Covalent Functionalization Research Articles

Effect of nanodiamond particles on the structure, mechanical, and thermal properties of polymer embedded ND/PMMA composites

Abstract Nanodiamonds (NDs), the allotropic carbon nanomaterials with nanosize, durable inert core, adjustable surface morphology, high thermal constancy, and super mechanical performances, possess the characteristics of promising reinforcement materials for various technological applications. However, ND particles hold a vigorous propensity to aggregate in liquid media, obstructing their implementation in mechanical and thermal sciences. This aggregation is caused by high surface to volume ratio. By reducing the surface energy and lowering cluster formation, the mechanical and thermal properties of NDs can be polished. Herein, we report on the covalent functionalization of NDs with amine moiety through ball milling method. Their dispersion was checked in ethanol and polymethyl methacrylate (PMMA polymer) against nonfunctionalized NDs. The dispersive behavior showed that ball mill functionalized NDs produced preferably stable aqueous dispersions in ethanol media. Furthermore, 0.1, 0.2, and 0.4 wt% ND/PMMA composites were synthesized, and their mechanical and thermal behaviors were studied in terms of hardness, compression, Young`s modulus, flexural strength, tensile strength, and thermogravimetric analysis (TGA). Results revealed that the composites containing 0.2 wt% functionalized ND loaded with PMMA matrix showed outstanding mechanical and thermal performances indicating that 0.2 wt% is the optimum amount for achieving excellent outcomes.

Open‐Bandgap Graphene‐Based Field‐Effect Transistor Using Oligo(phenylene‐ethynylene) Interfacial Chemistry

AbstractOrganic interfacial compounds (OICs) are required as linkers for the highly stable and efficient immobilization of bioprobes in nanobiosensors using 2D nanomaterials such as graphene. Herein, we first demonstrated the fabrication of a field‐effect transistor (FET) via a microelectromechanical system process after covalent functionalization on large‐scale graphene by introducing oligo(phenylene‐ethynylene)amine (OPE). OPE was compared to various OICs by density functional theory simulations and was confirmed to have a higher binding energy with graphene and a lower band gap than other OICs. OPE can improve the immobilization efficiency of a bioprobe by forming a self‐assembly monolayer via anion‐based reaction. Using this technology, Magainin I‐conjugated OGMFET (MOGMFET) showed a high sensitivity, high selectivity, with a limit of detection of 100 cfu mL−1. These results indicate that the OPE OIC can be applied for stable and comfortable interfacing technology for biosensor fabrication.

Open-Bandgap Graphene-Based Field-Effect Transistor Using Oligo(phenylene-ethynylene) Interfacial Chemistry.

Organic interfacial compounds (OICs) are required as linkers for the highly stable and efficient immobilization of bioprobes in nanobiosensors using 2D nanomaterials such as graphene. Herein, we first demonstrated the fabrication of a field-effect transistor (FET) via a microelectromechanical system process after covalent functionalization on large-scale graphene by introducing oligo(phenylene-ethynylene)amine (OPE). OPE was compared to various OICs by density functional theory simulations and was confirmed to have a higher binding energy with graphene and a lower band gap than other OICs. OPE can improve the immobilization efficiency of a bioprobe by forming a self-assembly monolayer via anion-based reaction. Using this technology, Magainin I-conjugated OGMFET (MOGMFET) showed a high sensitivity, high selectivity, with a limit of detection of 100 cfu mL-1 . These results indicate that the OPE OIC can be applied for stable and comfortable interfacing technology for biosensor fabrication.

