Presence Of Trisodium Citrate Research Articles

Data-Driven Optimization of Au Nanoparticle Synthesis with Automated Flow Microreaction System

We developed a flow microreaction system automated by a LabVIEW-based program enabling a control of flow rates of four pumps, an in-line UV–visible spectroscopic monitoring, and a process data logging including the pump pressures. The system was applied to the synthesis of gold nanoparticles (NPs) by a reduction of hydrogen tetrachloroaurate (III) (HAuCl4) with sodium tetrahydroborate (NaBH4) in the presence of trisodium citrate (Na3C6H5O7). Concentrations of the three reagents were controlled by changing the flow rates and were optimized so that the spectrum of the NPs gave higher peak at shorter wavelength. A gradual change in the concentrations from the dilute condition according to decision-tree algorithm as well as a careful monitoring of the pump pressures were shown to be effective for the optimization without clogging of the particles in the reactor.

Optimization of microfluidic synthesis of silver nanoparticles: A generic approach using machine learning

The properties of silver nanoparticles (AgNPs) are affected by various parameters, making optimisation of their synthesis a laborious task. This optimisation is facilitated in this work by concurrent use of a T-junction microfluidic system and machine learning approach. The AgNPs are synthesized by reducing silver nitrate with tannic acid in the presence of trisodium citrate, which has a dual role in the reaction as reducing and stabilizing agent. The study uses a decision tree-guided design of experiment method for the size of AgNPs. The developed approach uses kinetic nucleation and growth constants derived from an independent set of experiments to account for chemistry of synthesis, the Reynolds number and the ratio of Dean number to Reynolds number to reveal effect of hydrodynamics and mixing within device and storage temperature to account for particle stability after collection. The obtained model was used to define a parameter space for additional experiments carried out to improve the model further. The numerical results illustrate that well-designed experiments can contribute more effectively to the development of different machine learning models (decision tree, random forest and XGBoost) as opposed to randomly added experiments.

Synthesis and Catalytic Study of NiAg Bimetallic Core-Shell Nanoparticles.

This publication presents the synthesis of core-shell nanoparticles, where the core was Ni, and the shell was a Ag-Ni nano alloy. The synthesis was based on the reduction of Ni and Ag ions with sodium borohydride in the presence of trisodium citrate as a stabilizer. In order to determine the phase composition of the obtained nanoparticles, an XRD study was performed, and in order to identify the oxidation states of the nanoparticle components, an XPS spectroscopic study was performed. The composition and shape of the particles were determined using the HR-TEM EDS test. The obtained nanoparticles had a size of 11 nm. The research on catalytic properties was carried out in the model methylene blue reduction system. The investigation of the catalytic activity of colloids was carried out with the use of UV-Vis spectrophotometry. The Ag-Ni alloy was about ten times more active than were pure silver nanoparticles of a similar size.

Silver nanoparticles affect wheat (Triticum aestivum L.) germination, seedling blight and yield.

The aim of the study was to evaluate the effect of two types of negatively charged quasi-spherical silver nanoparticles (AgNPs) at concentrations of 10, 20 and 30mgL-1 and silver ions at a concentration of 30mgL-1 on the growth, selected physiological aspects and yielding of wheat (Triticum aestivum L.) cv. Tybalt, and on plant resistance to seedling blight. Seed germination, α-amylase activity in seeds, morphology and infestation of seedlings by pathogens were assessed in a hydroponic treatment. Growth rate, PSII efficiency, heading and yield of the same plants were then analysed in pot culture. Results showed that the AgNPs and silver ions had a negative effect on roots, but reduced seedling blight and improved leaf area compared to the control. In addition, the AgNPs reduced with sodium borohydride in the presence of trisodium citrate at concentrations of 10 and 20mgL-1 stimulated germination, α-amylase activity and shoot length, which was not observed in the case of silver ions and the AgNPs reduced with sodium hypophosphite in the presence of sodium hexametaphosphate. In a pot experiment, the AgNPs improved plant growth, PSII efficiency, accelerated heading and increased yield-related parameters compared with the control. Results revealed the interaction strength in the following order: TCSB-AgNPs>SHSH-AgNPs>silver ions. TCSB-AgNPs in the lowest concentration had the most favourable effect, indicating their great potential for use in improving wheat cultivation.

