Retailer service strategy on livestreaming platforms considering free riding behavior.

Livestreaming e-commerce is a significant and effective digital tool for retailers to boost sales during the COVID-19 outbreak. Services on livestreaming platforms may be provided by either the manufacturer or the retailer. As service free riding across products becomes increasingly prevalent, the key issues retailers face include selecting which product should be promoted and who should provide service on the livestreaming channel. Using a game-theoretic framework, we investigate a retailer's optimal livestreaming service strategy that considers free riding between the retailer's store brand and a manufacturer's national brand. Our main findings are as follows. When service resources on the livestreaming channel are limited, (1) the retailer should not promote products with extremely low base demand, and (2) given that the national brand is promoted, if the two brands exhibit either very similar or significantly different features, the retailer should provide service for the national brand personally; otherwise, the retailer should delegate the service to the manufacturer. When livestreaming resources are unlimited, it may be unnecessary for the retailer to promote both brands if the store brand has a large base demand.

The synergism between self-activated and impurity-related emissions of LiCa3ZnV3O12: lattice distortion, energy transfer and temperature sensing effect.

Some of the metal vanadates have special self-activated luminescence. In order to further enrich its luminous color, luminescent impurity ions can be introduced into its lattice. The interaction between the self-activated emission and the impurity-related emission remains to be studied. In this work, the synergism between the two kinds of emission in LiCa3ZnV3O12 was explored from these three aspects: lattice distortion, energy transfer and temperature effect. Eu3+ ions replace Ca2+ ions in the lattice of LiCa3ZnV3O12, leading to a lattice contraction of the LCZV host, which depresses the self-activating emission around 500 nm. The characteristic linear emissions of Eu3+ ions are also observed benefiting from the energy transfer from [VO4]3- to Eu3+. Since the temperature quenching effect is more sensitive for the self-activated emission than that for the Eu3+-related ones, the phosphor can be applied as a luminescent temperature sensor, with the absolute and relative temperature sensitivities of 0.012 K-1 and 1.56% K-1, respectively.

Interface Nanoarchitectonics of TiO2/g-C3N4 2D/2D Heterostructures for Enhanced Antibiotic Degradation and Cr(VI) Reduction.

Mixed-phase TiO2 nanosheets were loaded on superior thin g-C3N4 nanosheets by a one-step solvothermal synthesis to form unique two-dimensional (2D)/2D heterostructures, which increased the interface area between TiO2 and g-C3N4, resulting in the easy migration of photogenerated carriers between two components. The rate of photocatalytic reactions increased significantly. Ciprofloxacin, tetracycline hydrochloride, and oxytetracycline hydrochloride were selected as target substances to test the photocatalytic degradation properties of the sample. The photoreduction performance of Cr(VI) was also tested. The results indicate that the photocatalytic degradation rate of antibiotics using TiO2/g-C3N4 heterostructures under visible light irradiation was twice that of g-C3N4. It took only 30 min to remove Cr(VI) (20 mg/L) under full solar spectrum irradiation; the photoreduction rate of Cr(VI) is also nearly twice that of pure TiO2. The improved performance was attributed to the rich active sites brought by mixed-phase TiO2 nanosheets. The extensive interface made the rapid migration of photogenerated carriers possible. The heterostructures revealed a band gap of 2.81 eV, which is less than that of TiO2 (3.2 eV), resulting in the increased absorption of visible light. Meanwhile, the mixed phase of TiO2 was beneficial for the separation of photogenerated carriers.

Electrospun Zn Doped CuFe2O4 Nanofibers with Enhanced Photo Fenton-Like Catalytic Activity.

One dimensional Zn doped CuFe2O4 spinel ferrite nanofibers were successfully prepared via a facile electrospinning method followed by two different calcination routes. The results showed that the as-prepared nanofibers through two-step calcination exhibited more uniform size distribution in diameter compared with those calcined by one-step method. X-ray diffraction (XRD) results indicated that with the increase of Zn content the position of diffraction peaks of Zn doped CuFe2O4 slightly shift towards lower 2θ angle because the ionic sizes of the Zn2+ (0.74 Å) is larger than that of Cu2+ (0.69 Å). Fourier transform infrared spectroscopy (FTIR) results showed that with increasing Zn content the position of vibrational band (590 cm-1) shifted towards the smaller wavenumber. Generally, photo-generated carriers increased with the increasing of Zn content. The photo Fenton-like catalytic results revealed that the doping of Zn facilitated the enhancement of degradation efficiency of catalysts. Additionally, 10 at.% Zn doped CuFe2O4 exhibited the best photo Fenton-like catalytic activity and the degradation efficiency of Rhodamine B (RhB) could reach 100% in 40 min. Finally, the enhancement of photo Fenton-like catalytic mechanism of the Zn doped CuFe2O4 nanofibers was mainly attributed to actived spinel structure lattice by Zn doping, which allows more Cu2+ and Fe3+ ions are involved in the photo Fenton-like catalytic reaction.

