Molecular Attachment Research Articles

Mesomorphology of clathrate hydrates from molecular ordering.

Clathrate hydrates are crystals formed by guest molecules that stabilize cages of hydrogen-bonded water molecules. Whereas thermodynamic equilibrium is well described via the van der Waals and Platteeuw approach, the increasing concerns with global warming and energy transition require extending the knowledge to non-equilibrium conditions in multiphase, sheared systems, in a multiscale framework. Potential macro-applications concern the storage of carbon dioxide in the form of clathrates, and the reduction of hydrate inhibition additives currently required in hydrocarbon production. We evidence porous mesomorphologies as key to bridging the molecular scales to macro-applications of low solubility guests. We discuss the coupling of molecular ordering with the mesoscales, including (i) the emergence of porous patterns as a combined factor from the walk over the free energy landscape and 3D competitive nucleation and growth and (ii) the role of molecular attachment rates in crystallization-diffusion models that allow predicting the timescale of pore sealing. This is a perspective study that discusses the use of discrete models (molecular dynamics) to build continuum models (phase field models, crystallization laws, and transport phenomena) to predict multiscale manifestations at a feasible computational cost. Several advances in correlated fields (ice, polymers, alloys, and nanoparticles) are discussed in the scenario of clathrate hydrates, as well as the challenges and necessary developments to push the field forward.

Group contribution method for rapid estimation of crystal growth rates

The morphological evolution of organic crystals during crystallization depends on the face-specific growth rates. Classical growth rate models relate the face-specific growth rates to the crystal lattice, energy of stable facets, growth mechanism, and supersaturation. The complexities of these models have increased over time to account accurately for solution conditions, the structure of growth units, and their attachment rates. Such advanced growth rate models require several layers of computations to obtain attachment energies of facets, nucleation rates, kink density, and attachment rates. Among these, the most intensive and time-consuming computation is for attachment rates, which require molecular dynamic simulations. This substantially increases the overall computation time to predict the absolute growth rate for even one crystallization condition. Since it is nearly impossible to iterate such a growth rate model, optimization schemes cannot be implemented to identify solution conditions that favor specific crystal growth. To reduce the computational time for attachment rate calculations, we implement a group contribution method (GCM) that relates the properties of functional groups in a molecule to their attachment rates to the crystal lattice, thereby rapidly estimating the growth rates of organic crystals. The process of molecular attachment involves partial desolvation of a solvated molecule, referred to as a transition state, followed by total desolvation via spontaneous attachment to a crystal facet. The first step in GCM is to identify the equilibrium states of fully solvated and partially desolvated solute molecules. The degree of supersaturation dictates the extent of this equilibrium and, thereby, the activation barrier for the growth of crystals, according to transition state theory. Identifying this equilibrium phenomenon allows for capturing the functional-group-specific interactions that depend on molecular motion, which could be related to operating conditions such as temperature and pressure. The stochastic optimization technique with Monte-Carlo sampling allows an efficient optimization problem solution to obtain the group interaction parameters. The GCM approach is first validated for the estimation of growth rates of glutamic acid and L-histidine, and then extended to predict growth rates of alanine and glycine rapidly. The optimized parameters and GCM scheme can be used to estimate growth rates in other crystallization systems.

ДИССОЦИАТИВНЫЙ ЗАХВАТ ЭЛЕКТРОНОВ МОЛЕКУЛАМИ ДИГИДРОКУМАРИНА И 5,6-МЕТИЛЕНДИОКСИ-1-ИНДАНОНА

The molecules of dihydrocoumarin and 5,6-methylenedioxy-1-indanone were studied by the negative ion resonant electron capture mass spectrometry for slow (0-15 eV) electrons. Such studies of the structure of vacant molecular orbitals (VMO) and dissociative electron attachment (DEA) for isolated molecules of prospective organic semiconducting materials, which are of great interest in terms of use as elementary components of organic nanoelectronics devices, are the most promising, since a correspondence between the energies of vacant MO isolated molecules and the maxima of the density of states in the conduction band of thin films was revealed earlier. Also, there is an idea developing in modern science, that the results of studies of vacant orbitals of individual molecules in the gas phase, in particular, using the DEA method, are necessary to identify the features of the energy structure of the conduction band of molecular organic condensates, starting from energies below the vacuum level, by the amount of binding energy of molecules in the film. In particular, it was shown that the substances studied in this work cannot be used as monomeric compounds in the design of electrically conductive polymers in the future, since they do not form negative molecular ions in the gas phase at energies close to thermal.

