Morphology Genetic Metal-Organic Frameworks-Based Biocomposites for Efficient Photocatalytic Hydrogen Evolution.

Metal-organic frameworks (MOFs), MIL-125 and UiO-66, were modified on the butterfly wings (BWs) by chemical bonds, and CdS was grown in situ on them through a solvothermal approach. The BWs enable the biocomposites to possess a wider (>600 nm) and stronger light absorption. The in situ growth method can produce highly active and stable biocomposites. These novel morphologic MOF/CdS biocomposites were characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and so on. The resulting composites were tested for photocatalytic hydrogen production through water splitting with platinum and lactic acid as the co-catalyst and sacrificial agent, respectively. The two samples showed higher activity than bulk CdS, MOFs, or their composites. Therefore, this paper provides an appropriate method to obtain the MOF/CdS biocomposites, and the resulting biocomposites are proved to be efficient catalyst systems for hydrogen evolution from water under visible light with a wider wavelength.

Hierarchical Gelation of a Pd12L24 Metal-Organic Cage Regulated by Cholesteryl Groups.

The creation of supramolecular assemblies by assembly of structurally simple components via supramolecular interactions provides an opportunity to develop functional materials with hierarchical complexibility. Herein, we report an assembly approach to supramolecular gels based on metal-organic cages with tunable hierarchical structures and properties. A Pd12L24 cage (L is cholesteryl-functionalized 3,5-bis(4-pyridyl)benzene) bearing 24 cholesteryl groups is used as a supramolecular building unit and molecular platform for functionalization with tunable functional behaviors. The Pd12L24 cage motifs spontaneously self-assemble into gels where orthogonal metal-organic coordination and cholesteryl-cholesteryl interactions are involved in the gelation. The Pd12L24 cage exhibits a reversible transition between solution and aggregated gel states in response to temperature. The gelation and the mechanical property are rarely regulated by deuterated solvents and tetramethylsilane. The mechanical property of the gel materials is tunable by varying the content of cholesteryl groups of Pd12L24. Functional moieties (e.g., luminescent TPE group) can be introduced on the cage, and the luminescent property changes while the structure is maintained. The Pd12L24 gel shows visible anion-responsive behaviors arising from the hierarchical structure.

Gelation of Luminescent Supramolecular Cages and Transformation to Crystals with Trace-Doped-Enhancement Luminescence.

Supramolecular gels with hierarchical order and complexity have been assembled. The gels contain well-defined Ag4L2 luminescent supramolecular cages as cores, which are cross-linked via Ag-P coordination bonding. The resulting gels are highly luminescent and exhibit rich stimuli-responsive behaviors toward mechanical and chemical (nitroexplosive and anions) stimuli. The gels could be transformed to highly luminescent crystal materials upon addition of halogen anions, in which only traces of lumiphor are accommodated in a host crystal matrix.

[Research on the Spectrophotometry for Determination of Flavonoids in Waste Residue of Stevia Rebaudiana].

A spectrophotometric method for the determination of flavonoids content in Waste Residue of Stevia Rebaudiana was established by comparing the UV-Vis spectra with three spectrophotometric methods: Direct, AlCl3 and NaNO2-Al (NO3)3-NaOH method. The effects of spectrophotometric reaction were studied by analyzing the wavelength, the dosage of color development reagent, reaction time, temperature and pH. The further research was studied by analyzing linearity between the absorbance and the concentration, the stability of this color system, the recovery rate and so on. The results showed that NaNO2-Al(NO3)3-NaOH method was best. The wavelength was 500 nm. The standard sample was rutin. There was a good linear relationship in the ranges of 2 - 24 µg x mL(-1), correlation coefficient R2 = 0.999 5. The recovery of the additional sample was 96.0%-104.3%. The relative standard deviation(RSD) is respectively 3.75%. The dosages of NaNO2 and Al(NO3)3 both were 1.0 mL, both of their reaction time was 6 min. The dosage of NaOH was 15.0 mL and the reaction time was 15 min. The temperature in the whole process of the reaction must be maintained at 40 degrees C and pH is 5. The spectrophotometric condition was further improved on the determination of flavonoids content. This method, which is simple, rapid and accuracy, can be used in practical application.

