UV Irradiation Method Research Articles

Conductive Nanosheets Fabricated from Au Nanoparticles on Aqueous Metal Solutions under UV Irradiation.

Highly transparent, conductive nanosheets are extremely attractive for advanced opto-electronic applications. Previously, we have demonstrated that transparent, conductive Au nanosheets can be prepared by UV irradiation of Au nanoparticle (AuNP) monolayers spread on water, which serves as the subphase. However, thick Au nanosheets cannot be fabricated because the method is not applicable to large Au NPs. Further, in order to fabricate nanosheets with different thicknesses and compositions, it is necessary to prepare the appropriate NPs. A strategy is needed to produce nanosheets with different thicknesses and compositions from a single type of metal NP monolayer. In this study, we show that this UV irradiation technique can easily be extended as a nanosheet modification method by using subphases containing metal ions. UV irradiation of 4.7 nm AuNP monolayers on 480 µM HAuCl4 solution increased the thickness of Au nanosheets from 3.5 nm to 36.5 nm, which improved conductivity, but reduced transparency. On the other hand, the use of aqueous AgNO3 and CH3COOAg solutions yielded Au-Ag hybrid nanosheets; however, their morphologies depended on the electrolytes used. In Au-Ag nanosheets prepared on aqueous 500 µM AgNO3, Au and Ag metals are homogeneously distributed throughout the nanosheet. On the other hand, in Au-Ag nanosheets prepared on aqueous 500 µM CH3COOAg, AuNPs still remained and these AuNPs were covered with a Ag nanosheet. Further, these Au-Ag hybrid nanosheets had high conductivity without reduced transparency. Therefore, this UV irradiation method, modified by adding metal ions, is quite effective at improving and diversifying properties of Au nanosheets.

Photo-induced surface oxygen vacancies for effective promotion of the photocatalytic properties over hierarchical layered Bi2O2(OH)NO3

Semiconductor photocatalysts incorporating oxygen vacancies (OVs) have garnered significant attention and research efforts in the field of environmental remediation, but the methods for regulating oxygen vacancies are more demanding. In this work, a combination of UV irradiation and hydrothermal methods was used to create oxygen vacancy-rich Bi2O2(OH)NO3 (BON) photocatalysts, and the presence of oxygen vacancies was revealed by various experimental measurements and theoretical calculations, which regulate the band structure and optimizes the photogenerated carrier behavior of BON-30. The photocatalytic degradation performance of BON was subsequently investigated using the organic dye rhodamine B (RhB) under visible light illumination. The improved activity of BON-30 can be attributed to factors such as oxygen vacancies and reactive radicals O2–, which contribute to enhanced visible light absorption, narrowed band gap and reduced photoelectron-hole complexation ability. In addition, the stability of this photocatalyst shows great potential for application. This strategy provides a simple way to explore more efficient photocatalysts for environmental remediation.

A hydrogel gripper enabling fine movement based on spatiotemporal mineralization.

Fine tailoring of the subtle movements of a hydrogel actuator through simple methods has widespread application prospects in wearable electronics, bionic robots and biomedical engineering. However, to the best of our knowledge, this challenge is not yet completed. Inspired by the diffusion-reaction process in nature, a hydrogel gripper with the capability of fine movement was successfully prepared based on the spatiotemporal fabrication of the polypyrrole (PPY) pattern in a poly (N-isopropylacrylamide) (PNIPAM) hydrogel. The hydrogel was given gradient porous structures using a one-step UV irradiation method. Moreover, photothermal PPY patterns on the hydrogel were obtained through spatiotemporal mineralization of ferric hydroxide followed by the polymerization of pyrrole in a controllable manner. Taking advantage of the unique structures, the hydrogel gripper can not only achieve reversible grasping-releasing of substrates with the tuning of temperature (similar to that of hands), but also generate delicate movement under the irradiation of light (resembling that of finger joints). The strategy reported here is easily accessible and there is no need for sophisticated templates, therefore making it superior to other existing methods. We believe this work will provide references for the design and application of more advanced soft actuators.

Development of 3D-Printed Collagen Scaffolds with In-Situ Synthesis of Silver Nanoparticles.

