One-Pot Noninjection Synthesis of Cu-Doped Zn_<i>x</i>Cd_1‑<i>x</i>S Nanocrystals with Emission Color Tunable over Entire Visible Spectrum

Unlike Mn doped quantum dots (d-dots), the emission color of Cu dopant in Cu d-dots is dependent on the nature, size, and composition of host nanocrystals (NCs). The tunable Cu dopant emission has been achieved via tuning the particle size of host NCs in previous reports. In this paper, for the first time we doped Cu impurity in Zn_<i>x</i>Cd_1‑<i>x</i>S alloyed NCs and tuned the dopant emission in the whole visible spectrum via variation of the stoichiometric ratio of Zn/Cd precursors in the host Zn_<i>x</i>Cd_1‑<i>x</i>S alloyed NCs. A facile noninjection and low cost approach for the synthesis of Cu:Zn_<i>x</i>Cd_1‑<i>x</i>S d-dots was reported. The optical properties and structure of the obtained Cu:Zn_<i>x</i>Cd_1‑<i>x</i>S d-dots have been characterized by UV–vis spectroscopy, photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). The influences of various experimental variables, including Zn/Cd ratio, reaction temperature, and Cu dopant concentration, on the optical properties of Cu dopant emission have been systematically investigated. The as-prepared Cu:Zn_<i>x</i>Cd_1‑<i>x</i>S d-dots did show PL emission but with quite low quantum yield (QY) (typically below 6%). With the deposition of ZnS shell around the Cu:Zn_<i>x</i>Cd_1‑<i>x</i>S core NCs, the PL QY increased substantially with a maximum value of 65%. More importantly, the high PL QY can be preserved when the initial oil-soluble d-dots were transferred into aqueous media via ligand replacement by mercaptoundeconic acid. In addition, these d-dots have thermal stability up to 250 °C

Noninjection Facile Synthesis of Gram-Scale Highly Luminescent CdSe Multipod Nanocrystals

Nearly all reported approaches for synthesis of high quality CdSe nanocrystals (NCs) involved two steps of preparation of Cd or Se stock solution in advance and then mixing the two reactants via hot-injection in high temperature. In this manuscript, Gram-scale CdSe multipod NCs were facilely synthesized in a noninjection route with the use of CdO and Se powder directly as reactants in paraffin reaction medium containing small amount of oleic acid and trioctylphosphine. The influence of various experimental variables, including reaction temperature, nature and amount of surfactants, Cd-to-Se ratio, and the nature of reactants, on the morphology of the obtained CdSe NCs have been systematically investigated. After deposition of ZnS shell around the CdSe multipod NCs, the PL QY of the obtained CdSe/ZnS can be up to 85%. The reported noninjection preparation approach can satisfy the requirement of industrial production bearing the advantage of low-cost, reproducible, and scalable. Furthermore, this facile noninjection strategy provides a versatile route to large-scale preparation of other semiconductor NCs with multipod or other morphologies

Design of a Soft Sensor for Monitoring Phosphorous Uptake in an EBPR Process

Phosphorus (P) is a key nutrient targeted for removal by wastewater treatment, increasingly being achieved using biological processes such as enhanced biological phosphate removal (EBPR). However, commercial instrumentation for automated measurement of P is costly and provides only limited temporal resolution, constraining implementation of real-time controls in EBPR processes. This study designs a soft sensor for real-time controls using a suite of relatively low-cost sensors (ion-selective electrodes) to monitor P removal by measuring (1) secondary cations tightly coupled to bioP metabolism and (2) process bulk chemistry. Data collected from a highly instrumented lab scale reactor are used to evaluate which and how many sensors are required to achieve this goal. Machine learning (ML) approaches (support vector machines, nonlinear logistic regression, random forest, and Bayesian classification) are evaluated for sensor data fusion and coupled with a decision metric to operationalize the algorithm for reactor controls. Two key results emerge: (1) use of the slope of sensor data (mV/min) rather than raw data (mV) as the predictor signals significantly improves accuracy and resilience of the soft sensor-based system and (2) the K+ ion-selective electrode, in combination with any of the four ML algorithms, is sufficient to detect completion of P removal (within study sampling granularity of 4 min) with 100% accuracy in real time. High accuracy is maintained even as process chemistry is varied to increase the interference experienced by the sensors, indicating that this soft sensor is viable for use in real wastewater applications