Controlled ultrasonication for covalent functionalization of boron nitride nanotubes

Controlled ultrasonication for covalent functionalization of boron nitride nanotubes

Covalent functionalization of black phosphorus nanosheets via insensitive glycidyl azide polymer with durable stability

Covalent functionalization of black phosphorus nanosheets via insensitive glycidyl azide polymer with durable stability

A novel Fe3O4@TCH@Ni(II) nanoparticle: An efficient magnetically retrievable nanocatalyst for C–C and C–heteroatom bond formation reaction

Layered Ni(II) complex on magnetic nanoparticle as heterogeneous, efficient, novel, green, and reusable catalyst was used to cross‐coupling reaction, including carbon–carbon, carbon–nitrogen, and carbon–oxygen formations. The covalent functionalization of organic ligand, thiocarbohydrazide (TCH), on the surface of magnetic nanoparticle (Fe3O4) was determined that leading to an exceptional adsorptive ability for supporting Ni(II). The magnetic nano‐composite was characterized and investigated by using Fourier‐transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), energy dispersive X‐ray (EDX), X‐ray diffraction (XRD), scanning electron microscope (SEM), inductively coupled plasma–optical emission spectrometry (ICP‐OES), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET). Also, three cross‐coupling reactions in the presence of Fe3O4@TCH@Ni(II) were optimized in terms of temperature, amount of catalyst, solvent, and time.

Covalent Functionalization of Antimonene and Bismuthene Nanosheets.

Antimonene and bismuthene are promising members of the 2D pnictogen family with their tunable band gaps, high electronic conductivity, and ambient stability, making them suitable for electronic and optoelectronic applications. However, semi-metal to semiconductor transition occurs only in the mono/bilayer regime, limiting their applications. Covalent functionalization is a versatile method for tuning materials' chemical, electronic, and optical properties and can be explored for tuning the properties of pnictogens. In this work, emissions in liquid exfoliated antimonene and bismuthene are observed at ≈2.23 and ≈2.33eV, respectively. Covalent functionalization of antimonene and bismuthene with p-nitrobenzene diazonium salt proceeds with the transfer of lone pairs from Sb/Bi to the diazonium salt, introducing organic moieties on the surface attached predominantly via Sb/BiC bonds. Consequently, Sb/Bi signatures in Raman and X-ray photoelectron spectra are blue-shifted, implying lattice distortion and charge transfer. Interestingly, emission can be tailored upon functionalization to 2.18 and 2.27eV for antimonene and bismuthene respectively, and this opens the possibility of tuning the properties of pnictogens and related materials. This is the first report on covalent functionalization of antimonene and bismuthene. It sheds light on the reaction mechanism on pnictogen surfaces and demonstrates tunability of optical property and surface passivation.

Antibacterial Activity and Kinetic Release of Laureliopsis philippiana (Looser) Essential Oil from Nanostructured Porous Silicon with Surface-Functionalization Alternatives

In this work, the antibacterial activity of Laureliopsis philippiana (Looser) essential oil was studied, and its kinetic release performance using different surface-functionalized nanostructured porous silicon (nPSi) was analyzed. Experimental results showed the high inhibitory effect of Laureliopsis philippiana essential oil against Staphylococcus aureus and Klebsiella pneumoniae. In addition, the essential oil was successfully loaded into different kinds of functionalized nPSi. FTIR measurements indicated the formation of stable complexes in the nPSi functionalization process. Specifically, chemical oxidized nPSi (nPSi-Ox), 3-aminopropyltriethoxysilane functionalized nPSi (nPSi-APTS), undecylenic acid-functionalized nPSi (nPSi-UAc), chitosan (nPSi-Chi) and β-cyclodextrin (nPSi-βCD) polymer functionalization on nPSi were studied. nPSi-Ox, nPSi-APTS, and nPSi-UAc were covalent functionalization, and nPSi-Chi and nPSi-βCD were obtained by electrostatic attachment. The kinetic study demonstrated a controlled release of up to 4 h for all the samples following a quasi-Fickian diffusion mechanism. Moreover, the use of functionalized nPSi-APTS and nPSi-UAc structures allows a more controlled kinetic release of Laureliopsis philippiana essential oil in comparison to the rest of the functionalization, increasing its availability and exposure to the environment.

