Synthesis of hydroxyapatite/polyethylene glycol 6000 composites by novel dissolution/precipitation method: optimization of the adsorption process using a factorial design: DFT and molecular dynamic.

In this work, we presented a synthesis of a composite based on HAp and PEG 6000 using a new method of synthesis dissolution precipitation to be applied for application of wastewater purification from toxic metal ions. Multiple characterization methods were used to analyze the morphology and the structure of the well-prepared compounds including FT-IR, Raman, XRD, XPS, TGA and SEM were used to conduct a composite analysis. The adsorption effectiveness of this analysis towards Pb2+ and various other hazardous metal ions found in sewage was assessed. Batch experiments were conducted to optimize the various operational parameters including adsorbent dose, temperature, pH, contact time, and initial concentration. The Langmuir isotherm was used to fit the data, and it predicted monolayer adsorption with a maximum capacity of 67 mg g-1 for HAP PEG600 and 60 mg g-1 for HAp. A pseudo-second-order equation fits the adsorption process well (0.961-0.971). The thermodynamic data support the spontaneous metal bonding to the composite receptor sites. Theoretical calculations showed that the interaction strength is very strong and gets stronger when the PEG6000 is deprotonated. The results presented here are supported by evidence acquired from experiments. Theoretical computation using Monte Carlo (MC) and Molecular Dynamic (MD) simulation models showed excellent affinity of prepared foams for the model ion Pb2+ with highly negative adsorption energy values indicating vigorous interactions of Pb2+ with the adsorbate surfaces.

Effect of 1-(3-phenoxypropyl) pyridazin-1-ium bromide on steel corrosion inhibition in acidic medium.

The effect of 1-(3-phenoxypropyl) pyridazin-1-ium bromide, a new pyridazinium derivative, on steel corrosion in a HCl (1 M) solution was analyzed using electrochemical impedance and XPS spectroscopy. Experimental results indicated that the inhibition efficiency increased with an increase in an inhibitor concentration. Electrochemical impedance spectroscopy measurements revealed that an increase in the immersion time of steel in an acidic medium from 1 to 12 h and further to 24 h decreased the charge transfer resistance (Rct) and thus decreased the inhibition efficiency. The SEM and XPS analyses linked the inhibition effect to the adsorption of the inhibitor (1-(3-phenoxypropyl) pyridazin-1-ium bromide) on the steel surface.

Eco-friendly modification of a regenerated cellulose based film by silicon, carbon and N-doped carbon quantum dots.

Modification of a regenerated cellulose thin film by inclusion of different non-toxic nanodots (silicon-dots (SiDs), carbon-dots (CDs)) or nitrogen-doped carbon dots (N-CDs)) by aqueous nanodots solution immersion was performed. Nanodots presence into the cellulosic structure was evidenced by confocal microscopy images at different depth and changes in film mechanical, electrical and optical parameters. Our results reveal that the inclusion of the different nanodots in the cellulosic support increases, indifferent percentages, the mechanical resistance and electrical conductivity of modified films, but they hardly affect light transmittance. Particularly, modification with N-CDs largely favored film conductivity due to the presence of the higher number of charged functional groups (CNH2 and OCNH2) groups) on N-CDs surface, allowin gus the attainment of a flexible, fluorescent and transparent high conductive eco-friendly film. In fact, the non-toxic character of both support-film and nanodots, endorses the use of these new nano-engineering films in biomedical applications.

Enhanced electrochemical response of carbon quantum dot modified electrodes.

A glassy carbon electrode (GCE) was surface-modified with carbon quantum dots (CQDs) and applied for the effective enhancement of the electrochemical signal for dopamine and uric acid determination. CQDs were prepared from graphite by a green modification of the Hummers method. They were characterized by FTIR-ATR, XPS, solid-state NMR, fluorescence and Raman spectroscopies. TPD-MS analysis was applied to characterize the functionalization of the surface. The CQDs were assembled on the glassy carbon electrode by adsorption because of the large number of carboxy groups on their surface warrants effective adsorption. The modified GCE exhibits a sensitivity that is almost 10 times better than of the bare GCE. The lower limits of detection are 1.3µM for uric acid and 2.7µM for dopamine.

Characterization of cellulose membranes modified with luminescent silicon quantum dots nanoparticles.