UV-irradiation method has grown as an alternative approach to in situ synthetize silver nanoparticles (AgNPs) for avoiding the use of toxic reducing agents. In this work, an antimicrobial material by in situ synthesizing AgNPs within 3D-printed collagen-based scaffolds (Col-Ag) was developed. By modifying the concentration of AgNO3 (0.05 and 0.1 M) and UV irradiation time (2 h, 4 h, and 6 h), the morphology and size of the in situ prepared AgNPs could be controlled. As a result, star-like silver particles of around 23 ± 4 μm and spherical AgNPs of 220 ± 42 nm were obtained for Ag 0.05 M, while for Ag 0.1 M cubic particles from 0.3 to 1.0 μm and round silver precipitates of 3.0 ± 0.4 μm were formed in the surface of the scaffolds at different UV irradiation times. However, inside the material AgNPs of 10-28 nm were obtained. The DSC thermal analysis showed that a higher concentration of Ag stabilizes the 3D-printed collagen-based scaffolds, while a longer UV irradiation interval produces a decrease in the denaturation temperature of collagen. The enzymatic degradation assay also revealed that the in situ formed AgNPs act as stabilizing and reinforcement agent which also improve the swelling capacity of collagen-based material. Finally, antimicrobial activity of Col-Ag was studied, showing high bactericidal efficiency against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. These results showed that the UV irradiation method was really attractive to modulate the size and shape of in situ synthesized AgNPs to develop antimicrobial 3D-printed collagen scaffolds with different thermal, swelling and degradation properties.

Self-Strained Platinum Clusters with Finite Size: High-Performance Catalysts with CO Tolerance for PEMFCs.

Strained platinum-based materials with high performance have been regarded as the most promising electrocatalysts for proton exchange membrane fuel cells (PEMFCs) recently. Herein, self-strained platinum clusters with finite size (about 1 nm) are prepared by a combining liquid- and solid-phase UV irradiation cycle strategy. It started with a fresh H2PtCl6 solution irradiated by UV light and then mixed with a graphitized carbon, followed by the dried mixture being subjected to UV light to generate monodispersed Pt clusters on the carbon surface. The obtained platinum clusters feature narrower size distribution and higher loading on carbon, exhibiting significantly improved activity and durability, much higher than that of the-state-of-art commercial Pt/C for the oxygen reduction reaction. More importantly, the self-strained Pt clusters display a surprising CO tolerance, which can be attributed to the unique adaptive lattice compressive strain that triggers an electron enrichment phenomenon for the Pt clusters. Therefore, this stepwise UV irradiation method solves the long-standing problem of both wide size distribution and low loading of metal clusters fabricated by one-step photochemical reduction, providing a potential route for the synthesis of other metal clusters with strained structures.

Effective oxygenated boron groups of boron-doped photoreduced graphene oxide for photocatalytic removal of volatile organic compounds

The adverse health effects from indoor air pollutants such as volatile organic compounds (VOCs) has intrigued much attention. Photocatalytic oxidation (PCO) is a promising technique to degrade VOCs under ambient conditions. A metal-free photocatalyst, namely boron-doped photoreduced graphene oxide (BPRGO) was synthesized via a facile, scalable, and cost-effective UV irradiation method. The BPRGO photocatalyst managed to remove 80% of the VOCs (100 mg/m3 of methanol) within 6 h (0.283 h−1) under UV-A irradiation. Moreover, up to 91% of the VOCs were successfully mineralised into harmless CO2. The high photoactivity of BPRGO-1.0 was due to the high amount of oxygenated boron groups (OBGs) namely BC2O and BCO2 groups. The suitable amount of B dopants led to a higher hole carrier density and p-type conductivity. This had retarded the charge carrier recombination which improved the photocatalytic removal of VOCs. This work provides new insights of metal-free BPRGO photocatalyst for VOCs removal.

Rapid Flow-Based System for Separation of Radioactive Metals by Selective Complex Formation.