Novel H2S sensing mechanism derived from the formation of oligomeric sulfide capping the surface of gold nanourchins.

A gold nanourchin (AuNU) probe with a novel sensing mechanism for monitoring H2S was developed as a feasible colorimetric sensor. In this study, AuNUs that are selectively responsive to H2S were fabricated in the presence of trisodium citrate and 1,4-hydroquinone using a seed-mediated approach. Upon exposure of the AuNU solution to H2S, the hydrosulfide ions (HS-) in the solution are converted into oligomeric sulfides by 1,4-hydroquinone used as a reducing agent during the synthesis of AuNUs. The oligomeric sulfides formed in the AuNU solution upon the addition of H2S were found to coat the surface of the AuNUs, introducing a blue shift in absorption accompanied by a color change in the solution from sky blue to light green. This colorimetric alteration by the capping of oligomeric sulfides on the surface of AuNUs is unique compared to well-known color change mechanisms, such as aggregation, etching, or growth of nanoparticles. The novel H2S sensing mechanism of the AuNUs was characterized using UV-Vis spectroscopy, high-resolution transmission microscopy, X-ray photoelectron spectroscopy, surface-enhanced Raman spectroscopy, secondary ion mass spectroscopy, liquid chromatography-tandem mass spectrometry, and atom probe tomography. H2S was reliably monitored with two calibration curves comprising two sections with different slopes according to the low (0.3-15 μM) and high (15.0-300 μM) concentration range using the optimized AuNU probe, and a detection limit of 0.29 μM was obtained in tap water.

Surface properties-dependent antifungal activity of silver nanoparticles

Silver nanoparticles (AgNPs) exhibit unusual biocidal properties thanks to which they find a wide range of applications in diverse fields of science and industry. Numerous research studies have been devoted to the bactericidal properties of AgNPs while less attention has been focused on their fungicidal activity. Our studies were therefore oriented toward determining the impact of AgNPs characterized by different physicochemical properties on Fusarium avenaceum and Fusarium equiseti. The main hypothesis assumed that the fungicidal properties of AgNPs characterized by comparable morphology can be shaped by stabilizing agent molecules adsorbed on nanoparticle surfaces. Two types of AgNPs were prepared by the reduction of silver ions with sodium borohydride (SB) in the presence of trisodium citrate (TC) or cysteamine hydrochloride (CH). Both types of AgNPs exhibited a quasi-spherical shape. Citrate-stabilized AgNPs (TCSB-AgNPs) of an average size of 15 ± 4 nm were negatively charged. Smaller (12 ± 4 nm), cysteamine-capped AgNPs (CHSB-AgNPs) were characterized by a positive surface charge and higher silver ion release profile. The phytopathogens were exposed to the AgNPs in three doses equal to 2.5, 5 and 10 mg L−1 over 24 and 240 h. Additionally, the impact of silver ions delivered in the form of silver nitrate and the stabilizing agents of AgNPs on the fungi was also investigated. The response of phytopathogens to these treatments was evaluated by determining mycelial growth, sporulation and changes in the cell morphology. The results of our studies showed that CHSB-AgNPs, especially at a concentration of 10 mg L−1, strongly limited the vegetative mycelium growth of both species for short and long treatment times. The cell imaging revealed that CHSB-AgNPs damaged the conidia membranes and penetrated into the cells, while TCSB-AgNPs were deposited on their surface. The fungistatic (lethal) effect was demonstrated only for silver ions at the highest concentration for the F. equiseti species in the 240 h treatment. The number of spores of both Fusarium species was significantly reduced independently of the type of silver compounds used. Generally, it was found that the positively charged CHSB-AgNPs were more fungicidal than negatively charged TCSB-AgNPs. Thereby, it was established that the stabilizing agents of AgNPs and surface charge play a crucial role in the shaping of their fungicidal properties.