Bacillus cereus G2 Facilitates N Cycle in Soil, Further Improves N Uptake and Assimilation, and Accelerates Proline and Glycine Betaine Metabolisms of Glycyrrhiza uralensis Subjected to Salt Stress

Soil salinity is a severe abiotic stress that reduces crop productivity. Recently, there has been growing interest in the application of microbes, mainly plant-growth-promoting bacteria (PGPB), as inoculants for saline land restoration and plant salinity tolerance. Herein, the effects of the plant endophyte G2 on regulating soil N cycle, plant N uptake and assimilate pathways, proline and glycine betaine biosynthesis, and catabolic pathways were investigated in Glycyrrhiza uralensis exposed to salinity. The results indicated that G2 improved the efficiency of N absorption and assimilation of plants by facilitating soil N cycling. Then, G2 promoted the synthesis substrates of proline and glycine betaine and accelerated its synthesis rate, which increased the relative water content and reduced the electrolyte leakage, eventually protecting the membrane system caused by salt stress in G. uralensis. These findings will provide a new idea from soil to plant systems in a salinity environment

Image_2_Comprehensive physiological, transcriptomic, and metabolomic analyses reveal the synergistic mechanism of Bacillus pumilus G5 combined with silicon alleviate oxidative stress in drought-stressed Glycyrrhiza uralensis Fisch..tif

Glycyrrhiza uralensis Fisch. is often cultivated in arid, semi-arid, and salt-affected regions that suffer from drought stress, which leads to the accumulation of reactive oxygen species (ROS), thus causing oxidative stress. Plant growth-promoting bacteria (PGPB) and silicon (Si) have been widely reported to be beneficial in improving the tolerance of plants to drought stress by maintaining plant ROS homeostasis. Herein, combining physiological, transcriptomic, and metabolomic analyses, we investigated the response of the antioxidant system of G. uralensis seedlings under drought stress to Bacillus pumilus (G5) and/or Si treatment. The results showed that drought stress caused the overproduction of ROS, accompanied by the low efficiency of antioxidants [i.e., superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), the ascorbate (AsA)–glutathione (GSH) pool, total carotenoids, and total flavonoids]. Inversely, supplementation with G5 and/or Si enhanced the antioxidant defense system in drought-stressed G. uralensis seedlings, and the complex regulation of the combination of G5 and Si differed from that of G5 or Si alone. The combination of G5 and Si enhanced the antioxidant enzyme system, accelerated the AsA–GSH cycle, and triggered the carotenoid and flavonoid metabolism, which acted in combination via different pathways to eliminate the excess ROS induced by drought stress, thereby alleviating oxidative stress. These findings provide new insights into the comparative and synergistic roles of PGPB and Si in the antioxidant system of plants exposed to drought and a guide for the application of PGPB combined with Si to modulate the tolerance of plants to stress.</p

Color-Tunable Highly Bright Photoluminescence of Cadmium-Free Cu-Doped Zn–In–S Nanocrystals and Electroluminescence

A series of Cu doped Zn–In–S quantum dots (Cu:Zn–In–S d-dots) were synthesized via a one-pot noninjection synthetic approach by heating up a mixture of corresponding metal acetate salts and sulfur powder together with dodecanethiol in oleylamine media. After overcoating the ZnS shell around the Cu:Zn–In–S d-dot cores directly in the crude reaction solution, the resulting Cu:Zn–In–S/ZnS d-dots show composition-tunable photoluminescence (PL) emission over the entire visible spectral window and extending to the near-infrared spectral window (from 450 to 810 nm), with the highest PL quantum yield (QY) up to 85%. Importantly, the initial high PL QY of the obtained Cu:Zn–In–S/ZnS d-dots in organic media can be preserved when transferred into aqueous media via ligand exchange. Furthermore, electroluminescent devices with good performance (with a maximum luminance of 220 cd m^–2, low turn-on voltages of 3.6 V) have been fabricated with the use of these Cd-free low toxicity yellow-emission Cu:Zn–In–S/ZnS d-dots as an active layer in these QD-based light-emitting diodes

