β-CD Dimer-immobilized Ag Assembly Embedded Silica Nanoparticles for Sensitive Detection of Polycyclic Aromatic Hydrocarbons

Cyclodextrin-based architectures for electrochemical sensing: from molecular recognition to functional hybrids

This review surveys recent advances in the integration of cyclodextrins (CDs) with diverse materials for electrochemical detection of a wide range of analytes in environmental, pharmaceutical, and clinical contexts. CDs, featuring a hydrophobic cavity and a hydrophilic exterior, enable selective host-guest binding of small organic and inorganic molecules. By anchoring CDs onto electrode surfaces via strategies such as self-assembled monolayers, layer-by-layer deposition, or polymer entrapment, researchers have achieved improved selectivity and lower detection limits for target compounds. These CD-functionalized interfaces are further enhanced by combination with carbon nanotubes, graphene, metal nanoparticles, and redox mediators, providing synergistic effects that boost conductivity, catalysis, and signal amplification. Moreover, CD-based sensors exhibit reversible recognition, making them amenable to repeated use and continuous monitoring. Notably, derivatization of the CD ring expands its applicability, introducing functionalities such as chirality recognition, metal coordination, or improved solubility. Different detection modes, including voltammetry, impedance, and competitive displacement assays, have been reported for a variety of analytes, ranging from heavy metals and pesticides to pharmaceuticals and chiral compounds. The incorporation of CDs into advanced hybrid architectures also offers solutions to common issues like electrode fouling and limited selectivity, thus expanding their utility in harsh or complex sample environments. While challenges remain in ensuring reproducibility, large-scale manufacture, and robust performance in real-world applications, ongoing innovations in materials science and synthetic chemistry promise to make CD-based electrodes increasingly valuable for sensitive, portable, and cost-effective chemical analysis. Furthermore, novel integration with biological receptors, such as enzymes and aptamers, holds promise for multiplexed biosensing.

Synthesis and Application of Optical Nanomaterials

The field of optical nanomaterials stands at the forefront of technological innovation, driving advancements across a spectrum of scientific disciplines and industries [...].

Effects of Raman Labeling Compounds on the Stability and Surface-Enhanced Raman Spectroscopy Performance of Ag Nanoparticle-Embedded Silica Nanoparticles as Tagging Materials

Surface-enhanced Raman spectroscopy (SERS) tagging using silica(SiO2)@Ag nanoparticles (NPs) is easy to handle and is being studied in various fields, including SERS imaging and immunoassays. This is primarily due to its structural advantages, characterized by high SERS activity. However, the Ag NPs introduced onto the SiO2 surface may undergo structural transformation owing to the Ostwald ripening phenomenon under various conditions. As a result, the consistency of the SERS signal decreases, reducing their usability as SERS substrates. Until recently, research has been actively conducted to improve the stability of single Ag NPs. However, research on SiO2@Ag NPs used as a SERS-tagging material is still lacking. In this study, we utilized a Raman labeling compound (RLC) to prevent the structural deformation of SiO2@Ag NPs under various conditions and proposed excellent SiO2@Ag@RLC-Pre NPs as a SERS-tagging material. Using various RLCs, we confirmed that 4-mercaptobenzoic acid (4-MBA) is the RLC that maintains the highest stability for 2 months. These results were also observed for the SiO2@Ag NPs, which were unstable under various pH and temperature conditions. We believe that SERS tags using SiO2@Ag NPs and 4-MBA can be utilized in various applications on based SERS because of the high stability and consistency of the resulting SERS signal.

