Nonlinear Optics to Glucose Sensing: Multifunctional Nitrogen and Boron Doped Carbon Dots with Solid-State Fluorescence in Nanoporous Silica Films

Multifunctional triple color photoluminescent (PL) nitrogen–boron doped carbon quantum dots (CQDs) with high quantum yield (QY) of 58% are fabricated by one step femtosecond pulsed laser irradiation of a single precursor (2-aminopyrimidine-5-boronic acid) in solution. In situ generated non-linear and linear emissions are used to monitor CQDs formation which results in enhanced second harmonic generation, two photon absorption (2PA), and linear fluorescence; implying triple mode emission. These CQDs present blue, green, and possible red color rendering which are mostly independent to the respective excitation wavelengths (λ) with large stokes shift of 100 nm. Solid-state photoluminescence with QY of 46% is achieved by incorporating CQDs into thin transparent nanoporous silica (pSiO₂) films (thickness 50 µm) to form a CQDs-pSiO₂ composite which exhibits reverse saturable absorption at λ = 800 nm with 2PA coefficient and excited state absorption cross-section of 4.94 × 10⁻¹⁰ m W⁻¹ and 6.23 × 10⁻¹⁷ cm², respectively. CQDs-pSiO₂ is also sensitive to glucose concentration down to 1.0 mg dL⁻¹ in a wide linear range up to 100 mg dL⁻¹. This work therefore demonstrates facile, controllable, and up-scalable bottom-up fabrication of CQDs forming multifunctional solid-state CQDs-pSiO₂ with proven application in optical limiting and glucose sensing.     

Predictive Sequential Research Design to Study Complex Social Phenomena

Social phenomena in their simplest form share infinite complexities and relationships, and by interacting with other entities, their levels of complexity become exponentially inexplicable and incomprehensible. Using a single form of study in complex phenomena could be insufficient, and new forms of analysis should be opened that allow for observing the multidimensionality of study problems from integrative perspectives. The emergence of research using mixed methods attempts to reconcile these methodologies through integration, configuring a stage of interconnection between research paradigms that cause cuts and leaks that may or may not be consistent with the study’s object. At the time of integration, vices can be created by specific value and subjectivity judgments, with investigative diffraction being an alternative to extend integration through data fracture and redirecting the object of study. This work proposes a Predictive Sequential Research Design (DISPRE) for complex social phenomena, which uses fuzzy logic as a tool to solve the information biases caused by the investigative diffraction of each methodological approach as a strategy to capture, explain, understand and predict the intrinsic complexity of the social entity under study.     

Coverage-dependent molecular tilt of carbon monoxide chemisorbed on Pt{110}: A combined LEED and DFT structural analysis

The adsorption of carbon monoxide on the Pt{110} surface at coverages of 0.5 ML and 1.0 ML was investigated using quantitative low-energy electron diffraction (LEED IV) and density-functional theory (DFT). At 0.5 ML CO lifts the reconstruction of the clean surface but does not form an ordered overlayer. At the saturation coverage, 1.0 ML, a well-ordered p(2 × 1) superstructure with glide line symmetry is formed. It was confirmed that the CO molecules adsorb on top of the Pt atoms in the top-most substrate layer with the molecular axes tilted by ± 22° with respect to the surface normal in alternating directions away from the close packed rows of Pt atoms. This is accompanied by significant lateral shifts of 0.55 Å away from the atop sites in the same direction as the tilt. The top-most substrate layer relaxes inwards by ? 4% with respect to the bulk-terminated atom positions, while the consecutive layers only show minor relaxations. Despite the lack of long-range order in the 0.5 ML CO layer it was possible to determine key structural parameters by LEED IV using only the intensities of the integer-order spots. At this coverage CO also adsorbs on atop sites with the molecular axis closer to the surface normal (< 10°). The average substrate relaxations in each layer are similar for both coverages and consistent with DFT calculations performed for a variety of ordered structures with coverages of 1.0 ML and 0.5 ML.     

Solubility of Thiophene-, Furan- and Pyrrole-2-Carboxaldehyde Phenylhydrazone Derivatives in 2.82 mol⋅L−1 Aqueous DMSO at 298.15 K, Inhibition of Lymphoproliferation and Tubulin Polymerization: A Study Based on the Scaled Particle Theory

In this work, the solubilities of nine phenylhydrazone derivatives in water and in 2.82 mol?L^?1 aqueous DMSO at 298.15 K, expressed on the molar fraction scale, are reported. The estimated value of the standard Gibbs energy for transferring the solute from water to 2.82 mol?L^?1 DMSO, $\Delta G^{0}_{\mathrm{W}\rightarrow \mathrm{mix}}$ , for each system, indicates that it is a spontaneous process. Some of the phenylhydrazone derivatives inhibited the induction of T lymphocyte proliferation by phytohaemagglutinin (PHA) but only DPCT and NPCF efficiently inhibited Guinea pig brain tubulin polymerization. Scaled Particle Theory (SPT) was used to interpretate solubility and biological activity results. Based on the results we suggested that the difference in the work of cavity creation ΔΔG _c, associated with the transfer of the phenylhydrazone derivatives from water to 2.82 mol?L^?1 aqueous DMSO, is the dominant factor in the magnitude of $\Delta G^{0}_{\mathrm{W}\rightarrow \mathrm{mix}}$ . The later quantity was considered to be an indirect measurement of the hydrophobic character of these derivatives, and it can be used to interpret the biological results.     

