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The citrate-based thermoset elastomer is a promising candidate for bone scaffold material, but the harsh curing condition made it difficult to fabricate porous structure. Recently, poly (1, 8-octanediol-co-Pluronic F127 citrate) (POFC) porous scaffold was creatively fabricated by chitin nanofibrils (ChiNFs) supported emulsion-freeze-casting. Thanks to the supporting role of ChiNFs, the lamellar pore structure formed by directional freeze-drying was maintained during the subsequent thermocuring. Herein, bioactive glass (BG) was introduced into the POFC porous scaffolds to improve bioactivity. It was found the complete replacement of ChiNF particles with BG particles could not form a stable porous structure; however, existing at least 15 wt% ChiNF could ensure the formation of lamellar pore, and the interlamellar distance increased with BG ratios. Thus, the BG granules did not contribute to the formation of pore structure like ChiNFs, however, they surely endowed the scaffolds with enhanced mechanical properties, improved osteogenesis bioactivity, better cytocompatibility as well as quick degradation rate. Reasonably adjusting BG ratios could balance the requirements of porous structure and bioactivity.

An electromical sensor based on α-Fe2O3@Co3O4-NRGO composited glass carbon electrode (GCE) was constructed and used for ultrasensitive tyrosine detection. A series of characterization techniques including scanning electron microscopy, X-ray diffraction and electrochemical impedance spectroscopy technique and cyclic voltammetry were employed to investigate the modified electrode. Compared with the bare GCE, the α-Fe2O3@Co3O4-NRGO/GCE exhibited a strong current response to tyrosine because of the synergistic effect of ternary composite. Under optimized conditions, the peak currents that responded to tyrosine concentration had a linear relationship from the scope of 0.01 to 10 µM (R2 = 0.9977) by second derivative linear sweep voltammetry (SDLSV) and 8 nM (S/N = 3) is the detection limit. The sensor showed higher sensitivity, better repeatability, reproducibility and greater sensing stability related advantages over those in previous tyrosine detections. Furthermore, the sensor was successfully applied to trace tyrosine determination in practical samples such as milk and serum.

Degradable bioelastomers as porous scaffold materials have great potentials in tissue regeneration due to their compatible mechanical properties to the body’s soft tissues. A citrate-based elastomer is a recently developed bioelastomer possessing good surface affinities toward many cell types, but its insoluble and unmeltable characteristics caused difficulties in fabricating porous scaffolds. Herein, a new method where chitin nanocrystal (ChiNC) supported emulsion-freeze-casting was utilized to fabricate porous scaffolds of thermoset elastomer. ChiNC was initially used as a Pickering emulsifier to stabilize prepolymer latex spheres, then as a supporting agent to prevent ice-templated pores from collapse during thermocuring, and last as a biobased nanofiller to reinforce the porous scaffold. When ChiNC loading was at least 15% or greater, the directional porous structure were facilely obtained via use of a thick-walled Teflon container in a freezer at −40 °C. The nanocomposite elastomer porous scaffold ex...

Chitin nanocrystal (ChiNC) is a promising reinforcing nanofiller for biomedical polymers. However, its self-aggregation characteristics caused processing difficulty in developing ChiNC-based nanocomposites. Herein, a new degradable crosslinked bioelastomer, designated as poly(1,8-octanediol-co-Pluronic F127 citrate) (POFC) was synthesized by melt polycondensation of citric acid, 1,8-octanediol, and Pluronic F127. In comparison to poly(1,8-octanediol citrate) (POC), POFC pre-polymer exhibited self-emulsifying property. Once ChiNC was introduced into the emulsion, a ChiNC stabilized Pickering emulsion was formed. Coupled with a facile green emulsion casting/evaporation method, the ChiNC ultimately reinforced ChiNC/POFC nanocomposite elastomer was fabricated. The presence of F127 segments endowed POFC with better hydrophilicity and shorter degradation time relative to POC. The incorporation of ChiNC into POFC network led to highly increased tensile modulus and strength. In vitro cytotoxicity tests indicated that the ChiNC/POFC elastomer nanocomposite had a good cytocompatibility and it appeared as a potential biomaterial for tissue engineering application.

