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Detection of enantiomers is a challenging problem in drug development as well as environmental and food quality monitoring where traditional optical detection methods suffer from low signals and sensitivity. Application of surface enhanced Raman scattering (SERS) for enantiomeric discrimination is a powerful approach for the analysis of optically active small organic or large biomolecules. In this work, for enantio-selective sensing we proposed the coupling of disposable chiral plasmonic shurikens supporting the chiral near-field distribution with SERS active silver nanoclusters. As a result of the plasmonic coupling significant difference in SERS response of optically active analytes is observed. This is hypothesized and confirmed by numerical simulations to be a consequence of the silver particles being excited by superchiral fields generated at the surface or the probe molecules achieving additional polarization. The plasmon coupling phenomena was found to be extremely sensitive to slight variations in shuriken geometry, silver nanostructured layer parameters, and SERS excitation wavelength(s). Designed structures were able to discriminate cysteine enantiomers at concentrations in the nanomolar range and probe biomolecular chirality, using a common Raman spectrometer within several minutes. The combination of disposable plasmonic substrates with specific near-field polarization can make the SERS enantiomer discrimination a commonly available technique using standard Raman spectrometers.

Chiral nanophotonic platforms provide a means of creating near fields with both enhanced asymmetric properties and intensities. They can be exploited for optical measurements that allow enantiomeric discrimination at detection levels greater than 6 orders of magnitude than is achieved with conventional chirally sensitive spectroscopic methods based on circularly polarized light. The optimal approach for exploiting nanophotonic platforms for chiral detection would be to use spectroscopic methods that provide a local probe of changes in the near field environment induced by the presence of chiral species. Here we show that surface enhanced Raman spectroscopy (SERS) is such a local probe of the near field environment. We have used it to achieve enantiomeric discrimination of chiral helicoid nanoparticles deposited on left and right-handed enantiomorphs of a chiral metafilm. Hotter electromagnetic hotspots are created for matched combinations of helicoid and metafilms (left-left and right-right), while mismatched combinations leads to significantly cooler electromagnetic hotspots. This large enantiomeric dependency on hotspot intensity is readily detected using SERS with the aid of an achiral Raman reporter molecule. In effect we have used SERS to distinguish between the different EM environments of the plasmonic diastereomers produced by mixing chiral nanoparticles and metafilms. The work demonstrates that by combining chiral nanophotonic platforms with established SERS strategies new avenues in ultrasensitive chiral detection can be opened.

Recently, the utilization of plasmon assistance was demonstrated to be a useful tool for promoting various chemical transformations. Plasmon triggering can enhance the reaction rate or change the r...

Detection of trace amounts of poorly water-soluble pharmaceuticals or related (bio)solutions represents a key challenge in environment protection and clinical diagnostics. However, this task is complicated by low concentrations of pharmaceuticals, complex sample matrices, and sophisticated sample preparative routes. In this work, we present an alternative approach on the basis of an on-line flow extraction procedure and SERS measurements performed in a microfluidic regime. The advantages of our approach were demonstrated using ibuprofen (Ibu), which is considered as a common pharmaceutical contaminant in wastewater and should be monitored in various bioliquids. The extraction of Ibu from water to the dichloromethane phase was performed with an optimized microfluidic mixer architecture. As SERS tags, lipophilic functionalized gold multibranched nanoparticles (AuMs) were added to the organic phase. After microfluidic extraction, Ibu was captured by the functionalized AuM surface and recognized by on-line SERS measurements with up to 10-8 M detection limit. The main advantages of the proposed approach can be regarded as its simplicity, lack of need for preliminary sample preparation, high reliability, the absence of sample pretreatment, and low detection limits.

The increase of CO2 levels is becoming a global problem in the 21st century, leading to current requests for new advanced materials and methods of CO2 utilisation. Here, we propose a hybrid plasmonic catalyst for the transformation of CO2 to carbonates in quantitative yields under ambient conditions, in contrast to the commonly applied elevated temperature and pressure. The proposed catalyst presents a combination of gold nanoparticles modified by triazabicyclodec-5-ene (TBD). TBD is responsible for CO2 fixation, forming a zwitterionic adduct near the plasmonic surface. The terminating stage, namely the interaction of the zwitterionic adduct with the epoxide, is pumped by plasmonic triggering and is the first example of plasmon-assisted CO2 cycloaddition. Taking advantage of the proposed catalyst, we achieved an unprecedented turnover number, turnover frequency, and apparent quantum yield, even in the case of air as a CO2 source and light as an energy input. Control experiments, including variation of illumination conditions and temperature, prove that the photochemical pathway proceeds through plasmon excitation.