A highly hydrophilic planar membrane fabricated with regenerated cellulose (RC-4 membrane), a biocompatible polymer, was modified by inclusion of water-soluble silicon quantum dot nanoparticles (SiQDs). Both bare SiQDs and SiQDs coated with a PAMAM-OH dendrimer were employed in order to obtain luminescent and thermally stable membrane systems (RC-4/SiQDs and RC-4/SiQDs-PAMAM-OH membranes). Original and SiQDs-modified membranes were characterized by fluorescence spectroscopy (steady and confocal), derivative thermogravimetric analysis and impedance spectroscopy measurements. According to these results, both SiQDs-regenerated cellulose composite membranes present luminescent character as well as higher thermal resistance and conductivity than the original sample, although the dendrimer coverage of the SiQDs might partially shield such effects. Moreover, the permanence of SiQDs nanoparticles in the structure of the cellulosic support in aqueous environments and their effect on diffusive transport were determined by water uptake as well as by membrane potential measurements at different concentrations of a model electrolyte (KCl). These results demonstrate the possible use of these stable nano-engineered membranes, which are based on SiQDs nanoparticles, in electrochemical devices under flow conditions.

Synthesis of vinyl-terminated Au nanoprisms and nanooctahedra mediated by 3-butenoic acid: direct Au@pNIPAM fabrication with improved SERS capabilities.

Here we describe the first seedless synthesis of vinyl-terminated Au nanotriangular prisms (AuNTPs) and nanooctahedra (AuNOC) in aqueous media. This synthesis is performed by chemical reduction of chloroauric acid (HAuCl4) with 3-butenoic acid (3BA) in the presence of benzyldimethylammonium chloride (BDAC). The principal novelties of the presented method are the use of a mixture of 3BA and BDAC, the synthesis of gold prisms and octahedra with controllable size, and the presence of terminal double bonds on the metal surface. Initially this method produces a mixture of triangular gold nanoprisms and octahedra; however, both morphologies are successfully separated by surfactant micelle induced depletion interaction, reaching percentages up to ∼90%. Moreover, the alkene moieties present on the gold surface are exploited for the fabrication of hybrid core@shell particles. Gold octahedra and triangular prisms are easily encapsulated by free radical polymerization of N-isopropylacrylamide (NIPAM). Finally, in order to obtain a gold core with the most number of tips, AuNTP@pNIPAM microgels were subjected to gold core overgrowth, thus resulting in star-shaped nanoparticles (AuSTs@pNIPAM). We use 4-amino-benzenethiol as the model analyte for SERS investigations. As expected, gold cores with tips and high curvature sites produced the highest plasmonic responses.

Fluorescent sensor for Cr(VI) based in functionalized silicon quantum dots with dendrimers.

Highly luminescent nanoparticles based in Silicon quantum dots, coated by hydroxyl PAMAM dendrimer (PAMAM-OH) of 5th generation, were obtained by one step process by hydrothermal treatment of 3-Aminopropyl)triethoxysilane (APTES) in aqueous solution. Previous to the optimization of the synthesis procedure, different dendritic molecules of 5th generation were tested to obtain the most intense fluorescence signal. The influence of different parameters such ratio APTES/PAMAM-OH, pH and ionic strength on the fluorescence intensity was studied. The fluorescence spectra showed maximum excitation and emission wavelengths at 370 and 446 nm, respectively. The obtained silicon nanoparticles (SiQDs@PAMAM-OH) were characterized by TEM, DLS and XPS, and were found to detect selectively Cr(VI) in aqueous solutions at 2.7 µM level of detection, sensitivity of 0.2 µM with a RSD of 0.16% (n=10). To study the feasibility of the proposed system for Cr(VI) detection, it was tested in real electrochemical solution bath and a tanning effluent obtained from electrochemical industry and with two certified waters, demonstrating promising outcomes as nano-sensor.

Fluorescent chemosensor for pyridine based on N-doped carbon dots.