Short-lived radioactive metals are important tracers in clinical diagnosis. Radioactive metals for clinical use are produced from suitable target metals in cyclotrons. The trace amount of radioactive metal produced is contained in a relatively large amount of target metal. A rapid and effective method is required to isolate the radioactive metal. In the present study, selective complex formation followed by cation-exchange adsorption was performed in a continuous flow-based system. Ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) was selected as the ligand after simulation of the separation of radioactive Ga from the target (Zn). Selectively, the Ga-EDTA complex passed through the cation trap, while Zn2+ was trapped. This separation principle is opposite to that of typical solid-phase extraction, which captures the target ion. The proposed separation was performed in a flow-based system with a parallel, open-channel ion trap. The performance was optimized by altering the channel dimensions, channel-filling mesh, and flow rate. Finally, the target radioactive metal, Ga, was selectively and effectively (>99%) separated from a mixture of 50 fg Ga/L and 100 mg Zn/L. The concentration of Zn remaining in the Ga solution was 2.3 μg/L. The complexed Ga was converted to free Ga3+ by a simple UV irradiation method. The proposed method effectively and rapidly separates trace amounts of radioactive metals contained in larger amounts of target metals using a simple flow system that can be operated on site.

Fabrication of Fe2CuO4 nanoparticles via photolysis technique for improved performance in dye-sensitized solar cells

This paper created excellent photo-anode materials based on Fe2CuO4 Nanoparticles to efficiently convert the photoelectric into a dye-sensitized solar cell (DSSC). The Fe2CuO4 nanoparticles were prepared via the UV-Irradiation method. The synthesized nanoparticles morphology structure and optical properties were examined using various X-ray diffraction (XRD), Energy Dispersive X-Ray Analysis (EDX) / mapping, field emission scanning electron microscope (FE-SEM), Transmission Electron Microscopy (TEM), and photoluminescence spectroscopy (PL) are examples of these techniques. Transmission electron microscopes (TEM) images validated the Field emission scanning electron microscopy (FE-SEM) and crystal structure of the generated Fe2CuO4 NPs, which had an average particle size of (11.7 nm), and the X-ray diffraction analysis (XRD) investigation indicated no impurity peaks. Photoluminescence spectroscopy (PL) was used to examine the optical characteristics, and the energy gap was found to be 1.95 eV. Nano-powder has been used to develop a successful photo-sensitizing solar cell employing cibacron brilliant red b as a photosensitizer with an efficiency of about 6.47 to 10.39 % energy conversion. We have created a time-saving technology that is simple to regulate, which makes it possible to produce nano-particulate composites without a high testing need. Our findings could investigate an opportunity for nanomaterials to be synthesized with highly rapid answers and now photoanode.

Impact of Fe2NiO4 nanoparticles to increase efficiency of dye-sensitized solar cells

Excellent photo-anode materials based on Fe2NiO4 Nanoparticles were created to efficiently convert the photoelectric into a dye-sensitized solar cell (DSSC). The Fe2NiO4 nanoparticles were prepared via the UV-Irradiation method. The synthesized nanoparticles morphology structure and optical properties were examined using various X-ray diffraction (XRD), Energy Dispersive X-Ray Analysis (EDX)/mapping, field emission scanning electron microscope (FE-SEM), Transmission Electron Microscopy (TEM), and photoluminescence spectroscopy (PL) are examples of these techniques. The particles sizes of the samples were found to be range between 13 and 17 nm. Nano-powder has been used to develop a successful photo-sensitizing solar cell employing cibacron brilliant red b as a photosensitizer with an efficiency of about 4.4 to 7 % energy conversion. We have created a time-saving technology that is simple to regulate, which makes it possible to produce nano-particulate composites without a high testing need. Our findings could investigate an opportunity for nanomaterials to be synthesized with highly rapid answers and now photoanode.

Synthesis and characterization of lysozyme-conjugated Ag.ZnO@HA nanocomposite: A redox and pH-responsive antimicrobial agent with photocatalytic activity