Coordination environment evolution of Co(ii) during dehydration and re-crystallization processes of KCoPO4·H2O towards enhanced electrocatalytic oxygen evolution reaction.

Development of efficient and stable electrodes for electrocatalytic oxygen evolution reaction (OER) is essential for energy storage and conversion applications, such as hydrogen generation from water splitting, rechargeable metal-air batteries and renewable fuel cells. Alkali metal cobalt phosphates show great potential as OER electrocatalysts. Herein, an original electrode design strategy is reported to realize an efficient OER electrocatalyst through engineering the coordination geometry of Co(ii) in KCoPO4·H2O by a facile dehydration process. Experimental result indicated that the dehydration treatment is accompanied by a structural transformation from orthorhombic KCoPO4·H2O to hexagonal KCoPO4, involving a concomitant coordination geometry evolution of Co(ii) from octahedral to tetrahedral configuration. More significantly, the local structural evolution leads to an advantageous electronic effect, i.e. increased Co-O covalency, resulting in an enhanced intrinsic OER activity. To be specific, the as-produced KCoPO4 can deliver a current density of 10 mA cm-2 at a low overpotential of 319 mV with a small Tafel slope of 61.8 mV dec-1 in alkaline electrolyte. Thus, this present research provides a new way of developing alkali metal transition-metal phosphates for efficient and stable electrocatalytic oxygen evolution reaction.

Regenerated WO2.72 nanowires with superb fast and selective adsorption for cationic dye: Kinetics, isotherm, thermodynamics, mechanism.

Hydrothermally prepared nonstoichiometry tungsten oxide (WO2.72) nanowires possess super selective adsorption performance for methylene blue (MB). The effects of dye concentration, contact time, pH and temperature on the adsorption properties of WO2.72 were investigated. The experimental results indicated that WO2.72 nanowires have a high adsorption capacity (547.32 mg/g) under neutral pH and a fast adsorption rate (adsorbing 100% within 6 min) for MB dye. The kinetic data showed good correlation coefficient (R2 > 0.99) for the pseudo-second-order. The equilibrium data suggesting the monolayer coverage of adsorbate as it fits well with the Langmuir isotherm model (R2 > 0.99). The energy functions of chemical thermodynamics revealed the adsorbate transport across the phase boundary is spontaneous and exothermic. Electrostatic absorption was proposed as the main adsorption mechanisms. Calcination treatment was utilized to decompose MB adsorbed on WO2.72 and regenerate WO2.72. The adsorption efficiency of WO2.72 nanowires can still reach 86.54% after recycling five times, which indicated that as-obtained WO2.72 nanowires are a very promising high-efficiency adsorbent for practical purification of dyeing waste water.

Cu2+ and Fe2+ Sensor Based on CdTe QD@ZIF-8 Composites.

TGA capped CdTe QDs have been encapsulated in miroporous ZIF-8, with no obvious deterioration of their photoluminescence property. The resulted CdTe QD@ZIF-8 composites show a higher luminescent stability in various buffer solution. The material has successfully been used as a luminescent indicator for the detection of Cu2+ and Fe2+ ions. The luminescence of CdTe QD@ZIF-8 composite quenches only in the presence of Cu2+ or Fe2+ ions. The linear ranges of detection have been estimated as 1~50 uM for Cu2+ ions and 1~60 uM for Fe2+ ions, respectively. A "competing transmission" mechanism has been proposed to explain the selectivity of the sensor to detecting Cu2+ and Fe2+ ions. Luminescent quenching can only occurred when the bonding power of QD surface surpasses the adsorptivity of the outside ZIF-8 to the metal ions.

A vanadate-based white light emitting luminescent material for temperature sensing.

