News On Plasmonics

In this days, Light: Science & Applications Journal publishes a new paper entitled as “Simple experimental procedures to distinguish photothermal from hot-carrier processes in plasmonics”

Abstract– Light absorption and scattering of plasmonic metal nanoparticles can lead to non-equilibrium charge carriers, intense electromagnetic near-fields, and heat generation, with promising applications in a vast range of fields, from chemical and physical sensing to nanomedicine and photocatalysis for the sustainable production of fuels and chemicals. Disentangling the relative contribution of thermal and non-thermal contributions in plasmon-driven processes is, however, difficult. Nanoscale temperature measurements are technically challenging, and macroscale experiments are often characterized by collective heating effects, which tend to make the actual temperature increase unpredictable.
This work is intended to help the reader experimentally detect and quantify photothermal effects in plasmon-driven chemical reactions, to discriminate their contribution from that due to photochemical processes and to cast a critical eye on the current literature. To this aim, we review, and in some cases propose, seven simple experimental procedures that do not require the use of complex or expensive thermal microscopy techniques. These proposed procedures are adaptable to a wide range of experiments and fields of research where photothermal effects need to
be assessed, such as plasmonic-assisted chemistry, heterogeneous catalysis, photovoltaics, biosensing, and enhanced molecular spectroscopy.




News On Plasmonics

In this days, Science China Physics, Mechanics & Astronomy Journal publishes a new paper entitled as “Chiral plasmonics and enhanced chiral light-matter interactions”

Chirality, which describes the broken mirror symmetry in geometric structures, exists macroscopically in our daily life as well as microscopically down to molecular levels. Correspondingly, chiral molecules interact differently with circularly polarized light exhibiting opposite handedness (left-handed and right-handed). However, the interaction between chiral molecules and chiral light is very weak. In contrast, artificial chiral plasmonic structures can generate “super-chiral” plasmonic near-field, leading to enhanced chiral light-matter (or chiroptical) interactions. The “super-chiral” near-field presents different amplitude and phase under opposite handedness incidence, which can be utilized to engineer linear and nonlinear chiroptical interactions. Specifically, in the interaction between quantum emitters and chiral plasmonic structures, the chiral hot spots can favour the emission with a specific handedness. This article reviews the state-of-the-art research on the design, fabrication and chiroptical response of different chiral plasmonic nanostructures or metasurfaces. This review also discusses enhanced chiral light-matter interactions that are essential for applications like chirality sensing, chiral selective light emitting and harvesting. In the final part, the review ends with a perspective on future directions of chiral plasmonics.




News On Plasmonic sensors

In this days, Nanophotonics Journal Publishes a new paper entitled as “Direct detection of charge and discharge process in supercapacitor by fiber-optic LSPR sensors”

Supercapacitors with high power density, ultralong lifespan and wide range operating temperature have drawn significant attention in recent years. However, monitoring the state of charge in supercapacitors in a cost-effective and flexible way is still challenging. Techniques such as transmission electron microscopy and X-ray diffraction can analyze the characteristics of supercapacitor well. But with large size and high price, they are not suitable for daily monitoring of the supercapacitors’ operation. In this paper, a low cost and easily fabricated fiber-optic localized surface plasmon resonance (LSPR) probe is proposed to monitor the state of charge of the electrode in a supercapacitor. The Au nanoparticles were loading on the fiber core as LSPR sensing region. In order to implant the fiber in the supercapacitor, a reflective type of fiber sensor was used. The results show that this tiny fiber-optic LSPR sensor can provide online monitoring of the state of charge during the charging and discharging process in situ. The intensity shift in LSPR sensor has a good linear relationship with the state of charge calculated by standard galvanostatic charging and discharging test. In addition, this LSPR sensor is insensitive to the temperature change, presenting a great potential in practical applications.




