“Two‐Step” Raman Imaging Technique To Guide Chemo‐Photothermal Cancer Therapy

Graphene oxide‐wrapped gold nanorods (GO@AuNRs) offer efficient drug delivery as well as NIR laser photothermal therapy (PTT) in vitro and in vivo. However, no real‐time observation of drug release has been reported to better understand the synergy of chemotherapy and PTT. Herein, surface‐enhance Raman spectroscopy (SERS) is employed to guide chemo‐photothermal cancer therapy by a two‐step mechanism. In the presence of GO as an internal standard, SERS signals of DOX (doxorubicin) loaded onto GO@AuNRs are found to be pH‐responsive. Both DOX and GO show strong SERS signals before the DOX@GO@AuNRs are endocytic. However, when the DOX@GO@AuNRs enter acidic microenvironments such as endosomes and/or lysosomes, the DOX signals start decreasing while the GO signals remain the same. This plasmonic antenna could be used to identify the appropriate time to apply the PTT laser during chemo‐photothermal therapy.     

Probing Interfacial Electronic and Catalytic Properties on Well‐Defined Surfaces by Using In Situ Raman Spectroscopy

Heterogeneous metal interfaces play a key role in determining the mechanism and performance of catalysts. However, in situ characterization of such interfaces at the molecular level is challenging. Herein, two model interfaces, Pd and Pt overlayers on Au single crystals, were constructed. The electronic structures of these interfaces as well as effects of crystallographic orientation on them were analyzed by shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) using phenyl isocyanide (PIC) as a probe molecule. A clear red shift in the frequency of the C≡N stretch (ν_NC) was observed, which is consistent with X‐ray photoelectron spectroscopy (XPS) data and indicates that the ultrathin Pt and Pd layers donate their free electrons to the Au substrates. Furthermore, in situ electrochemical SHINERS studies showed that the electronic effects weaken Pt?C/Pd?C bonds, leading to improved surface activity towards CO electrooxidation.     

Thorough tuning of the aspect ratio of gold nanorods using response surface methodology

In the present work a central composite design based on response surface methodology (RSM) is employed for fine tuning of the aspect ratios of seed-mediated synthesized gold nanorods (GNRs). The relations between the affecting parameters, including ratio of l-ascorbic acid to Au³⁺ ions, concentrations of silver nitrate, CTAB, and CTAB-capped gold seeds, were explored using a RSM model. It is observed that the effect of each parameter on the aspect ratio of developing nanorods highly depends on the value of the other parameters. The concentrations of silver ions, ascorbic acid and seeds are found to have a high contribution in controlling the aspect ratios of NRs. The optimized parameters led to a high yield synthesis of gold nanorods with an ideal aspect ratio ranging from 1 (spherical particle) to 4.9. In addition, corresponding tunable surface Plasmon absorption band has been extended to 880 nm. The resulted nanorods were characterized by UV–visible spectrometry and transmission electron microscopy.     

In Situ Synthesis and Characterization of Poly(aryleneethynylene)‐Grafted Reduced Graphene Oxide

Using highly soluble bromo‐functionalized reduced graphene oxide (RGBr) as a key graphene template for surface‐directing Sonogashira–Hagihara polymerization, a novel soluble poly(arylene‐ethynylene)‐grafted reduced graphene oxide, hereafter abbreviated as PAE‐g‐RGO, was prepared in situ. The entirely different electron distribution of LUMO and HOMO of PAE‐g‐RGO suggested the existence of a charge‐transfer (CT) state (PAE^.?–RGO^.+). The negative ΔG_CS value (?2.57 eV) indicates that the occurrence of the charge separation via ¹RGO* in o‐DCB is exothermic and favorable. Upon irradiation with 365 nm light, the light‐induced electron paramagnetic resonance (LEPR) spectrum of PAE‐g‐RGO showed a decrease in the spin‐state density owing to photoinduced intramolecular electron transfer events in this system. A sandwich‐type Al/PAE‐g‐RGO/ITO device showed representative bistable electrical switching behavior. The nonvolatile memory performance was attributed to the CT‐induced conductance changes, which was supported by molecular computation results and conductive atomic force microscopy (C‐AFM) images.     

Crystalline Covalent Triazine Frameworks by In Situ Oxidation of Alcohols to Aldehyde Monomers

Covalent triazine frameworks (CTFs) with aromatic triazine linkages have recently received increasing interest for various applications because of their rich nitrogen content and high chemical stability. Owing to the strong aromatic C=N bond and high chemical stability, only a few CTFs are crystalline, and most CTFs are amorphous. Herein we report a new general strategy to give highly crystalline CTFs by in situ formation of aldehyde monomers through the controlled oxidation of alcohols. This general strategy allows a series of crystalline CTFs with different monomers to be prepared, which are shown to have higher thermal stability and enhanced performance in photocatalysis as compared with the less crystalline or amorphous CTFs. This open‐system approach is very simple and convenient, which presents a potential pathway to large‐scale industrial production of crystalline CTFs.     

