Photothermal Excitation Research Articles

Nonlinear Thermoplasmonics in Graphene Nanostructures.

The linear electronic dispersion relation of graphene endows the atomically thin carbon layer with a large intrinsic optical nonlinearity, with regard to both parametric and photothermal processes. While plasmons in graphene nanostructures can further enhance nonlinear optical phenomena, boosting resonances to the technologically relevant mid- and near-infrared (IR) spectral regimes necessitates patterning on ∼10 nm length scales, for which quantum finite-size effects play a crucial role. Here we show that thermoplasmons in narrow graphene nanoribbons can be activated at mid- and near-IR frequencies with moderate absorbed energy density, and furthermore can drive substantial third-harmonic generation and optical Kerr nonlinearities. Our findings suggest that photothermal excitation by ultrashort optical pulses offers a promising approach to enable nonlinear plasmonic phenomena in nanostructured graphene that avoids potentially invasive electrical gating schemes and excessive charge carrier doping levels.

A novel approach to analyzing the stability of physical fields in semiconductor materials under photothermal excitation

This work employs a new approach to study the stability heating effects caused by the thermal influence of photothermal theory. In addition, our investigation identified stability mechanisms occurring at the limits of the semiconductor (SC) medium. We have examined the interactions of photosensitive, thermic, and mechanical waves inside a medium's half-space using the theory of photo-thermoelectricity. The establishment of governing equations is achieved by utilizing one-dimensional elastic-optoelectronic deformation. Utilizing advanced mathematical techniques, such as Laplace transform with short-time approximations, we transform the foremost physical domains to the frequency domain, imposing conditions on the free surface of the elastic medium to enhance stability. Employing the homotopy perturbation method, the stability of the main physical quantities is obtained, with silicon as the chosen material. Graphical analyses and discussions elucidate the physical fields after applying the numerical Laplace inverse technique with the effect of some factors like the thermo-electric coupling parameter. Comparisons between some materials like silicon and germanium are being investigated. The stability of main physical quantities with various values of eigenvalues approaches are obtained with the dual solutions of the eigenvalues.

Vibration Study of Functionally Graded Microcantilever Beams in Fluids Based on Modified Couple Stress Theory by Considering the Physical Neutral Plane

Theoretical studies on the vibration of microcantilever beams in fluids, which are commonly used in micro- and nanoelectromechanical systems (MEMS/NEMS). When microcantilever beams are subjected to photo-thermal excitation, they show that the material properties such as the dynamic response and the one-dimensional temperature field will show significant differences from the macroscopic properties when the size appearance of the microbeam decreases to the scale below a dozen micrometers. In this paper, by correcting the scale constants of the beams, the photothermal vibration model of the microbeam is established using the physical neutral plane theory. The one-dimensional heat transfer equations and scale-corrected temperature field of the microcantilever beam under laser excitation are derived, which are solved by Galerkin’s method, based on the theory of thermoelasticity, the hydrodynamic model of the beams vibrating in incompressible liquids proposed by Sader et al. and the theory of Euler–Bernoulli beams. The equations governing the vibration of micro-cantilever beams corrected for scale effects in different fluids when subjected to photothermal excitation are obtained. The results show that the temperature field, resonant frequency, and quality factor of the microbeam will have a significant upward drift when the size of the microbeam is close to the scale parameter, and the scale effect has a non-negligible influence on the macroscopic performance parameters; the upward drift is gradually weakening when the thickness to scale ratio gradually increases. Finally, the property of the beam is almost the same as that of the theory when the thickness of the beam is 10 times the scale constant. The correction of the theory by the scale effect is insignificant.