Hydroxyapatite (HA) is extensively used for implantable device coating; however, it lacks antibacterial property, leading to potential bacterial infection during orthopedic implantation surgery. Herein, to enhance the antibacterial activity of HA, a redox- and pH-responsive HA nanocomposite with photocatalytic activity was designed. A photosensitive heterostructure, zinc oxide/hydroxyapatite (ZnO.HA), was coated with Ag nanoparticles (AgNPs) with assisted gallic acid using the UV-irradiation method. An antibacterial enzyme, lysozyme, was then conjugated on the surface of the nanocomposite by a cleavable disulfide linker, resulting in a redox-sensitive nanoplatform. In comparison with bare HA, the designed nanocomposites as Lyso.CAGZ@HA displayed much higher antibacterial activity (> 5-fold) toward Escherichia coli (E. coli) owing to the synergistic antibacterial effects of ZnONPs, AgNPs, gallic acid, and lysozyme on the surface of the nanocomposite. However, antibacterial and antifouling effects are much more enhanced in Lyso.CAGZ@HA-treated bacteria as they were subjected to UVA irradiation. Moreover, the cellular uptake of nanocomposite and intracellular glutathione depletion enhanced in the presence of UVA light, resulting in reactive oxygen specious generation enhancement. Further, in vitro cytotoxicity experiments on mammalian cells (human foreskin fibroblast) revealed that nanocomposite has no cytotoxic effects. Hence, this study demonstrated that Lyso.CAGZ@HA could be considered as a potential therapeutic approach against bacterial infectious diseases.

Preparation and (TiO2-ZnO) Polyethelene for Food Preservation

The polymer nanocomposite was prepared using low-density polyethylene and each of (titanium oxide and zinc oxide) nanoparticles by casting method. The nanoparticles were synthesized via the UV-irradiation method. structural properties of TiO2 and ZnO nanoparticles studied by x-ray diffractions so the grain size of nanoparticles ranged between (10-12) nm. mechanical properties of the nanocomposites improve as the ratio of nanoparticles in polymer increased, compared to pure LDPE. Given that studies show that using this 2.5 Gy of gamma Rayes irradiated of nanocomposites improved that fantastic for use as food packaging. Besides, the polymer nanocomposites proved that antimicrobial properties against the E. coli, since it releases the nanoparticle’s cations.

Subnanoscale Platinum by Repeated UV Irradiation: From One and Few Atoms to Clusters for the Automotive PEMFC.

The unaffordable costs of the automotive proton exchange membrane fuel cell (PEMFC), remaining a roadblock for commercial applications as an alternative to combustion engine vehicles, can be overcome partially by remarkably increasing the utilization of irreplaceable platinum (Pt). Herein, atomically precise Pt with scalable atoms ranging from 1 to 43 atoms, stabilized by a homemade carbon from white radish without any ligands, is prepared by a repeated UV irradiation method that is industrially scalable. Compared with the isolated Pt1 in the form of Pt-N4, octahedral Pt6, and icosahedron Pt13, the ordered Pt43 cluster (∼0.75 nm) with higher metal coordination number displays much higher oxygen reduction reaction performance with a mass activity, which is about 1036% higher than that obtained by state-of-the-art Pt/C, an increase by a factor of ∼3.3 as compared with the DOE 2020 target (0.44 A mgPt-1). The utilization rate of Pt atoms reaches up to 94.7%, much higher than that of Pt (2 nm, 56%), capable of further reducing the amount of platinum that is required for PEMFCs. Moreover, the cluster exhibits an outstanding stability due to the improved Pt vacancy formation energy raised by stronger atom interaction in the close-packed cluster. The cluster exhibits a unique finite size effect from self-tuned energy band and strain levels. A clear strain effect on the d-band center is first presented for pure Pt without distortion from ligands like a second metal. Therefore, the assembly of subnanometer Pt with atom alteration opens up new horizons in designing efficient platinum group metal (PGM) catalysts by reducing the size to subnanometer scale.

Fabrication of Cu(BDC)0.5(BDC-NH2)0.5 metal-organic framework for superior H2S removal at room temperature