Fluorescent carbon dots (CDs) and its nitrogen doped (N-CDs) nanoparticles have been synthesized from lactose as precursor using a bottom-up hydrothermal methodology. The synthesized nanoparticles have been characterized by elemental analysis, FTIR, Raman, TEM, DLS, XPS, and steady-state and life-time fluorescence. The synthesized carbon nanoparticles, CDs and N-CDs, have a size at about 7.7±2.4 and 50±15nm, respectively, and quantum yields of 8% (CDs) and 11% (N-CDs). These techniques demonstrated the effectiveness of the synthesis procedure and the functionalization of the CDs surface with amine and amide groups in the presence of NH3 in aqueous media. The effect of excitation wavelength and pH on the luminescent properties was studied. Under the optimal conditions, the nitrogen doped nanoparticles can be used as pyridine sensor in aqueous media because they show an enhancement of its fluorescence with a good linear relationship. The analytical method is simple, reproducible and very sensitive for pyridine determination.

Microwave-assisted synthesis of carbon dots and its potential as analysis of four heterocyclic aromatic amines.

Fluorescent water soluble carbon nanoparticles, in short carbon dots (CDs), was synthesized from lactose by microwave assisted hydrochloric acid method. Characterized by TEM and DLS to obtain the morphology shape (average 10nm in size), with a higher negative surface charge supported by the composition was obtained by XPS spectroscopy. The maximum of the emission was centered at 450 nm with a lifetime of 2.1 ns. Without further functionalization of the CDs a nanosensor was obtained that responded exponentially to HAAs in the 0.35-0.45 mg L(-1) concentration range by fluorescence static quenching, demonstrated by the lifetime analysis of the CDs in presence of HAAs. Some amino compounds were selected as model for interferences to evaluate the selectivity of this method, showing a notorious added value, with recoveries around 98%. The accuracy of the method was in terms of RSD about 2.5%. The results suggest their promising applications in chemical sensing.

Carbon dots obtained using hydrothermal treatment of formaldehyde. Cell imaging in vitro.

Highly photoluminescent carbon dots have been prepared in a one step procedure by hydrothermal treatment of formaldehyde at 180 °C. They show green fluorescence under UV light exposure and emission spectra are centered at 440 nm. Fluorescence lifetimes comprise between 0.7 and 2.70 ns, when the synthesis process lasted for 1-7 days. TEM images of nanoparticles showed a homogeneous size/shape distribution. When the thermal treatment process was carried out for a long time (30 days) formation of aggregates occurred. Carbon dots were further analyzed using (1)H and (13)C-NMR, Raman and FTIR spectroscopy techniques and XPS. Cell imaging of nanoparticles was carried out by using mouse MC3T3-E1 pre-osteoblasts as a model. The nanoparticles were selectively localized in the cytoplasm without further functionalization and could be realized by cellular phagocytosis, so that the fluorescence of these can be used for live cell imaging in vitro.

Component analysis of fluorescence spectra of thiol DAB dendrimer/ZnSe-PEA nanoparticles.

The fluorescence spectroscopy technique is an accurate method and has great utility in the interpretation of complex systems based on several emission bands. An interpretation of the system requires determination of the number, positions and intensities of the spectral components. In this work, the emission spectra of the synthesized ZnSe complex coated with O-phosphorylethanolamine (ZnSe-PEA), both with and without thiol DAB dendrimer generation 5 (S-DAB G5), were analyzed using a combination of asymmetric (log-normal) and symmetric (Gaussian) models. The method applied for the deconvolution of fluorescence spectra has proven to be very sensitive for observing the stability of the ZnSe-PEA complex after binding with S-DAB. The ZnSe-PEA emission spectrum contains two components. The positions of the emission maxima of these two components are not significantly affected by the presence of S-DAB G5 in the complex, which revealed the presence of a stable complex at a pH of 7. By applying the spectral deconvolution method, strong evidence was obtained that suggested that the ZnSe-PEA complex is stable after complexation with S-DAB G5.

Thiolated DAB dendrimer/ZnSe nanoparticles for C-reactive protein recognition in human serum.

A nanocomposite obtained by a thiol DAB-dendrimer (generation 5), coated with fluorescent ZnSe quantum dots, was successfully synthesized for the selective recognition of C-reactive protein. The procedure presented was carried out by a novel, cheap and non-toxic bottom up synthesis. The nanocomposite showed an excitation at 180 nm, with two emission bands at 411 and 465 nm, with a full-width at half-maximum of 336 nm. The Stokes shift was influenced by the presence of coating molecules and the intensity was dependent on pH due to the presence of a charge transfer process. The transmission electron microscopy images demonstrated that the spherical nanoparticles obtained displayed a regular shape of 30 nm size. The fluorescence intensity was markedly quenched by the presence of C-reactive protein, with a dynamic Stern-Volmer constant of 0.036 M(-1). The quenching profile shows that about 51% of the ZnSe QDs are located in the external layer of the thiol dendrimer accessible to the quencher. The precision of the method obtained as relative standard deviation was 3.76% (4 mg L(-1), n=3). This water soluble fluorescent nanocomposite showed a set of favorable properties to be used as a sensor for the C-reactive protein in serum samples, at concentrations of risk levels.

