Controlled Surface Functionalization Research Articles

Deposition kinetics and adhesion behavior of polydopamine-based capsules on cellulose fibrous substrates

Polydopamine (PDA)-based capsules have been broadly used to functionalize cellulose-based fabrics owing to their enhanced adhesion properties. However, the deposition kinetics and adhesion behavior of PDA-based capsules on the fabrics remain understudied. In this work, the sizes, concentrations, and deposition time of PDA particles, as well as the electrostatic force between PDA particles and the fabrics were investigated to study the deposition kinetics and adhesion behavior of PDA particles on Lyocell fibers. The introduction of electrostatic interaction significantly enhanced both the deposition amount and the uniformity of PDA particles onto the fiber surface. The deposition kinetics of PDA particles on the fibers could be accurately described using a modified collision model, with the coverage of PDA particles conforming to a monolayer deposition pattern. The adhesion behavior of PDA particles was investigated by molecular dynamics simulation and isothermal titration calorimetry. The results indicated the driving forces during the deposition process were mainly hydrogen bonds, electrostatic force and van der Waals force. The van der Waals force was increased by around 106 %, and electrostatic force was even increased by approximately 201 % after the fiber cationization. This study provided a theoretical foundation for achieving controllable and quantitative surface functionalization of cellulose fibrous substrates.

Controllable surface functionalization of rice husk-derived porous carbon by atomic layer deposition for highly-efficient microwave absorption

Multilayer absorbers, characterized by their distinctive structures and numerous heterogeneous interfaces, possess the potential to become exceptionally efficient and stable electromagnetic wave absorbers. Herein, we have ingeniously engineered multilayer ZnO/NiCo/C (ZNC) composite absorbers, utilizing a combination of an annealing procedure and atomic layer deposition (ALD) process. From the SEM images, the ZnO layers composed of ZnO nanoparticles (NPs) fabricated via ALD almost completely cover the surface of rice husk-derived carbon and the NiCo NPs residing on the surface. Benefiting from the specific multilayer structure, the well-designed ternary dielectric/magnetic components, and the synergistic interplay between dipole polarization relaxation and interfacial polarization relaxation, coupled with good impedance matching, the ZNC150 and ZNC200 composites exhibit best microwave absorption capacities. Through the precise control of the electromagnetic parameters by the deposition circle modifications, the minimum reflection loss reaches −52.5 dB and the effective bandwidth extends to 4.96 GHz with thin thickness of 1.52 mm.

Dye-encapsulated metal–organic frameworks as highly sensitive fluorescent sensors for tetracycline antibiotics in water

As a type of porous material with highly controllable pore structure and surface functionalization, metal–organic frameworks (MOFs) have unique advantages in antibiotic content detection in the environment. Herein, we successfully regulated the luminescent properties of MOF-808 through the in-situ loading of fluorescent dye molecules, and achieved excellent luminescent sensing detection performance for tetracycline antibiotics in water environments (LOD = 79.9 ppb). Additionally, the construction of a convenient luminescent detection test paper sensor provides a new approach and method for the rapid, recyclable detection and monitoring of antibiotics.

Fluorescent Nanocarbons: From Synthesis and Structure to Cancer Imaging and Therapy.

Nanocarbons are emerging at the forefront of nanoscience, with diverse carbon nanoforms emerging over the past two decades. Early cancer diagnosis and therapy, driven by advanced chemistry techniques, play a pivotal role in mitigating mortality rates associated with cancer. Nanocarbons, with an attractive combination of well-defined architectures, biocompatibility, and nanoscale dimension, offer an incredibly versatile platform for cancer imaging and therapy. This paper aims to review the underlying principles regarding the controllable synthesis, fluorescence origins, cellular toxicity, and surface functionalization routes of several classes of nanocarbons: carbon nanodots, nanodiamonds, carbon nanoonions, and carbon nanohorns. This review also highlights recent breakthroughs regarding the green synthesis of different nanocarbons from renewable sources. It also presents a comprehensive and unified overview of the latest cancer-related applications of nanocarbons and how they can be designed to interface with biological systems and work as cancer diagnostics and therapeutic tools. The commercial status for large-scale manufacturing of nanocarbons is also presented. Finally, it proposes future research opportunities aimed at engendering modifiable and high-performance nanocarbons for emerging applications across medical industries. This work is envisioned as a cornerstone to guide interdisciplinary teams in crafting fluorescent nanocarbons with tailored attributes that can revolutionize cancer diagnostics and therapy.