The efficiency of green hydrogen production through photo- or electrochemical splitting of water depends strongly on the catalyst used. Several 2D materials have recently been proposed as effective catalysts or co-catalysts, and among them, oxygen-terminated MXenes deserve significant attention for both electro- and photo-induced water splitting. In this work, we described a hybrid photo-electrochemical approach based on the coupling of Ti3C2Tx MXene flakes on a plasmon-supported Au grating and light triggering of the electrocatalytic activity of the generated hybrid structure in a water splitting half reaction, namely, the hydrogen evolution reaction (HER). In particular, MXene flakes with both fluor and oxygen surface terminations were deposited on a periodic patterned gold surface that was capable of supporting surface plasmon-polariton (SPP) excitation under visible and near-infrared (NIR) light illumination. SPP excitation allows sub-diffraction focusing of light energy and effective enhancement of the electrocatalytic performance of Ti3C2Tx flakes. Under illumination, a significant enhancement of the HER kinetics was observed, as well as tuning of the HER rate-determining step from the Volmer step to the Heyrovsky step. In turn, we observed several-fold enhanced hydrogen evolution, which was attributed to plasmon-assisted hot charge carrier injection, with an additional contribution from the plasmon heating effect. The proposed Au grating/Ti3C2Tx hybrid structure allows utilization of the NIR part of the solar spectrum, which is commonly not used in water photolysis but achieves better efficiency in renewable energy-assisted green hydrogen production.

The nature of plasmon interaction with organic molecules is a subject of fierce discussion about thermal and non-thermal effects. Despite the abundance of physical methods for evaluating the plasmonic effects, chemical insight has not been reported yet. In this contribution, we propose a chemical insight into the plasmon effect on reaction kinetics using alkoxyamines as an organic probe through their homolysis, leading to the generation of nitroxide radicals. Alkoxyamines (TEMPO- and SG1-substituted) with well-studied homolysis behavior are covalently attached to spherical Au nanoparticles. We evaluate the kinetic parameters of homolysis of alkoxyamines attached on a plasmon-active surface under heating and irradiation at a wavelength of plasmon resonance. The estimation of kinetic parameters from experiments with different probes (Au–TEMPO, Au–SG1, Au–SG1–TEMPO) allows revealing the apparent differences associated with the non-thermal contribution of plasmon activation. Moreover, our findings underline the dependency of kinetic parameters on the structure of organic molecules, which highlights the necessity to consider the nature of organic transformations and molecular structure in plasmon catalysis., Kinetic study of alkoxyamine homolysis revealed the impact of non-thermal effects in plasmon-assisted reactions.

Two-dimensional (2D) transition-metal dichalcogenides have become promising candidates for surface-enhanced Raman spectroscopy (SERS), but currently very few examples of detection of relevant molecules are available. Herein, we show the detection of the lipophilic disease marker beta-sitosterol on few-layered MoTe2 films. The chemical vapor deposition (CVD)-grown films are capable of nanomolar detection, exceeding the performance of alternative noble-metal surfaces. We confirm that the enhancement occurs through the chemical enhancement (CE) mechanism via formation of a surface-analyte complex, which leads to an enhancement factor of approximate to 10(4), as confirmed by Fourier transform infrared (FTIR), UV-vis, and cyclic voltammetry (CV) analyses and density functional theory (DFT) calculations. Low values of signal deviation over a seven-layered MoTe2 film confirms the homogeneity and reproducibility of the results in comparison to noble-metal substrate analogues. Furthermore, beta-sitosterol detection within cell culture media, a minimal loss of signal over 50 days, and the opportunity for sensor regeneration suggest that MoTe2 can become a promising new SERS platform for biosensing.