Synthesis and Mechanism of Spherical Ag-doped Polypyrrole Assisted by Complexing Agents

Highly dispersed Ag-doped Polypyrrole (PPy) spherical composites can be efficiently synthesized via oxidative polymerization of pyrrole with FeCl3 in an aqueous Ag+-containing solution in the presence of trisodium citrate, followed by concentrated ammonia treatment. However, the formation mechanisms involved in how to control the shape and how to get the metallic Ag0 need further investigation. In order to elucidate the formation mechanisms, the intermediates in different reaction stage were collected and investigated. Combining the experimental phenomenon and the structure characterization of the samples, it was found that citrate ions make a role of complexing Ag+ to produce [Ag3(C6H5O7)n+1]3n− complexes in the early reaction stage, then mainly play a role of steric stabilizer of AgCl micelles and are responsible for the shape tailoring of PPy composite as well as the reduction of Ag+ in the process of ammonia treatment. Evidently, negative-charged AgCl micelles become the main nucleation sites of pyrrole polymerization through the electrostatic attraction between the negative and positive ions. Concentrated ammonia is adopted to eliminate AgCl cores from the precursor of Ag-doped PPy composites obtained by chemical redox reaction and provides an accelerated reaction condition for reduction of Ag+ by reductants (citrate ion or pyrrole monomer). Ag-containing micelles induction method is a facial chemical method to obtain uniform Ag-doped composites and can be broadened to design other Ag-containing functional materials.

Reduced Graphene Oxide Sheets as Inhibitors of the Photochemical Reactions of α-Lipoic Acid in the Presence of Ag and Au Nanoparticles.

The influence of Ag and Au nanoparticles and reduced graphene oxide (RGO) sheets on the photodegradation of α-lipoic acid (ALA) was determined by UV-VIS spectroscopy. The ALA photodegradation was explained by considering the affinity of thiol groups for the metallic nanoparticles synthesized in the presence of trisodium citrate. The presence of excipients did not induce further changes when ALA interacts with Ag and Au nanoparticles with sizes of 5 and 10 nm by exposure to UV light. Compared to the Raman spectrum of ALA powder, changes in Raman lines’ position and relative intensities when ALA has interacted with films obtained from Au nanoparticles with sizes between 5 and 50 nm were significant. These changes were explained by considering the chemical mechanism of surface-enhanced Raman scattering (SERS) spectroscopy. The photodegradation of ALA that had interacted with metallic nanoparticles was inhibited in the presence of RGO sheets.

Ag nanofluids synthesis in presence of citrate at different stirring rotation and their post reaction stability

Ag nanofluids have been synthesized by the single pot synthesis method reducing silver nitrate (AgNO3) applying sodium borohydride (NaBH4) as a reducing agent in the presence of trisodium citrate (TSC) in water base fluid. Stirring effect on the synthesis has been studied in terms of rotation per minute (RPM) using a digitally displayed electronically controlled mechanical stirrer and a decreasing tendency of mean particle sizes has been observed on increasing RPM from 250 to 950 at the interval of 100. Time dependent Surface Plasmon Resonance (SPR) Spectra have been recorded by UV-Visible spectrometer from 1 h to 36 h at the interval of almost 12 h and the particle size distribution have been estimated by the deconvolution of the spectra. The size distribution has been quantified correlating deconvoluted peaks and their area under the curves proportionated to that of the entire spectrum. The mean particle sizes have been observed to vary from 20 nm to 100 nm and the variations depend on both RPM and time. The RPM and time dependent area under the curve of each spectrum have been analyzed to find the nanofluid stabilization and 450 has been recorded as most stabilizing RPM accounting by 0.35% change in it. The histograms of particle size distribution have been analyzed by mathematical modeling, arithmetic progression and geometric progression. Histogram that fits arithmetic progression indicates Ag+ seeding by its reduction on Ag nanoparticles to grow bigger particles and histogram that fits geometric progression indicates agglomeration of Ag nanoparticles for sedimentation.

Hyaluronic Acid-Modified Au-Ag Alloy Nanoparticles for Radiation/Nanozyme/Ag+ Multimodal Synergistically Enhanced Cancer Therapy.