Hazards of polycyclic aromatic hydrocarbons: a review on occurrence, detection, and role of green nanomaterials on the removal of PAH from the water environment

Organic pollutant contamination in the environment is a serious and dangerous issue, especially for developing countries. Among all organic pollutants, polycyclic aromatic hydrocarbons (PAHs) are the more frequently discovered ones in the environment. PAH contamination is caused chiefly by anthropogenic sources, such as the disposal of residential and industrial waste and automobile air emissions. They are gaining interest due to their environmental persistence, toxicity, and probable bioaccumulation. The existence of PAHs may result in damage to the environment and living things, and there is widespread concern about the acute and chronic threats posed by the release of these contaminants. The detection and elimination of PAHs from wastewater have been the focus of numerous technological developments during recent decades. The development of sensitive and economical monitoring systems for detecting these substances has attracted a lot of scientific attention. Using several nanomaterials and nanocomposites is a promising treatment option for the identification and elimination of PAHs in aquatic ecosystems. This review elaborated on the sources of origin, pathogenicity, and widespread occurrence of PAHs. In addition, the paper highlighted the use of nanomaterial-based sensors in detecting PAHs from contaminated sites and nanomaterial-based absorbents in PAH elimination from wastewater. This review also addresses the development of Graphene and Biofunctionalized nanomaterials for the elimination of PAHs from the contaminated sites.

On-site detection of pyrene from mixture with ppb level sensitivity by plasmonic TLC-DSERS

Polycyclic aromatic hydrocarbons are a kind of persistent organic pollutants, which bring harmful effects to the ecological environment and human health. Therefore, it is critical to identify PAHs. In this study, we developed a highly efficient device for on-site identification of pyrene in edible oil using high performance plasmonic thin layer chromatography (PTLC) and dynamic surface-enhanced Raman spectroscopy (DSERS). PAHs in the mixture sample were efficiently separated on the PTLC plate and visualized under UV light, in which the plasmonic feature of the stationary phase could enhance the fluorescence of PAH. Then DSERS measurement was developed on a portable Raman spectrometer. The smaller size of Au NPs in the stationary phase could provide a lower theoretical plate height and provide higher separation efficiency. The sensitivity of the PTLC-DSERS method is down to 0.1 ppb, that nearly 4 orders of magnitude higher than current TLC-SERS method. The results indicate that this PTLC-DSERS method has the potential for on-site and sensitive identification of pyrene in the mixture.

Silica Shell Thickness-Dependent Fluorescence Properties of SiO2@Ag@SiO2@QDs Nanocomposites

Silica shell coatings, which constitute important technology for nanoparticle (NP) developments, are utilized in many applications. The silica shell's thickness greatly affects distance-dependent optical properties, such as metal-enhanced fluorescence (MEF) and fluorescence quenching in plasmonic nanocomposites. However, the precise control of silica-shell thicknesses has been mainly conducted on single metal NPs, and rarely on complex nanocomposites. In this study, silica shell-coated Ag nanoparticle-assembled silica nanoparticles (SiO₂@Ag@SiO₂), with finely controlled silica shell thicknesses (4 nm to 38 nm), were prepared, and quantum dots (QDs) were introduced onto SiO₂@Ag@SiO₂. The dominant effect between plasmonic quenching and MEF was defined depending on the thickness of the silica shell between Ag and QDs. When the distance between Ag NPs to QDs was less than ~10 nm, SiO₂@Ag@SiO₂@QDs showed weaker fluorescence intensities than SiO₂@QD (without metal) due to the quenching effect. On the other hand, when the distance between Ag NPs to QDs was from 10 nm to 14 nm, the fluorescence intensity of SiO₂@Ag@SiO₂@QD was stronger than SiO₂@QDs due to MEF. The results provide background knowledge for controlling the thickness of silica shells in metal-containing nanocomposites and facilitate the development of potential applications utilizing the optimal plasmonic phenomenon.