Pt/Ag‐PEG‐Ce6 Nanosystem with Enhanced Near‐Infrared Absorption and Peroxidase‐Like Activity for Synergistic Photodynamic/Photothermal Therapy

AbstractNoble metals and their alloy‐based nanomaterials are widely used in biomedicine, especially in the fields of photodynamic therapy (PDT) and photothermal therapy (PTT) on tumors, due to their remarkable physicochemical properties. Nonetheless, novel doping strategies with unexpected efficacies are still challenging and formidable. Herein, a photosensitizer‐alloy nanosystem is designed for highly efficient PDT and PTT. Specifically, the optimized Pt/Ag alloy nanoparticles are facilely synthesized in one step at room temperature and are simultaneously endowed with enhanced peroxidase‐like activity and photothermal conversion, and further activated cytotoxic singlet oxygen (1O2) productivity after covalent functionalization of chlorin e6 (Ce6). A small amount of Ag doping can kill two birds with one stone by simultaneously enhancing the synergistic PDT and PTT potential of Pt/Ag‐PEG‐Ce6 nanoparticles. Both in vitro and in vivo experimental results indicate that the significant temperature increase triggered by 808 nm laser and a large amount of toxic 1O2 excited by 671 nm laser synergistically and strongly kill tumor cells. Therefore, through proper doping and improved physicochemical properties, this nanosystem achieves effective PDT and PTT of tumors and also inspires the advanced design of noble metal‐based nanomedicine.

A sustainable gel-state ionic liquid-based dye-sensitized solar cell with a novel synthesized lansoprazole functionalized graphene oxide

Using environmental-friendly ionic liquid-based (IL) composite electrolytes to assemble gel-DSSC can restrict volatile organic solvent electrolyte leakage and improve device flexibility and sustainability. Through a covalent functionalization technique, a new class of 2- {(3-methyl-4-(2, 2, 2-trifluoroethoxy) pyridin-2-yl) methylsulfinyl}-1H-benzo(d)imidazole (lansoprazole, LNS) was covalently grafted onto graphene oxide sheets (GO). The incorporation of GO-LNS nanofillers could enhance the redox couple diffusion and conductivity of IL-based electrolytes due to the increased number of electronic and spatial active sites of mobile defects of GO by electron-rich nitrogen, oxygen, and sulphur heteroatoms. A gel-DSSC device fabricated with optimized GO-LNS/IL showed nearly 93% higher ionic conductivity and almost less than twice charge transfer resistance compared to the device made with standard IL-based electrolyte. The excellent electronic properties of GO-LNS containing electrolytes developed the photoelectrochemical characterization considerably. Thus, the overall performance of the gel-DSSC devices showed the maximum power conversion efficiency of 7.158% instead of 3.127% for the bare IL-based electrolyte. Such excellent efficiency correlating with the induced N, S, O, and F atoms localized at the LNS functional group can change the electronic states of graphitic carbon, which results in active sites for catalyzing I3− to I− decrease. On the other hand, fluorine atoms in the trifluoroethoxy group can provide binding sites for I2 molecules. This covalent modification of GO with lansoprazole assembly may develop effective strategies for practical application through an advanced class of environmentally friendly and sustainably produced IL-based nanocomposites.

New insights into the covalent functionalization of black and blue phosphorene

Herein, we studied the reactivity of black and blue phosphorene. They presented similar reaction energies, except for sulfur, benzynes, and nitrenes, which were more strongly bound to blue-phosphorene. Phosphorene is significantly more reactive than graphene and hexagonal-BN. The reaction energies did not reveal a significant variation for coverages around 6–1.5 %, for black-phosphorene. However, if the functional groups are agglomerated, reaction energies were improved by 16–17 kcal/mol. For blue-phosphorene, carbenes or nitrenes can promote significant structural changes at lower coverages, which are manifested by the appearance of three and five-membered rings. We provide evidence that the reported covalent functionalization of phosphorene with azodiisobutyronitrile radicals does not occur as physisorption is preferred. Nitrenes and carbenes do not undergo a [2 + 1] cycloaddition, favoring the formation of open structures. Organic reagents and sulfur are the functional groups that can pave the way toward synthesizing phosphorene monolayers with superior stability.