In this work the preparation of fibers array with electric field switchable wettability is described. Piezoelectric properties of polyvinylidene fluoride (PVDF) and chemical reactivity of polymethylmethacrylate (PMMA) are used. Electrospinning blend fibers were fabricated from both of polymers and deposited on glass (non-conductive) and aluminum (conductive) substrates. The samples were modified with diazonium salts (ADT-C8F17), causing the hydrophobic surface characteristics. Applying an external electric field (EF) on these surfaces results in fibers rearrangement and dramatic changes in surface hydrophilicity. The wettability of the surface and the shape of the droplet were studied reporting the effect of varying the orientation of the electric field and using different substrates with different conductivity, which allowed us to control the shape of the deionized water drop interfering with the applied voltage. Moreover, reporting the results of shifting the polarity of the water by dissolving NaCl salt in different concentrations was reported.

Nanofibers are an attractive option in drug release, especially as antibacterial materials. However, there is no universal antibacterial material and little attention has been devoted to bacteria-nanofiber attachment. Poly(

The properties of materials at the nanoscale open up new methodologies for engineering prospective materials usable in high-end applications. The preparation of composite materials with a high content of an active component on their surface is one of the current challenges of materials engineering. This concept significantly increases the efficiency of heterogeneous processes moderated by the active component, typically in biological applications, catalysis, or drug delivery. Here we introduce a general approach, based on laser-induced optomechanical processing of silver colloids, for the preparation of polymer surfaces highly enriched with silver nanoparticles (AgNPs). As a result, the AgNPs are firmly immobilized in a thin surface layer without the use of any other chemical mediators. We have shown that our approach is applicable to a broad spectrum of polymer foils, regardless of whether they absorb laser light or not. However, if the laser radiation is absorbed, it is possible to transform smooth surface morphology of the polymer into a roughened one with a higher specific surface area. Analyses of the release of silver from the polymer surface together with antibacterial tests suggested that these materials could be suitable candidates in the fight against nosocomial infections and could inhibit the formation of biofilms with a long-term effect.

Supercapacitors based on nonresponsive polymer hydrogels are gaining significant attention due to their fabrication simplicity and high potential for wearable electronics. However, the use of smart hydrogels in supercapacitor design remains unexplored. In this work, a smart externally controlled supercapacitor based on a temperature-responsive hydrogel doped with polypyrrole nanotubes (PPyNTs) is proposed. The redistribution of PPyNTs in the poly(N-isopropylacrylamide) (PNIPAm) hydrogel can be reversibly controlled by light illumination or temperature increase, leading to on-demand formation/disruption of the nanotube conductive network, due to release/entrapping of the nanotubes from PNIPAm globule volume on surface. The switchable material was introduced in a supercapacitor design as an active and smart electrode, responsible for external control of charge transport and storage. The created device showed a switchable supercapacitor performance with an ability to significantly and rapidly change capacity under heating/cooling or light illumination. The external trigger was applied for static or dynamic control of supercapacitor behavior: prolongation of discharge time (with constant electric loading) or vice-versa pronounced acceleration of supercapacitor discharge. The proposed smart material-based supercapacitor can find a range of attractive applications in backup energy storage or high power pulse generation.

Bacterial environmental colonization and subsequent biofilm formation on surfaces represents a significant and alarming problem in various fields, ranging from contamination of medical devices up to safe food packaging. Therefore, the development of surfaces resistant to bacterial colonization is a challenging and actively solved task. In this field, the current promising direction is the design and creation of nanostructured smart surfaces with on-demand activated amicrobial protection. Various surface activation methods have been described recently. In this review article, we focused on the “physical” activation of nanostructured surfaces. In the first part of the review, we briefly describe the basic principles and common approaches of external stimulus application and surface activation, including the temperature-, light-, electric- or magnetic-field-based surface triggering, as well as mechanically induced surface antimicrobial protection. In the latter part, the recent achievements in the field of smart antimicrobial surfaces with physical activation are discussed, with special attention on multiresponsive or multifunctional physically activated coatings. In particular, we mainly discussed the multistimuli surface triggering, which ensures a better degree of surface properties control, as well as simultaneous utilization of several strategies for surface protection, based on a principally different mechanism of antimicrobial action. We also mentioned several recent trends, including the development of the to-detect and to-kill hybrid approach, which ensures the surface activation in a right place at a right time.

The design of the icephobic surface represents an urgent challenge in the field of surface engineering with high application potential. In this work, we proposed the introduction of icephobic surfa...