Calcium magnesium vanadate-europium vanadate powders with a homogeneous distribution have been prepared by a sol-gel method followed by a sintering process. The as-prepared powders show both broadband emission around 520 nm and sharp peak emission at 617 nm under UV light excitation, which are ascribed to the one-electron charge transfer transition in the VO4 tetrahedra and the typical 5D0 → 7F2 transition of Eu3+. Energy transfer occurs between the vanadate and Eu ions. The emission color of the products can be tuned by controlling the Eu concentration and temperature. White light emission can be obtained at the Eu concentration of 15% and at room temperature. The temperature related luminescence properties have been studied for the sample with 15 mol% Eu. The intensity ratio between the broadband emission (due to VO4 tetrahedra) and the sharp peak emission (due to Eu3+ ions) decreases as the temperature increases in a linear relationship. The relative sensitivity (S R) of this luminescent temperature sensor has been calculated and a maximum has been gained at 455 K with the value equal to 1.83% K-1.

Synthesis and Photoluminescence of Red to Near-Infrared-Emitting CdTe( x) Se(1−x) /CdZnS Core/Shell Quantum Dots.

Red to near-infrared (NIR)-emitting ternary-alloyed CdTe (x) Se(1−x) (x = 0­0.3) quantum dots (QDs) with tetrapod and dot morphologies have been synthesized by a facile method using oleic acid (OA) as single capping agent. The controlled dot-shaped and tetrapod-shaped CdTe( x) Se(1−x) QDs can be successfully obtained by adjusting the content of Te element. It is clear that CdTe (x) Se(1−x) QDs display the tunable emission peaks from the visible light (613.4 nm) to the NIR range (791.6 nm). With an inorganic CdZnS shell coated on the surface of CdTe(0.1)Se(0.9) cores, the stability and PL efficiency of the resulting core/shell QDs can be improved dramatically, accompanied with the red-shift of emission peaks to longer wavelength (795.6 nm). Peculiarly, a large blue shift of emission spectrum of CdTe(0.3)Se(0.7)/CdZnS core/shell QDs is observed, which is mainly ascribed to the shrink of the size of QDs by the fracture of tetrapod arms.

Morphology Controlling of ZnO Sub-Micron- and Micro-Structures from Sub-Micron Zinc Citrate Precursor.

A wet-chemical route has been demonstrated to investigate the morphology evolution of high crystalline ZnO sub-micron- and micro-structures created from a zinc citrate precursor consisted of zinc citrate nanoparticles. The concentrations of precursor zinc citrate and the addition of trisodium citrate were key factors in the controlling of ZnO micro-morphology. Assembled growth resulted in the formation of ZnO sub-micron- and micro-structure with twin-cone and flower-like morphologies. The ZnO flower was consisted of cone petals. The shape of ZnO microstructures was further adjusted using trisodium citrate to created thin and thick hexagonal-plates. In the case of a high Zn concentration, thick hexagonal-plates were split into a flower-like morphology. The investigation of morphological evolution indicated that trisodium citrate is critical to control the growth rate of polar (0001) plane. The formation of a flower-like structure is ascribed to the assembly of crystal units with a high zinc citrate concentration.

Synthesis and Optical Properties of CdTe(x)Se(1-x)-Based Red to Near-Infrared Emitting Quantum Dots.

A series of red to near-infrared (NIR) emitting quantum dots (QDs) with spherical morphologies and tunable photoluminescence (PL) properties have been synthesized by a facile organic route using octadecene (ODE) as solvent and oleic acid (OA) as single capping agent. CdSe cores with the average size of 4.5 nm display the typical optical behaviors with the PL emission peak around 610 nm. The coating CdZnS shells are introduced on the surface of CdSe cores for improving the photostability and PL efficiency of the initial QDs. As the thickness of CdZnS shells increasing, the gradual red-shift of emission wavelength varying from 617 to 634 nm of the resulting QDs can be observed, along with the remarkable increase of PL quantum yield (QY). The composition-dependent CdTe(x)Se(1-x) (CdTeSe) cores with the emission in NIR region are easily carried out by adjusting the molar ratio of Se/Te. The abnormal variation of optical bowling effect is mainly ascribed to the composition effect of alloyed QDs. Compared with CdTe0.1Se0.9/CdZnS core/shell QDs, the introducing of CdZnS shells on CdTe0.05Se0.95 cores can exhibit better passivation effect on surface status, consequently leading to the red-shifted emission peaks in the range of 739-752 nm with the maximum PL QY reaching up to 45.09%. The unique PL properties of CdTeSe-based QDs in the red to NIR range make these core/shell QDs attractive for future biological sensing and labeling applications.