Optimization and Artifacts of Photothermal Excitation of Microresonators

AbstractThe excitation of microresonators using focused intensity modulated light, known as photothermal excitation, is gaining significant attention due to its capacity to accurately excite microresonators without distortions, even in liquid environments, which is driving key advancements in atomic force microscopy and related technologies. Despite progress in the development of coatings, the conversion of light into mechanical movement remains largely inefficient, limiting resonator movements to tens of nanometers even when milliwatts of optical power are used. Moreover, how photothermal efficiency depends on the relative position of a microresonator along the propagation axis of the photothermal beam remains poorly studied, hampering the understanding of the conversion of light into mechanical motion. Here, photothermal measurements are performed in air and water using cantilever microresonators and a custom‐built picobalance, to determine how photothermal efficiency changes along the propagation beam axis. It is identified that far out‐of‐band laser emission can lead to visual misidentification of the beam waist, resulting in a drop of photothermal efficiency of up to one order of magnitude. The measurements also unveil that the beam waist is not always the position of highest photothermal efficiency, and can reduce the efficiency up to 20% for silicon cantilevers with trapezoidal cross section.

Bottom-Illuminated Photothermal Nanoscale Chemical Imaging with a Flat Silicon ATR in Air and Liquid.

We demonstrate a novel approach for bottom-illuminated atomic force microscopy and infrared spectroscopy (AFM-IR). Bottom-illuminated AFM-IR for measurements in liquids makes use of an attenuated total reflection setup where the developing evanescent wave is responsible for photothermal excitation of the sample of interest. Conventional bottom-illuminated measurements are conducted using high-refractive-index prisms. We showcase the advancement of instrumentation through the introduction of flat silicon substrates as replacements for prisms. We illustrate the feasibility of this technique for bottom-illuminated AFM-IR in both air and liquid. We also show how modern rapid prototyping technologies enable commercial AFM-IR instrumentation to accept these new substrates. This new approach paves the way for a wide range of experiments since virtually any established protocol for Si surface functionalization can be applied to this sample carrier. Furthermore, the low unit cost enables the rapid iteration of experiments.

Elasto-Thermodiffusive Microtemperature Model Induced by a Mechanical Ramp-Type of Nanoscale Photoexcited Semiconductor

ABSTRACT In this study, a novel theoretical approach to describe thermo-optical elastic materials is proposed. This formulation offers insights into the relationship between plasma waves and thermomechanical waves when the microtemperature properties of semiconductor materials such as silicon are taken into account. The proposed model involves incorporating the concept of microtemperature effect according to photothermal (PT) excitation processes in nonlocal photo-thermoelasticity. The investigation of the electron-hole interaction concerning the elasto-thermodiffusion (ETD) theory in the context of thermoelastic (TD) and electronic (ED) deformation is the main focus of the work. The advanced model is utilized to analyze how the mechanical loading of ramp-like structures impacts the unrestricted nonlocality semiconductor material on a free outer plane. The Laplace transform approach in one-dimensional (1D) provides an analytical solution for main non-dimensional thermo-photo-elastic fields (the hole charge carrier field, the displacement (acoustic) wave, thermal wave, and plasma wave (carrier density). The primary fields in the Laplace domain are obtained analytically, and boundary conditions are established using a mechanical ramp type. Using a numerical inverse Laplace transform, full time domain solutions for the fundamental fields are obtained numerically according to the Riemann-sum approximation approach. The graphical representations illustrate and discuss the outcomes of the main physical fields.

Semiconductor elastic medium with electromagnetic porosity, photothermal excitation, and the Thomson effect

The Thomson influence on semiconductors can be studied by investigating the connection between the presence of thermoelectric and magnetic fields and porosity and the photothermal transport mechanism. Elastic waves, voids, magnetic fields, and thermoelectric effects in plasma are investigated. The governing equations were analyzed for a uniformly distributed and isotropic medium under two-dimensional [electronic and elastic (plasmaelastic)] deformations. The charge density is considered solely dependent on the induced electric current over time. The Laplace-Fourier transforms method in two dimensions is employed to obtain solutions for the primary variables. The recombination process results in the application of electro-mechanical loads and thermal effects on the free surface of a porous medium. The Laplace-Fourier transformations inversion operations help obtain comprehensive solutions in this study. The effects of porosity parameters and silicon (Si) on a semiconductor porous material are considered, and the resulting physical field distributions are analyzed and represented graphically.