Initial Recognition and Attachment of the Zika Virus to Host Cells: A Molecular Dynamics and Quantum Interaction Approach.

The zika virus (ZIKV), transmitted to humans from the bites of Aedes Aegypti and Aedes Albopictus mosquitoes produces Zika fever and neurodegenerative disorders that despite affecting millions of people, most recently in Africa and the Americas, has been declared a neglected tropical disease by the World Health Organization. In this work, atomistic molecular dynamics simulations followed by rigorous analysis of the intermolecular interactions reveal crucial aspects of the initial virus⋯cell molecular recognition and attachment, events that trigger the infectious cycle. Previous experimental studies have shown that Dermatan Sulfate (DS) and Chondroitin Sulfate A (CSA), two glycosaminoglycans which are actually epimers to each other and that are structural constituents of receptors expressed in cell membranes, are the preferred anchorage sites, with a marked preference for DS. Our calculations rationalize this preference from a molecular perspective as follows: when free of the virus, DS has one sulfate group that does not participate in intramolecular strong hydrogen bonds, thus, it is readily available to interact with the envelope protein of the virus (Zika-E), then, after formation of the complexes, Zika-E⋯DS exhibits ten strong salt brides connecting the two fragments against only six salt bridges and two hydrogen bonds in Zika-E⋯CSA. Our results complement the current view of the interaction between the virus and the receptor glycosoaminoglycans revealing that the negatively charged carboxylate groups in CSA and DS are just as important as the sulfates because of the formation of equally strong salt bridges with the positively charged Arginine and Lysine aminoacids in the envelope protein of the virus.

CRISPR/Cas9-mediated LINC00511 knockout strategies, increased apoptosis of breast cancer cells via suppressing antiapoptotic genes

BackgroundThe growing detection of long noncoding RNAs (lncRNAs) required the application of functional approaches in order to provide absolutely precise, conducive, and reliable processed information along with effective consequences. We utilized genetic knockout (KO) techniques to ablate the Long Intergenic Noncoding RNA 00,511 gene in several humans who suffered from breast cancer cells and at the end we analyzed and examined the results.ResultsThe predictive relevance of LINC00511 expression pattern was measured by using a pooled hazard ratio (HR) with a 95% confidence interval (CI). The link among LINC00511 expression profiles and cancer metastasis was measured by using a pooled odds ratio (OR) with a 95% confidence interval. This meta- analysis was composed of fifteen studies which contained a total of 1040 tumor patients. We used three distinct CRISPR/Cas9-mediated knockdown techniques to prevent the LINC00511 lncRNA from being transcribed. RT-PCR was used to measure lncRNA and RNA expression. We used CCK-8, colony formation tests, and the invasion transwell test to measure cell proliferation and invasion. The stemness was measured by using a sphere-formation test. To validate molecular attachment, luciferase reporter assays were performed. The functional impacts of LINC00511 gene deletion in knockdown breast cancer cell lines were confirmed by using RT-qPCR, MTT, and a colony formation test. This meta-analysis was composed of 15 trials which contained a total of 1040 malignant tumors. Greater LINC00511 expression was ascribed to a lower overall survival (HR = 1.93, 95% CI 1.49–2.49, < P 0.001) and to an increased proportion of lymph node metastasis (OR = 3.07, 95% CI 2.23–4.23, P < 0.001) in the meta‐analysis. It was found that the role of LINC00511 was overexpressed in breast cancer samples, and this overexpression was ascribed to a poor prognosis. The gain and loss-of-function tests demonstrated findings such as LINC00511 increased breast cancer cell proliferation, sphere-forming ability, and tumor growth. Additionally, the transcription factor E2F1 binds to the Nanog gene's promoter site to induce transcription. P57, P21, Prkca, MDM4, Map2k6, and FADD gene expression in the treatment group (LINC00511 deletion) was significantly higher than in the control group (P < 0.01). In addition, knockout cells had lower expression of BCL2 and surviving genes than control cells P < 0.001). In each of the two target alleles, the du-HITI approach introduced a reporter and a transcription termination signal. This strategy's donor vector preparation was significantly easier than "CRISPR HDR," and cell selection was likewise much easier than "CRISPR excision." Furthermore, when this approach was used in the initial transfection attempt, single-cell knockouts for both alleles were generated.ConclusionsThe methods employed and described in this work could be extended to the production of LINC00511 knockout cell lines and, in theory, to the deletion of other lncRNAs to study their function.