Real-time analysis of self-assembled nucleobases by Venturi easy ambient sonic-spray ionization mass spectrometry.

In this study, the real-time analysis of self-assembled nucleobases was employed by Venturi easy ambient sonic-spray ionization mass spectrometry (V-EASI-MS). With the analysis of three nucleobases including 6-methyluracil (6MU), uracil (U) and thymine (T) as examples, different orders of clusters centered with different metal ions were recorded in both positive and negative modes. Compared with the results obtained by traditional electrospray ionization mass spectrometry (ESI-MS) under the same condition, more clusters with high orders, such as [6MU7+Na](+), [6MU15+2NH4](2+), [6MU10+Na](+), [T7+Na](+), and [T15+2NH4](2+) were detected by V-EASI-MS, which demonstrated the soft ionization ability of V-EASI for studying the non-covalent interaction in a self-assembly process. Furthermore, with the injection of K(+) to the system by a syringe pumping, the real-time monitoring of the formation of nucleobases clusters was achieved by the direct extraction of samples from the system under the Venturi effect. Therefore, the effect of cations on the formation of clusters during self-assembly of nucleobases was demonstrated, which was in accordance with the reports. Free of high voltage, heating or radiation during the ionization, this technique is much soft and suitable for obtaining the real-time information of the self-assembly system, which also makes it quite convenient for extraction samples from the reaction system. This "easy and soft" ionization technique has provided a potential pathway for monitoring and controlling the self-assembly processes.

Synthesis of Ag nanoparticles with tunable sizes using N,N-dimethyl formamide.

Ag nanoparticles (NPs) were fabricated using N,N-Dimethyl formamide (DMF) as a solvent and reducing agent together with polyvinyl pyrrolidone (PVP) through a solvothermal method. The position of surface plasmon resonance (SPR) band of as-prepared Ag NPs changed with the chain length of PVP and red shifted with increasing the molecular weight of PVP. The concentration of PVP and reaction time affected the position of absorption peaks. The selective adsorption of PVP on the {100} and {111} facets of Ag depended on the kinds of solvents, which determined the driving force of the growth process of nanostructures. For comparison, ethylene glycol, water, and ethanol was added serving as solvents in the presence of PVP. The result indicates that DMF is a vital factor to kinetically control the formation of Ag NPs. Therefore the favorable facets of Ag nanostructures are {111} facets in a DMF solution. Ag nanoplates together with nanowires were observed in the system of ethanol and water, respectively.

Aqueous synthesis of MPA-capped CdTe nanocrystals emitted in near infrared with high quantum yield.

The high luminescent near infrared (NIR)--emitting CdTe nanocrystals (NCs) with 3-mercaptopropionic acid (MPA) as the stabilized molecules had been sucessfully fabricated by a facile and simple water-reflux method. By virtue of the characterizations for the as-prepared MPA-capped CdTe NCs, such as UV-Vis absorption, steady-state photoluminescence (PL), time-resolved PL spectra and PL image, the optical properties, diameters and morphologies of the CdTe NCs were investigated detailedly. With the increase of reflux time, the PL peak wavelength of NCs gradually shifted from red light to NIR spectra range within 7 h, and the PL quantum yield (QY) was increased firstly and then decreased slightly. It was worth noted that the NCs still showed a relative high PL QY of 47% as well as a narrow full width at half maximum (FWHM) of PL spectra even when the NCs emitted at the NIR wavelength of 754 nm. In addition, the average PL lifetime also exhibited an obvious increase as the growth of CdTe NCs due to the formation of thin CdS shell on the surface of CdTe. The PL stabilities for these NIR-emitting NCs (754 nm) in phosphate-buffered saline (PBS) buffer solution with various concentrations ranged from 0.005 to 0.1 M were also checked accordingly, and the results indicated that the as-prepared NIR-emitting CdTe NCs had a satisfied PL stability, implying a potential application in the biological field. Hopefully, all the superiority of these NIR-emitting CdTe NCs, such as high PL QY and PL lifetime, narrow FWHM of PL spectra, high PL stability in PBS solution, would make them to be a good candidate for biological applications in future.

Magnetic and noble metallic nanoparticles deposited on silica spheres via silanization.