Probing the Photophysics of Covalently and Non‐covalently Bonded Graphene Quantum Dots‐Tetraaminophenylporphyrin Nanohybrids

AbstractHerein, we scrutinize the photophysical and electronic changes on graphene quantum dots (GQDs) which occurs as a consequence of both type of covalent and non‐covalent functionalization using Tetraaminophenylporphyrin (TAPP). Covalent functionalization resulted in amide bond between GQD and TAPP (GQD‐CONH‐TAPP), while electrostatic interactions, hydrogen bonding and π‐π interactions together contribute to the binding in non‐covalent functionalization. Outstanding difference between both of the functionalized GQDs were observed in their UV‐Visible absorption spectra, photoluminescence (PL) spectra and time‐correlated single photon counting (TCSPC) measurements. GQD‐CONH‐TAPP acts as a charge separated system having C1 point group. In case of GQD‐TAPP, the non‐covalent nanohybrid system, photoinduced electron transfer from TAPP to GQD occurs with a dynamic quenching constant of 21.89×103 M−1 and bimolecular rate constant of 2.77×1014 M−1s−1. Feasibility of this electron transfer is reinforced by the negative ΔGPET value and the theoretical studies.

Demonstration of a Sensitive and Stable Chemical Gas Sensor Based on Covalently Functionalized MoS2

Demonstration of a Sensitive and Stable Chemical Gas Sensor Based on Covalently Functionalized MoS₂

(Bio)Sensing Strategies Based on Ionic Liquid-Functionalized Carbon Nanocomposites for Pharmaceuticals: Towards Greener Electrochemical Tools.

The interaction of carbon-based nanomaterials and ionic liquids (ILs) has been thoroughly exploited for diverse electroanalytical solutions since the first report in 2003. This combination, either through covalent or non-covalent functionalization, takes advantage of the unique characteristics inherent to each material, resulting in synergistic effects that are conferred to the electrochemical (bio)sensing system. From one side, carbon nanomaterials offer miniaturization capacity with enhanced electron transfer rates at a reduced cost, whereas from the other side, ILs contribute as ecological dispersing media for the nanostructures, improving conductivity and biocompatibility. The present review focuses on the use of this interesting type of nanocomposites for the development of (bio)sensors specifically for pharmaceutical detection, with emphasis on the analytical (bio)sensing features. The literature search displayed the conjugation of more than 20 different ILs and several carbon nanomaterials (MWCNT, SWCNT, graphene, carbon nanofibers, fullerene, and carbon quantum dots, among others) that were applied for a large set (about 60) of pharmaceutical compounds. This great variability causes a straightforward comparison between sensors to be a challenging task. Undoubtedly, electrochemical sensors based on the conjugation of carbon nanomaterials with ILs can potentially be established as sustainable analytical tools and viable alternatives to more traditional methods, especially concerning in situ environmental analysis.

Fundamental Charge Transfer Dynamics in 2D TMDCs for Use in Novel Heterostructures

Efficient transfer of charge carriers and/or excitons between small organic molecules and two-dimensional (2D) semiconductor interfaces is being explored for applications in photovoltaics and quantum information processing.Interfaces of small molecules and 2D semiconductors such as graphene, nanocrystals, quantum dots and transition metal dichalcogenides (TMDCs) are capable of charge, energy, and spin singlet transfer. The long excited state lifetimes of spin triplet excitons makes triplet exciton transfer across such interfaces advantageous for exciton harvesting and photon upconversion. However, to date, triplet energy transfer between physisorbed small molecules and monolayer TMDCs has only been reported in a single study. To our knowledge, the process where photoexcitation of a TMDC/organic interface yields triplet excitons in the TMDC layer has not been reported. In quantum dot (QD) systems, direct covalent attachment of organic molecules to QD surfaces has shown to facilitate triplet energy transfer across the QD/molecule interface, but this covalent approach has not been widely applied to TMDC/molecule interfaces.Here we present a systematic study of covalently functionalized TMDC/molecule interfaces employing synthetically tailored thiolated acenes. We create tunable amounts of sulfur vacancies, which allows for subsequent covalent acene functionalization. We study the impact of covalent bonding on the charge transfer (CT) dynamics of TMDC/organic interfaces with energy level offsets suitable for charge and energy transfer (ET) as well as triplet acceptance and sensitization. We characterize the interfaces with a variety of steady-state and time-resolved spectroscopic techniques and initial results show success in selective isolation of CT vs ET pathways. Figure 1