Controlled surface functionalization using aryldiazonium salts with bulky protecting groups for the development of DNA-based sensing platforms

Developing a comprehensive procedure for tuning the surface and interfacial properties of DNA biorecognition interfaces is crucial for a wide range of analytical applications, but proves to be a difficult task. This study aims to address the challenge by exploiting the significant advantages of surface grafting with protected aryldiazonium salts and “click” azide-alkyne functionalization reactions. In order to control the surface density of reactive alkyne moieties over a wide range, suitable for the immobilization of large biomolecules, we explored novel protecting groups such as triphenylsilyl (TPS) and tris(biphen-4-yl)silyl (TBPS), which are bulkier than the triisopropylsilyl (TIPS) group employed in previous studies. We prepare phenylethynyl-grafted glassy carbon substrates using a two-step protocol consisting in electrografting with the corresponding silyl-protected diazonium salt, followed by nucleophilic cleavage of the protecting group. Using appropriate derivatization reagents and a combination of electrochemical and surface analytical techniques, we find a strong correlation between the protecting group size and the surface coverage of phenylethynyl groups. Next, using the phenylethynyl-grafted substrates for the immobilization of an azide-modified cocaine/quinine aptamer as model bioreceptor, we demonstrate that the surface density of ssDNA decreases with increasing size of the protecting group employed in the grafting procedure. Finally, we prove that our strategy can be effectively employed to fine-tune the analytical performance of an aptasensing platform for quinine detection.

Nanogap engineering of 3D nanoraspberries into 2D plasmonic nanoclusters toward improved SERS performance.

3D raspberry-like core/satellite nanostructures were prepared by controlled surface functionalization of silica spheres using crosslinked poly(4-vinylpyridine) (P4VP) chains with known binding affinity for gold nanoparticles (AuNPs). The 3D SiO2-g-P(4VP-co-DVB)/AuNP nanoraspberries can be further transformed into 2D plasmonic nanoclusters by etching the silica core with hydrofluoric acid (HF). After the transformation, the interparticle distance between the AuNPs dramatically reduced from a 10 nm scale to sub 2 nm. Owing to the strong electromagnetic field generated by the plasmonic coupling between AuNPs in very close proximity, the established P(4VP-co-DVB)/AuNP nanoclusters provided strong and undisturbed Raman signals as a SERS substrate. In addition, benefiting from the stabilizing effect of the crosslinked P(4VP-co-DVB) network, the prepared SERS substrate has the advantages of good uniformity, stability and reproducibility, as well as strong SERS enhancement, endowing it with great potential for rapid and efficient SERS detection.

Controlled Surface Functionalization Using Aryldiazonium Salts for the Development of Aptasensing Platforms

It is well known that both the aptamer surface density and surface chemistry can have a strong influence on the analytical performance of aptasensors based on target-induced conformational changes1. In this context, we report here an improved protocol for obtaining aptasensing platforms which allows fine-tuning the DNA aptamer surface coverage. First, glassy carbon substrates were functionalized with ethynylphenyl groups through the electrochemical reduction of silyl-protected ethynylphenyl diazonium tetrafluoroborates followed by deprotection with tetrabutylammonium fluoride2. The successful removal of the protecting groups (triisopropylsilyl-, triphenylsilyl- and tris(biphen-4-yl)silyl-) was confirmed by X-ray photoelectron spectroscopy and cyclic voltammetry in the presence of Fe(CN)6 3-/4- as soluble redox probe. Following “click” post-modification with suitable derivatization reagents, the surface coverage with ethynylphenyl groups was assessed using complementary techniques such as XPS, cyclic voltammetry and chronocoulometry. For example, the F/C surface ratio of substrates derivatized with 1-(2,2,2-trifluoroethoxy)-6-azidohexane provided an indication of the functionalization degree, and the integration of Fc/Fc+ voltammetric peaks for substrates modified with N-(6-azidohexyl)ferrocenecarboxamide allowed a quantitative determination of the surface coverage. Both techniques showed a good correlation between the protective group size and the surface coverage with alkyne groups. Likewise, we observed a similar trend for substrates derivatized with azide-modified oligonucleotides, where the surface packing density was determined based on the chronocoulometric response of Ru(NH3)6 3+, a cationic redox probe which binds with the negatively charged phosphate groups from the oligonucleotide backbone. As proof of concept, we further developed an electrochemical molecular beacon aptasensor employing a ferrocene-labeled quinine aptamer. We demonstrate that the aptamer surface density, and ultimately the analytical performance of molecular beacon aptasensors, can be effectively fine-tuned by employing silyl protecting groups of different sizes.Acknowledgements This work was supported by a grant from the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2020-2474, within PNCDI III. References Onaş, A. M., Dascălu, C., Raicopol, M. D. & Pilan, L. Critical Design Factors for Electrochemical Aptasensors Based on Target-Induced Conformational Changes: The Case of Small-Molecule Targets. Biosensors 12, (2022).Leroux, Y. R., Fei, H., Noël, J.-M. M., Roux, C. & Hapiot, P. Efficient covalent modification of a carbon surface: Use of a silyl protecting group to form an active monolayer. J. Am. Chem. Soc. 132, 14039–14041 (2010).