CdSe and ZnSe quantum dots capped with PEA for screening C-reactive protein in human serum.

A fluorescence chemical sensor for C-reactive protein (CRP) was developed based on the selective interaction with CdSe and ZnSe quantum dots (QDs) coated with O-phosphorylethanolamine (PEA). Synthesis procedure and analytical parameters such as pH and ionic strength were studied. The decrease in the fluorescence emission intensity was explained due to the specific interaction of the QDs-PEA with CRP, and a correlation was observed between the quenching of the fluorescence and the concentration of CRP. The accuracy of the proposed method was 0.37% as RSD. The proposed method was applied to screen serum samples, and showed to be sensible at the C-reactive protein concentrations of risks levels.

Determination of enantiomeric excess by chiral liquid chromatography without enantiomerically pure starting standards.

A facile approach for the enantiomeric excess determination of enantiomeric mixtures without the necessity of pure enantiomer standards is presented. Promethazine and trimeprazine commercial nonracemic mixtures were used as cases study to probe the validity of the method. Chromatographic resolutions obtained with a chiral column AGP in reverse phase mode were 1.32-1.16 (promethazine) and 1.20-0.93 (trimeprazine) for the three detectors (circular dichroism, photometric and fluorimetric) in series. Results obtained showed that enantiomeric excess was 10.4, 8.71 and 8.58% for promethazine and 1.60, 1.23 and 1.80% for trimeprazine (medium values of 9.23 ± 1.01% and 1.54 ± 0.29%, respectively). Recovery assay over human serum samples, at three concentration levels, spiked with prometazine and submitted to solid-phase extraction, gave values of 99.09-93.48% [S-(-) enantiomer] and 98.51-91.89% [R-(+)-enantiomer]. Detection limits of promethazine enantiomers were between 0.02 µg (fluorimetric) and 1 µg (circular dichroism), and 0.02-1.1 µg for trimeprazine.

Thiolated DAB dendrimers and CdSe quantum dots nanocomposites for Cd(II) or Pb(II) sensing.

Four different generation of thiol-DAB dendrimers were synthesized, S-DAB-G(x) (x=1, 2, 3 and 5), and coupled with CdSe quantum dots, to obtain fluorescent nanocomposites as metal ions sensing. Cd(II) and Pb(II) showed the higher enhancement and quenching effects respectively towards the fluorescence of S-DAB-G(5)-CdSe nanocomposite. The fluorescence enhancement provoked by Cd(II) can be linearized using a Henderson-Hasselbalch type equation and the quenching provoked by Pb(II) can be linearized by a Stern-Volmer equation. The sensor responds to Cd(II) ion in the 0.05-0.7µM concentration range and to Pb(II) ion in the 0.01-0.15mM concentration range with a LOD of 0.06mM. The sensor has selectivity limitations but its dendrimer configuration has analytical advantages.

[Postoperative recurrence of subdural empyema]. / Recidiva de empiema subdural postquirúrgico.

We present a case of recurrent subdural post-surgical empyema by Proprionibacterium acnes after a first drained empyema in which no microbiological diagnosis was reached. P. acnes is a gram-positive anaerobic organism which is part of the saprophytic flora of the skin and others parts of the body. However, it can cause infections, as in the central nervous system, especially post-surgical infections in which can be the second more frequent organism after Staphylococcus aureus. P. acnes grows slowly and shows better growth in liquid anaerobic media. It is usually resistant to metronidazol and sensitive to penicillin. In postoperative central nervous system infections we must take into account the possibility of this organism, process the sample properly and keep touch with the Microbiology Department.

Hybrid porous phosphate heterostructures as adsorbents of Hg(II) and Ni(II) from industrial sewage.