Gold nanoparticles (AuNPs) have been widely documented as tumor radiosensitizers via enhanced energy deposition of ionizing radiation. However, the sensitization efficiency of AuNPs is still far from satisfactory owing to the irradiation on nontarget tissues and the tumor radio-resistance. To address these issues, we report herein the rational design and development of hyaluronic acid-modified Au-Ag alloy nanoparticles (Au-Ag@HA NPs) with effective tumor radiosensitization by receptor mediated tumor targeting as well as microenvironment-activated hydroxyl radicals (•OH) generation. In our work, Au-Ag@HA NPs were synthesized by the coreduction of HAuCl4 and AgNO3 in the presence of trisodium citrate, followed by surface modification of HA to the Au-Ag alloy NPs. HA modification affords the alloy NPs with specific targeting to 4T1 breast cancer cells overexpressing CD44 receptor, while the introduction of Ag atom imparts the alloy NPs with superior multienzyme-like activities to the monometallic AuNPs for efficient tumor catalytic therapy. More importantly, the ionizing radiation and peroxidase-like activity of Au-Ag@HA NPs boost the production of •OH and the release of toxic Ag+ in the tumor sites, thereby leading to effective tumor therapeutic outcome. This work provides a promising treatment paradigm for radiation/nanozyme/Ag+ combined therapy against cancer and will advance the design and development of multifunctional nanoplatforms for synergetically enhanced tumor therapy.

SERS Activity of Silver Nanosphere, Triangular Nanoplates, Hexagonal Nanoplates and Quasi-Spherical Nanoparticles: Effect of Shape and Morphology

In this work, we prepared different morphologies of silver nanoparticles: nanosphere, triangular nanoplates, hexagonal nanoplates, and quasi-spherical shapes, through one-step synthesis. Hydrogen peroxide was used as the oxidizing agent during the reduction of silver nitrate by sodium borohydride, in the presence of tri-sodium citrate and poly-vinyl-pyrrolidone. The obtained silver nanoparticles were fully characterized by UV-Vis spectroscopy, Dynamic Light Scattering and Scanning Electron Microscopy, and successfully used as Surface Enhanced Raman Scattering (SERS) substrates. The effect of shape and morphology on the Raman scattering enhancement was evaluated by using methylene blue as target molecules. The Raman measurements demonstrated that the prepared substrates are reliable and sensitive with analytical enhancement factors, estimated to be around 105 with a concentration of methylene blue 1 μM. When triangular and hexagonal nanoplates were tested with different concentrations of analyte, they demonstrated a good linearity in Raman intensity with a good detection of methylene blue 0.1 μM.

Rational Design of Electrocatalytic Interfaces: Cd UPD Mediated Nitrate Reduction on Pd:Au Bimetallic Surfaces

INTRODUCTION Efforts in our laboratories have been focused on the rational design and assembly of bifunctional electrocatalytic interfaces incorporating two electrocatalysts acting in series as a means of improving both the overall activity and specificity of redox processes involving multiple transfer of electrons. This strategy was recently implemented to promote the reduction of NO3 - on Au NP dispersed on the surface of glassy carbon, GC, by adsorbed hemin (Hm), an iron porphyrin, in aqueous electrolytes containing Cd2+.1 This work represents an extension of this previous study in which Hm has been replaced by Pd nanoparticles, NP, co-dispersed with Au NP on GC, a tactic that virtually eliminates the formation of Au|Pd alloys. Impetus for this selection was provided by the much lower overpotential for NO2 - reduction on Pd compared to that on adsorbed Hm, a factor that would lead to overall activities surpassing those found earlier for the Cd(UPD)|Hm system. EXPERIMENTAL All electrochemical measurements were performed in an all-glass, three-compartment cell, filled with deaerated (Ar, Airgas, PP300) 0.1 M HClO4 solutions prepared from ultrapure perchloric acid (OmniTrace Ultra) and ultra-high purity water, UPW, generated by a Barnstead system (18.2 MΩ cm). A carbon rod (Alfa Aesar, diameter 6.15 mm) and a Ag/AgCl (Basi, MF2052) were used as counter and reference electrodes, respectively. Experiments were carried out with a GC disk electrode, GCE, (Pine Instruments, disk area, 0.196 cm2) using a commercial rotator (Pine Instruments, Model AFMSRX) and a Metrohm Autolab (PGSTAT302N). Cadmium perchlorate, Cd(ClO4)2 (Sigma-Aldrich, 99.999%), and sodium nitrate, NaNO3, (Sigma Aldrich, ACS reagent) were used as received. Nanoparticles, NP of Au and Pd were synthesized and cleaned using a methodology previously described in which an aqueous solution of the corresponding metallic precursor (HAuCl4 or H2PdCl4) was reduced with ice-cold and freshly prepared NaBH4 solution in the presence of trisodium citrate.2 Stock suspensions of each type of NP were prepared by mixing 1 volume of the original, as received, NP, with 3 volumes of UPW. To prepare either Au or Pd dispersions on the GCE, denoted hereafter as Au|GCE or Pd|GCE, 10 µL of the diluted NP aqueous suspensions were delivered to the GC surface using a micropipette, and then allowed to dry with a gentle stream of Ar. To prepare the co-dispersed Pd and Au NP on a GC disk, Pd:Au|GCE, 500 µL of each dilute NP suspension were mixed in a vial and following sonication, 10 µL of the mixture then delivered on the GCE using a micropipette, and allowed to dry under Ar. RESULTS AND DISCUSSION Shown in 1 are cyclic voltammograms recorded with Au|GCE (magenta), Pd|GCE (black) and Pd:Au|GCE (green) in pristine 0.1 N HClO4, displayed features believed to be characteristic of the metals involved. Integration of the characteristic reduction peaks in green in Fig 1 were found to be approximately half of those in either the Au|GCE or Pd|GCE (see magenta and black curves), and thus consistent with the relative amounts of each of the NP in the Pd:Au|GCE. Shown in Panel A, Fig. 2 are cyclic voltammograms obtained with these NP modified GCE surfaces in 0.1 M HClO4 containing 1 mM Cd(ClO4)2 and 2 mM NaNO3. Cursory inspection of these data reveals much higher activity for the Pd:Au|GCE, even though the amount of each NP was decreased to half, compared to the single metal surfaces. The same overall trend was found for measurements performed under forced convection, as shown in Panel B in this figure which reinforces the view that the two catalysts are indeed acting in series, i.e., Cd UPD on Au is responsible for the conversion of NO3 - to NO2 -, whereas Pd reduces NO2 - further to products of lower oxidation states. REFERENCES Y. Chen, H. Zhu, M. Rasmussen and D. Scherson, J. Phys. Chem. Lett., 1, 1907 (2010).C. M. Sanchez-Sanchez, F. J. Vidal-Iglesias, J. Solla-Gullon, V. Montiel, A. Aldaz, J. M. Feliu and E. Herrero, Electrochim. Acta, 55, 8252 (2010). ACKNOWLEDGEMENTS: This work was supported by a grant from NSF, CHE-1412060. Figure 1