Broadband focused waves with compensated spatial dispersion: transverse versus axial balance

We determine the constraints an ABCD optical system must verify to achieve, at the focal region, broadband waves with compensated spatial dispersion either along the optical axis, called on-axis isodiffracting fields, or in the lateral direction, here named in-plane isodiffracting beams. An optical configuration is identified for generating both types of achromatic broadband focused wave fields. An experimental verification is also provided.     

Controllable generation of partially coherent light pulses with direct space-to-time pulse shaper

We demonstrate the possibility of creating user-defined partially coherent light pulses by means of a slight modification of the direct space-to-time pulse shaper. Specifically, we generate a mutual coherence function that corresponds to the independent-elementary-pulse representation model. The theoretical limits in the parameter of global coherence and the efficiency of the system are studied. Our result opens the door to a new way of quantum control in laser-assisted chemical reactions, namely, control by partial coherence.     

Chiral CE separation of dopamine-derived neurotoxins.

An enantiomeric separation of dopamine-derived neurotoxins by capillary electrophoresis has been developed. Tetrahydroisoquinoline (TIQ), dopamine (DA), (R/S)-1-benzyl-TIQ (BTIQ), (R/S)-6,7-dihydroxy-1-methyl-TIQ (salsolinol, Sal), and (R/S)-6,7-dihydroxy-1, 2-dimethyl-TIQ (N-methyl-salsolinol, NMSal) were studied as model compounds. The CE running buffer (50 mM phosphate buffer at pH 3.0) contained 1.5 M urea and 12 mM beta-CD as a chiral selector. During separation, the (R)-enantiomers formed more stable inclusion complexes with beta-CD, and thus had a longer migration time than their optical antipodes. It was noticed that the recovery rates of these TIQ derivatives were very poor (< 15%) during protein precipitation, a procedure widely used for cleaning up biological samples. The recovery was significantly improved by pre-mixing the sample with a surfactant (e.g., sodium hexanesulfonate or Triton X-100) to reduce the co-precipitation. The present method in combination with electrospray ionization tandem mass spectrometry (ESI-MS/MS) was applied to study samples obtained from in vitro incubation of two catecholamines, dopamine and epinine, with aldehydes forming neurotoxins including (S)- and (R)-NMSal enantiomers. The later is known to induce Parkinsonism in rats.     

Thicker is Better? Synthesis and Evaluation of Well‐Defined Polymer Brushes with Controllable Catalytic Loadings

Polymer brushes (PBs) have been used as supports for the immobilization of palladium complexes on silicon surfaces. The polymers were grown by surface‐initiated atom‐transfer radical polymerization (SI‐ATRP) and postdecorated with dipyridylamine (dpa) ligands. The pendant dpa units were in turn complexed with [Pd(OAc)₂] to afford hybrid catalytic surfaces. A series of catalytic samples of various thicknesses (ca. 20–160 nm) and associated palladium loadings (ca. 10–45 nmol cm^?2) were obtained by adjusting the SI‐ATRP reaction time and characterized by ellipsometry, X‐ray reflectivity, X‐ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry (ICP‐MS). ICP‐MS revealed a near‐linear relationship between thickness of the polymer brush and palladium content, which confirmed the robustness of the preparation and postmodification sequence presented herein, rendering possible the creation of functional architectures with predefined catalytic potential. The activities of the catalytic PBs were determined by systematically exploring a full range of substrate‐to‐catalyst ratios in a model palladium(0)‐catalyzed reaction. Quantitative transformations were observed for loadings down to 0.03 mol % and a maximum turnover number (TON) of around 3500 was established for the system. Comparison of the catalytic performances evidenced a singular influence of the thickness on conversions and TONs. The limited recyclability of the hairy catalysts has been attributed to palladium leaching.     

The synthesis of indazoles via 2,3-dihydroindazoles

The preparation and oxidation of 2,3-dihydroindazoles to 1H, 2H or 3H-indazoles is described. A method for the synthesis of indazole 2-oxides has been found. Oxidation of 2-acetyl-2,3-dihydro-3,3-disubstituted indazoles 5a and 5c gave quinoid compounds 20a, 20b, 24a and 24b , which could be isomerized to 3H-indazoles upon removal of the acetyl group. A quinoid compound 21 was also obtained on treatment of 5a with tetracyanoethylene.