Silver Nanostructures on Graphene Oxide as the Substrate for Surface-Enhanced Raman Scattering (SERS)

Nanosized surface-enhanced Raman scattering (SERS) substrates fabricated by the controlled growth of metal nanostructures on water-dispersed two-dimensional nanomaterials can open a new avenue for SERS analysis of liquid samples in biological fields. In this work, regular and uniform Ag nanostructures were grown on the surface of graphene oxide (GO) through a microwave-assisted hydrothermal method. Polyamidoamine (PAMAM) dendrimers were assembled on the surface of GO to form GO/PAMAM templates for growing Ag nanostructures, which are primarily comprised of Ag dimers and trimers. The prepared Ag/GO nanocomposites are highly dispersed and stable in aqueous solution and may be used as substrates for enhanced Raman detection of rhodamine 6?G (R6G) in aqueous solution. This special substrate provides high-performance SERS and suppresses R6G fluorescence in aqueous solution and is promising as a nanosized material for the enhanced Raman detection of liquid samples in biological diagnostics.     

In Situ Raman Monitoring of Silver(I)‐Aided Laser‐Driven Cleavage Reaction of Cyclobutane

The cyclobutane cleavage reaction is an important process and has received continuous interest. Herein, we demonstrate the visible laser‐driven cleavage reaction of cyclobutane in crystal form by using in situ Raman spectroscopy. Silver(I) coordination‐induced strain and thermal effects from the laser irradiation are the two main driving forces for the cleavage of cyclobutane crystals. This work may open up a new avenue for studying cyclobutane cleavage reactions, as compared to the conventional routes using ex situ techniques.     

One‐step in situ growth of magnesium ferrite nanorods on graphene and their microwave‐absorbing properties

The magnesium ferrite nanorods/graphene (MgFe₂O₄ NR/G) composites were prepared by a facile one‐step surfactant‐assisted solvothermal method. The structure and morphology of as‐prepared composite materials were characterized by electron microscopy, energy dispersive spectrometry, Raman spectrometry, X‐ray diffraction, FT‐IR and X‐ray photoelectron spectroscopy. The homogeneous MgFe₂O₄ nanorods with a typical diameter of about 100 nm were well distributed on graphene. The electromagnetic parameters were measured using a vector network analyzer. A minimum reflection loss (RL) of ?40.3 dB was observed at 14.9 GHz with a thickness of 3 mm, and the effective absorption frequency (RL  <   ? 10 dB) ranged from 12.0 to 18.0 GHz, indicating the remarkable microwave absorption performance of the MgFe₂O₄ NR/G composites. The absorbing property of as‐obtained composites was better than that of the pure MgFe₂O₄ nanorods. The synergistic effect of MgFe₂O₄ and graphene was responsible for the enhanced absorbing performance.     

Direct In Situ Investigation of Milling Reactions Using Combined X‐ray Diffraction and Raman Spectroscopy

The combination of two analytical methods including time‐resolved in situ X‐ray diffraction (XRD) and Raman spectroscopy provides a new opportunity for a detailed analysis of the key mechanisms of milling reactions. To prove the general applicability of our setup, we investigated the mechanochemical synthesis of four archetypical model compounds, ranging from 3D frameworks through layered structures to organic molecular compounds. The reaction mechanism for each model compound could be elucidated. The results clearly show the unique advantage of the combination of XRD and Raman spectroscopy because of the different information content and dynamic range of both individual methods. The specific combination allows to study milling processes comprehensively on the level of the molecular and crystalline structures and thus obtaining reliable data for mechanistic studies.     

Assembly of layer-by-layer films of superoxide dismutase and gold nanorods:A third generation biosensor for superoxide anion

Based on the layer-by-layer self-assembly of positively charged cetyltrimethylammonium bromide (CTAB) wrapped gold na- norods (AuNRs) and negatively charged superoxide dismutase (SOD) from their aqueous solutions on cysteine modified gold electrode (Cys/Au), a third generation electrochemical biosensor ((SOD/AuNRs)2/Cys/Au) for superoxide anion (O2·-) was developed. The two layers assembly of SOD/AuNRs can significantly enhance the direct electron transfer between SOD and the electrode. The functional enzym...     

Electrochemiluminescence Based Enzymatic Urea Sensor Using Nanohybrid of Isoluminol‐gold Nanoparticle‐graphene Oxide Nanoribbons

This study evaluates on the possibility of using gold nanoparticles functionalized with the luminol derivative N‐(aminobutyl)‐N‐(ethylisoluminol) (ABEI) and hybridized with graphene oxide nanoribbons on a carbon based screen‐printed electrode (ABEI‐AuNP‐GONR/SPE) as an enzymatic electrochemiluminescence (ECL) urea sensor. The electrocatalytic activity and ECL intensity of ABEI‐AuNP‐GONR/SPE were found to increase proportionally with the concentration of urea in the analyte sample, owing to the rise in pH value. These phenomena are attributed to increased formation of luminol monoanion precursors for further electrochemical oxidation, which in turn produce either luminol radicals or excited 3‐amino‐phthalate molecules. The luminescence is most likely caused by the interaction of luminol radicals with superoxide radicals formed from dissolved oxygen. The sensitivity of our sensor was determined to be 170.58 mM⁻¹ and 16.23 mM⁻¹ for urea concentrations from 2 to 5.82 mM and from 5.82 to 30 mM, respectively, covering the normal urea level in human blood.     

