Deep Learning for Additive Screening in Perovskite Light-Emitting Diodes.

Additive engineering with organic molecules is of critical importance for achieving high-performance perovskite optoelectronic devices. However, experimentally finding suitable additives is costly and time consuming, while conventional machine learning (ML) is difficult to predict accurately due to the limited experimental data available in this relatively new field. Here, we demonstrate a deep learning method that can predict the effectiveness of additives in perovskite light-emitting diodes (PeLEDs) with a high accuracy up to 96 % by using a small dataset of 132 molecules. This model can maximize the information of the molecules and significantly mitigate the duplicated problem that usually happened with previous models in ML for molecular screening. Very high efficiency PeLEDs with a peak external quantum efficiency up to 22.7 % can be achieved by using the predicated additive. Our work opens a new avenue for further boosting the performance of perovskite optoelectronic devices.

Layer-by-layer self-assembly xylenol orange functionalized CdSe/CdS quantum dots as a turn-on fluorescence lead ion sensor.

A new turn-on fluorescence sensor based on xylenol orange (XO) functionalized CdSe/CdS quantum dots (QDs) is developed for the determination of lead ion. CdSe/CdS QDs were first modified by mercaptoacetic acid (MAA). The MAA-modified QDs were then capped with the natural biopolymer chitosan and the negatively charged XO. The XO-functionalized QDs were formed via the layer-by-layer self-assembly reaction. The fluorescence of the QDs was quenched by electron transfer mechanism after XO was bound to the QDs. Upon the addition of Pb(2+), a dramatic enhancement of the fluorescence intensity was observed, which resulted from the coordination between Pb(2+) and XO on QDs surface and the disruption of the electron transfer mechanism. Hence the fluorescence of the QDs was recovered. The recovery of the fluorescence intensity showed a good linear relationship with the concentration of Pb(2+) added from 0.05 to 6 µmol L(-1). A detection limit of 0.02 µmol L(-1) was achieved. This method was successfully applied to the determination of lead in real samples with satisfactory results.

Removal of ammonia nitrogen from wastewater using an aerobic cathode microbial fuel cell.

A new system for removing ammonia nitrogen was developed, which integrated a microbial fuel cell (MFC) with an aerobic bioreactor. A three-chamber reactor consisted of an anode chamber, a middle chamber and a cathode chamber. The chambers were separated by an anion exchange membrane and a cation exchange membrane (CEM), respectively. Driven by the power generated by the MFC, NH4(+) in the middle chamber could migrate through CEM into the cathode chamber. The migrated NH4(+) further removed via biological denitrification in the cathode chamber. Up to 90.2% of total NH4(+)-N could be removed with an initial concentration of 100 mg/L in 98 h. Affecting factors were investigated on the removal efficiency including cathode surface area, electrode spacing, chemical oxygen demand concentration, dissolved oxygen concentration, and NH4(+)-N concentration. The system was characterized by simple configuration and high efficiency, and was successfully applied to the treatment of brewery wastewater.

Dithizone functionalized CdSe/CdS quantum dots as turn-on fluorescent probe for ultrasensitive detection of lead ion.

An ultrasensitive fluorescent probe is developed for the determination of lead ion by utilizing dithizone (Dz) functionalized CdSe/CdS quantum dots (QDs). Dithizone was bound to the QDs via a surface coordinating reaction to form QDs-Dz conjugates and quench fluorescence of the QDs by fluorescence resonance energy transfer (FRET) mechanism. Upon the addition of Pb(2+), a dramatic enhancement of the fluorescence intensity was observed, which resulted from the FRET pathway shutting off, and hence the fluorescence of the QDs was recovered. Two successive linear ranges of 0.01-1000 nmol L(-1) and 1-20 µmol L(-1) allow a very wide determination of Pb(2+) concentration from 0.01 nmol L(-1) to 20 µmol L(-1), with a detection limit of 0.006 nmol L(-1). The fluorescent probe was successfully applied to the determination of lead in environmental samples with satisfactory results.

DNAzyme-based turn-on chemiluminescence assays in homogenous media.

In this work, novel biosensing systems were developed for DNAzyme-based assays in homogenous aqueous media. The two halves of a horseradish peroxidase mimicking DNAzyme were assembled onto different gold nanoparticle surfaces through hybridization with corresponding linking DNA sequences. In the analyses, the target molecules were recognized by the linking DNA. This recognition broke the hybridization and released the DNAzyme halves from the nanoparticle surface into the solution. Together, both the DNAzyme halves combined with a cofactor hemin and turned into a catalytic hemin/G-quadruplex structure, which amplified the luminol oxidation for a turn-on chemiluminescence signaling. Based on this nanoparticle-based DNAzyme-halves design, only low background noise showed up within the homogenous solution and no separation was required in the detection steps. Aptasensor and DNA sensor were developed and analyses of the target molecules adenosine and target DNA were achieved down to 0.7 µM and 0.3 nM respectively with satisfactory selectivity.