A Study on the Preparation of a Vulcanizing Mixture and Its Application in Natural Rubber Latex.

The traditional preparation process of natural rubber latex requires tedious treatment of a variety of rubber additives. In this paper, a new process of wet mixed grinding was used to prepare a reinforced vulcanization mixture and a rapid vulcanization effect. The effect of different amounts of vulcanization mixtures on the mechanical properties of natural latex film was studied, and the pre-vulcanization process of latex and the vulcanization process of film were optimized. The results showed that with the increase in the amount of vulcanization mixture, the tensile strength increased from 5.96 MPa to 29.28 MPa, and the tear strength increased from 7.59 kN/m to 52.81 kN/m. When the vulcanization temperature of the latex film is heated from 80 °C to 100 °C, the vulcanization time is shortened by 5~6 times. The new vulcanization mixture prepared in this work has the characteristics of simple production and fast vulcanization speed, which provides a new solution for the development of the latex product industry.

Enzyme-Assisted Amplification and Copper Nanocluster Fluorescence Signal-Based Method for miRNA-122 Detection.

At present, a large number of studies have demonstrated that miRNAs can be used as biological indicators for the diagnosis and treatment of diseases such as tumours and cancer, so it is important to develop a new miRNA detection platform. In this work, miRNA-122 is used as the basis for targeting detection agents. We have designed an unlabelled DNA1 that undergoes partial hybridisation and has a 20 T base long strand. The fluorescent signal in this experiment is derived from copper nanoclusters (CuNCs) generated on the circular T-long strand of DNA1. At the same time, DNA1 is able to react with miRNA-122 and achieve hydrolysis of the part bound to miRNA-122 via the action of nucleic acid exonuclease III (Exo III), leaving a part of the DNA, called DNA3, while releasing miRNA-122 to participate in the next reaction, thus achieving circular amplification. DNA3 is able to react with DNA2, which is bound to streptavidin magnetic beads (SIBs) and separated from the reaction solution via the application of a magnetic field. Overall, this is a fluorescence signal reduction experiment, and the strength of the fluorescence signal from the copper nanoclusters can determine whether the target miRNA-122 is present or not. The degree of fluorescence reduction indicates how much DNA1, and thus the amount of target miRNA-122, has been hydrolysed. By evaluating the variations in the fluorescence signal under optimised conditions, we discovered that this method has good sensitivity, with a detection limit as low as 0.46 nM, better than many other previous works on fluorescence signal-based biosensors for miRNA detection. This technique offers high discrimination and selectivity and can serve as a persuasive reference for early diagnosis.

APTES-Modified Remote Self-Assembled DNA-Based Electrochemical Biosensor for Human Papillomavirus DNA Detection.

High-risk human papillomavirus (HPV) infection is an important cause of cervical cancer formation; therefore, being able to detect high-risk HPV (e.g., HPV-16) is important for the early treatment and prevention of cervical cancer. In this study, a combination of a 3-aminopropyltriethoxysilane (APTES) modified gold electrode and a super sandwich structure was creatively developed, resulting in the development of a biosensor that is both sensitive and stable for the detection of HPV-16. The electrochemical biosensor possesses a lower detection limit compared with previous studies with an LOD of 5.475 × 10-16 mol/L and it possesses a wide linear range from 1.0 × 10-13 mol/L to 1.0 × 10-6 mol/L (R2 = 0.9923) for the target DNA. The experimental data show that the sensor has good stability, and there is no significant decrease in the current response value after 7 days in the low-temperature environment. In addition, the sensor proved to be a powerful clinical tool for disease diagnosis because it showed good interference resistance in complex human serum samples.

Gold Nanoparticle-Based Enzyme-Assisted Cyclic Amplification for the Highly-Sensitive Detection of miRNA-21.