The action of fuel cells with proton-exchanged membranes (PEMs) requires the implementation of the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) on the opposite sides of the PEMs. Recently, based on several models of electrochemical reactions a significant decrease in the thermodynamic activation barrier of both reactions under plasmon assistance was reported. In this work, we propose the design of a PEM fuel cell with a plasmon-active catalytic surface providing plasmonic triggering and enhancement of fuel cell efficiency. In particular, we deposited bimetallic (Au@Pt) nanostructures on the PEM surface and integrated them into the fuel cell design. Plasmon excitation occurs on the Au nanostructures under light illumination at the corresponding NIR wavelength, while the Pt shell is responsible for the introduction of catalytic sites. Light illumination results in a significant enhancement of the electric current produced by the fuel cell. In particular, the electric current increased several times. Control experiments indicated that the observed enhancement takes place only when the light wavelength is in compliance with the plasmon absorption band and the contribution from thermal effects is negligible. The present approach for the introduction of plasmon assistance into the design of advanced fuel cells makes them suitable for increasing the fuel cell efficiency under sunlight.

The chiral recognition of organic compounds is of vital importance in the field of pharmacology and medicine. Unfortunately, the common analytical routes used in this field are significantly restricted by time spent and equipment demands. In this work, we propose an unprecedented alternative, aimed at enantiomer discrimination and estimation of their concentrations in an uncomplicated and instantaneous manner. The proposed approach is based on the creation of an optical fiber probe with two pronounced plasmonic bands attributed to gold and silver. The gold or silver surfaces were grafted with moieties, able to enunciating entrap chiral amines from solution, resulting in a wavelength shift corresponding to each plasmonic metal. As a model compound of chiral amine, we chose the DOPA, also taking in mind its high medical relevancy. For chiral detection, the optical fiber probe was simply immersed in an analytical solution of DOPA, and the selective shift of gold or silver plasmon bands was observed in the reflected light depending on DOPA chirality. The observed shifts depend on the concentration of DOPA enantiomers. In the case of a racemic mixture, the shifts of both plasmonic bands emerge, making possible the simultaneous determination of enantiomer concentrations and their ratio. The analytical cycle takes several minutes and requires very simple laboratory equipment.

Remote detection of hydrogen, without the utilization of electronic component or elevated temperature, is one of the hot topics in the hydrogen technology and safety. In this work, the design and realization of the optical fiber-based hydrogen sensor with unique characteristics are proposed. The proposed sensor is based on the gold-coated multimode fiber, providing the plasmon properties, decorated by the IRMOF-20 layer with high selectivity and affinity toward hydrogen. The IRMOF-20 layer was grown by a surface-assisted technique, and its formation and properties were studied using X-ray photoelectron spectroscopy, Raman, X-ray diffraction, and Brunauer-Emmett-Teller techniques. Simultaneous ellipsometry results indicate the apparent changes of the refractive index of the IRMOF-20 layer due to hydrogen sorption. As results, the presence of hydrogen led to the pronounced changes of plasmon band wavelength position as well as its intensity increase. The proposed hydrogen sensors were favorably distinguished by a high response/recovery rate, excellent selectivity toward the hydrogen, very low temperature dependency, functionality at room or lower temperature, insensitivity toward the humidity, and the presence of CO2, CO, or NO2. Additionally, the proposed hydrogen sensor showed good reversibility, reproducibility, and long-term stability.

In this work, we propose the preparation and investigation of advanced microfluidic surface-enhanced Raman spectroscopy (SERS) chip with a design allowing high SERS enhancement and analysis reprodu...

The preparation of light-activated hybrid antibacterial agent combining the porphyrin molecules, bound to the silver nanoparticles (AgNPs) surface is reported. AgNPs were synthesized by N-methyl-2-pyrrolidone-initiated reduction without additional reducing agents. The chemical structure of protoporphyrin IX was modified with the aim to introduce thiol groups. The size distribution and shape features of AgNPs were checked using TEM and HRTEM microscopies. The introduction of thiol groups into the porphyrin was proved by IR spectroscopy. The AgNPs-porphyrin binding was performed in solution and confirmed by fluorescence quenching, Raman spectroscopy and energy-filtered transmission electron microscopy (EFTEM). The antibacterial tests were performed against S. epidermidis and E. coli upon to LED illumination and in the dark. The synergetic effect of AgNPs and porphyrin as well as light activation of the created antibacterial conjugates were observed.

