SrAlSi4N7:Eu2+

The new nitridoalumosilicate phosphor SrAlSi4N7:Eu2+ has been synthesized under nitrogen atmosphere at temperatures up to 1630°C in a radio-frequency furnace starting from Sr metal, α-Si3N4, AlN, and additional Eu metal. The crystal structure of the host compound SrAlSi4N7 has been solved and refined on the basis of single-crystal and powder X-ray diffraction data. In the solid, there is a network structure of corner-sharing SiN4 tetrahedra incorporating infinite chains of all edge-sharing AlN4 tetrahedra running along [001] (SrAlSi4N7: Pna21 (No. 33), Z = 8, a = 11.742(2) Å, b = 21.391(4) Å, c = 4.966(1) Å, V = 12.472(4) Å3, 2739 reflections, 236 refined parameters, R1 = 0.0366). The Eu2+-doped compound SrAlSi4N7:Eu2+ shows typical broadband emission originating from dipole-allowed 4f6(7FJ)5d1 → 4f7 (8S7/2) transitions in the orange-red spectral region (λmax = 632 nm for 2% Eu doping level, 450 nm excitation) with a spectral width of FWHM = 2955 (± 75) cm−1 and a Stokes shift ΔS = 4823 (± 100) cm−1. The luminescence properties make the phosphor an attractive candidate material as red component in trichromatic warm white light LEDs with excellent color rendition properties

Constructing Z-scheme LaTiO\u3csub\u3e2\u3c/sub\u3eN/g-C\u3csub\u3e3\u3c/sub\u3eN\u3csub\u3e4\u3c/sub\u3e@Fe\u3csub\u3e3\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e magnetic nano heterojunctions with promoted charge separation for visible and solar removal of indomethacin

© 2020 Elsevier Ltd Pharmaceutical effluents in water bodies pose hazards to the ecosystem because of their potent biological toxicity. Focusing on the removal of such toxic complicated pharmaceutical residues, an innovative LaTiO2N/g-C3N4@Fe3O4 heterojunction photocatalyst was assembled by a simplistic route for visible and solar light degradation of anti-inflammatory drug indomethacin (IDM). The LCF-20 catalyst (with LaTiO2N:g-C3N4 -0.2:1) shows excellent performance for visible light photodegradation of IDM, as evidenced by 97.3 % removal in just 45 min exposure which is about 13 times faster than bare g-C3N4. 83.4 % of total organic carbon removal was achieved by LVF-20 under visible light. Also, with natural sunlight, nearly 80 % of IDM was removed in 90 min irradiation. The heterojunction\u27s extensive intimate interfacial interactions amid LaTiO2N and g-C3N4 reduce the shortcomings of the two for a better photo-activity. The high visible activity, diminished recombination, high charge transfer is attributed to effective Z-scheme transfer facilitated by Fe3O4 nanoparticles. Scavenging experiments prove the importance of superoxide radicals as the dominant species responsible for photodegradation reaction. By mass spectrometry and total organic carbon analysis, a reaction mechanism was also reasonably proposed. The photocatalytic mechanism was discussed in light of conventional and Z-scheme transfer for better insight. The catalyst is stable, recyclable and magnetically separable. This investigation offers a new perspective in the rational design and manufacture of organic-inorganic nitrides based magnetically recoverable heterojunctions as LaTiO2N/g-C3N4@Fe3O4. Such heterojunctions present a new class of robust hierarchical photocatalytic materials which are capable of remediation of pharmaceutical residues under practical conditions

Hydrogen bonds in blends of poly(N-isopropylacrylamide), poly(n-ethylacrylamide) homopolymers, and carboxymethyl cellulose

Recently, it was reported that the physical crosslinking exhibited by some biopolymers could provide multiple benefits to biomedical applications. In particular, grafting thermoresponsive polymers onto biopolymers may enhance the degradability or offer other features, as thermothickening behavior. Thus, different interactions will affect the different hydrogen bonds and interactions from the physical crosslinking of carboxymethyl cellulose, the lower critical solution temperatures (LCSTs), and the presence of the ions. This work focuses on the study of blends composed of poly(N-isopropylacrylamide), poly(N-ethylacrylamide), and carboxymethyl cellulose in water and water/methanol. The molecular features, thermoresponsive behavior, and gelation phenomena are deeply studied. The ratio defined by both homopolymers will alter the final properties and the gelation of the final structures, showing that the presence of the hydrophilic groups modifies the number and contributions of the diverse hydrogen bonds.The authors want to acknowledge the funding obtained from the National Science Foundation of China (21574086), Shenzhen Fundamental Research Funds (No. KC2014ZDZJ0001A), Shenzhen Sci & Tech research grant (ZDSYS201507141105130), and China Postdoctoral Science Foundation Grant (2018M633119)