Crystal transformation and self-assembly theory of microbially induced calcium carbonate precipitation.

Microbially induced calcium carbonate precipitation (MICP) is ubiquitous in the earth's lithosphere and brings the inspiration of bionic cementation technology. Over recent years, MICP has been proposed as a potential solution to address many environmental and engineering issues. However, the stability of cemented precipitations generated via MICP technology, especially the characteristics and change mechanism of crystal forms, is still unclear, which substantially hindered the understanding of biomineralization and prohibited the application and upscaling of MICP technology. Here, Sporosarcina pasteurii was selected as a model microbe to induce calcium carbonate mineralization in a series of standard nutrient solutions. The authors studied the process of precipitation from amorphous calcium carbonate to calcite crystal form and revealed the assembly behavior and mechanism of precipitations by FTIR, SEM, TEM and EDS. In the two crystal forms of induced calcium carbonate, the relative position and content of C, O, N, P and Ca elements were only slightly different. The molecular attachment and structural match of organic matrix made the crystals form change. Finally, a self-assembly theory was proposed to MICP, and it provided a solid theoretical basis for the technical specification of MICP technology in engineering application. KEY POINTS: • Organic matrix is intensively involved in MICP by forming functional groups. • Molecular attachment and structural match cause calcite crystal evolution. • A self-assembly theory is proposed for MICP.

The Role of Spike Protein Mutations in the Infectious Power of SARS-COV-2 Variants: A Molecular Interaction Perspective.

Specific S477N, N501Y, K417N, K417T, E484K mutations in the receptor binding domain (RBD) of the spike protein in the wild type SARS‐COV‐2 virus have resulted, among others, in the following variants: B.1.160 (20A or EU2, first reported in continental Europe), B1.1.7 (α or 20I501Y.V1, first reported in the United Kingdom), B.1.351 (β or 20H/501Y.V2, first reported in South Africa), B.1.1.28.1 (γ or P.1 or 20J/501Y.V3, first reported in Brazil), and B.1.1.28.2 (ζ, or P.2 or 20B/S484K, also first reported in Brazil). From the analysis of a set of bonding descriptors firmly rooted in the formalism of quantum mechanics, including Natural Bond Orbitals (NBO), Quantum Theory of Atoms In Molecules (QTAIM) and highly correlated energies within the Domain Based Local Pair Natural Orbital Coupled Cluster Method (DLPNO‐CCSD(T)), and from a set of computed electronic spectral patterns with environmental effects, we show that the new variants improve their ability to recognize available sites to either hydrogen bond or to form salt bridges with residues in the ACE2 receptor of the host cells. This results in significantly improved initial virus⋅⋅⋅cell molecular recognition and attachment at the microscopic level, which trigger the infectious cycle.

Biomimetic double network hydrogels: Combining dynamic and static crosslinks to enable biofabrication and control cell‐matrix interactions

AbstractHydrogels are promising candidates for recapitulation of the native extracellular matrix (ECM), yet recreating molecular and spatiotemporal complexity within a single network remains a challenge. Double network (DN) hydrogels are a promising step towards recapitulating the multicomponent ECM and have enhanced mechanical properties. Here, we investigate DNs based on dynamic covalent and covalent bonds to mimic the dynamicity of the ECM and enable biofabrication. We also investigate the spatiotemporal molecular attachment of a bioactive adhesive peptide within the networks. Using oxidized alginate (dynamic network, Schiff base) and polyethylene glycol diacrylate (static network, acrylate polymerization) we find an optimized procedure, where the dynamic network is formed first, followed by the static network. This initial dynamically cross‐linked hydrogel imparts self‐healing, injectability, and 3D printability, while the subsequent DN hydrogel improves the stability of the 3D gels and imparts toughness. Rheology and compression testing show that the toughening is due to the combination of energy dissipation (dynamic network) and elasticity (static network). Furthermore, where we place adhesive sites in the network matters; we find distinct differences when an adhesive peptide, Arg‐Gly‐Asp (RGD), is attached to the different networks. This DN strategy bring us closer to understanding and recreating the complex multicomponent ECM—pushing us past a materials view of cell adhesion—while enabling injectabiltiy and printing of tough hydrogels.