Vibrational analysis of size-dependent thermo-piezo-photo-electric semiconductor medium under memory-dependent Moore–Gibson–Thompson photo-thermoelasticity theory

This study presents a comprehensive approach to vibrational analysis in a size-dependent, orthotropic thermo-piezo-photo-electric semiconductor half-space under Moore–Gibson–Thompson (MGT) photo-thermoelasticity theory with memory-dependent derivatives. Following Eringen’s nonlocal elasticity theory, the governing equations for the considered material are derived. The normal mode technique is applied to investigate the photothermal excitation process. Focusing on the interface adjacent to the vacuum, the study considers plasma, thermal, and mechanical stress boundary conditions to determine fundamental physical quantities. Through a detailed exploration, this research examines the impact of various thermo-piezo-photo-electric models, time, nonlocal parameters, and spatial coordinates on different physical quantities. The effects are meticulously analyzed and visually represented through graphical illustrations. While the literature survey reveals numerous studies on vibrational analysis in thermo-piezo-photo-electric semiconductor mediums under different thermoelasticity theories, to the best of the authors’ knowledge, no research emphasizing vibrational analysis in a size-dependent thermo-piezo-photo-electric semiconductor medium has been conducted. Moreover, the effect of memory-dependent MGT photo-thermoelasticity theory on a size-dependent thermo-piezo-photo-electric semiconductor half-space has not been illuminated until now, significantly defining the novelty of the conducted research.

Synthesis of Multifunctional Mn3O4-Ag2S Janus Nanoparticles for Enhanced T1-Magnetic Resonance Imaging and Photo-Induced Tumor Therapy.

The global burden of cancer is increasing rapidly, and nanomedicine offers promising prospects for enhancing the life expectancy of cancer patients. Janus nanoparticles (JNPs) have garnered considerable attention due to their asymmetric geometry, enabling multifunctionality in drug delivery and theranostics. However, achieving precise control over the self-assembly of JNPs in solution at the nanoscale level poses significant challenges. Herein, a low-temperature reversed-phase microemulsion system was used to obtain homogenous Mn3O4-Ag2S JNPs, which showed significant potential in cancer theranostics. Structural characterization revealed that the Ag2S (5-10 nm) part was uniformly deposited on a specific surface of Mn3O4 to form a Mn3O4-Ag2S Janus morphology. Compared to the single-component Mn3O4 and Ag2S particles, the fabricated Mn3O4-Ag2S JNPs exhibited satisfactory biocompatibility and therapeutic performance. Novel diagnostic and therapeutic nanoplatforms can be guided using the magnetic component in JNPs, which is revealed as an excellent T1 contrast enhancement agent in magnetic resonance imaging (MRI) with multiple functions, such as photo-induced regulation of the tumor microenvironment via producing reactive oxygen species and second near-infrared region (NIR-II) photothermal excitation for in vitro tumor-killing effects. The prime antibacterial and promising theranostics results demonstrate the extensive potential of the designed photo-responsive Mn3O4-Ag2S JNPs for biomedical applications.

Photo-thermo-piezo-elastic waves in semiconductor medium subject to distinct two temperature models with higher order memory dependencies

PurposeThis study aims to examine the impacts of higher memory dependencies on a novel semiconductor material that exhibits generalized photo-piezo-thermo-elastic properties. Specifically, the research focuses on analyzing the behavior of the semiconductor under three distinct temperature models.Design/methodology/approachThe study assumes a homogeneous and orthotropic piezo-semiconductor medium during photo-thermal excitation. The field equations have been devised to encompass higher order parameters, temporal delays and a specifically tailored kernel function to address the problem. The eigenmode technique is used to solve these equations and derive analytical expressions.FindingsThe research presents graphical representations of the physical field distribution across different temperatures, higher order plasma heat conduction models and time. The results reveal that the amplitude of the distribution profile is markedly affected by factors such as the memory effect, time, conductive temperature and spatial coordinates. These factors cannot be overlooked in the analysis and design of the semiconductor.Research limitations/implicationsSpecific cases are also discussed in detail, offering the potential to advance the creation of precise models and facilitate future simulations.Practical implicationsThe research offers valuable information on the physical field distribution across various temperatures, allowing engineers and designers to optimize the design of semiconductor devices. Understanding the impact of memory effect, time, conductive temperature and spatial coordinates enables device performance and efficiency improvement.Originality/valueThis manuscript is the result of the joint efforts of the authors, who independently initiated and contributed equally to this study.