A sol-gel technique has been developed to deposit various nanoparticles (NPs) on silica spheres. The silanization of the silica spheres using 3-mercaptopropyltrimethoxysilane (MPS) with mercapto groups (-SH) plays an important role for the deposition. After being functionalized by MPS, the deposition of magnetic and noble metallic NPs was performed by the reduction of Au3+ and Ag+ ions in-situ using sodium borohydride (NaBH4) or the co-precipitation reaction of Fe2+/Fe3+ ions and ammonia (NH3 H2O) at low reactant concentrations at room temperature. The transmission electron microscope (TEM) observation of samples exhibited the homogeneous deposition of Ag, Au, and Fe3O4 NPs on the silica spheres, in which the average size of Au and Ag NPs is 5 nm in diameter while the ones of Fe3O4 NPs is about 10 nm. In the case of without the silanization of silica spheres, the nucleation and growth of the NPs in solutions occur instead of the homogenous deposition. The results demonstrates that MPS containing the -SH metal-chelating functionality, can grow a layer in an ethanol solution on the silica spheres, thus improving the performance of the silica surface by grafting -SH groups. These hybrids offer a high absorption capacity for metal ions, all kinds of NPs can be deposited on the surface by co-precipitation channel on the basis of such property. The results presented hear may open up a novel and simple approach for the preparation of composite NPs.

Characterization of rhodamine self-assembled films using desorption electrospray ionization mass spectrometry.

Growth process information and molecular structure identification are very important for characterization of self-assembled films. Here, we explore the possible application of desorption electrospray ionization mass spectrometry (DESI-MS) that provides the assembled information of rhodamine B (Rh B) and rhodamine 123 (Rh 123) films. With the help of lab-made DESI source, two characteristic ions [Rh B](+) and [Rh 123](+) are observed directly in the open environment. To evaluate the reliability of this technique, a comparative study of ultraviolet-visible (UV-vis) spectroscopy and our method is carried out, and the result shows good correlation. According to the signal intensity of characteristic ions, the layer-by-layer adsorption process of dyes can be monitored, and the thicknesses of multilayer films can also be comparatively determined. Combining the high sensitivity, selectivity, and speed of mass spectrometry, the selective adsorption of similar structure molecules under different pH is recognized easily from extracted ion chronograms. The variation trend of dyes signalling intensity with concentration of polyelectrolyte is studied as well, which reflects the effect of surface charge on dyes deposition. Additionally, the desorption area, surface morphology, and thicknesses of multilayer films are investigated using fluorescence microscope, scanning electron microscope (SEM), and atomic force microscopy (AFM), respectively. Because the desorption area was approximately as small as 2 mm(2), the distribution situation of organic dyes in an arbitrary position could be gained rapidly, which means DESI-MS has advantages on in situ analysis.

CdSe/Cd(x)Zn1-xS core/shell nanocrystals: core morphology and luminescent property.

CdSe cores with rod (an aspect ratio of 1.8, d-5 nm) and spherical (an aspect ratio of 1, d-5 nm) morphologies were fabricated by two kinds of organic approaches through adjusting growth processes. Because of large difference of size and morphology, two kinds of cores revealed different absorption spectra. However, these cores exhibited almost same photoluminescence (PL) spectra with a red-emitting PL peak of around 625 nm. This is ascribed that they have a similar size in diameter. A graded Cd(x)Zn1-xS shell of larger band gap was grown around CdSe rods and spheres using oleic acid as a capping agent. Based on the growth kinetics of CdS and ZnS, interfacial segregation was created to preferentially deposit CdS near the core, providing relaxation of the strain at the core/shell interface. For spherical CdSe cores, the homogeneous deposition of the Cd(x)Zn1-xS shell created spherical core/shell nanocrystals (NCs) with a size of 7.1 nm in diameter. In the case of using CdSe cores with rod morphology, the anisotropic aggregation behaviors of CdS monomers on CdSe rods led to the size (approximately 10 nm in diameter) of spherical CdSe/Cd(x)Zn1-xS core/shell NCs with a small difference to the length of the CdSe rod (approximately 8.9 nm). The resulting spherical core/shell NCs created by the rod and spherical cores exhibited almost same PL peak wavelength (652 and 653 nm for using rod and spherical cores, respectively), high PL efficiency up to 50%, and narrow PL spectra (36 and 28 nm of full with at half maximum of PL spectra for the core/shell NCs with CdSe spheres and rods, respectively). These core/shell NCs provide an opportunity for the study of the evolution of PL properties as the shape of semiconductor NCs.