Designing of bentonite based nanocomposite hydrogel for the adsorptive removal and controlled release of ampicillin

© 2020 In pharmacy, semisynthetic antibiotics with beta-lactam ring are the most prominently used drugs. The use of these drugs for humans and animals is continuously expanding. Their presence in the water system even at low concentrations can prove to be fatal to living beings. Also, they can even grow antibiotic-resistant bacteria and thus elimination of such drugs becomes very essential. Our study is focused on batch experiments for adsorptive removal of ampicillin (AMP) and its cumulative release in different solutions using xanthan gum-cl-poly(itaconic acid)/bentonite (XG-cl-poly(IA)/BN) nanocomposite hydrogel. It was synthesized by facile microwave method. The adsorption data of AMP was analyzed using various isotherm models such as Langmuir, Freundlich, Temkin and kinetic models such as Pseudo-first order, Pseudo-second order and Intraparticle diffusion. The maximum adsorption capacity as determined from Langmuir model was 245.09 mg/g at 318 K and solution pH 7. Also, XG-cl-poly(IA)/BN nanocomposite hydrogel was evaluated for AMP release in distilled water and at different pH solutions (2.2, 5.4, 7.4 and 9.4). The maximum AMP release was observed at pH 2.2 (37%)

Effect of hydrophobic interactions on lower critical solution temperature for poly(N-isopropylacrylamide-co-dopamine methacrylamide) copolymers

For the preparation of thermoresponsive copolymers, for e.g., tissue engineering scaffolds or drug carriers, a precise control of the synthesis parameters to set the lower critical solution temperature (LCST) is required. However, the correlations between molecular parameters and LCST are partially unknown and, furthermore, LCST is defined as an exact temperature, which oversimplifies the real situation. Here, random N-isopropylacrylamide (NIPAM)/dopamine methacrylamide (DMA) copolymers were prepared under a systematical variation of molecular weight and comonomer amount and their LCST in water studied by calorimetry, turbidimetry, and rheology. Structural information was deduced from observed transitions clarifying the contributions of molecular weight, comonomer content, end-group effect or polymerization degree on LCST, which were then statistically modeled. This proved that the LCST can be predicted through molecular structure and conditions of the solutions. While the hydrophobic DMA lowers the LCST especially the onset, polymerization degree has an important but smaller influence over all the whole LCST range.This research was funded by Shenzhen Fundamental Research Funds number KC2014ZDZJ0001A, the Shenzhen Sci & Tech research grant number ZDSYS201507141105130, and the China Postdoctoral Science Foundation Grant number 2018M633119

Intelligent Machine Learning: Tailor-Making Macromolecules

Nowadays, polymer reaction engineers seek robust and effective tools to synthesize complex macromolecules with well-defined and desirable microstructural and architectural characteristics. Over the past few decades, several promising approaches, such as controlled living (co)polymerization systems and chain-shuttling reactions have been proposed and widely applied to synthesize rather complex macromolecules with controlled monomer sequences. Despite the unique potential of the newly developed techniques, tailor-making the microstructure of macromolecules by suggesting the most appropriate polymerization recipe still remains a very challenging task. In the current work, two versatile and powerful tools capable of effectively addressing the aforementioned questions have been proposed and successfully put into practice. The two tools are established through the amalgamation of the Kinetic Monte Carlo simulation approach and machine learning techniques. The former, an intelligent modeling tool, is able to model and visualize the intricate inter-relationships of polymerization recipes/conditions (as input variables) and microstructural features of the produced macromolecules (as responses). The latter is capable of precisely predicting optimal copolymerization conditions to simultaneously satisfy all predefined microstructural features. The effectiveness of the proposed intelligent modeling and optimization techniques for solving this extremely important ‘inverse’ engineering problem was successfully examined by investigating the possibility of tailor-making the microstructure of Olefin Block Copolymers via chain-shuttling coordination polymerization

Construction of dual Z-scheme g-C3N4/Bi4Ti3O12/Bi4O5I2 heterojunction for visible and solar powered coupled photocatalytic antibiotic degradation and hydrogen production: Boosting via I−/I3− and Bi3+/Bi5+ redox mediators