Nano-Ag: Environmental applications and perspectives

Silver nanoparticles (AgNPs) are promising bactericidal agents and plasmonic NPs for environmental applications, owing to their various favorable properties. For example, AgNPs enables reactive oxygen species (ROS) generation, surface plasmon resonance (SPR), and specific reaction selectivities. In fact, AgNPs-based materials and their antimicrobial, optical, and electrical effects are at the forefront of nanotechnology, having applications in environmental disinfection, elimination of environmental pollutants, environmental detection, and energy conversions. This review aims to comprehensively summarize the advanced applications and fundamental mechanisms to provide the guidelines for future work in the field of AgNPs implanted functional materials. The state-of-art terms including (photo)(electro)catalytic reactions, heterojunction formation, the generation and attacking of ROS, genetic damage, hot electron generation and transfer, localized surface plasmon resonance (LSPR), plasmon resonance energy transfer (PERT), near field electromagnetic enhancement, structure-function relationship, and reaction selectivities have been covered in this review. It is expected that this review may provide insights into the rational development in the next generation of AgNPs-based nanomaterials with excellent performances.

Prospects of Surface-Enhanced Raman Spectroscopy for Biomarker Monitoring toward Precision Medicine

Future precision medicine will be undoubtedly sustained by the detection of validated biomarkers that enable a precise classification of patients based on their predicted disease risk, prognosis, and response to a specific treatment. Up to now, genomics, transcriptomics, and immunohistochemistry have been the main clinically amenable tools at hand for identifying key diagnostic, prognostic, and predictive biomarkers. However, other molecular strategies, including metabolomics, are still in their infancy and require the development of new biomarker detection technologies, toward routine implementation into clinical diagnosis. In this context, surface-enhanced Raman scattering (SERS) spectroscopy has been recognized as a promising technology for clinical monitoring thanks to its high sensitivity and label-free operation, which should help accelerate the discovery of biomarkers and their corresponding screening in a simpler, faster, and less-expensive manner. Many studies have demonstrated the excellent performance of SERS in biomedical applications. However, such studies have also revealed several variables that should be considered for accurate SERS monitoring, in particular, when the signal is collected from biological sources (tissues, cells or biofluids). This Perspective is aimed at piecing together the puzzle of SERS in biomarker monitoring, with a view on future challenges and implications. We address the most relevant requirements of plasmonic substrates for biomedical applications, as well as the implementation of tools from artificial intelligence or biotechnology to guide the development of highly versatile sensors.

Cyclodextrin-assisted surface-enhanced Raman spectroscopy: a critical review

Numerous approaches have been proposed to overcome the intrinsically low selectivity of surface-enhanced Raman spectroscopy (SERS), and the modification of SERS substrates with diverse recognition molecules is one of such approaches. In contrast to the use of antibodies, aptamers, and molecularly imprinted polymers, application of cyclodextrins (CDs) is still developing with less than 100 papers since 1993. Therefore, the main goal of this review is the critical analysis of all available papers on the use of CDs in SERS analysis, including physicochemical studies of CD complexation and the effect of CD presence on the Raman enhancement. The results of the review reveal that there is controversial information about CD efficiency and further experimental investigations have to be done in order to estimate the real potential of CDs in SERS-based analysis.

Carbon Nanomaterials for Biomedical Application

The use of carbon-based nanomaterials (CNs) with outstanding properties has been rising in many scientific and industrial application fields. These CNs represent a tunable alternative for applications with biomolecules, which allow interactions in either covalent or noncovalent way. Diverse carbon-derived nanomaterial family exhibits unique features and has been widely exploited in various biomedical applications, including biosensing, diagnosis, cancer therapy, drug delivery, and tissue engineering. In this chapter, we aim to present an overview of CNs with a particular interest in intrinsic structural, electronic, and chemical properties. In particular, the detailed properties and features of CNs and its derivatives, including carbon nanotube (CNT), graphene, graphene oxide (GO), and reduced GO (rGO) are summarized. The interesting biomedical applications are also reviewed in order to offer an overview of the possible fields for scientific and industrial applications of CNs.