(Invited) Cavity Coupled Multi-Emitters in Carbon Nanotubes

The development of covalent diazonium functionalization of carbon nanotubes brings unique oportunities in terms of original quantum sources of light. In particular, it should be possible to create a linear ensemble of closely packed single-photon sources along the carbon nanotube backbone. The physical proximity of several dopants would make it possible to couple them simultaneous to a resonant cavity mode and to induce original dynamics and light emission properties. Here, we investigate experimentally the case of a series of four quantum emitters attached to the same carbon nanotube coupled to a high finesse fiber cavity. We explore their properties through PLE, polarization and superlocalization measurements and their light emission properties using time-correlation techniques, photo-luminescence decay measurements.

Exploring the Role of Photosensitizer in Guanine Functionalization of Single-Wall Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs) have attracted a great deal of attention during the past two decades because of their unique optoelectronic properties and their potential applications in biomedical theranostics as well as nanoelectronics. It was recently discovered that it is possible to spatially modulate the exciton band gap of carbon nanotubes through a process known as guanine functionalization. In this reaction, the guanine nucleotides of an ssDNA strand wrapping a nanotube become covalently bonded to sidewall carbon atoms upon exposure to singlet oxygen.1 In the original work, the authors used xanthene derivatives such as rose bengal and erythrosine B as photosensitizers in order to generate singlet oxygen. It was assumed that this process was an independent step that did not involve the nanotube. However, we have found that rose bengal has a strong tendency to form a charge transfer complex with SWCNTs, and these complexes appear to be essential in the functionalization reaction.We have studied the complexation through a spectroscopic study of SWCNT fluorescence quenching and the appearance of a charge transfer absorption feature near 600 nm. Both are interpreted as results of nanotube p-doping when the dye adsorbs to the sidewall. We also observe that the charge transfer complex formation accelerates when the rose bengal is optically excited, apparently proceeding through the dye’s triplet state. A correlation between extent of guanine functionalization and the concentration of charge transfer complexes is found as ionic strength is changed. We infer that the functionalization reaction is enabled by adsorbed photosensitizers. Interestingly, the extent of SWCNT fluorescence quenching by rose bengal is found to vary significantly with (n,m) structure. This quenching effect therefore provides a simple approach to monitor structure-specific interactions between SWCNTs and coatings, including ssDNA and conventional ionic surfactants.(1) Zheng, Y.; Bachilo, S. M.; Weisman, R. B. Controlled Patterning of Carbon Nanotube Energy Levels by Covalent DNA Functionalization. ACS Nano 13, 5222 (2019). https://doi.org/10.1021/acsnano.9b03488.

Single-Walled Carbon Nanotubes Charge Management By Controlled Functionalization

Managing the density of charges in carbon nanotubes opens new ways to tune their optical response, their transport properties, and their physico-chemical features. Charge transfer from molecules adsorbed onto the sidewall or filled within the hollow cavity of the nanotubes has already been demonstrated, yet a fine-tunable control of the surface coverage/filling fraction (and thus the amount of transferred charge) remains challenging to achieve. Alternatively, we developed an optically nonperturbing covalent functionalization technique based on the inclusion of a triazine derivative into the carbon network [1]. The nitrogen atom sustaining the attached group becomes an integrated part of the pi-conjugated network and contributes with its lone electron pair to uplifting the position of the Fermi level of the tube. Since the density of attached groups can be varied by adapting the synthetic conditions, this technique offers the advantage of controlling the amount of charge injected into the tubes. Additional groups attached onto the other end of the triazine moiety, moreover, are able to inject charge into the tubes as well. This, for example, allowed us to modulate the photoluminescence of the tubes, switching their emission on and off through the attachment of the switchable spiropyran/merocyanine system [2]. Here we focus on a class of charge-transfer agents that either donate or withdraw electrons depending on the arrangements of their building units [3] and how their decoration affects the properties of the tubes. Figure: Different number of methoxy groups can be attached onto aniline at different positions, resulting in compounds that can either donate or withdraw electrons from the tubes they are attached onto [3].[1] Setaro et al. Nature Communications 8, 14281 (2017).[2] Godin et al. Science Advances 5, eaax1166 (2019).[3] Fiebor et al. J. Phys. Chem. C. 125, 19925 (2021). Figure 1