A novel approach to measuring local mechanical properties via photothermal excitation of an atomic force microscope probe using an optical pump–probe inspired design

Obtaining and improving measurements of mechanical properties at the nanoscale has been made possible through the continuous advancement of atomic force microscopy (AFM) techniques over the past several decades. Among these advancements include implementing multifunctional AFM probes and developing new detection schemes that enable sensitivity to local mechanical properties. In this work, we demonstrate a proof-of-concept for a detection scheme that enables a standard AFM configuration to produce qualitative local mechanical property maps through the use of an optical pump–probe scheme, alleviating a common requirement of incorporating additional piezoelectric actuators. Data from this work are presented for silicon carbide and epitaxially grown graphene on silicon carbide. Through preliminary analysis of resonant frequency maps acquired through dual-frequency resonance tracking, the local stiffness and elastic modulus can be estimated at each point. This work contributes to the field of scanning probe microscopy by providing a new opportunity for AFM systems that are not currently equipped for a mechanical mode to obtain local mechanical property data.

Fractional and MDD analysis of piezo-photo-thermo-elastic waves in semiconductor medium

This manuscript examines the effects of memory-dependent and fractional-order derivatives on a novel generalized piezo-thermo-elastic semiconductor model. The medium is homogenous and orthotropic, subjected to photo-thermal excitation. The governing equations include fractional-order parameters, relaxation time, time delay, and kernel function tailored to specific problem requirements. Normal mode method use to solve the equations, yielding analytical expressions. Graphical representations show physical field distribution across various fractional-order parameters, kernel functions, time delay, and frequency values. This study has the potential to advance precise model development and future simulations.

Effects of changing thermal conductivity on photothermal excitation in non-local semiconductor material subjected to moisture diffusion and laser pulses

A novel model is presented in this study for the situation of wave interference in a non-local stimulated semiconductor medium, including thermal, plasma, and elastic waves. Moisture diffusion in one dimension (1D) has been included in the governing equations by varying the non-local medium's thermal conductivity under the impact of laser pulse according to the non-Gaussian temporal profile. The dimensionless model was characterized by linear transformations. Analytical solutions were obtained by applying Laplace transforms to a description of the governing equations based on the photo-thermoelasticity theory based on moisture diffusivity and variable thermal conductivity. When applying certain of the circumstances (thermal ramp type and non-Gaussian plasma shock), linear solutions are achieved in the time domain using various numerical techniques based on inverse Laplace transforms. Some of the physical variables being studied are visually shown via numerical simulation. The present investigation has produced numerous important concrete instances. Using graphs and theoretical descriptions, several contrasts are drawn, while certain physical factors, such as relaxation durations, changing thermal conductivity, non-local parameters, and reference moisture values, are in play.

Moore–Gibson–Thompson model with the influence of moisture diffusivity of semiconductor materials during photothermal excitation

In the present work, the semiconductor material is used to study the moisture diffusivity when a modified Moore–Gibson–Thompson (MGT) model is taken into account. The influence of moisture concentration is included in the governing equations throughout the photothermal transfer process. Based on the dissimilar relaxation durations of the coupled optoelectronic and thermoelastic waves, the MGT model is used to investigate the issue at hand. The method of the Laplace transform is used to obtain analytical solutions for the physical quantities, constitutive relationships, elastic waves, carrier density, heat equation conduction, and moisture diffusivity for the thermo-elastic medium. To extract the primary physical quantities in the space–time domain, the boundary conditions, temperature, plasma, displacement, and mechanical stress are inverted numerically using the Laplace transform. The effect of the new parameter like the reference moisture parameter with various values is discussed graphically on the primary physical quantities. The comparison between silicon and germanium is taken into account to achieve numerical computations.