Surface Engineering of MoS2 Quantum Dots via Cyclodextrin-Based Host-Guest Chemistry as Versatile Platforms for Enhanced Cell Imaging Application.

Transition metal chalcogenide quantum dots (QDs), especially MoS2 QDs, are an emerging class of novel optical probes for versatile bioanalytical applications owing to their distinct physicochemical properties. However, the reasonable use of these QDs for biological imaging has been largely restricted due to the challenge of controllable surface functionalization. In this work, we report a new strategy to engineer the surface of MoS2 QDs by taking advantage of cyclodextrin (CD)-based host-guest chemistry. The prepared β-CD-modified QDs (β-CD-MoS2 QDs) exhibit enhanced fluorescence properties, excellent biocompatibility, and good stability, making them promising as novel optical probes for bioimaging. Cellular imaging experiments revealed that these β-CD-MoS2 QDs can enter living cells through multiple internalization pathways, which differs significantly from pristine QDs. Particularly, we observed that the intracellular accumulation of MoS2 QDs in lipid droplets was enhanced owing to the specific binding of β-CD to cholesterol, which was then harnessed for monitoring the lipid metabolism in living cells via fluorescence imaging. Furthermore, we also demonstrated the potential use of β-CD-MoS2 QDs for targeted cell imaging and microplate-based cell recognition, which can be easily achieved via bioconjugation with functional motifs (e.g., folate acid) through host-guest chemistry. Altogether, these results illustrate the great potential of engineering the surface of MoS2 QDs and other analogous materials via CD-based host-guest chemistry for advancing their cell imaging applications.

Super-assembled mesoporous thin films with asymmetric nanofluidic channels for sensitive and reversible electrical sensing

Bioinspired artificial nanochannels have emerged as promising candidates for developing smart nanofluidic sensors due to their highly controllable size and surface functionality. However, little attention has been paid to the role of the outer surface of the nanochannels in enhancing the detection sensitivity. Herein, an asymmetric nanochannel-based responsive detection platform with ultrathin tannic acid modified mesoporous silica (TA-MS) layer and alumina oxide (AAO) thin film is prepared through super-assembly strategy. The functional TA-MS outer surface layer provides abundant phenolic groups on the nanochannels for ions and molecules transport, which paves the way for the development of heterochannels for label-free, reversible and highly sensitive dopamine (DA) detection based off of cation displacement effect. Notably, by engineering optimal thickness of the TA-MS, the sensing performance can be further improved. After optimization, the linear response ranges for DA detection are 0.001–1 μM, 1–10 μM and 10–200 μM with the detection limit of 0.1 nM. The prepared sensor exhibits stable reversibility after several detection cycles. In addition, this method was successfully applied for DA detection in fetal bovine serum sample. Theoretical calculations further prove the detection mechanism. This work opens a new horizon of using mesoporous materials to construct nanofluidic sensors for ultrasensitive small molecule detection and recognition.

Optimization of Nanosubstrates toward Molecularly Surface-Functionalized Raman Spectroscopy.