Two-dimensional CuIn1−xGaxSe2 nano-flakes by pulse electrodeposition for photovoltaic applications

Fabrication of Cu(In,Ga)Se2 (CIGS) absorber layers containing two-dimensional nano-flake structures using a single stage pulse electrodeposition technique is reported for the first time, wherein CuCl2, InCl3, GaCl3 and H2SeO3 are used as precursors in a pH 3 buffer. The method employs tri-sodium citrate as complexing agent. The phenomenon of intrinsic electrochemical dissolution associated with pulse electrodeposition technique is efficiently utilized to obtain CIGS nano-flakes. The presence of tri-sodium citrate and the relaxation time during pulse electrodeposition play crucial role in achieving control over composition and morphology of CIGS films thereby aiding in the formation of nano-flakes. Evolution of nano-flake structures is systematically investigated with the increase in deposition time during pulse electrodeposition. Elemental analysis reveals the stoichiometric composition of nano-flake films while the formation of chalcopyrite phase-pure CIGS is confirmed by XRD and Raman analyses. The bandgap of CIGS nano-flakes is inferred to be about 1.21 eV from Tauc’s plot. Mott-Schottky studies unveil the p-type conductivity of the CIGS with a flat-band potential and carrier density values of −0.15 V and 5.2 × 1016 cm−3, respectively. Photoelectrochemical characterization of CIGS films affirms their photoactivity and the photoresponse is almost 20 times compared to the traditional planar CIGS films. Nanostructured CIGS films fabricated by low-cost pulse electrodeposition method reduce materials consumption while promising excellent photoresponse and are suitable for photovoltaic and photoelectrochemical applications.