Molecularly Imprinted Electrochemical Sensor Based on Modified Reduced Graphene Oxide‐gold Nanoparticles‐polyaniline Nanocomposites Matrix for Dapsone Determination

This work was designed to develop an electrochemical sensor based on molecular imprinted polyaniline membranes onto reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) modified glassy carbon (GC) electrode for dapsone (DDS) determination. The prepared RGO/AuNPs/PANI‐MIPs nanocomposite was characterized by Ultra‐Violet‐Visible (UV‐Vis), Fourier transform infrared spectroscopy (FT‐IR) and scanning electronic microscopy (SEM) images. The feature of the imprinted electrode was evaluated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and impedance spectroscopy (IS). Throughout this study several analytical parameters, such as incubation time, pH value, concentration of monomer/template molecules and electro‐polymerization cycles were investigated. Under the optimized conditions, the experimental results showed best analytical performances for DDS detection with a sensitivity of 0.188 Ω/mol L^?1, a linear range from 1.0×10^?7 M to 1.0×10^?3 M and a detection limit of 6.8×10^?7 M. The bioanalytical sensor was applied to the determination of dapsone in real samples with high selectivity and recovery.     

Gold nanoparticles supported on thiol‐functionalized reduced graphene oxide as effective recyclable catalyst for synthesis of tetrahydro‐4H‐chromenes in aqueous media

Gold nanoparticles supported on thiol‐functionalized reduced graphene oxide (AuNPs@RGO‐SH) were found to be a biocompatible, stable, recyclable heterogeneous catalyst. The catalysts were characterized by field emission scanning electron microscopy (FE‐SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT‐IR), thermal gravimetric analysis (TGA), and X‐ray diffraction spectroscopy (XRD). The obtained catalyst was used in synthesis of tetrahydro‐4H‐chromenes in aqueous media with excellent yields. The catalysts could be easily separated from the reaction mixture and recovered several times without a significant loss of activity.     

Poly(N‐vinylcarbazole) chemically modified graphene oxide

A new soluble donor‐acceptor type poly(N‐vinylcarbazole)‐covalently functionalized graphene oxide (GO‐PVK) has been synthesized by reaction of DDAT (S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐aceticacid)trithiocarbonate)‐PVK with GO‐toluene‐2,4‐diisocynate. The incorporation of sufficient amount of PVK chains makes the modified GO nanosheets readily dispersible in organic solvents. The resulting material exhibits an enhanced solubility of 10 mg/mL in organic solvents. Covalent grafting of PVK onto the edge and surface of GO nanosheets did not change the carbazole absorption in the ultraviolet region, but substantially reduced the absorption intensity of GO in the visible region. The intensity of the emission band of GO‐PVK at 437 nm was a little bit quenched when compared with that of DDAT‐PVK, suggesting intramolecular quenching from PVK to GO. Such intramolecular quenching process may involve energy or electron transfer between the excited singlet states of the PVK moiety and the GO moiety. The HOMO/LUMO values and the energy bandgap of GO‐PVK experimentally estimated by the onset of the redox potentials are ?5.60, ?3.58, and 2.02 eV, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2642–2649, 2010     

Multilayered construction of glucose oxidase on gold electrodes based on layer-by-layer covalent attachment

A feasible approach to construct multilayered enzyme film on the gold electrode surface for use as biosensing interface is described. The film was fabricated by alternate layer-by-layer deposition of periodate-oxidized glucose oxidase (GOx) and poly(allylamine) (PAA). The covalent attachment process was followed and confirmed by electrochemical impedance spectroscopy (EIS). X-ray diffraction (XRD) experiments revealed that the film was homogeneous and formed in an ordered manner with a thickness of 2.6 ± 0.1 nm per bilayer. The gold electrodes modified with the GOx/PAA multilayers showed excellent electrocatalytical response to the oxidation of glucose when ferrocenemethanol was used as an artificial redox mediator, which was studied by cyclic voltammetry (CV). From the analysis of voltammetric signals, the coverage of active enzyme on the electrode surface was estimated, which had a linear relationship with the number of GOx/PAA bilayers. This suggests that the analytical performance such as sensitivity, detection limit, and so on, is tunable by controlling the number of attached bilayers. The six GOx/PAA bilayer electrode exhibited a sensitivity of 15.1 μA mM⁻¹ cm⁻² with a detection limit of 3.8 × 10⁻⁶ M. In addition, the sensor exhibited good reproducibility and stability.