A mixed ligand Cu-based MOF, Cu(BDC)0.5(BDC-NH2)0.5 was synthesized by a rapid ultrasonication method for the adsorptive removal of hydrogen sulfide (H2S) gas at room temperature. The MOF has a sheet-like morphology with 100 nm thickness crystallized in the monoclinic symmetry (a = 11.27 Å, b = 14.82 Å, c = 7.95 Å, β = 110.8°) with C2/m space group. The surface area and pore volume was 19.4 m2 g−1 and 0.024 cm3 g−1, respectively. The XPS analysis confirmed a near equal proportion of Cu(I) and Cu(II)-sites in the MOF. The MOF showed the H2S adsorption capacity of 128.4 mg g−1 for 500 ppm of H2S flowing at a rate of 100 mL min−1, which is among the highest values reported for Cu-based MOFs. The spent MOF was regenerated by a methanol and UV-irradiation method, which significantly improved the adsorption capacity. The H2S adsorbed onto the MOF by breaking Cu-carboxylate bonds with the formation of covellite CuS nanoparticles and sulfates. The spectroscopic analysis predicted a Cu(OH)-type sites after UV-irradiation along with increased surface area, which were responsible for an enhanced adsorption capacity of the regenerated sample.

Green fabrication, characterization of silver nanoparticles using aqueous leaf extract of Ocimum americanum (Hoary Basil) and investigation of its in vitro antibacterial, antioxidant, anticancer and photocatalytic reduction

Green fabrications of metallic nanoparticles are rapidly developing the research era, due to their broad spectrum of applications in the field of biomedical sciences. In the present study, the green fabrication of silver nanoparticles (AgNPs) has been demonstrated by a highly stable, biocompatible, and environmental friendly aqueous leaf extract of Ocimum americanum for their antibacterial, anticancerous, and photocatalytic dye degradation efficiency. The synthesized AgNPs were confirmed by UV–Visible spectroscopy, which indicates the surface plasmon resonance λmax band at 435 nm. The FE-SEM and HR-TEM micrographs showed spherical shaped AgNPs, and EDX analysis confirmed the crystalline purity of green fabricated AgNPs. Fourier transform infrared (FT-IR) technique indicated the presence of active functional groups such as O‒H, C˭C, C‒H, C‒N involved in the reduction and surface capping agent of green fabricated AgNPs. The XRD analysis of synthesized AgNPs showed the face-centered cubic (fcc) crystalline structure. The DLS measurement showed average particle size of distribution was 48.25 nm and Zeta potential value at −20.2 mV revealed high stability of fabricated AgNPs. Further, the synthesized AgNPs has exhibited potential antibacterial activity against pathogenic Gram +ve and Gram −ve bacteria and in-vitro antioxidant activity assessed by DPPH, H2O2 and reducing power assays. The in-vitro cytotoxic effects of fabricated AgNPs against A549 lung cancer cells displayed apoptotic cell death confirmed by fluorescent staining techniques and the cellular apoptotic induction of G0/G1 cell cycle arrest confirmed with the flow cytometry analysis. On the other hand, the AgNPs exhibited efficient photocatalytic dye degradation of eosin yellow (EY) under sunlight and UV-irradiation method. The AgNPs did not lyse the hemoglobin from human red blood cells and showed its biocompatibility on human cells. Herein, the present study proves an effective, economical, and multifunctional AgNPs for improved therapeutic and catalytic applications.

Anion Exchange Membranes for High Performance Neutral Aqueous Organic Redox Flow Battery

Neutral pH aqueous organic redox flow batteries (AORFB) employing water-soluble dimethyl viologen (MV) and N,N,N-2,2,6,6-heptamethylpiperi-dinyl oxy-4-ammonium chloride (TMA-TEMPO) molecules have been demonstrated as a high-performing RFB1,2. As a key component, the membrane allows the transport of counter ions while preventing the intermixing of the redox-active molecules in the electrolyte solutions, despite of which, appropriate membranes designed for the system are usually overlooked in many studies3. Therefore, synthesis of a suitable membrane, which shows a high (chloride) ion conductivity and selectivity, optimized water uptake, adapted mechanical strength, is required 4.In this work, first, in-depth correlations between polymer structure - membrane properties and TMA-TEMPO/MV–based AORFB cell cycling stability and performance were investigated. Four anion-exchange membranes (AEMs) based on poly (phenylene oxide) (PPO) grafted with various amounts of poly(diallylpiperidinium chloride) cations were fabricated via a rapid UV-irradiation method and tested in a 5 cm2 TMA-TEMPO/MV-based AORFB. The trend in available capacity after 100 cycles at 80 mA/cm2 was closely related to the initial resistance of the membranes and their corresponding degree of cross-contamination. Membranes with moderate membrane resistance and low crossover was found to display the best overall cell performance. Our results show quite a promising understanding on the correlations between the different membrane properties and their corresponding cell performance and stability.Furthermore, a series of flexible and conductive anion-exchange membranes (AEMs) composed of PPO with six carbon side chain ended with quaternary ammonium (Diazabicyclo[2.2.2]octane)-DABCO or Trimethylamine - TMA) were fabricated via casting and tested in the TMA-TEMPO/MV–based AORFB single cell. The PPO-DABCO AEM with low water uptake and high chloride conductivity exhibited much higher peak power density than a well-performing commercial membrane (FAA-3-50®Fumatech) (388 vs 244 mW/cm2) (Figure 1). Moreover, our membrane permitted to obtain excellent coulombic efficiency (>99%) and a high energy efficiency (80% vs. 78%) than the commercial membrane. Our results show an excellent membrane candidate to improve the cell performance of AORFBs.

