman recipes and Lead lined pots for brewing poisons esteemed as delicious by the ancient Roman aristocrats, is given. It is concluded that decline and eventual fall of the Roman Empire was a net result of many causes and not the Lead Poisoning alone, as generally believed. It is also a mistaken belief that Lead Poisoning was an occupational hazard. Lead alkyls used in Gasoline are environmental poisons subtly poisoning human populations globally. Inspite of strict regulations for removing most of the lead in gasoline, food cans, glazes, paints and medicines, it will continue to poison the mankind and earth’s biosphere to a significant extent for a long time.

ChemInform Abstract: Stimulating Excursions into Organolead Chemistry: Modular Domino Sequences Triggered by Oxidative Cleavage

AbstractReview: [123 refs.

Solubility product and heat of formation of lead alkyl xanthates by microcalorimetric titration

Microcalorimetric titration of lead ions with various alkyl xanthate ions was used to determine the solubility product (Kso) and the heat of formation (ΔH0) of lead alkyl xanthates (PbX2). The titration was carried out at 25°C in a 25mL size isoperibol reactor containing lead aqueous solutions with an ionic strength of 0.01M and pH6. Sodium ethyl xanthate, potassium propyl xanthate, potassium butyl xanthate and potassium amyl xanthate were used in this study. A new relationship was found for the Kso and the number of carbon atoms (N) in the xanthate alkyl chain, namely logKso=−10.033−1.049N. The relationship between ΔH0 and N was found to be ΔH0=−62.29−7.218N, in kJ/mol PbX2. The Kso and ΔH0 values that were determined by microcalorimetry were compared to those theoretically calculated taking into account the transfer of the xanthate alkyl chain from the aqueous solution to the lead xanthate solid phase. There was an excellent agreement between theoretical and calorimetric ΔH0. Low deviation was found between theoretical and calculated Kso.

Material Exchange Property of Organo Lead Halide Perovskite with Hole-Transporting Materials

Using X-ray diffraction (XRD), it was confirmed that the deposition of hole-transporting materials (HTM) on a CH3NH3PbI3 perovskite layer changed the CH3NH3PbI3 perovskite crystal, which was due to the material exchanging phenomena between the CH3NH3PbI3 perovskite and HTM layers. The solvent for HTM also changed the perovskite crystal. In order to suppress the crystal change, doping by chloride ion, bromide ion and 5-aminovaleric acid was attempted. However, the doping was unable to stabilize the perovskite crystal against HTM deposition. It can be concluded that the CH3NH3PbI3 perovskite crystal is too soft and flexible to stabilize against HTM deposition.