In this paper, a nanocomposite of cuprous oxide and electrochemically reduced graphene oxide (Cu2O‒ERGO) was prepared by a simple and low-cost method, hereby, a new method for the electrochemical determination of tryptophan (Trp) by this composite modified glassy carbon electrode (GCE) is proposed. The prepared materials and modified electrodes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and cyclic voltammetry (CV). The results showed that Cu2O‒ERGO/GCE had good electrocatalytic activity for Trp. The effects of supporting electrolyte, scanning rate, accumulation potential, and accumulation time on the determination of Trp were studied. Under the optimum experimental conditions, Trp was quantitatively analyzed by square-wave voltammetry (SWV). The oxidation peak current of Trp had a good linear relationship with its concentration in the range of 0.02‒20 &mu, M, and the detection limit was 0.01 &mu, M (S/N = 3). In addition, the modified electrode has high sensitivity, good repeatability, and long-term stability. Finally, the proposed method has been successfully applied in the determination of Trp concentration in practical samples.

The nanohybrid of electrochemically-reduced graphene oxide (ERGO) nanosheets decorated with MnO2 nanorods (MnO2 NRs) was modified on the surface of a glassy carbon electrode (GCE). Controlled potential reduction was applied for the reduction of graphene oxide (GO). The characterization was performed by scanning electron microscopy, X-ray diffraction and cyclic voltammetry. Compared with the poor electrochemical response at bare GCE, a well-defined oxidation peak of sunset yellow (SY) was observed at the MnO2 NRs-ERGO/GCE, which was attributed to the high accumulation efficiency as well as considerable electrocatalytic activity of ERGO and MnO2 NRs on the electrode surface. The experimental parameters for SY detection were optimized in detail. Under the optimized experiment conditions, the MnO2 NRs-ERGO/GCE showed good linear response to SY in concentration range of 0.01&ndash, 2.0 &mu, M, 2.0&ndash, 10.0 &mu, M and 10.0&ndash, 100.0 &mu, M with a detection limit of 2.0 nM. This developed method was applied for SY detection in soft drinks with satisfied detected results.

In recent years, small-sized electrodes have drawn widespread attraction in electroanalysis due to high sensitivity, rapid response and low cost. Hereby, a sub-millimeter paste electrode with inner diameter of 0.8 mm was prepared by combining the excellent properties of reduced graphene oxide (rGO) and acetylene black (AB), and the electrochemical behavior of tyrosine (Tyr) on the modified electrode (denoted as rGO/ABPE) was investigated in detail. The electrochemical responses obtained on the sub-millimeter rGO/ABPE were compared with that obtained on a conventional size electrode with diameter of 3 mm. The results showed that the 0.8 mm one has better performance than that of 3 mm. Compared with the paste electrode made of graphite powder, the oxidation peak current of Tyr increased significantly due to the synergistic effect of rGO and AB. Under the optimized experimental conditions, the calibration curve of Tyr showed a linear relationship between 0.1 and 100 μM (R = 0.9995) with good sensitivity of 3.314 μA μM−1 cm−2, and the detection limit was 0.06 μM. By comparison with conventional size electrode, the detection of Tyr on the sub-millimeter electrode shows higher sensitivity, wider linear range and lower detection limit. In addition, the excellent reproducibility, stability and selectivity of the sub-millimeter rGO/ABPE make it suitable for Tyr analysis in both food and biological samples.

Citrate-based thermoset bioelastomer has numerous tissue engineering applications. However, its insoluble and unmeltable features restricted processing techniques for fabricating complex scaffolds. Herein, direct ink writing (DIW) was explored for 3D printing of poly(1, 8-octanediol-co-Pluronic F127 citrate) (POFC) bioelastomer scaffolds considering that POFC prepolymer (pre-POFC) was waterborne and could form a stable emulsion. The pre-POFC emulsion couldn't be printed, however, chitin nanocrystal (ChiNC) could be as a rheological modifier to tune the flow behavior of pre-POFC emulsion, and thus DIW printing of POFC scaffolds was successfully realized; moreover, ChiNC was also as a supporting agent to prevent collapse of filaments during thermocuring, and simultaneously as a biobased nanofiller to reinforce scaffolds. The rheological analyses showed the pre-POFC/ChiNC inks fulfilled the requirements for DIW printing. The printed scaffolds exhibited low swelling, and good performances in strength and resilence. Furthermore, the entire process was easily performed and eco-friendly.