Anchoring succinonitrile by solvent-Li+ associations for high-performance solid-state lithium battery

In this work, a new type of highly Li+ conductive, scalable, deformable succinonitrile-based composite solid-state electrolyte (denoted as SN-CSSE) is proposed as a promising solid electrolyte for room-temperature solid-state lithium battery (SSLB). The electrospinning poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) framework and UV-irradiation method are applied to improve the mechanical properties of SN. To overcome the side reactions on lithium (Li) anode, the concentrated lithium salt is exploited to anchor SN molecules within solvent-Li+ associations, which avoids direct contact between SN and Li metal and realize uniform Li deposition. Owing to the unique structural integration, the SN-CSSE exhibits high ionic conductivity of 1.1 × 10−3 S·cm−1 at 30 °C, wide electrochemical window (0 ~ 5.1 V vs. Li+/Li), favorable mechanical strength (4.76 MPa), and excellent interfacial compatibility with Li (stable at a current density of 0.2 mA·cm−2 for over 500 h). The LiFePO4/Li cells provide an outstanding rate capability (5C) and cycling performance (a retention of 95% after 800 cycles at 1C). Moreover, the solid-state pouch cell displays a favorable capacity of 15.6 mAh and maintains good cycling stability without significant capacity degradation after 150 cycles. Even under different abuse conditions, the cell still operated well, portending high application potential in safety-required battery systems.

Compostable Polylactide and Cellulose Based Packaging for Fresh-Cut Cherry Tomatoes: Performance Evaluation and Influence of Sterilization Treatment.

For food packaging, plastic materials display large appeal, mostly due to their versatility, mechanical, optical and barrier properties. However, they play an important role in environmental concerns and waste management issue. Compostable bioplastics represent alternative materials designed for a lower environmental impact. In this work, a biobased compostable packaging, constituted by polylactide (PLA) trays and NatureFlex™ film, was evaluated for fresh-cut cherry tomato. A comparative analysis was accomplished using traditional packaging materials, that is, polyethylene terephtalate (PET) trays and polypropylene (PP Coex) film. Structural stability under food contact conditions, mechanical and physical-chemical properties were investigated. Tensile mechanical properties, puncture resistance, contact angle (CA) and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), before and after UV or radiofrequency (RF) sterilization treatment, were evaluated. UV irradiation method resulted the less invasive one. Therefore, oxygen and water vapor transmission rate (OTR and WVTR), overall chemical migration test, biodegradation assessment by biochemical oxygen demand (BOD) according to ISO 14851 and disintegration test by ISO 20200 were carried out to establish the further influence of UV sterilization on the packaging. Overall, data showed that the biobased compostable packaging for a prolonged shelf-life of fresh-cut cherry tomato has better properties that were surprisingly enhanced by the UV treatment.

UV-assisted one-pot synthesis of bimetallic Ag-Pt decorated reduced graphene oxide for colorimetric determination of hydrogen peroxide.