Development of affinity between target analytes and substrates in surface enhanced Raman spectroscopy for environmental pollutant detection

Environmental pollution has long been a social concern due to the variety of pollutants and their wide distribution, persistence and being detrimental to health. It is therefore necessary to develop rapid and sensitive strategies to trace and detect these compounds. Among various detection methodologies, surface enhanced Raman spectroscopy (SERS) has become an attractive option as it enables accurate analyte identification, simple sample preparation, rapid detection and ultra-high sensitivity without any interference from water. For SERS detection, an essential yet challenging step is the effective capture of target analytes onto the surface of metal nanostructures with a high intensity of enhanced electromagnetic field. This review has systematically summarized recent advances in developing affinity between targets and the surface of SERS substrates via direct adsorption, hydrophobic functional groups, boronate affinity, metal organic frameworks (MOFs), DNA aptamers and molecularly imprinted polymers (MIPs). At the end of this review, technical limitations and outlook have been provided, with suggestions on optimizing SERS techniques for real-world applications in environmental pollutant detection.

Silver Nano/Microparticles: Modification and Applications 2.0

Currently, nano/microparticles are widely used in various fields [...].

Facile Histamine Detection by Surface-Enhanced Raman Scattering using SiO2@Au@Ag Alloy Nanoparticles

Histamine intoxication associated with seafood consumption represents a global health problem. The consumption of high concentrations of histamine can cause illnesses ranging from light symptoms, such as a prickling sensation, to death. In this study, gold-silver alloy-embedded silica (SiO2@Au@Ag) nanoparticles were created to detect histamine using surface-enhanced Raman scattering (SERS). The optimal histamine SERS signal was measured following incubation with 125 μg/mL of SiO2@Au@Ag for 2 h, with a material-to-histamine solution volume ratio of 1:5 and a phosphate-buffered saline-Tween 20 (PBS-T) solvent at pH 7. The SERS intensity of the histamine increased proportionally with the increase in histamine concentration in the range 0.1-0.8 mM, with a limit of detection of 3.698 ppm. Our findings demonstrate the applicability of SERS using nanomaterials for histamine detection. In addition, this study demonstrates that nanoalloys could have a broad application in the future.

Biofunctionalized nanomaterials for in situ clean-up of hydrocarbon contamination: A quantum jump in global bioremediation research

Interfacing organic or inorganic nanoparticles with biological entities or molecules or systems with the aim of developing functionalized nano-scale materials or composites for remediation of persistent organic hydrocarbon pollutants (such as monocyclic and polycyclic aromatic hydrocarbons, MAH/PAH) has generated great interest and continues to grow almost unabated. However, the usefulness and potency of these materials or conjugates hinges over several key barriers, including structural assembly with fine-tuned control over nanoparticle/biomolecule ratio, spatial orientation and activity of biomolecules, the nano/bio-interface strategy and hierarchical architecture, water-dispersibility and long term colloidal stability in environmental media, and non-specific toxicity. The present review thus critically analyses, discusses and interprets recently reported attempts and approaches to functionalize nanoparticles with biomolecules. Since there is no comprehensive and critical reviews on the applications of nanotechnology in bioremediation of MAHs/PAHs, this overview essentially captures the current global scenario and vision on the use and future prospects of biofunctionalized nanomaterials with respect to their strategic interactions involved at the nano/bio-interface essential to understand and decipher the structural and functional relationships and their impact on persistent hydrocarbon remediation.

Sensors, Biosensors, and Analytical Technologies for Aquaculture Water Quality

In aquaculture industry, fish, shellfish, and aquatic plants are cultivated in fresh, salt, or brackish waters. The increasing demand of aquatic products has stimulated the rapid growth of aquaculture industries. How to effectively monitor and control water quality is one of the key concerns for aquaculture industry to ensure high productivity and high quality. There are four major categories of water quality concerns that affect aquaculture cultivations, namely, (1) physical parameters, e.g., pH, temperature, dissolved oxygen, and salinity, (2) organic contaminants, (3) biochemical hazards, e.g., cyanotoxins, and (4) biological contaminants, i.e., pathogens. While the physical parameters are affected by climate changes, the latter three are considered as environmental factors. In this review, we provide a comprehensive summary of sensors, biosensors, and analytical technologies available for monitoring aquaculture water quality. They include low-cost commercial sensors and sensor network setups for physical parameters. They also include chromatography, mass spectrometry, biochemistry, and molecular methods (e.g., immunoassays and polymerase chain reaction assays), culture-based method, and biophysical technologies (e.g., biosensors and nanosensors) for environmental contamination factors. According to the different levels of sophistication of various analytical techniques and the information they can provide (either fine fingerprint, highly accurate quantification, semiquantification, qualitative detection, or fast screening), we will comment on how they may be used as complementary tools, as well as their potential and gaps toward current demand of real-time, online, and/or onsite detection.