Image_1_Comprehensive physiological, transcriptomic, and metabolomic analyses reveal the synergistic mechanism of Bacillus pumilus G5 combined with silicon alleviate oxidative stress in drought-stressed Glycyrrhiza uralensis Fisch..tif

Glycyrrhiza uralensis Fisch. is often cultivated in arid, semi-arid, and salt-affected regions that suffer from drought stress, which leads to the accumulation of reactive oxygen species (ROS), thus causing oxidative stress. Plant growth-promoting bacteria (PGPB) and silicon (Si) have been widely reported to be beneficial in improving the tolerance of plants to drought stress by maintaining plant ROS homeostasis. Herein, combining physiological, transcriptomic, and metabolomic analyses, we investigated the response of the antioxidant system of G. uralensis seedlings under drought stress to Bacillus pumilus (G5) and/or Si treatment. The results showed that drought stress caused the overproduction of ROS, accompanied by the low efficiency of antioxidants [i.e., superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), the ascorbate (AsA)–glutathione (GSH) pool, total carotenoids, and total flavonoids]. Inversely, supplementation with G5 and/or Si enhanced the antioxidant defense system in drought-stressed G. uralensis seedlings, and the complex regulation of the combination of G5 and Si differed from that of G5 or Si alone. The combination of G5 and Si enhanced the antioxidant enzyme system, accelerated the AsA–GSH cycle, and triggered the carotenoid and flavonoid metabolism, which acted in combination via different pathways to eliminate the excess ROS induced by drought stress, thereby alleviating oxidative stress. These findings provide new insights into the comparative and synergistic roles of PGPB and Si in the antioxidant system of plants exposed to drought and a guide for the application of PGPB combined with Si to modulate the tolerance of plants to stress.</p

Size- and Composition-Dependent Energy Transfer from Charge Transporting Materials to ZnCuInS Quantum Dots

We studied the energy transfer processes from organic charge transporting materials (CTMs) to ZnCuInS (ZCIS) quantum dots (QDs) with different emission wavelength by steady-state and time-resolved photoluminescence (PL) spectroscopy. The change in the PL excitation intensity of the ZCIS QDs and the PL decay time of the CTMs clearly demonstrated an efficient energy transfer process in the ZCIS/CTM blend films. It was found that the efficiency of Förster resonance energy transfer significantly increases with increasing the particle size and decreasing the Zn content in the QDs, which is well consistent with the estimated Förster radii (<i>R</i>₀) varying from 3 to 5 nm. In addition, the PL quenching of the QDs related to the charge separation process was also observed in some of the samples. The energy transfer and charge separation processes in the films were well explained based on the band alignment between the ZCIS QDs and CTMs

Dual Emissive Manganese and Copper Co-Doped Zn–In–S Quantum Dots as a Single Color-Converter for High Color Rendering White-Light-Emitting Diodes

Novel white light emitting diodes (LEDs) with environmentally friendly dual emissive quantum dots (QDs) as single color-converters are one of the most promising high-quality solid-state lighting sources for meeting the growing global demand for resource sustainability. A facile method was developed for the synthesis of the bright green–red-emitting Mn and Cu codoped Zn–In–S QDs with an absorption bangdgap of 2.56 eV (485 nm), a large Stokes shift of 150 nm, and high emission quantum yield up to 75%, which were suitable for warm white LEDs based on blue GaN chips. The wide photoluminescence (PL) spectra composed of Cu-related green and Mn-related red emissions in the codoped QDs could be controlled by varying the doping concentrations of Mn and Cu ions. The energy transfer processes in Mn and Cu codoped QDs were proposed on the basis of the changes in PL intensity and lifetime measured by means of steady-state and time-resolved PL spectra. By integrating these bicolor QDs with commercial GaN-based blue LEDs, the as-fabricated tricolor white LEDs showed bright natural white light with a color rendering index of 95, luminous efficacy of 73.2 lm/W, and color temperature of 5092 K. These results indicated that (Mn,Cu):Zn–In–S/ZnS QDs could be used as a single color-converting material for the next generation of solid-state lighting