Diethyldithiocarbamate functionalized CdSe/CdS quantum dots as a fluorescent probe for copper ion detection.

A new fluorescent probe for copper ion detection is reported that it is based on the quenching of the fluorescence of the diethyldithiocarbamate (DDTC)-functionalized quantum dots (QDs) in the presence of copper ions. DDTC was bound to the QDs via the surface ligand exchange to form DDTC-QDs conjugates following the capping of 2-mercaptoacetic acid on the core-shell CdSe/CdS QDs. It was found that the fluorescence intensity of the conjugates was quenched after coordinated with Cu(2+). A linear relationship existed between the extent of quenching and the concentration of copper in the range of 0-100 µg L(-1), with a detection limit of 0.29 µg L(-1) (3σ). The DDTC-functionalized QDs showed excellent selectivity for Cu(2+) over other metal cations. The fluorescent probe was successfully used for the determination of copper in environmental samples.

Electricity generation in a membrane-less microbial fuel cell with down-flow feeding onto the cathode.

A novel membrane-less microbial fuel cell (MFC) with down-flow feeding was constructed to generate electricity. Wastewater was fed directly onto the cathode which was horizontally installed in the upper part of the MFC. Oxygen could be utilized readily from the air. The concentration of dissolved oxygen in the influent wastewater had little effect on the power generation. A saturation-type relationship was observed between the initial COD and the power generation. The influent flow rate could affect greatly the power density. Fed by the synthetic glucose wastewater with a COD value of 3500 mg/L at a flow rate of 4.0 mL/min, the developed MFC could produce a maximum power density of 37.4 mW/m(2). Its applicability was further evaluated by the treatment of brewery wastewater. The system could be scaled up readily due to its simple configuration, easy operation and relatively high power density.

Gas-phase chemiluminescence with ozone oxidation for the determination of total tin in environmental samples using flow injection hydride generation and cryotrapping.

The gas-phase chemiluminescence detection system based on the ozonization of gaseous hydride was exploited and utilized for the determination of total tin in environmental samples. After sample treatment, tin was reduced to stannane by sodium borohydride in a phosphate buffer medium of pH 5.8. Flow injection technique was used to control the reaction precisely and reproducibly. The generated stannane, carried by helium, was separated from liquid and dried using an ice-salt cryogenic bath and subsequently trapped in a glass U-tube immersed in liquid nitrogen. The cryotrapped stannane was vaporized by bringing the tube to room temperature and subsequently carried in a flow of helium to a reaction chamber where ozone was used to oxidize the stannane. Chemiluminescence was produced during the oxidation process, which was utilized for the measurement of tin. Under optimal conditions, a detection limit of 0.32 µg L(-1) was achieved with a relative standard deviation of 3.1% (10.0 µg L(-1) Sn, n=11). Interferences from transition metal ions and other hydride forming elements were reduced by the addition of 1,10-phenanthroline and through optimized hydride generation conditions. The proposed system was applied to the determination of Sn in water and soil samples with satisfactory results.

Determination of antimony in environment samples by gas phase chemiluminescence detection following flow injection hydride generation and cryotrapping.

A novel method for the determination of antimony in environmental samples was developed with gas phase chemiluminescence detection following flow injection hydride generation and cryotrapping. The stibine, generated from samples by borohydride reduction of antimony using flow injection technique, was separated by using a new gas-liquid separator, dried with an ice-salt cryogenic bath and concentrated in a glass U-tube immersed in liquid nitrogen. Re-vaporization of stibine based on its boiling point was achieved by allowing the tube to warm at room temperature. A gas phase chemiluminescence signal was produced during the ozonation of the hydride in a reflective chamber. Under optimal conditions, the proposed method was characterized by a wide linear calibration range from 1.0microgL(-1) to 10.0mgL(-1) with a detection limit of 0.18microgL(-1) (n=11). The relative standard deviation for 10.0microgL(-1) antimony was 3.56% (n=11) and the sampling rate was 15 samples h(-1). Blank signal was reduced by the purification of reagents and the interference from transition metal ions was eliminated by the addition of L-cysteine into samples. The method was applied to the determination of antimony in environmental samples with satisfactory results.