Congratulations for Our new paper in journal of Optical material express

Blue-shift ultrasensitivity using rhombus-shape plasmonic crystal on Si3N4 membrane

Foozieh Sohrabi1,2, Dordaneh Etezadi2, Yasaman Jahani2, Ershad Mohammadi2,3, Bahareh Ghadiani2, Mahdi Tamizifar2, Seyedeh Mehri Hamidi1,*

Harnessing ultrasensitivity from optical structures to detect tiny changes in the targeted samples is the main goal of scientists in the field of sensor design.  In this study, an uncommon rhombus-shape plasmonic structure is proposed for providing blue-shift ultrasensitivity. The physical origin of this optical response relies on multi-faces of gold rhombus and their electromagnetic coupling with their induced images in a high-refractive-index substrate (Si3N4). A characteristic of blue-shift emerges as the Fano resonance in the reflection spectrum. We have experimentally shown that this novel structure has the surface sensitivity to the refractive index difference in the order of 10-5. This characteristic have been applied for non- and conditioned- cell culture medium with refractive difference in this order. Such a level of sensitivity is interesting for enhanced fingerprinting of minute quantities of targeted molecules and the interfacial ion redistribution.




News On Plexcitonics

In this days, Nature Communications Journal publishes a new paper entitled as “Nonlinear plasmon-exciton coupling enhances sum-frequency generation from a hybrid metal/semiconductor nanostructure”

The integration of metallic plasmonic nanoantennas with quantum emitters can dramatically enhance coherent harmonic generation, often resulting from the coupling of fundamental plasmonic fields to higher-energy, electronic or excitonic transitions of quantum emitters. The ultrafast optical dynamics of such hybrid plasmon–emitter systems have rarely been explored. Here, we study those dynamics by interferometrically probing nonlinear optical emission from individual porous gold nanosponges infiltrated with zinc oxide (ZnO) emitters. Few-femtosecond time-resolved photoelectron emission microscopy reveals multiple longlived localized plasmonic hot spot modes, at the surface of the randomly disordered nanosponges, that are resonant in a broad spectral range. The locally enhanced plasmonic near-field couples to the ZnO excitons, enhancing sum-frequency generation from individual hot spots and boosting resonant excitonic emission. The quantum pathways of the coupling are uncovered from a two-dimensional spectrum correlating fundamental plasmonic excitations to nonlinearly driven excitonic emissions. Our results offer new opportunities for enhancing and coherently controlling optical nonlinearities by exploiting nonlinear plasmonquantum emitter coupling.




Congratulations for our new paper in journal of نانومقیاس

برهم‌کنش نانومقیاس اتم-پلاسمون در مرز جدایی لایه نازک
طلا-بخار فلز قلیایی

محمد مصلح، ملیحه رنجبران، سیده مهری حمیدی

امکان محصور کردن نور در ابعاد نانو در ساختارهای پلاسمونی اثرات منحصری به فردی از جمله تقویت برهم‌کنش‌های نور-ماده را به همراه دارد. از این تقویت می‌توان به خوبی در سامانه‌های تشدیدی جفت‌شده اتمی-پلاسمونی بهره گرفت. در چنین سامانه جفت‌شده‌ای، تشدید پلاسمونی پهن در مقابل تشدید اتمی باریک قرار گرفته و امکان طیف‌نگاری بازتابی با قابلیت تفکیک ترازهای اتم را فراهم می‌سازد. در این مقاله با مدل‌سازی طیف بازتابی از لایه نازک طلا در مجاورت بخار فلز قلیایی روبیدیوم در هندسه کرشمن، تغییر شکل خطوط جذبی در طیف ترازهای ساختار فوق‌ریز اتم بررسی شد. با تنظیم زاویه نور فرودی به نحوی که بتوان فرکانس تشدید مد پلاسمون-پلاریتون را نسبت به فرکانس خطوط جذب تشدیدی اتم تغییر داد، پدیده‌های گذار القایی و هم چنین تشدید .فانو در طیف بازتاب به وضوح مشاهده شد




News On Plasmonic Biosensors

In this days, ACS Nano Journal publishes a new paper entitled as “Dual-Functional Plasmonic Photothermal Biosensors for Highly Accurate Severe Acute Respiratory Syndrome Coronavirus 2 Detection”