Diagnostic advancements require continuous developments of reliable analytical sensors, which can simultaneously fulfill many criteria, including high sensitivity and specificity for a broad range of target analytes. Incorporating the highly sensitive attributes of surface-enhanced Raman spectroscopy (SERS) combined with highly specific analyte recognition capabilities via molecular surface functionalization could address major challenges in molecular diagnostics and analytical spectroscopy fields. Herein, we have established a controllable molecular surface functionalization process for a series of textured gold surfaces. To create the molecularly surface-functionalized SERS platforms, self-assembled benzyl-terminated and benzoboroxole-terminated monolayers were used to compare which thicknesses and root-mean-square (RMS) roughness of planar gold produced the most sensitive and specific surfaces. Optimal functionalization was identified at 80 ± 8 nm thickness and 7.2 ± 1.0 nm RMS. These exhibited a considerably higher SERS signal (70-fold) and improved sensitivity for polysaccharides when analyzed using principal component analysis (PCA) and self-organizing maps (SOM). These findings lay the procedure for establishing the optimal substrate specifications as an essential prerequisite for future studies aiming at developing the feasibility of molecular imprinting for SERS diagnostic applications and the subsequent delivery of advanced, highly selective, and sensitive sensing devices and analytical platforms.

Controllable surface functionalization of boron nitride by heat treatment

Herein, boron nitride with functional groups (f-BN), which was obtained by the calcination of melamine-boric acid complex, was further functionalized using L-lactic acid. Observations revealed that L-lactic acid was grafted onto f-BN via two main functionalization routes by heat treatment: amidation and boronate ester formation routes. Since the functionalization degree of L-BN could be adjusted depending on the heating conditions, it is an effective strategy that would be applied to various further applications.

Mesoporous Silica Nanoparticle-Based Imaging Agents for Hepatocellular Carcinoma Detection.

Hepatocellular carcinoma (HCC) is characterized by poor prognosis and high mortality. The treatment of HCC is closely related to the stage, and the early-stage of HCC patients usually accompanies a more long-term survival rate after clinical treatment. Hence, there are critical needs to develop effective imaging agents with superior diagnostic precision for HCC detection at an early stage. Recently, mesoporous silica nanoparticles (MSNs) based imaging agents have gained extensive attentions in HCC detection, which can serve as a multifunctional nanoplatform with controllable size and facile surface functionalization. This perspective summarizes recent advances in MSNs based imaging agents for HCC detection by the incorporation of several clinical imaging modalities. Multi-modal imaging system has been developed for higher spatial resolution and sensitivity. Even though some limitations and challenges need to be overcome, we envision the development of novel MSNs based imaging agents will offer great potential applications in clinical HCC detection.

An IR Spectroscopy Study of the Degradation of Surface Bound Azido-Groups in High Vacuum.

Controlled surface functionalization with azides to perform on surface "click chemistry" is desired for a large range of fields such as material engineering and biosensors. In this work, the stability of an azido-containing self-assembled monolayer in high vacuum is investigated using in situ Fourier transform infrared spectroscopy. The intensity of the antisymmetric azide stretching vibration is found to decrease over time, suggesting the degradation of the azido-group in high vacuum. The degradation is further investigated at three different temperatures and at seven different nitrogen pressures ranging from 1 × 10-6 mbar to 5 × 10-3 mbar. The degradation is found to increase at higher temperatures and at lower nitrogen pressures. The latter supporting the theory that the degradation reaction involves the decomposition into molecular nitrogen. For the condition with the highest degradation detected, only 63% of azides is found to remain at the surface after 8 h in vacuum. The findings show a significant loss in control of the surface functionalization. The instability of azides in high vacuum should therefore always be considered when depositing or postprocessing azido-containing layers.

Nanoscale zeolitic imidazolate framework–8 encapsulates crude extract of Ajuga bracteosa wall ex. Benth and enhanced their antibacterial efficiency