Lithium-oxygen thin films were deposited by atomic layer deposition (ALD) on the surface of silicon and stainless-steel using lithium bis (trimethylsilyl) amide (LiHMDS) and different counter-reagents (water, ozone, oxygen plasma). The deposited films were non-stable at storage in the air atmosphere. Results of scanning electron microscopy showed that films show a tendency to crystallization and peeling from the substrate surface. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy revealed that films mainly consist of LiOH/Li2CO3. Coating the surface of lithium-oxygen films with an aluminum oxide layer using the ALD trimethylaluminum (TMA) and water as precursors did not lead to a significant improvement in stability. Nevertheless, the stable films can be obtained using ALD supercycles consisting of sequential pulsing of LiHMDS-water-TMA-water at 250°C.

In this work, we proposed the functionalization of a surface plasmon-polariton (SPP)-supported gold grating surface with the metal-organic framework (MOF-5) for sensitive, selective and reproducible surface-enhanced Raman scattering (SERS) detection of organophosphorus pesticides. Homogeneous distribution of plasmon intensity along the Au grating surface ensures the high reproducibility of SERS results (deviation of Raman peak intensity does not exceed the 4% along the sample). The surface-assisted growth of thin MOF-5 film was accomplished in two steps procedure: (i) covalent grafting by 4-carboxyphenyl groups and (ii) the immersion of samples in the mother liquid of MOF-5. Proposed SERS chip proved itself to be a perfect analytical probe for the detection of organophosphorus pesticides with high reliability and low detection limit up to 10−12 M. Moreover, selective detection and recognition of several relevant organic contaminants (azo-dye, mycotoxin, and pesticide) from the simulated soil was successfully demonstrated. All SERS measurements were performed using portable Raman spectrometer and can easily be expanded to environmental conditions. Our work combines the high affinity of organic contaminants to the MOF-5 with excellent plasmonic excitation on the surface plasmon-polariton supported structure and shows the way to the realization of closed-to-ideal analytical SERS chip.

Label-free SERS-based detection of DNA is considered as one of the most prospective analytical methods for portable and express bioanalysis. In this work, the SERS platform based on the functional surface plasmon polariton supported ordered structure is proposed as an extremely convenient and effective tool for the detection of specific DNA sequences. The designed SERS structure makes possible DNA analyses in near-real time using the portable Raman spectrometer, with high reproducibility and accuracy of the results and the detection limits of the order of 10−14 M. In order to overcome challenges, connected to meticulous affiliation and evaluation of Raman signals, principal component analysis (PCA) of raw SERS data was used for data evaluation. SERS results reproducibility was achieved through the creation of a periodical structure with homogenous distribution of plasmon energy, when the analysis functionality was implemented through the grafting of the oligonucleotide to gold surface and its further interaction with complementary, mispaired and noncomplementary oligonucleotides. It was demonstrated experimentally that with the SERS platform it is possible not only to detect and recognize pure DNA but also the simultaneous presence of complementary and mispaired DNA with estimation of their relative concentrations. Moreover, the developed SERS sensor demonstrated the perfect stability over 3 months storage period without loss of functionality.

The excitation of localized plasmon resonance on nanoparticles followed by the interaction with organic molecules leads to new pathways of chemical reactions. Although a number of physical factors (temperature, illumination regime, type of nanoparticles, etc.) are affecting this process, the role of the chemical factors is underestimated. Challenging this assumption, here we studied the kinetic of plasmon-induced homolysis of five alkoxyamines (AAs) with different chemical and electronic structures using electron paramagnetic resonance (EPR). The kinetic data revealed the dependence of plasmonic homolysis rate constant (kd) with the HOMO energy of AAs, which cannot be described by the kinetic parameters derived from thermal homolysis experiments. The observed trend in kd allowed to suggest the key role of intramolecular excitation mechanism supported by the TDFDT calculations, additional spectroscopic characterization, and control experiments. Our work sheds light on the role of the electronic structure of organic molecules in plasmonic chemistry.