In this paper, acetylene black paste electrode (ABPE) was prepared and modified by oxygen-functionalized multi-walled carbon nanotubes (MWCNT-COOH). The fabricated MWCNT-COOH/ABPE was further used for the investigation on the electrochemical behavior of tyrosine by cyclic voltammetry and second-order derivative linear sweep voltammetry. In 0.1 M pH 2.6 phosphate buffer solution, a well-defined anodic peak appeared at 924 mV, which was attributed to the electrooxidation of tyrosine on the modified electrode. The electrochemical parameters of tyrosine on the modified electrode were calculated. Under the optimal conditions, the oxidation peak current of tyrosine varies linearly with its concentration in the range of 0.04−1.0 μ M, 1.0−60 μ M and 60−600 μ M, and the detection limit is 0.02 μM. The MWCNT-COOH/ABPE was applied to the determination of tyrosine in food with satisfactory results.

Here we report a facile and cost-effective preparation of nickel nanoparticle S/Nitrogen-carbon nanohybrid (Ni NPS/N-C) based on formamide condensation and carbonization, used for highly sensitive and selective electrochemical determination of tryptophan (Trp) in practical samples. The crystallographic phase, surface morphology, elemental distribution, and chemical state of the Ni NPS/N-C nanohybrid were analyzed by XRD, SEM, TEM, EDS, XPS, FTIR, TGA and Raman spectra. The results show that high content of Ni NPs (6.62 wt%) were distributed in the nanohybrid, and a large number of bamboo-like nanotubes were formed during pyrolysis, which dramatically increases the specific surface area, and remarkably promotes the electrical conductivity as well as the catalytic activity of the nanohybrid. The electrochemical behavior of Trp was investigated on the nanohybrid modified carbon paste electrode (Ni NPS/N-C/CPE) and the measurement parameters were optimized. As expected, the modified electrode can remarkably enhance the electrochemical oxidation signal of Trp. Under the optimal experimental conditions, a linear relationship in the range of 0.01–20 μM and 20–80 μM for Trp was established with detection limit of 5.7 nM (S/N = 3). Finally, the proposed sensor was practically applied by evaluation and determination of Trp from various sourcing samples including human serum and pharmaceutical samples.

Vanillin is widely used as a flavoring and fragrance enhancer in foods. Rapid detection of vanillin is of vital significance and necessity for food safety. In this work, a sensitive voltammetric sensor to detect trace vanillin of nanomolarity in food samples was demonstrated by using manganese dioxide nanowires hybridized electrode. Firstly, a modified glassy carbon electrode was prepared using manganese dioxide nanowires functionalized reduced graphene oxide as a modifier (MnO2 NWs-rGO/GCE). Then the MnO2 NWs-rGO/GCE were characterized by scanning electron microscopy, X-ray diffraction (XRD) and cyclic voltammetry (CV). Vanillin's electrochemical behavior in the solution of 0.1 M H2SO4 was studied in detail. The results showed that the modified electrode had an electrocatalytic activity for vanillin oxidation. The adsorption capacity (Γs) and standard rate constant (ks) on the modified electrode were calculated by chronocoulometry (CC). Subsequently, after systematic investigation of second derivative linear sweep voltammetry (SDLSV) under the optimal conditions, the oxidation peak current was linearly correlated with vanillin concentration in the separate ranges of 0.01–20 μM (R2= 0.9808) and 20–100 μM (R2= 0.9964), yielding the detection limit of 6.0 nM (S/N = 3). In addition, MnO2 NWs-rGO/GCE showed the advantages of surface renewal, excellent reproducibility, good stability, and simple preparation. The method was applied to the nanomolarity determination of vanillin in commercial foods with satisfactory results.