Because microRNAs (miRNAs) are biological indicators for the diagnosis, treatment, and monitoring of tumors, cancers, and other diseases, it is significant to develop a rapid, sensitive, and reliable miRNA detection platform. In this study, based on miRNA-21 detection, DNA-a with a 3' end overhang and Texas Red fluorophore-labeled 5' end was designed, which reacts with miRNA-21 and hybridizes with exonuclease III (Exo III), where the part connected to miRNA-21 is hydrolyzed, leaving a-DNA. At the same time, miRNA-21 is released to participate in the following reaction, to achieve cyclic amplification. a-DNA reacts with DNA-b conjugated to gold nanoparticles to achieve fluorescence quenching, with the quenching value denoted as F; additionally, after adding DNA-d and linked streptavidin immunomagnetic beads (SIBs), fluorescence recovery was achieved using DNA-c, with the recovered fluorescence recorded as F0. By comparing the difference in the fluorescence (F0 - F) between the two experiments, the amount of DNA-a hydrolyzed to produce a-DNA was established to determine the target miRNA-21 content. Under optimized conditions, by comparing the changes in the fluorescence signal, the developed strategy shows good sensitivity and repeatability, with a detection limit of 18 pM, good discriminative ability and selectivity, and promise for the early diagnosis of breast and intestinal cancers.

Stability, Stimuli-Responsiveness, and Versatile Sorption Properties of a Dynamic Covalent Acylhydrazone Gel.

Gel adsorbents are promising for pollutant removal from the wastewater. Herein, an acylhydrazone gel is developed from acylhydrazide-terminated pentaerythritol (PAT) and 2,4,6-triformylphloroglucinol (TFP) based on dynamic covalent acylhydrazone chemistry. PAT-TFP gel is stable under various conditions, while it shows reversible Cu2+ adsorption and desorption. PAT-TFP gel is studied as a versatile adsorbent for the capture of a range of (bulky) organic contaminants and heavy metal ions from aqueous solutions. Fast and good adsorption capacities are achieved for various dyes (rhodamine B and methyl orange), amines (aniline, p-chloroaniline, 4-methylaniline, and p-aminobenzoic acid), phenols (phenol, 1-naphthol, p-methylphenol, and bisphenol A), and metal ions (Cu2+, Cr3+, and Hg2+). The maximum adsorption capacity is 107.5 mg g-1 for Cu2+ and the equilibrium adsorption time is 30 min. PAT-TFP gel can be regenerated efficiently and used repeatedly.

A tetraphenylethylene-based acylhydrazone gel for selective luminescence sensing.

A supramolecular gel based on dynamic covalent acylhydrazone bonding assembled from small molecules has been reported. The gel shows aggregation-induced emission for selective and sensitive Cu2+ and subsequent CN- detection.

Metal-Organic Gel Material Based on UiO-66-NH2 Nanoparticles for Improved Adsorption and Conversion of Carbon Dioxide.

Metal-organic frameworks (MOFs) including the UiO-66 series show potential application in the adsorption and conversion of CO2 . Herein, we report the first tetravalent metal-based metal-organic gels constructed from Zr(IV) and 2-aminoterephthalic acid (H2 BDC-NH2 ). The ZrBDC-NH2 gel materials are based on UiO-66-NH2 nanoparticles and were easily prepared under mild conditions (80 °C for 4.5 h). The ZrBDC-NH2 -1:1-0.2 gel material has a high surface area (up to 1040 m(2) g(-1) ) and showed outstanding performance in CO2 adsorption (by using the dried material) and conversion (by using the wet gel) arising from the combined advantages of the gel and the UiO-66-NH2 MOF. The ZrBDC-NH2 -1:1-0.2 dried material showed 38 % higher capture capacity for CO2 at 298 K than microcrystalline UiO-66-NH2 . It showed high ideal adsorbed solution theory selectivity (71.6 at 298 K) for a CO2 /N2 gas mixture (molar ratio 15:85). Furthermore, the ZrBDC-NH2 -1:1-0.2 gel showed activity as a heterogeneous catalyst in the chemical fixation of CO2 and an excellent catalytic performance was achieved for the cycloaddition of atmospheric pressure of CO2 to epoxides at 373 K. In addition, the gel catalyst could be reused over multiple cycles with no considerable loss of catalytic activity.