© 2020 Elsevier B.V. Inspired by waste to energy production, we report construction of dual Z-scheme advanced photocatalyst g-C3N4/Bi4Ti3O12/Bi4O5I2 heterojunction for coupled photocatalytic H2 evolution and degradation of antibiotics with high efficiency. The optimal CTBT-30 i.e (40 %g-C3N4/Bi4Ti3O12)/30 % Bi4O5I2 photocatalyst exhibited an excellent rate of H2 production under visible light (56.2 mmol g−1 h−1) along with simultaneous 87.1 % ofloxacin (OFL) removal. The H2 production rate is manifolds higher than in ultrapure water, sulfadiazine, rhodamine B and higher in hole scavenging triethanolamine. The interfacial intimate coupling with well-matched energy bands, foster the charge separation with effective Z-scheme transfer facilitated by I3−/I− and Bi3+/Bi5+ and redox mediators. The scavenging of majority of holes for direct oxidation or via [rad]OH radical formation leaves photogenerated electrons (at CB of g-C3N4 and Bi4O5I2) free for H2 evolution from H2O. Such work is promising for designing high photo-absorbing heterojunction photocatalysts for dual functionalities of clean energy production and environmental detoxification

E-beam irradiation of poly(vinylidene fluoride-trifluoroethylene) induces high dielectric constant and all-trans conformation for highly ionic conductive solid-state electrolytes

Polymer matrices have limited abilities to dissociate lithium salts and transport ions, thus making most solid-state polymer electrolytes (SPEs) have extremely low ionic conductivities (10−7–10−5 S/cm) at 25 ℃. In this work, a high-energy electron-beam (e-beam) irradiation is applied to a poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] SPE to improve the ionic conductivity. P(VDF-TrFE) easily shows pure all-trans (TTTT) conformation with all fluorine atoms located on one side of the carbon chain to provide an ion transport highway. E-beam irradiation keeps large amounts of TTTT conformation of P(VDF-TrFE) and produces –CF3 side groups, where the latter expands the interchain distance to split the large ferroelectric domains into nanosize to induce a unique relaxor ferroelectric behavior. This enhances the dielectric constant of the irradiated P(VDF-TrFE) from 15 to 20 and thus facilitates lithium salt dissociation. As a consequence, the ionic conductivity of the irradiated P(VDF-TrFE) SPE is increased from 5.8 × 10−5 to 1.6 × 10−4 S cm−1 at 25 ℃. The solid-state Li//Li symmetrical cell cycles for more than 3000 h at 25 ℃ without a short circuit. Furthermore, the solid-state LFP//Li cell cycles stably for more than 350 cycles with a capacity retention of around 91.3% at 1 C and 25 ℃. This study paves a new way to prepare high-performance SPEs by inducing high dielectric constants and abundant TTTT conformations through e-beam irradiation

Silicate glass matrix@Cu\u3csub\u3e2\u3c/sub\u3eO/Cu\u3csub\u3e2\u3c/sub\u3eV\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e7\u3c/sub\u3e p-n heterojunction for enhanced visible light photo-degradation of sulfamethoxazole: High charge separation and interfacial transfer

© 2020 Elsevier B.V. Focusing on the treatment of pharmaceuticals contaminated water by advanced oxidation processes, a novel three dimensional silicate glass matrix (3-DG) coupled Cu2O/Cu2V2O7 p-n heterojunction was constructed by in-situ hydrothermal technique. The optimal Cu2O/Cu2V2O7 with 30 wt % Cu2V2O7 (CV-30) degrades 90.1 % sulfamethoxazole (SMX) in 60 min and nearly 100 % removal in 45 min via coupling with 3-DG. Under natural sunlight ∼ 80 % SMX removal was observed. The internal electric field of the p-n junction facilitates the electron flow via the interface. 3-D silicate glass increases the visible light absorption dramatically via internal reflection which facilitates higher exposure for the junction and shortens the diffusion length of charge carriers. The effect of reaction parameters suggests that HCO3− and CO32− ions substantially escalate the SMX removal rate. Scavenging experiments and ESR probe suggest [rad]O2− as the main active species followed by [rad]OH radicals. The degradation products were detected by LC–MS analysis and a degradation mechanism was also predicted. The photocatalytic mechanism was explained in terms of the electron transfer facilitated by conventional transfer and Z-scheme. This strategy to construct such highly visible and solar active p-n heterojunctions will pave way for future opportunities for the degradation of recalcitrant pharmaceutical pollutants