Improving the textural properties of camel milk acid gel by treatment with trisodium citrate and transglutaminase

This study aimed to solve the problems of the weak acid-induced gelation ability of camel milk by the synergistic effect of trisodium citrate and microbial transglutaminase (mTGase). As the trisodium citrate concentration increased from 0 to 30 mmol/L, the final storage modulus of mTGase-treated camel milk acid gels increased from 11.9 ± 0.3 to 72.5 ± 2.4 Pa, the firmness increased from 0.7 ± 0.2 to 1.8 ± 0.1 N, and water holding capacity increased from 41.0 ± 1.8% to 99.6 ± 0.8%. A denser gel network structure with the smallest pore size was observed with 30 mmol/L trisodium citrate, which was selected as the optimum concentration. The number average diameter of the casein particles decreased significantly from 183.5 ± 5.9 to 37.4 ± 3.0 nm and the degree of crosslinking of the acid gel increased significantly from 19.3 ± 1.2% to 38.9 ± 2.4% in the presence of trisodium citrate. This study indicated that smaller casein particles with a higher level of covalent crosslinking can form a camel milk gel with better textural properties, which has enormous potential for manufacture of acid-induced camel milk gel products.

Supported Pd nanoparticle catalysts with high activities and selectivities in liquid-phase furfural hydrogenation

Highly dispersed and ultrafine Pd nanoparticles (NPs) deposited on carbon, silica, and alumina supports were prepared by chemical reduction (CR) using sodium borohydride, in the presence of trisodium citrate as a stabilizer. For comparison, supported Pd catalysts were also prepared through impregnation followed by thermal reduction (TR) and capillary inclusion of the colloidal Pd NPs (CI). The activities and selectivities of the prepared catalysts were evaluated in the liquid-phase furfural (FAL) hydrogenation reaction under 20 bar H2 at 180 °C. Under these conditions, FAL was converted via two distinct pathways to produce either furan via decarbonylation or furfuryl alcohol (FA) via aldehyde hydrogenation. Subsequently, furan and FA were converted to tetrahydrofuran and tetrahydrofurfuryl alcohol (THFA), respectively, via ring hydrogenation. 2-Methylfuran was also produced from the hydration of FAL. To verify the efficiency of the preparation methods, the size of the Pd NPs, the degree of metal dispersion, and the type of supports were correlated with the catalytic conversions and selectivities of FAL hydrogenation. It was confirmed that the 5 wt% Pd/C catalysts possessed highly dispersed small Pd NPs with large metallic Pd surface areas, which resulted in high conversions and selectivities towards THFA in the FAL hydrogenation reaction compared to conventional supported catalysts.

Carbon dot capped gold nanoflowers for electrochemiluminescent aptasensor of thrombin

A simple method has been developed to synthesize carbon dot capped gold nanoflower (CD/AuNF) nanohybrids. In principle, anodic electrochemiluminescent (ECL) carbon dots (CDs) with a lot of reductive functional groups were used to react with oxidative hydrogen tetrachloroaurate trihydrate in the presence of trisodium citrate. The obtained globular CD/AuNF nanohybrids had uniform sizes of 50–60 nm. The CD/AuNF nanohybrids were composed of gold nanoparticle aggregates in the centers and CDs on the surfaces. The easy self-assembly with some bio-molecules of AuNFs and the unique ECL activities of the CDs, made the obtained CD/AuNF nanohybrids promising in biosensing. For instance, a novel ECL aptasensor for thrombin (TB) detection has been developed based on the CD/AuNF nanohybrids. The aptasensor showed good selectivity towards TB. Furthermore, it presented a wide linear response range from 0.5 nM to 40 nM and a low detection limit (S/N = 3) of 0.08 nM.

Switchable on/off drug release from gold nanoparticles-grafted dual light- and temperature-responsive hydrogel for controlled drug delivery

A switchable dual light- and temperature-responsive drug carrier using gold nanoparticles (Au NPs)-grafted poly(dimethylacrylamide-co-acrylamide)/poly acrylic acid [P(DMA-co-AAm)/PAAc] hydrogel was prepared by free radical polymerization procedure using N,N-methylenebisacrylamide as cross-linker and ammonium persulfate as initiator. Initial P(DMA-co-AAm) hydrogel and uniformly-distributed stable Au NPs, prepared by reduction of hydrogen tetrachloroaureate (III) hydrate in the presence of trisodium citrate, were synthesized separately. Then, the prepared P(DMA-co-AAm) and Au NPs were added to an acrylic acid solution along with the cross-linker and initiator to prepare PAAc hydrogel within the mixture. This improves the swelling ratio and stabilizes Au NPs in networks. Furthermore, a cross-linked P(DMA-co-AAm-co-AAc) random hydrogel was also prepared with the same monomer compositions as the above hydrogel for comparison of their properties. Then, swelling, thermal sensitivity and thermal and optical switching properties of the prepared hydrogels were investigated in two acidic (pH=1.2) and neutral (pH=7.4) buffered solutions to simulate stomach and intestine body conditions. Finally, loading and cumulative release (%) of ofloxacin antibiotic as model drug were considered in both thermal and optical switching conditions. Based on these results, pulsatile release vehicle was obtained which have the “on” state at higher temperatures and the “off” state at lower temperatures.