ABSTRACT: The ongoing outbreak of the novel coronavirus disease (COVID-19) has spread globally and poses a threat to public health in more than 200 countries. Reliable laboratory diagnosis of the disease has been one of the foremost priorities for promoting public health interventions. The routinely used reverse transcription polymerase chain reaction (RT-PCR) is currently the reference method for COVID-19 diagnosis. However, it also reported a number of false-positive or -negative cases, especially in the early stages of the novel virus outbreak. In this work, a dual-functional plasmonic biosensor combining the plasmonic photothermal (PPT) effect and localized surface plasmon resonance (LSPR) sensing transduction provides an alternative and promising solution for the clinical COVID-19 diagnosis. The two-dimensional gold nanoislands (AuNIs) functionalized with complementary DNA receptors can perform a sensitive detection of the selected sequences from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) through nucleic acid hybridization. For better sensing performance, the thermoplasmonic heat is generated on the same AuNIs chip when illuminated at their plasmonic resonance frequency. The localized PPT heat is capable to elevate the in situ hybridization temperature and facilitate the accurate discrimination of two similar gene
sequences. Our dual-functional LSPR biosensor exhibits a high sensitivity toward the selected SARS-CoV-2 sequences with a lower detection limit down to the concentration of 0.22 pM and allows precise detection of the specific target in a multigene mixture. This study gains insight into the thermoplasmonic enhancement and its applicability in the nucleic acid tests and viral disease diagnosis.




Congratulations for our new paper in journal of Optical and quantum electronics

Manipulating Plasmon-Exciton Interactions in the Plasmonic Waveguide Structure based on the Dispersion Relations Concept

M. Mirahmadi, T. Mahinroosta, S. M. Hamidi*

We have introduced a new two-dimensional plexcitonic waveguide structure based on two dimensional plasmonic crystal covered by rhodamine B (RhB) and poly-vinyl-pirolydone (PVP) layer. The study ability to focus and confine optical energy in subwavelength regions at the nanoscale have been subjects of research recently. For this purpose, we fabricate gold nano structure by nano imprint lithography and cover it by RhB dye and PVP layer. To investigate propagation constant and thus light confinement in Gold/ RhB region, we use dispersion relation concept, by the aid of kramers-kronig relation in theoretical end experimental way, which confirms that we have enhance in light matter interaction in plexcitonic structure which is very useful for many applications such as plexcitonic switches.




News On Magneto-plasmonic

In this days, Light: Science & Applications Journal publishes a new paper entitled as “Enhanced magnetic modulation of light polarization exploiting hybridization with multipolar dark plasmons in magnetoplasmonic nanocavities”

Abstract – Enhancing magneto-optical effects is crucial for reducing the size of key photonic devices based on the non-reciprocal propagation of light and to enable active nanophotonics. Here, we disclose a currently unexplored approach that exploits hybridization with multipolar dark modes in specially designed magnetoplasmonic nanocavities to achieve a
large enhancement of the magneto-optically induced modulation of light polarization. The broken geometrical symmetry of the design enables coupling with free-space light and hybridization of the multipolar dark modes of a plasmonic ring nanoresonator with the dipolar localized plasmon resonance of the ferromagnetic disk placed inside the ring. This hybridization results in a low-radiant multipolar Fano resonance that drives a strongly enhanced magneto-optically induced localized plasmon. The large amplification of the magneto-optical response of the nanocavity is the result of the large magneto-optically induced change in light polarization produced by the strongly enhanced radiant magneto-optical dipole, which is achieved by avoiding the simultaneous enhancement of reemitted light with incident polarization by the multipolar Fano resonance. The partial compensation of the magnetooptically induced polarization change caused by the large re-emission of light with the original polarization is a critical limitation of the magnetoplasmonic designs explored thus far and that is overcome by the approach proposed here.




News on Plasmonics

In this days, Chemical Physics Journal published a paper entitled as “Nanoelectrode-emitter spectral overlap amplifies surface enhanced electrogenerated chemiluminescence”

Electrogenerated chemiluminescence (ECL) is a promising technique for low concentration molecular detection. To improve the detection limit, plasmonic nanoparticles have been proposed as signal boosting antennas to amplify ECL. Previous ensemble studies have hinted that spectral overlap between the nanoparticle antenna and the ECL emitter may play a role in signal enhancement. Ensemble spectroscopy, however, cannot resolve heterogeneities arising from colloidal nanoparticle size and shape distributions, leading to an incomplete picture of the impact of spectral overlap. Here, we isolate the effect of nanoparticle-emitter spectral overlap for a model ECL system, coreaction of tris(2,2bipyridyl) dichlororuthenium (II) hexahydrate and tripropylamine, at the single-particle level while minimizing other factors influencing ECL intensities. We found a 10-fold enhancement of ECL among 952 gold nanoparticles. This signal enhancement is attributed exclusively to spectral overlap between the nanoparticle and the emitter. Our study provides new mechanistic insight into plasmonic enhancement of ECL, creating opportunities for low concentration ECL sensing.