Changes in Interaction Between Accessory Protein 8 and IL-17RA in UK Isolates Caused by Mutations in the SARS-CoV-2 Open Reading Frame 8

SARS-CoV-2 is the infectous agent of Covid-19, one of the most important health problems of the twenty-first century. IL-17RA is an crucial receptor in the generation of the host immune response. ORF8 is the viral accessory protein of SARS-CoV-2 that suppresses the host immune response. Mutations can alter the viral properties and clinical course of SARS-CoV-2. In this study, we investigated the changes that SARS-CoV-2 ORF8 mutations may cause in the interaction of IL-17RA with ORF8. The study was carried out using 825 complete genome sequences from UK isolates. Mutation analyzes were performed using RDP4 and MEGAX. The protein model was created using the Swiss Model. Protein protein interaction was analyzed by Haddock ver 2.4. Analysis of changes in protein stability was performed using SDM2, mCSM stability and DUET tools. The change in ORF8 - IL-17RA binding affinity before and after the mutation was evaluated using mCSM-PPI2. We detected P30S, R52I, Y73C and L118V mutations in SARS-CoV-2 ORF8. Mutations have been shown to reduce protein stability and affinity. After the mutation, the binding dynamics of ORF8 to IL-17RA were changed. Molecular attachment scores were -78.0±3.4 kcal.mol-1 and -76.3±11.9 kcal.mol-1, for wild type and mutant, respectively. After the mutations, the hydrogen bond number and position between ORF8 and IL-17RA changed. While establishing ten hydrogen bonds between the wild type and IL-17RA, four hydrogen bonds were established between the mutant ORF8 and IL-17RA. The decreased affinity between ORF8 and IL-17RA can be seen as a stronger immune response and a milder clinical course. Although our results contain important data for understanding ORF8, which is an important drug target, it needs to be repeated with in-vivo and crystallgraphy studies.

Interfacial detection with nanotube pipette laden graphene quantum dots electrode

Single-cell analysis is an emerging technology that can provide a mechanistic understanding of complex biological systems and cell heterogeneity. Any disruption of its activity can be monitored through interfacial bioelectrochemistry. A new glass nanopipette electrode laden with graphene quantum dots (20–50 nm) has been constructed for in vitro interfacial bioelectrochemical studies. A platinum or copper wire (0.0006″ dia) was placed inside the glass nanopipette with a tip size of 1 mm which was subsequently covered with graphene by dip coating. The glass nanopipette has been characterized by X-ray fluorescence as containing Si (96.82%), K (2.65%), and Fe (0.20%). The suitability of the electrode for studies involving oxidative stress produced by p-aminophenol (PAP) that results in membrane disruption and the frequency of molecular attachment of PAP to graphene has been relevant to the understanding of cell disruption. In this context, the electrochemical oxidation of PAP has been probed in vitro through differential pulse voltammetry (DPV) using the glass nanopipette electrode. The new electrode shows promise for examining electroactive neurotransmitter during its functioning in chronic diseases.

Atomic force microscopy as an imaging tool to study the bio/nonbio complexes.