A rapid dual-channel readout approach for sensing carbendazim with 4-aminobenzenethiol-functionalized core–shell Au@Ag nanoparticles

In this study, a 4-aminobenzenethiol-functionalized silver-coated gold nanoparticle (Au@Ag-4ABT NP) system was designed for the rapid sensing of carbendazim (CBZ) using a combination of naked-eye colorimetry and SERS dual-channel approach.

Mono-6-Deoxy-6-Aminopropylamino-β-Cyclodextrin on Ag-Embedded SiO2 Nanoparticle as a Selectively Capturing Ligand to Flavonoids

It has been increasingly important to develop a highly sensitive and selective technique that is easy to handle in detecting levels of beneficial or hazardous analytes in trace quantity. In this study, mono-6-deoxy-6-aminopropylamino-β-cyclodextrin (pr-β-CD)-functionalized silver-assembled silica nanoparticles (SiO2@Ag@pr-β-CD) for flavonoid detection were successfully prepared. The presence of pr-β-CD on the surface of SiO2@Ag enhanced the selectivity in capturing quercetin and myricetin among other similar materials (naringenin and apigenin). In addition, SiO2@Ag@pr-β-CD was able to detect quercetin corresponding to a limit of detection (LOD) as low as 0.55 ppm. The relationship between the Raman intensity of SiO2@Ag@pr-β-CD and the logarithm of the Que concentration obeyed linearity in the range 3.4-33.8 ppm (R2 = 0.997). The results indicate that SiO2@Ag@pr-β-CD is a promising material for immediately analyzing samples that demand high sensitivity and selectivity of detection.

Functionalized β-Cyclodextrin Immobilized on Ag-Embedded Silica Nanoparticles as a Drug Carrier

Cyclodextrins (CDs) have beneficial characteristics for drug delivery, including hydrophobic interior surfaces. Nanocarriers with β-CD ligands have been prepared with simple surface modifications as drug delivery vehicles. In this study, we synthesized β-CD derivatives on an Ag-embedded silica nanoparticle (NP) (SiO₂@Ag NP) structure to load and release doxorubicin (DOX). Cysteinyl-β-CD and ethylenediamine-β-CD (EDA-β-CD) were immobilized on the surface of SiO₂@Ag NPs, as confirmed by transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectrophotometry, and Fourier transform infrared (FTIR) spectroscopy. DOX was introduced into the β-CD on the SiO₂@Ag NPs and then successfully released. Neither cysteinyl-β-CD and EDA-β-CD showed cytotoxicity, while DOX-loaded cysteinyl-β-CD and EDA-β-CD showed a significant decrease in cell viability in cancer cells. The SiO₂@Ag NPs with β-CD provide a strategy for designing a nanocarrier that can deliver a drug with controlled release from modified chemical types.