Certain disease-causing bacterial strains invade the body; they multiply and cause disease. The development of nanoparticles and self-assembled nanomaterial-based therapeutics has developed into a flourishing section in nanomedicine. Zeolitic imidazole framework-8 (ZIF-8) comprises zinc ions and 2-methylimidazole showing good biocompatibility, known for their large porosity with high surface area, tunable shapes, large pore sizes, and controllable surface functionality. We report a ZIF-8 based agent with excellent antibacterial effectiveness against gram-positive (Bacillus subtilis) and gram-negative (Pseudomonas aeruginosa) bacteria by agar diffusion method. We are the first to encapsulate Ajuga bracteosa extract (ABE) into the ZIF-8 framework, forming a nanoconjugate (ABE@ZIF-8). The mechanism by which the synthesized ABE@ZIF-8 NPs are inhibiting bacterial growth is likely to be the adsorbance of ABE@ZIF-8 NPs on the bacterial cell membrane because of the electrostatic attraction between positively charged ABE@ZIF-8 NPs and the negatively charged bacterial cell membrane. UV–vis absorption spectra, PXRD, SEM, TEM, BET, TGA, DLS, zeta potential characterized ABE@ZIF-8 NPs. Zone of inhibition (ZOI) and minimum inhibitory concentration (MIC) of ABE@ZIF-8 NPs are studied against the Bacillus subtilis and Pseudomonas aeruginosa compared to gentamicin, ZIF-8, ABE, and methanol. The results reported ABE@ZIF-8 nanoconjugate has better antibacterial efficiency against gram-positive and gram-negative bacteria.

Encapsulation of Pharmaceutical and Nutraceutical Active Ingredients Using Electrospinning Processes.

Electrospinning is an inexpensive and powerful method that employs a polymer solution and strong electric field to produce nanofibers. These can be applied in diverse biological and medical applications. Due to their large surface area, controllable surface functionalization and properties, and typically high biocompatibility electrospun nanofibers are recognized as promising materials for the manufacturing of drug delivery systems. Electrospinning offers the potential to formulate poorly soluble drugs as amorphous solid dispersions to improve solubility, bioavailability and targeting of drug release. It is also a successful strategy for the encapsulation of nutraceuticals. This review aims to briefly discuss the concept of electrospinning and recent progress in manufacturing electrospun drug delivery systems. It will further consider in detail the encapsulation of nutraceuticals, particularly probiotics.

Controlled surface functionalization of Ni-S nanostructures for pH-responsive selective and superior pollutants adsorption

Herein, we developed a synthetic strategy to functionalize Ni-S nanostructures (NS) using a facile precipitation method at moderate temperature. The surface functionality of NS is controlled by varying amount of mixed surfactants to achieve the pH-responsive selective adsorption of anionic and cationic dyes and the adsorption of ciprofloxacin (CIP) and tetracycline (TC) antibiotics. Powder XRD diffraction pattern revealed the phase of NS was changed from α-NiS to mixed phases after functionalization. The surface area of functionalized NS was significantly enhanced by ~5 times of that unfunctionalized NS as 6.6 m2g−1 to 30.3 m2g−1. The NS selectively adsorbed methyl orange (MO) at pH 4.5 and methylene blue (MB) at pH 11.5 with separation efficiency values of 94.2% and 97.9% respectively. The maximum adsorption capacity for MO, MB, TC and CIP are obtained as 1526.3, 1031.2, 1540.8 and 632.4 mg g−1, respectively. The electrostatic interaction is predominantly involved in the adsorption of dyes whereas adsorption of antibiotics changed to hydrogen bonding and metal coordination. Thermodynamics parameters indicated exothermic and spontaneous adsorption of dyes. The optimized adsorbent is easily recyclable. Thus, the developed strategy of functionalization of nanostructures unveils a practical approach towards selective and efficient adsorption of organic pollutants.

Three-Dimensional Interfacing of Cells with Hierarchical Silicon Nano/Microstructures for Midinfrared Interrogation of In Situ Captured Proteins.

Label-free optical detection of biomolecules is currently limited by a lack of specificity rather than sensitivity. To exploit the much more characteristic refractive index dispersion in the mid-infrared (IR) regime, we have engineered three-dimensional IR-resonant silicon micropillar arrays (Si-MPAs) for protein sensing. By exploiting the unique hierarchical nano- and microstructured design of these Si-MPAs attained by CMOS-compatible silicon-based microfabrication processes, we achieved an optimized interrogation of surface protein binding. Based on spatially resolved surface functionalization, we demonstrate controlled three-dimensional interfacing of mammalian cells with Si-MPAs. Spatially controlled surface functionalization for site-specific protein immobilization enabled efficient targeting of soluble and membrane proteins into sensing hotspots directly from cells cultured on Si-MPAs. Protein binding to Si-MPA hotspots at submonolayer level was unambiguously detected by conventional Fourier transform IR spectroscopy. The compatibility with cost-effective CMOS-based microfabrication techniques readily allows integration of this novel IR transducer into fully fledged bioanalytical microdevices for selective and sensitive protein sensing.