Bimetallic Ag-Pt nanoparticles decorated on the surface of reduced graphene oxide (Ag-Pt/rGO) were designed and selected as a nanozyme for the assay ofhydrogen peroxide. The nanocomposites were prepared through a one-pot reduction of potassium chloroplatinate, silver nitrate, and graphene oxide under ultraviolet irradiation without using any extra chemical reducing agents or surfactants. The successful formation of Ag-Pt/rGO nanocomposites was confirmed by transmission electron microscopy, energy disperse spectroscopy mapping, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. Significantly, Ag-Pt/rGO nanocomposites possessed excellent peroxidase-like activity toward the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine to form a blue product in the presence of hydrogen peroxide. Steady-state kinetics studies suggested that Ag-Pt/rGO nanocomposites had high affinity to hydrogen peroxide. Based on these properties, a convenient and sensitive method for the colorimetric determination of hydrogen peroxide was developed. Under optimal conditions, the absorbance at 652nm increases linearly in the 10-100μM and 100μM-1mM ranges of hydrogen peroxide concentration, and the detection limit is 0.9μM (S/N = 3). The method was successfully applied to the determination of hydrogen peroxide in real water samples. Graphical abstract Ag-Pt/rGO nanocomposites were prepared by a one-pot UV irradiation method and used as a novel nanozyme for colorimetric determination of H2O2.

The removal of zinc ions from their aqueous solutions by Cr2O3 nanoparticles synthesized via the UV-irradiation method

A modification of an UV-irradiation method is used to synthesis of Cr2O3 nanoparticles. It is a simple and easy way to produce small particles of chromium oxide at a range of 2 – 30 nm according to the transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterizations. In this study, the synthesized nanoparticles are used as an adsorbent for zinc ions from their aqueous solutions under effect of different temperatures 15, 25, 35, 45 and 55 oC. The adsorption process of zinc ions is endothermic (ΔH is 10.33 kJ/mol ) and its data fitted well with the Freundlich isotherm model (R2=0.9601). The data of adsorption show non-spontaneously in nature when the thermodynamic parameter ΔG is positive (1.515 kJ/mol). However, the ΔG changes to a negative value with the temperature rising and the process begins spontaneously because the adsorption capacity increases with increase in temperature.

Synthesis of temperature and light sensitive mixed polymer brushes via combination of surface-initiated PET–ATRP and interface-mediated RAFT polymerization for cell sheet application

In this study, a series of temperature and light sensitive mixed polymer brushes consisting of poly(2-(2-methoxyethoxy) ethyl methacrylate) [poly(MEO2MA)] and poly(N-[4-[(4-nitrophenyl) azo] phenyl] acrylamide) [poly(NPAPAA)] units were grown on silicon wafer via the combination of surface-initiated photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP) and interface-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization. This process was realized in five consecutive steps: (i) coupling of previously synthesized (3-aminopropyl) triethoxysilane-2-bromoisobutyryl bromide (APTES-BIBB) and (3-aminopropyl) triethoxysilane-t-butoxycarbonyl (APTES-t-BOC) mixtures to the Si-OH surface under self-assembly monolayer conditions (ii) synthesis of poly(MEO2MA) units via surface-initiated PET-ATRP (iii) replacement of terminal-Br atoms at poly(MEO2MA) units with biocompatible maleimide molecules (iv) removal of the t-BOC group from APTES-t-BOC and bonding of the RAFT agent to the APTES, and (v) synthesis of poly(NPAPAA) units via the interface-mediated RAFT polymerization. The surface compositions of APTES-BIBB and APTES-t-BOC molecules were determined by the water contact angle data analyzed with the Israelachvili-Gee model and by the X-ray photoelectron spectroscopy measurements. The grafting density (σ, chains nm−2) and the average distance between grafting points (D, nm) of the mixed polymer brushes are about 0.56 chains nm−2 and 1.52 nm, respectively, indicating high grafting density. The lower critical solution temperatures (LCSTs), trans-cis and cis-trans transition times were in the range of 24.6–29.2 °C, 10–25 min and 8–20 min, respectively, depending on the surface composition of the polymer brushes. Cell culture studies revealed successful cell detachment either via the temperature reduction or UV irradiation methods. The cell recovery ratios were recorded as 99.05 ± 0.45% and 83.95% ± 0.58%, respectively. These experimental findings provided basic information at the molecular level in the preparation of temperature and light- sensitive bioactive surfaces for cell sheet preparation and detachment state.