A novel CdSe/CdS quantum dot-based competitive fluoroimmunoassay for the detection of clenbuterol residue in pig urine using magnetic core/shell Fe3O4/Au nanoparticles as a solid carrier.

Quantum dots (QDs) are semiconductor fluorescent nanoparticles, which can be used for food safety or environmental monitoring with high sensitivity. This work demonstrates the feasibility of detecting clenuterol residue in pig urine using CdSe/CdS quantum dots as fluorescent labels based magnetic core/shell Fe3O4/Au nanoparticles (MCFN) as solid carriers. The detection of clenbuterol is carried out by a fluoroimmunoassay-based biosensor using competitive binding between conjugated clenbuterol antigen-CdSe/CdS QDs and free clenbuterol with immobilized clenbuterol antibodies on MCFN. This assay method allows for clenbuterol determination in a linear working range of 0.5-20000 pg mL(-1). It would provide a simple, rapid, and ultra-sensitive detection method for clenbuterol or other biomolecular analysis.

Spectrophotometric determination of triclosan in personal care products.

A spectrophotometric method for the determination of triclosan in personal care products was proposed. It was based on the reaction of sodium nitrite with p-sulfanilic acid in an acidic medium to form diazonium ion, with which triclosan further formed an azo compound in an alkaline medium. The resulting yellow colored product has a maximum absorption at 452 nm. A good linear relationship (r=0.9999) was obtained in the range of 0-30 mg L(-1) triclosan. A detection limit of 0.079 gL(-1) was achieved and the relative standard deviation was 0.24% (n=11) at 14 mg L(-1) triclosan. The proposed method has been applied to the analyses of triclosan in several personal care products and the results were in good agreement with those obtained by high-performance liquid chromatography.

Determination of formaldehyde in foodstuffs by flow injection spectrophotometry using phloroglucinol as chromogenic agent.

A spectrophotometric method for the determination of formaldehyde in foodstuffs was described by using phloroglucinol as the chromogenic agent. The reaction between formaldehyde and phloroglucinol could occur rapidly at room temperature under mild conditions. The spectrophotometric measurements were conducted at 474nm of an unstable intermediate orange product of the reaction, which greatly increased the sample throughput. Flow injection technique was used to control the merging and reaction timing of the reagents and sample. A detection limit (3sigma) of 0.023microg ml(-1) was achieved. The relative standard deviation was 0.29% for the determination of 7microg ml(-1) formaldehyde (n=11). The proposed method was applied to the analyses of formaldehyde in several preserved foodstuffs and the results were in good agreement with those obtained by a standard method.

Determination of trace amounts of lead, arsenic, nickel and cobalt in high-purity iron oxide pigment by inductively coupled plasma atomic emission spectrometry after iron matrix removal with extractant-contained resin.

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was applied to the determination of lead, arsenic, nickel and cobalt in high-purity iron oxide pigment. Samples were dissolved with hydrochloric acid and hydrogen peroxide. The digest was passed through a column, which was packed with a polymer resin containing a neutral organophosphorus extractant, tri-n-butylphosphate. Iron was sorbed selectively on the resin and the analytes of interest passed through the column, allowing the effective separation of them from the iron matrix. Conditions of separation were optimized. The detection limits (3sigma) in solution were 10, 40, 7 and 5 microg L(-1), and in pigment were 0.2, 0.8, 0.14 and 0.1 mg kg(-1) for lead, arsenic, cobalt and nickel, respectively. The recoveries ranged from 95% to 107% when sample digests were spiked with 5 microg of the analytes of interest, and relative standard deviations (n=6) were 1.5-17.6% for the determination of the spiked samples. The method was successfully applied to the determination of trace amounts of these elements in high-purity iron oxide pigment samples.

[Rapid analysis of mercury in sediments by laser ablation inductively coupled plasma mass spectrometry].

Laser ablation inductively coupled plasma mass spectrometry was used for the rapid analysis of mercury in sediment samples. The ground samples were simply briquetted prior to laser ablation. The effects of internal standardization, particle size and elemental speciation on the analytical performance were investigated. Direct analysis of sediment samples without internal standardization could yield satisfactory results. Elemental speciation and particle size within the studied range did not significantly affect the measurements. The calibration curve was obtained simply by analyzing one soil and two sediment reference materials. With the proposed LA-ICP-MS system, a detection limit of 0.02 mg x kg(-1) was achieved with a sample through put of 10 h(-1). Analytical results of sediment samples using the current system were in good agreement with those by isotope dilution hydride-generation ICP-MS.