Multilayer Ag-Embedded Silica Nanostructure as a Surface-Enhanced Raman Scattering-Based Chemical Sensor with Dual-Function Internal Standards

Surface-enhanced Raman scattering (SERS) spectroscopy is attractive in various detection analysis fields. However, the quantitative method using SERS spectroscopy remains as an area to be developed. The key issues in developing quantitative analysis methods by using SERS spectroscopy are the fabrication of reliable SERS-active materials such as nanoparticle-based structures and the acquisition of the SERS signal without any disturbance that may change the SERS signal intensity and frequency. Here, the fabrication of seamless multilayered core-shell nanoparticles with an embedded Raman label compound as an internal standard (ML_RLC dots) for quantitative SERS analysis is reported. The embedded Raman label compound in the nanostructure provides a reference value for calibrating the SERS signals. By using the ML_RLC dots, it is possible to gain target analyte signals of different concentrations while retaining the Raman signal of the internal standard. The ML_4-BBT dots, containing 4-bromobenzenethiol (4-BBT) as an internal standard, are successfully applied in the quantitative analysis of 4-fluorobenzenethiol and thiram, a model pesticide. Additionally, ratiometric analysis was proved practical through normalization of the relative SERS intensity. The ratiometric strategy could be applied to various SERS substrates for quantitative detection of a wide variety of targets.

SERS active Ag-SiO2 nanoparticles obtained by laser ablation of silver in colloidal silica

Highly stable Ag-SiO₂ nanoparticle composites were first obtained by laser ablation of a silver target in an aqueous colloidal dispersion of silica and examined by UV-vis absorption spectroscopy, transmission electron microscopy and Raman spectroscopy. The surface enhanced Raman scattering (SERS) activity of these nanocomposites was tested using 2,2'-bipyridine as a molecular reporter and excitation in the visible and near-IR spectral regions. The computational DFT approach provided evidence of ligand adsorption on positively charged adatoms of the silver nanostructured surface, in a very similar way to the metal/molecule interaction occurring in the corresponding Ag(I) coordination compound.

Thin silica shell coated Ag assembled nanostructures for expanding generality of SERS analytes

Surface-enhanced Raman scattering (SERS) provides a unique non-destructive spectroscopic fingerprint for chemical detection. However, intrinsic differences in affinity of analyte molecules to metal surface hinder SERS as a universal quantitative detection tool for various analyte molecules simultaneously. This must be overcome while keeping close proximity of analyte molecules to the metal surface. Moreover, assembled metal nanoparticles (NPs) structures might be beneficial for sensitive and reliable detection of chemicals than single NP structures. For this purpose, here we introduce thin silica-coated and assembled Ag NPs (SiO2@Ag@SiO2 NPs) for simultaneous and quantitative detection of chemicals that have different intrinsic affinities to silver metal. These SiO2@Ag@SiO2 NPs could detect each SERS peak of aniline or 4-aminothiophenol (4-ATP) from the mixture with limits of detection (LOD) of 93 ppm and 54 ppb, respectively. E-field distribution based on interparticle distance was simulated using discrete dipole approximation (DDA) calculation to gain insight into enhanced scattering of these thin silica coated Ag NP assemblies. These NPs were successfully applied to detect aniline in river water and tap water. Results suggest that SiO2@Ag@SiO2 NP-based SERS detection systems can be used as a simple and universal detection tool for environment pollutants and food safety.

Silver Nanoparticle Generators: Silicon Dioxide Microspheres

A green and simple approach has been developed to synthesize un-coated Ag nanoparticles (AgNPs) in situ on the surface of thiol-group-functionalized silica dioxide microspheres (TSMs) in the aqueous solution. As soon as the Ag⁺ ions attach onto the surface of TSMs, nucleation and growth of AgNPs can spontaneously complete within one minute without other reducing agents or capping agents. The main reason is that the self-assembled silane-layer formed by mercaptosilane molecules could reduce the Ag⁰ formation energy, transport electrons efficiently, improve the nucleation density, and protect AgNPs against oxidation. Thus, the supported AgNPs show excellent chemical/photochemical stability in air and solution. Meanwhile, the size of as-prepared AgNPs could be controlled by tuning the concentration of Ag⁺ ions. This process provides a general route to generate bare AgNPs on the surface of silica dioxide in situ, which might be extended to other materials and is promising in developing novel methodologies for making supported noble metal NPs with desired structure and properties.