Atomic force microscopy (AFM) besides X-ray crystallography and electron microscopy is one of the most attractive methods to study bio/nonbio complexes. Information on how biomacromolecules interact with nanomaterials under different environmental conditions has important implications for the practice of nanomedicine and concerning the safety of nanomaterials. These complexes cover a broad range both in terms of stability and composition. AFM offers a wealth of structural and functional data about such assemblies. The variety of samples investigated using AFM in biology includes nanometre-sized proteins, lipids, DNA, amyloid fibrils, as well as larger objects such as cells. Herein we choose to review the significance of AFM to study various biological aspects of selected assemblies. We have focused on the exploitation of AFM operating in the air. The presented AFM research offers a unique and often unexpected insight into the structure and function of the bio/nonbio complexes. LAY DESCRIPTION: Atomic force microscopy (AFM) besides X-ray crystallography and electron microscopy is one of the most attractive methods to study bio/nonbio complexes. Information on how biomacromolecules interact with nanomaterials under different environmental conditions has important implications for the practice of nanomedicine and concerning the safety of nanomaterials. These complexes cover a broad range both in terms of stability and composition. AFM offers a wealth of structural and functional data about such assemblies. The variety of samples investigated using AFM in biology includes nanometre-sized proteins, lipids, DNA, amyloid fibrils, as well as larger objects such as cells. Herein we choose to review the significance of AFM to study various biological aspects of selected assemblies. The presented AFM research offers a unique and often unexpected insight into the structure and function of the bio/nonbio complexes. Nature has set us a perfect example of how to elegantly optimise and fine tune different types of processes. The relatively young field of nanotechnology has studied biological processes and exploited their unique strengths as novel materials. The resulting area of bionanotechnology has adopted interaction schemes presented to us by biology, to provide enhanced selectivity, efficiency or versatility of molecular attachment strategies. Two scenarios of this synergistic scheme are: the conjugation of nanostructures as a tool for research in biological science and the conjugation of biological particles as a tool for nanotechnology. The use of nanotechnologies for medical applications raises high expectations regarding diagnosis, drug delivery, gene therapy, and tissue engineering. There is an increasing number of reports using AFM as a nanodiagnostic tool with patient cells. The use of AFM, in combination with more conventional analytical approaches, could inform decisions related to recommendations for treatments. Applying AFM techniques in nanomedicine is becoming well established. Atomic force microscopy (AFM) is one of the most functional and powerful microscopy technology for studying biological and material samples at the nanoscale. It is advantageous because an atomic force microscope can image three-dimensional topography of very small objects. It also provides various types of surface measurements to the needs of scientists and engineers if combined with other electromagnetic waves. It is powerful because an AFM can generate images at atomic resolution with 10-9 m scale resolution height information, with minimum sample preparation. AFM gives details on how biological molecules, such as nucleic acids, proteins, and amyloid aggregates, interact with nanomaterials under different environmental conditions. Here, we have shown several examples of relevant applications of AFM to study structural, functional and mechanical properties useful for the medicine and concerning the safety of nanomaterials.

Molecular Nanowire Bonding to Epitaxial Single-Layer MoS2 by an On-Surface Ullmann Coupling Reaction.

Lateral heterostructures consisting of 2D transition metal dichalcogenides (TMDCs) directly interfaced with molecular networks or nanowires can be used to construct new hybrid materials with interesting electronic and spintronic properties. However, chemical methods for selective and controllable bond formation between 2D materials and organic molecular networks need to be developed. As a demonstration of a self-assembled organic nanowire-TMDC system, a method to link and interconnect epitaxial single-layer MoS2 flakes with organic molecules is demonstrated. Whereas pristine epitaxial single-layer MoS2 has no affinity for molecular attachment, it is found that single-layer MoS2 will selectively bind the organic molecule 2,8-dibromodibenzothiophene (DBDBT) in a surface-assisted Ullmann coupling reaction when the MoS2 has been activated by pre-exposing it to hydrogen. Atom-resolved scanning tunneling microscopy (STM) imaging is used to analyze the bonding of the nanowires, and thereby it is revealed that selective bonding takes place on a specific S atom at the corner site between the two types of zig-zag edges available in a hexagonal single layer MoS2 sheet. The method reported here successfully combining synthesis of epitaxial TMDCs and Ullmann coupling reactions on surfaces may open up new synthesis routes for 2D organic-TMDC hybrid materials.

Charge Transport in Sequence-Defined Conjugated Oligomers

A major challenge in synthetic polymers lies in understanding how primary monomer sequence affects materials properties. In this work, we show that charge transport in single molecule junctions of conjugated oligomers critically depends on the primary sequence of monomers. A series of sequence-defined oligomers ranging from two to seven units was synthesized by an iterative approach based on the van Leusen reaction, providing conjugated oligomers with backbones consisting of para-linked phenylenes connected to oxazole, imidazole, or nitro-substituted pyrrole. The charge transport properties of these materials were characterized using a scanning tunneling microscope-break junction (STM-BJ) technique, thereby enabling direct measurement of molecular conductance for sequence-defined dimers, trimers, pentamers, and a heptamer. Our results show that oligomers with specific monomer sequences exhibit unexpected and distinct charge transport pathways that enhance molecular conductance more than 10-fold. A systematic analysis using monomer substitution patterns established that sequence-defined pentamers containing imidazole or pyrrole groups in specific locations provide molecular attachment points on the backbone to the gold electrodes, thereby giving rise to multiple conductance pathways. These findings reveal the subtle but important role of molecular structure including steric hindrance and directionality of heterocycles in determining charge transport in these molecular junctions. This work brings new understanding for designing molecular electronic components.