A new electrochemical sensor for nanomolar rutin detection based on amine-functionalized Fe3O4 nanoparticles and electrochemically reduced graphene oxide nanocomposite modified glassy carbon electrode (NH2-Fe3O4 NPs-ErGO/GCE) was fabricated through a simple method, and the X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and electrochemical technique were used to characterize the modified electrode. The electrochemical behavior of rutin on the Fe3O4 NPs-ErGO/GCE was studied in detail. The electrochemical response of rutin at this modified electrode was remarkably higher than that of the bare GCE or other modified GCE (GO/GCE, Fe3O4 NPs-GO/GCE, and ErGO/GCE). Under the optimum determination conditions, Fe3O4 NPs-ErGO/GCE provided rutin with a broader detection range of 6.0 nM&ndash, 0.1 &micro, M, 0.1&ndash, 8.0 &micro, M and 8.0&ndash, 80 &micro, M, a minimum detectable concentration of 4.0 nM was obtained after 210 s accumulation. This novel method was applied in determination of rutin in pharmaceutical tablets and urine samples with satisfactory results.

Objectives. With the rapid development of EEG-based wearable healthcare devices and brain-computer interfaces (BCIs), reliable and user-friendly EEG sensors for EEG recording especially at the forehead sites are highly desirable and challenging. However, the existing EEG sensors cannot meet the requirements, since wet electrodes require tedious setup and conductive pastes or gels, and most dry electrodes show unacceptable high contact impedance. In addition, the existing electrodes cannot absorb sweat effectively, which would cause cross-interferences even short circuits between adjacent electrodes, especially in the moving scenarios, or hot and humid environment. To resolve these problems, a novel printable flexible Ag/AgCl dry electrode array was developed for EEG acquisition at forehead sites, mainly consisting of screen-printing Ag/AgCl coating, conductive sweat-absorbable sponges and flexible tines. Approach. A systematic method was also established to evaluate the flexible dry electrode array. Main results. The experimental results show the flexible dry electrode array have reproducible electrode potential, relative low electrode-skin impedance, and good stability. Moreover, the EEG signals can be effectively captured with high quality that is comparable with that of wet electrodes. Significance. All the results confirmed that the feasibility for forehead EEG recording in real-world scenarios using the proposed flexible dry electrode array, with a rapid and facile operation as well as advantages of self-application, user-friendliness and wearing comfort.

A novel tantalum pentoxide nanoparticle-electrochemically reduced graphene oxide nanocomposite-modified glassy carbon electrode (Ta2O5-ErGO/GCE) was developed for the detection of oxytetracycline in milk. The composition, structure and morphology of GO,Ta2O5, and Ta2O5-ErGO were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Oxytetracycline electrochemical behavior on the bare GCE, GO/GCE, ErGO/GCE, and Ta2O5-ErGO/GCE was studied by cyclic voltammetry. The voltammetric conditions (including scan rate, pH, deposition potential, and deposition time) were systematically optimized. With the spacious electrochemical active area, the Ta2O5-ErGO/GCE showed a great magnification of the oxidation signal of oxytetracycline, while that of the other electrodes (GCE, GO/GCE, ErGO/GCE) could not reach the same level. Under the optimum conditions, the currents were proportional to the oxytetracycline concentration in the range from 0.2 to 10 &mu, M, and a low detection limit of 0.095&mu, M(S/N= 3) was detectable. Moreover, the proposed Ta2O5-ErGO/GCE performed practically with satisfactory results. The preparation of Ta2O5-ErGO/GCE in the current work provides a minor outlook of detecting trace oxytetracycline in milk.

Developing simple and accurate QY detection methods is of great significant importance in ensuring food safety including drinks. Manganese dioxide nanoparticles (MnO2 NPs) with different morphologies were synthesized by hydrothermal method. Manganese dioxide/graphene (MnO2/GR) nanocomposites were directly prepared on the surface of glassy carbon electrode (GCE) by electrochemical reduction. The materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The effects of nano-MnO2 with different morphologies on the performance of quinoline yellow (QY) detection was investigated. The experimental findings revealed that MnO2 nanorods (MnO2 NRs) had better properties than both MnO2 nanowires (MnO2 NWs) and MnO2 nanotubes (MnO2 NTs). Under optimal experimental conditions, a good linear relationship between peak current of QY on GR/MnO2 NRs/GCE and concentrations ranging between 0.1 μM˜6.0 μM and 6.0 μM˜60 μM were observed, and 0.04 μM was the detection limit. The fabricated sensor was successfully tested to detect QY in soft drinks.