(Invited, Digital Presentation) Molecular Self-assembly and Reactivity on 2D Layered Materials

In the first part, we will focus on the principles of self-assembled molecular network formation at the liquid-solid interface on surfaces such as graphite, MoS2, and graphene. Then we will discuss how lateral confinement, induced by covalent functionalization of graphite and graphene, affects self-assembly. Several strategies will be demonstrated to realize two-dimensional lateral confinement, all based on the covalent modification of the surface, making use of bottom-up approaches or a combination of bottom-up and top-down approaches. The impact of these various types of confinement on the formation of self-assembled molecular networks will be discussed, including aspects such as nucleation and growth, directional self-assembly, on-surface chirality, polymorphism, and reactivity.In a second part, we will focus on the formation of porous two-dimensional covalent organic frameworks at the liquid-solid interface, and reveal various interesting aspects at the molecular level such as nucleation and growth mechanisms, and the impact local electric fields may have on (de)polymerization processes.The relevance and importance of scanning probe microscopes to investigate (and control) self-assembly and reactivity on surfaces will be illustrated. C. Rodríguez González, A. Leonhardt, H. Stadler, S. Eyley, W. Thielemans, S. De Gendt, K. S. Mali, S. De Feyter, ACS Nano, 2021, 15, 10618–10627Verstraete, S. De Feyter, Chem. Soc. Rev., Chemical Society Reviews, 2021, 50, 5884–5897Bragança, A. Minoia, R. Steeno, J. Seibel, B. E. Hirsch, L. Verstraete, O. Ivasenko, K. Müllen, K. S. Mali, R. Lazzaroni, S. De Feyter, J. Am. Chem. Soc., 2021, 143, 11080–11087Tahara, Y. Kubo, S. Hashimoto, T. Ishikawa, H. Kaneko, A. Brown, B. E. Hirsch, S. De Feyter, Y. Tobe, J. Am. Chem. Soc., 2020, 142, 7699–7708Zhan, Z.-F. Cai, M. Martínez-Abadía, A. Mateo-Alonso, S. De Feyter, J. Am. Chem. Soc. 2020, 142, 5964–5968

Probing Charge Transport in Sp 3-Functionalized Single-Walled Carbon Nanotubes with Terahertz Spectroscopy

The covalent functionalization of semiconducting single-walled carbon nanotubes (SWCNTs) with luminescent sp 3-hybridized defects gives rise to tunable, narrowband emission in the near-infrared and increases their photoluminescence quantum yields [ACS Nano 2019, 13, 9259]. To enable their application in electrically driven light sources, a detailed understanding of the impact of sp 3 defects on charge transport within individual nanotubes and nanotube networks is required. Here, we investigate the ultrafast carrier dynamics in sp 3-functionalized, polymer-sorted (6,5) SWCNT dispersions and thin films using optical-pump terahertz-probe (OPTP) spectroscopy. OPTP spectroscopy relies on the photo-generation of charge carriers that are subsequently probed by a single-cycle terahertz pulse, rendering it a highly suitable technique for the determination of intrinsic charge transport properties (e.g., carrier mobility) in a quantitative and contact-free fashion. We observe a large transient photoconductivity of pristine and functionalized nanotubes that is dominated by the contribution of free charge carriers. The photoconductivity intensity and lifetime decrease upon functionalization, corroborating the impact of sp 3 defects on intra-nanotube charge transport. Through combination of (temperature-dependent) OPTP measurements of sp 3-functionalized SWCNT dispersions and films with electrical measurements of ambipolar, light-emitting field-effect transistors based on functionalized SWCNT networks [ACS Nano 2021, 15, 10451], we can separate the contributions of sp 3 defects (intra-nanotube) and nanotube junctions (inter-nanotube) to charge transport in such networks and distinguish the short- and long-range transport characteristics. Fig. 1: Ultrafast optical-pump terahertz-probe spectroscopy is a highly suitable technique to study the intrinsic charge transport properties of sp 3-functionalized (6,5) SWCNTs in dispersions and thin films. Figure 1