Direct Imaging of Individual Molecular Binding to Clean Nanopore Edges in 2D Monolayer MoS2.

We use annular dark-field scanning transmission electron microscopy (ADF-STEM) to study how solution-deposited molecules bind to the edges and surface regions around nanopores in MoS2 monolayers. Nanopores with clean atomically flat edges and controllable mean diameter were generated by time-dependent large-area electron beam exposure during an in situ heating process, ready for subsequent molecular attachment. An organic molecule was designed to have a dithiolane end group that binds to Mo-terminated sites and a ligand structure that incorporates a single transition metal atom (Pt) marker for ADF-STEM detection. Pt atoms were used to track molecular binding around zigzag edges of MoS2 and to predict the orientations and conformations of molecules upon binding. We found that the molecules preferred to reside on the surface of the MoS2, pointing inward when attaching to the edge, rather than dangling out from the edge into free space, which is attributed to van der Waals interactions between the aromatic core of the molecule and the MoS2 basal planes. These results help us understand the way solution-deposited single molecules attach to free-standing edges of 2D crystals and the influence of van der Waals forces in guiding molecular binding.

(Invited) Atomic Layer Deposition for Stabilizing Surface-Bound Molecules for Photoelectrochemistry and Catalysis

Molecularly sensitized devices that rely on surface bound molecules to impart functionality are keenly susceptible to device degradation via hydrolysis of anchor group chemistries and subsequent molecule detachment. Recent commercialization success in dye-sensitized solar cells is largely possible due to brute-force encapsulation engineering. However, using molecular sensitizers in aqueous environments as water oxidation catalysts or biological sensors poses an even greater challenge. This talk will highlight advances in the use of low temperature atomic layer deposition (ALD) applied after surface functionalization to drastically improve molecular attachment in aqueous environs. We have shown that ultrathin (< 1 nm) ALD coatings of inorganic oxides "surrounding" the molecular sensitizers improve attachment by orders of magnitude. These “coated” molecules still function as light absorbers, electron transfer agents, and catalytic species. The current state-of-the-science will be discussed including what has been learned about the changes in chemical structure upon ALD processing via in-situ FTIR spectroscopy and ex situ sum frequency generation spectroscopy. Finally, we will show the utility of this approach in creating new hybrid catalysts that combine the selectivity of homogeneous molecular catalysts with the recoverability of heterogeneous inorganic catalysts.

Molecular attachment to a microscope tip: inelastic tunneling, Kondo screening, and thermopower.

The vibrational excitation related transport properties of a manganese phthalocyanine molecule suspended between the tip of a scanning tunneling microsope (STM) and a surface are investigated by combining the local manipulation capabilities of the STM with inelastic electron tunneling spectroscopy. By attachment of the molecule to the probe tip, the intrinsic physical properties similar to those exhibited by a free standing molecule become accessible. This technique allows one to study locally the magnetic properties, as well as other elementary excitations and their mutual interaction. In particular a clear correlation is observed between the Kondo resonance and the vibrations with a strong incidence of the Kondo correlation on the thermopower measured across the single-molecule junction.

Photonic crystal nanobeam biosensors based on porous silicon.

Photonic crystal (PhC) nanobeams (NB) patterned on porous silicon (PSi) waveguide substrates are demonstrated for the specific, label-free detection of oligonucleotides. These photonic structures combine the large active sensing area intrinsic to PSi sensors with the high-quality (Q) factor and low-mode volume characteristic of compact resonant silicon-on-insulator (SOI) PhC NB devices. The PSi PhC NB can achieve a Q-factor near 9,000 and has an approximately 40-fold increased active sensing area for molecular attachment, compared to traditional SOI PhC NB sensors. The PSi PhC NB exhibits a resonance shift that is more than one order of magnitude larger than that of a similarly designed SOI PhC NB for the detection of small chemical molecules and 16-base peptide nucleic acids. The design and fabrication of PSi PhC NB sensors are compatible with CMOS processing, sensor arrays, and integration with lab-on-chip systems.