Porous phosphate heterostructures (PPH), functionalized with different ratios of aminopropyl and mercaptopropyl groups, labelled as N(x=5,25,50)-PPH and S(x=5,25,50)-PPH, respectively, were tested as adsorbents for Ni(II) and Hg(II) found in industrial sewage from electroplating processes and button battery recycling. X-ray diffraction was used to study the structures. The specific surface area of the pristine material (PPH) was 620 m(2)g(-1), whereas the specific surface areas of the modified mercaptopropyl (S(5)-PPH) and aminopropyl (N(5)-PPH) were 472 and 223 m(2)g(-1), respectively. The adsorption data were fitted to a Langmuir isotherm model. The S(5)-PPH material was saturated by 120 mmol Hg(II) per 100g of material, whereas for Ni(II) adsorption, N(25)-PPH material displayed the highest adsorption with a saturation value of 43.5 mmol per 100g. These results suggest that functionalized PPH materials may be promising toxic metal scavengers and that they may provide an alternative environmental technology.

CdSe quantum dots capped PAMAM dendrimer nanocomposites for sensing nitroaromatic compounds.

The detection of nitroaromatic compounds, best known as raw materials in explosives preparations, is important in many fields including environmental science, public security and forensics. CdSe quantum dots capped with PAMAM-G(4) dendrimer were synthetized in water and used for the detection of trace amounts of three nitroaromatic compounds: 4-methoxy-2-nitrophenol (MNP), 2-amine-5-chloro-1,3-dinitrobenzene (ACNB) and 3-methoxy-4-nitrobenzoic acid (MNB). To increase the apparent water solubility of these compounds α-cyclodextrin (α-CD) was used to promote the formation of inclusion complexes. The studied nitroaromatic compounds (plus α-CD) significantly quenched the fluorescence intensity of the nanocomposite with linear Stern-Volmer plots. The Stern-Volmer constants (standard deviation in parenthesis) were: MNB, K(SV)=65(5)×10(4) M(-1); ACNB, K(SV)=19(2)×10(4) M(-1); and, MNP, K(SV)=33(1)×10(2) M(-1). These constants suggest the formation of a ground state complex between the nitroaromatric compounds and the sensor which confers a relatively high analytical sensitivity. The detection sensibilities are about 0.01 mg L(-1) for MNB and ACNB and about 0.1 mg L(-1) for MNP. No interferences or small interferences are observed for trinitrotoluene [K(SV)=10(2)×10(2)×M(-1)], 2,4-dinitrotoluene [K(SV)=20(3)×10 M(-1)], 2,6-dinitrotoluene [K(SV)=11(4)×10 M(-1)] and nitrobenzene [K(SV)=2(1)×10(3)×M(-1)].

Recidiva de empiema subdural postquirúrgico / Postoperative recurrence of subdural empyema

Se presenta un caso de recidiva de infección postquirúrgica en forma de empiema subdural por Proprionibacterium acnes tras un primer empiemadrenado en el que no se llegó al diagnóstico microbiológico. P acnes es un microorganismo gram positivo, anaerobio, que forma parte de la flora saprófita de la piel y de otras zonas del organismo. Sin embargo puede producir infecciones, entre otras localizaciones, en el sistema nervioso central (SNC), especialmente infecciones postquirúrgicas en las que puede llegar a ser el segundo germen en frecuencia después de Staphylococcusaureus. Es de crecimiento lento y suele crecer mejor en medios anaeróbicos líquidos. Suele ser resistente almetronidazol y sensible a penicilinas. En las infecciones postquirúrgicas del sistema nervioso central hay que tener en cuenta la posibilidad de este microorganismo, procesar las muestras de forma adecuada y mantenernos en contacto con el Servicio de Microbiología (AU)

We present a case of recurrent subdural postsurgical empyema by Proprionibacterium acnes after a first drained empyema in which no microbiological diagnosis was reached. P. acnes is a grampositive anaerobic organism which is part of the saprophytic flora of the skin and others parts of the body. However, it can cause infections, as in the central nervous system, especially postsurgical infections in which can be the second more frequent organism after Staphylococcus aureus. P. acnes grows slowly and shows better growth in liquid anaerobic media. It is usually resistant to metronidazol and sensitive to penicillin. In postoperative central nervous system infections we must take into account the possi- bility of this organism, process the sample properly and keep touch with the Microbiology Department (AU)