SERS-Based Flavonoid Detection Using Ethylenediamine-β-Cyclodextrin as a Capturing Ligand

Ethylenediamine-modified β-cyclodextrin (Et-β-CD) was immobilized on aggregated silver nanoparticle (NP)-embedded silica NPs (SiO₂@Ag@Et-β-CD NPs) for the effective detection of flavonoids. Silica NPs were used as the template for embedding silver NPs to create hot spots and enhance surface-enhanced Raman scattering (SERS) signals. Et-β-CD was immobilized on Ag NPs to capture flavonoids via host-guest inclusion complex formation, as indicated by enhanced ultraviolet absorption spectra. The resulting SiO₂@Ag@Et-β-CD NPs were used as the SERS substrate for detecting flavonoids, such as hesperetin, naringenin, quercetin, and luteolin. In particular, luteolin was detected more strongly in the linear range 10-7 to 10-3 M than various organic molecules, namely ethylene glycol, β-estradiol, isopropyl alcohol, naphthalene, and toluene. In addition, the SERS signal for luteolin captured by the SiO₂@Ag@Et-β-CD NPs remained even after repeated washing. These results indicated that the SiO₂@Ag@Et-β-CD NPs can be used as a rapid, sensitive, and selective sensor for flavonoids.

Silver Nanoparticle-Embedded Thin Silica-Coated Graphene Oxide as an SERS Substrate

A hybrid of Ag nanoparticle (NP)-embedded thin silica-coated graphene oxide (GO@SiO₂@Ag NPs) was prepared as a surface-enhanced Raman scattering (SERS) substrate. A 6 nm layer of silica was successfully coated on the surface of GO by the physical adsorption of sodium silicate, followed by the hydrolysis of 3-mercaptopropyl trimethoxysilane. Ag NPs were introduced onto the thin silica-coated graphene oxide by the reduction of Ag⁺ to prepare GO@SiO₂@Ag NPs. The GO@SiO₂@Ag NPs exhibited a 1.8-fold enhanced Raman signal compared to GO without a silica coating. The GO@SiO₂@Ag NPs showed a detection limit of 4-mercaptobenzoic acid (4-MBA) at 0.74 μM.

Ag Nanoparticle-Functionalized Open-Ended Freestanding TiO₂ Nanotube Arrays with a Scattering Layer for Improved Energy Conversion Efficiency in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) were fabricated using open-ended freestanding TiO₂ nanotube arrays functionalized with Ag nanoparticles (NPs) in the channel to create a plasmonic effect, and then coated with large TiO₂ NPs to create a scattering effect in order to improve energy conversion efficiency. Compared to closed-ended freestanding TiO₂ nanotube array-based DSSCs without Ag or large TiO₂ NPs, the energy conversion efficiency of closed-ended DSSCs improved by 9.21% (actual efficiency, from 5.86% to 6.40%) with Ag NPs, 6.48% (actual efficiency, from 5.86% to 6.24%) with TiO₂ NPs, and 14.50% (actual efficiency, from 5.86% to 6.71%) with both Ag NPs and TiO₂ NPs. By introducing Ag NPs and/or large TiO₂ NPs to open-ended freestanding TiO₂ nanotube array-based DSSCs, the energy conversion efficiency was improved by 9.15% (actual efficiency, from 6.12% to 6.68%) with Ag NPs and 8.17% (actual efficiency, from 6.12% to 6.62%) with TiO₂ NPs, and by 15.20% (actual efficiency, from 6.12% to 7.05%) with both Ag NPs and TiO₂ NPs. Moreover, compared to closed-ended freestanding TiO₂ nanotube arrays, the energy conversion efficiency of open-ended freestanding TiO₂ nanotube arrays increased from 6.71% to 7.05%. We demonstrate that each component-Ag NPs, TiO₂ NPs, and open-ended freestanding TiO₂ nanotube arrays-enhanced the energy conversion efficiency, and the use of a combination of all components in DSSCs resulted in the highest energy conversion efficiency.