Enhancement of Hydrophobicity of Fish Skin Gelatin via Molecular Modification with Oxidized Linoleic Acid

Fish gelatin possesses hydrophilicity in nature since it contains a few hydrophobic amino acids and a large portion of hydrophilic amino acids. Low hydrophobicity of fish gelatin results in poor water vapor barrier and water resistance of gelatin films. This can limit its usage as packaging material. To overcome this drawback, the molecular attachment of hydrophobic domains can effectively improve the hydrophobicity of fish gelatin. In this study, fish skin gelatin modified with oxidized linoleic acid (OLA) prepared under various conditions using different molar ratios of OLA/free amino group content was characterized. When OLA was prepared at 60 and 80°C for various oxidation times (0–24 h), the peroxide value (PV) increased continuously up to 9 and 12 h when reaction was performed at 80 and 60°C, respectively. Consequently, the PV decreased until the end of the reaction (24 h). Thiobarbituric acid reactive substances (TBARS) of OLA were increased sharply up to 12 h, regardless of reaction temperatures. Thus, primary and secondary lipid oxidation products mainly occurred within the first 12 h. As gelatin was modified with different OLA at various OLA/free amino group molar ratios, the one modified with OLA prepared at 60°C for 24 h at a molar ratio of 10 : 1 had the highest increases in surface hydrophobicity and carbonyl content with the coincidentally lowest free amino group content, compared with control gelatin (without OLA modification). Fourier transforms infrared (FTIR) spectra also reconfirmed the presence of fatty acid covalently attached to resulting gelatin. Therefore, OLA could be used to modify gelatin and increase its hydrophobicity.

Stable Molecular Surface Modification of Nanostructured, Mesoporous Metal Oxide Photoanodes by Silane and Click Chemistry.

Binding functional molecules to nanostructured mesoporous metal oxide surfaces provides a way to derivatize metal oxide semiconductors for applications in dye-sensitized photoelectrosynthesis cells (DSPECs). The commonly used anchoring groups, phosphonates and carboxylates, are unstable as surface links to oxide surfaces at neutral and high pH, leading to rapid desorption of appended molecules. A synthetically versatile molecular attachment strategy based on initial surface modification with a silyl azide followed by click chemistry is described here. It has been used for the stable installation of surface-bound metal complexes. The resulting surfaces are highly stabilized toward complex loss with excellent thermal, photochemical, and electrochemical stabilities. The procedure involves binding 3-azidopropyltrimethoxysilane (APTMS) to nanostructured mesoporous TiO2 or tin-doped indium oxide (ITO) electrodes by silane attachment followed by azide-terminated, Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions with an alkyne-derivatized ruthenium(II) polypyridyl complex. The chromophore-modified electrodes display enhanced photochemical and electrochemical stabilities compared to phosphonate surface binding with extended photoelectrochemical oxidation of hydroquinone for more than ∼6 h with no significant decay.

Lateral Graphene p–n Junctions Realized by Nanoscale Bipolar Doping Using Surface Electric Dipoles and Self‐Organized Molecular Anions

AbstractLateral p–n junctions take the unique advantages of 2D materials, such as graphene, to enable single‐atomic layer microelectronics. A major challenge in fabrication of the lateral p–n junctions is in the control of electronic properties on a 2D atomic sheet with nanometer precision. Herein, a facile approach that employs decoration of molecular anions of bis‐(trifluoromethylsulfonyl)‐imide (TFSI) to generate p‐doping on the otherwise n‐doped graphene by positively polarized surface electric dipoles (pointing toward the surface) formed on the surface oxygen‐deficient layer “intrinsic” to an oxide ferroelectric back gate is reported. The characteristic double conductance minima V Dirac− and V Dirac + illustrated in the obtained lateral graphene p–n junctions can be tuned in the range of −1 to 0 V and 0 to +1 V, respectively, by controlling the TFSI anions and surface dipoles quantitatively. The unique advantage of this approach is in adoption of polarity‐controlled molecular ion attachment on graphene, which could be further developed for various lateral electronics on 2D materials.