Antifouling Manganese Oxide Nanoparticles: Synthesis, Characterization, and Applications for Enhanced MR Imaging of Tumors

Antifouling manganese oxide (Mn3O4) nanoparticles (NPs) were synthesized by solvothermal decomposition of tris(2,4-pentanedionato) manganese(III) in the presence of trisodium citrate, followed by surface modification with polyethylene glycol and l-cysteine. The as-prepared nanoparticles have a uniform size distribution, good colloidal stability and good cytocompatibility. The modification of l-cysteine rendered the particles with much longer blood circulation time (half-decay time of 28.4 h) than those without l-cysteine modification (18.5 h), and decreased macrophage cellular uptake. Thanks to desirable antifouling property and relatively high r1 relaxivity (3.66 mM-1 s-1), the l-cysteine-modified Mn3O4 NPs can be used for enhanced tumor magnetic resonance imaging applications.

Seed mediated synthesis of highly mono-dispersed gold nanoparticles in the presence of hydroquinone

Gold nanoparticles (AuNPs) are being studied for several biomedical applications, including drug delivery, biomedical imaging, contrast agents and tumor targeting. The synthesis of nanoparticles with a narrow size distribution is critical for these applications. We report the synthesis of highly mono-dispersed AuNPs by a seed mediated approach, in the presence of tri-sodium citrate and hydroquinone (HQ). AuNPs with an average size of 18 nm were used for the synthesis of highly mono-dispersed nanocrystals of an average size 40 nm, 60 nm, 80 nm and ∼100 nm; but the protocol is not limited to these sizes. The colloidal gold was subjected to UV–vis absorbance spectroscopy, showing a red shift in lambda max wavelength, peaks at 518.47 nm, 526.37 nm, 535.73 nm, 546.03 nm and 556.50 nm for AuNPs seed (18 nm), 40 nm, 60 nm, 80 nm and ∼100 nm respectively. The analysis was consistent with dynamic light scattering and electron microscopy. Hydrodynamic diameters measured were 17.6 nm, 40.8 nm, 59.8 nm, 74.1 nm, and 91.4 nm (size by dynamic light scattering—volume %); with an average poly dispersity index value of 0.088, suggesting mono-dispersity in the size distribution, which was also confirmed by transmission electron microscopy analysis. The advantage of a seed mediated approach is a multi-step growth of nanoparticle size that enables us to control the number of nanoparticles in the suspension, for size ranging from 24.5 nm to 95.8 nm. In addition, the HQ-based synthesis of colloidal nanocrystals allowed control of the particle size and size distribution by tailoring either the number of seeds, amount of gold precursor or reducing agent (HQ) in the final reaction mixture.

Facial Synthesis of Silver-incorporated Conductive Polypyrrole Submicron Spheres for Supercapacitors

Spherical silver-incorporated conductive polypyrrole (PPy) composite is successfully prepared via oxidative polymerization of pyrrole in an aqueous Ag+-containing solution in the presence of trisodium citrate. Citrate produces stable and charged micelles, thus tailoring the facial polymerization of the pyrrole. Monodispersed submicron spheres of silver/PPy composite are obtained by maintaining the molar ratio of citrate anion to silver cation at 3:1. Highly dispersed metallic Ag is uniformly incorporated in the PPy matrix, thus increasing the charge transfer ability of PPy materials. The as-prepared Ag/PPy material exhibits ideal capacitive behavior and has excellent cyclic stability. Charge-discharge measurements demonstrate a maximum specific capacitance of 315.8Fg−1 for the Ag/PPy electrode, which is much higher than that of a pure PPy electrode (153.2Fg−1). A high specific energy density of 43.9 Wh kg−1 can be achieved at 50W Kg−1 for PPy in the Ag/PPy electrode, and 30 Wh kg−1 remains at 500W Kg−1. The facially synthesized Ag/PPy composite possesses promising properties for use as an electrode material for supercapacitors.