Two-phase synthesis is an advantageous alternative to the traditional synthetic method, due to its less toxicity, controllable, mild synthetic conditions and easy large-scale synthesis. However, meeting novel synthesis, the conventional trial-and-error approach could not provide a clear understanding. We herein report synthesis and mechanism investigation of CdS quantum dots in octadecene/glycerol two-phase system. The effects of different reaction parameters and conditions including reaction temperature, reaction time, reactant concentrations, and synthesis routes (one-step and two-step approach) on both nucleation and particle growth were investigated. It was found that the synthesis course was a growth dominated process depending on both CdS(monomer) and CdS(nuclei), and controlled by the interface of ODE/glycerol. The present work provided a new and clear understanding about two-phase system synthesis on semiconductor quantum dots, noble metal nanocrystals and some alloy nanomaterials.

In this paper, the preparation, characterization, and electrochemical application of Cu2O nanoparticles and an electrochemical reduced graphene oxide nanohybrid modified glassy carbon electrode (denoted as Cu2O NPs‒ERGO/GCE) are described. This modified electrode was used as an electrochemical sensor for the catalytic oxidation of rhodamine B (RhB), and it exhibited an excellent electrochemical performance for RhB. The oxidation potential of RhB was decreased greatly, and the sensitivity to detect RhB was improved significantly. Under optimum conditions, a linear dynamic range of 0.01&ndash, 20.0 &mu, M and a low detection limit of 0.006 &mu, M were obtained with the Cu2O NPs‒ERGO/GCE by using second‒order derivative linear sweep voltammetry. In addition, the selectivity of the prepared modified electrode was analyzed for the determination of RhB. The practical application of this sensor was investigated for the determination of RhB in food samples, and satisfactory results were obtained.

4-nitrophenol (4-NP) is a hazardous waste and a priority toxic pollutant identified by US Environmental Protection Agency (EPA). Hence, in this paper, a voltammetric sensor was proposed for the direct and sensitive detection of 4-nitrophenol (4-NP) at nanomolar level in complex matrices by using graphene and acetylene black paste hybridized electrode (GR/ABPE). Under optimal conditions, the calibration curve demonstrates a linear relationship for 4-NP in the range from 20 nM to 8.0 &mu, M and 8.0 &mu, M to 0.1 mM separately with the detection limit of 8.0 nM. In addition to it, the performance of the GR/ABPE in practical applications was evaluated by detecting 4-NP in various water samples, and satisfactory recoveries were realized. Therefore, GR/ABPE may have a great potential application for facile and sensitive detection of 4-NP in complex matrices at nanomolar level.

For the first time, we study the parametric amplification process of multi-wave mixing (PA-MWM) signal and cascaded-nonlinearity process (CNP) in sodium vapors both theoretically and experimentally, based on a conventional phase-conjugate MWM and a self-diffraction four-wave mixing (SD-FWM) processes, which are pumped by laser or amplified spontaneous emission (ASE), respectively. For laser pumping case, SD-FWM process serves as a quantum linear amplifier (a CNP) out (inside) of the resonant absorption region. While for ASE case, only the CNP occurs and the output linewidth is much narrower than that of the MWM signal due to the second selected effect of its electromagnetically induced transparency window. In addition, the phase-sensitive amplifying process seeded by two MWM processes is discussed for the first time. Theoretical fittings agree well with the experiment. The investigations have important potential applications in quantum communication.

In this letter, we show polarized dressing suppression and enhancement of six-wave mixing involving Rydberg in a multi-Zeeman-level atomic system. By scanning the frequency detuning of the dressing field, we observe the suppression and enhancement of Rydberg six-wave mixing with different polarization of the probe field in thermal vapors. Since different polarization states of the dressing field can select different transitions among multi-Zeeman levels, the polarization dependence of Rydberg dressing is investigated for the first time. Theoretical calculations are given and are in good agreement with the experimental results.