The excitation of localized plasmon resonance on nanoparticles followed by the interaction with organic molecules leads to new pathways of chemical reactions. Although a number of physical factors (temperature, illumination regime, type of nanoparticles, etc.) are affecting this process, the role of the chemical factors is underestimated. Challenging this assumption, here we studied the kinetic of plasmon-induced homolysis of five alkoxyamines (AAs) with different chemical and electronic structures using electron paramagnetic resonance (EPR). The kinetic data revealed the dependence of plasmonic homolysis rate constant (kd) with the HOMO energy of AAs, which cannot be described by the kinetic parameters derived from thermal homolysis experiments. The observed trend in kd allowed to suggest the key role of intramolecular excitation mechanism supported by the TDFDT calculations, additional spectroscopic characterization, and control experiments. Our work sheds light on the role of the electronic structure of organic molecules in plasmonic chemistry.

Novel photoactive and enzymatically active nanomotors were developed for efficient organic pollutant degradation. The developed preparation route is simple and scalable. Light-absorbing polypyrrole nanoparticles were equipped with a bi-enzyme [glucose oxidase/catalase (GOx/Cat)] system enabling the simultaneous utilization of light and glucose as energy sources for jet-induced nanoparticle movement and active radical production. The GOx utilizes glucose to produce hydrogen peroxide, which is subsequently degraded by Cat, resulting in the generation of active radicals and/or oxygen bubbles that propel the particles. Uneven grafting of GOx/Cat molecules on the nanoparticle surface ensures inhomogeneity of peroxide creation/degradation, providing the nanomotor random propelling. The nanomotors were tested for their ability to degrade chlorophenol, under various experimental conditions, that is, with and without simulated sunlight illumination or glucose addition. In all cases, degradation was accelerated by the presence of the self-propelled nanoparticles or light illumination. Light-induced heating also positively affects enzymatic activity, further accelerating nanomotor diffusion and pollutant degradation. In fact, the chemical and photoactivities of the nanoparticles led to more than 95% removal of chlorophenol in 1 h, without any external stirring. Finally, the quality of the purified water and the extent of pollutant removal were checked using an eco-toxicological assay, with demonstrated significant synergy between glucose pumping and sunlight illumination.

Plasmon assistance promotes a range of chemical transformations by decreasing their activation energies. In a common case, thermal and plasmon assistance work synergistically: higher temperature results in higher plasmon-enhanced catalysis efficiency. Herein, we report an unexpected tenfold increase in the reaction efficiency of surface plasmon-assisted Huisgen dipolar azide–alkyne cycloaddition (AAC) when the reaction mixture is cooled from room temperature to −35 °C. We attribute the observed increase in the reaction efficiency to complete plasmon-induced annihilation of the reaction barrier, prolongation of plasmon lifetime, and decreased relaxation of plasmon-excited-states under cooling. Furthermore, control quenching experiments supported by theoretical calculations indicate that plasmon-mediated substrate excitation to an electronic triplet state may play the key role in plasmon-assisted chemical transformation. Last but not least, we demonstrated the possible applicability of plasmon assistance to biological systems by AAC coupling of biotin to gold nanoparticles performed at −35 °C., The decrease of reaction temperature can potentially lead to an increase of plasmon-assisted catalytic efficiency.

Amphiphilic nanoparticles (NPs) with a spatially selective distribution of grafted functional groups have great potential in the field of sensing, advanced imaging, and therapy due to their unique surface properties. The main techniques for the spatially selective functionalization of NPs utilize the surface-assisted approaches, which significantly restrict their production throughput. In this work, we propose an alternative plasmon-based route for the spatially selective grafting of anisotropic gold nanorods (AuNRs) using iodonium and diazonium salts. Utilization of longer laser wavelengths leads to the excitation of longitudinal plasmon resonances on AuNR tips, plasmon-assisted homolysis of the C-I bond in iodonium salts and the formation of aryl radicals, which are further grafted to the tips of AuNRs. The sides of AuNRs were subsequently decorated through spontaneous diazonium surface grafting. As a result, the AuNRs with spatially separated functional groups were prepared in a versatile way, primarily in solution and without the need for a sophisticated technique of NP immobilization or surface screening. The versatility of the proposed approach was proved on three kinds of AuNRs with different architectures and wavelength positions of plasmon absorption bands. Moreover, the applicability of the prepared amphiphilic AuNRs was shown by efficient trapping and SERS sensing of amphiphilic biomolecules.