Synthesis and characterization of ZEin-based Low Density Porous Absorbent (ZELDA) for oil spill recovery

Removal of spilled petroleum oil from water bodies using hydrophobic porous absorbent has garnered considerable attention due to the simplicity, large-scale adaptability and robustness of the process. However, the use of nonbiodegradable synthetic oil absorbent during cleanup has raised a secondary concern such as generating plastic pollutants that can accumulate in marine and other ecosystems. To encounter this potential hazard, there is a need to find new biocompatible alternatives to currently used non-degradable porous materials. Here we present ZEin-based Low Density porous Absorbent (ZELDA) synthesized from an emulsion templating method as a new class of naturally derived porous material with tunable hydrophobicity for oil spill recovery. Corn-derived zein nanoparticles are first used to form oil-in-water Pickering emulsion. The addition of polymeric zein into the continuous aqueous phase of the emulsion, and its gradual phase separation enables the formation of a porous matrix. The pore diameter, surface wettability, and oil uptake capacity of ZELDA can be programmed by tuning oil-to-water phase volume ratio of the Pickering emulsion and its selective surface functionalization using flaxseed oil. The synthesis of ZELDA can be further modified with iron oxide nanoparticles to induce magnetic response, which enables its contactless maneuverability and removal from spilled site. The study outlines a new method of synthesis of zein-based porous materials and introduces synthetic routes for controlled surface functionalization, wettability, and stimuli responsiveness of the porous material. The synthesized plant-based material provides an ecofriendly alternative to commercially used nonbiodegradable oil sorbents for spilled oil remediation.

Dual‐Function HKUST‐1: Templating and Catalyzing Formation of Graphitic Carbon Nitride Quantum Dots Under Mild Conditions

AbstractGraphitic carbon nitride quantum dots (g‐CNQDs) are highly promising photoresponsive materials. However, synthesis of monodispersed g‐CNQDs remains challenging. Here we report the dual function of MOF [Cu3BTC2] (HKUST‐1) as a catalyst and template simultaneously to prepare g‐CNQDs under mild conditions. Cyanamide (CA), a graphitic carbon nitride precursor, catalytically dimerized inside the larger MOF cavities at 90 °C and condensed into g‐CNQDs at 120 °C in a controlled fashion. The HKUST‐1 template was stable under the reaction conditions, leading to uniform g‐CNQDs with a particle size of 2.22±0.68 nm. The as prepared g‐CNQDs showed photoluminescence emission with a quantum yield of 3.1 %. This concept (MOF dual functionality) for catalyzing CA polycondensation (open metal sites (OMSs) effect) and controlling the produced particle size (pore‐templating effect), together with the tunable MOF porosity, is expected to produce unique g‐CNQDs with controllable size, morphology, and surface functionality.

Dual-Function HKUST-1: Templating and Catalyzing Formation of Graphitic Carbon Nitride Quantum Dots Under Mild Conditions.

Graphitic carbon nitride quantum dots (g‐CNQDs) are highly promising photoresponsive materials. However, synthesis of monodispersed g‐CNQDs remains challenging. Here we report the dual function of MOF [Cu3BTC2] (HKUST‐1) as a catalyst and template simultaneously to prepare g‐CNQDs under mild conditions. Cyanamide (CA), a graphitic carbon nitride precursor, catalytically dimerized inside the larger MOF cavities at 90 °C and condensed into g‐CNQDs at 120 °C in a controlled fashion. The HKUST‐1 template was stable under the reaction conditions, leading to uniform g‐CNQDs with a particle size of 2.22±0.68 nm. The as prepared g‐CNQDs showed photoluminescence emission with a quantum yield of 3.1 %. This concept (MOF dual functionality) for catalyzing CA polycondensation (open metal sites (OMSs) effect) and controlling the produced particle size (pore‐templating effect), together with the tunable MOF porosity, is expected to produce unique g‐CNQDs with controllable size, morphology, and surface functionality.