Photothermal excitation in non-local semiconductor materials with variable moisture thermal conductivity according to moisture diffusivity

In this work, a new model is described for the case of interference between thermal, plasma and elastic waves in a non-local excited semiconductor medium. The governing equations have been put under the influence of moisture diffusion in one dimension (1D) when the moisture thermal conductivity of the non-local medium is taken in variable form. Linear transformations were used to describe the dimensionless model. The photo-thermoelasticity theory according to moisture diffusivity was applied to describe the governing equations using Laplace transforms to obtain analytical solutions. In the time domain, complete solutions are obtained linearly when the conditions are applied (thermal ramp type and non-Gaussian plasma shock) to the surface through numerical methods of inverse Laplace transforms. Numerical simulation is used to display the basic physical quantities under study graphically. The current research has yielded several specific examples of great significance. Many comparisons are made under the influence of fundamental physical variables such as relaxation times, variable thermal conductivity, non-local parameters, and reference moisture parameters through graphing and describing them theoretically.

Low frequency photothermal excitation of AFM microcantilevers

Photothermal excitation at frequencies below the mechanical resonance of the atomic force microscopy (AFM) microcantilever can be utilized in force modulation microscopy, fast force displacement curve acquisition, and tip-based mass spectroscopy. To understand the microcantilever bending response in these modes, accurate models of the thermoelastic response of the AFM microcantilever are needed. We study the sub-resonance photothermal vibrational response of coated and uncoated AFM microcantilevers as a function of laser modulation frequency and spot location. The sub-resonance microcantilever response shows distinct thermoelastic regimes. Below the microcantilever's thermal roll-off frequency, the vibration amplitude is mostly constant. Past this frequency, the vibration amplitude decreases with increasing frequency. At modulation frequencies below the thermal roll-off frequency, the most efficient photothermal laser spot to excite harmonic motion is near the free end of both coated and uncoated microcantilevers. For the tested coated microcantilevers, the most efficient photothermal laser location migrates from near the free end of the microcantilever to near the fixed end as modulation frequency increases. For the tested uncoated microcantilever, the most efficient photothermal laser location remains unchanged at the tested frequencies. To predict the bending response of the coated microcantilever, a bilayer bending model is implemented. At low frequencies, this model underpredicts the bending response compared to experiments by up to 90%. This may be due to neglecting microcantilever bending contributed by a through-thickness temperature gradient. Our results illustrate different aspects of the frequency-dependent photothermal laser spot optimization that can guide users to maximizing microcantilever response to a given input power.

Non-local semiconductor photothermal excitation medium in moisture diffusivity subjected to heating by pulsed laser

Non-local semiconductor photothermal excitation medium in moisture diffusivity subjected to heating by pulsed laser

Ultrafast Plasmonic Nucleic Acid Amplification and Real-Time Quantification for Decentralized Molecular Diagnostics.

Point-of-care real-time reverse-transcription polymerase chain reaction (RT-PCR) facilitates the widespread use of rapid, accurate, and cost-effective near-patient testing that is available to the public. Here, we report ultrafast plasmonic nucleic acid amplification and real-time quantification for decentralized molecular diagnostics. The plasmonic real-time RT-PCR system features an ultrafast plasmonic thermocycler (PTC), a disposable plastic-on-metal (PoM) cartridge, and an ultrathin microlens array fluorescence (MAF) microscope. The PTC provides ultrafast photothermal cycling under white-light-emitting diode illumination and precise temperature monitoring with an integrated resistance temperature detector. The PoM thin film cartridge allows rapid heat transfer as well as complete light blocking from the photothermal excitation source, resulting in real-time and highly efficient PCR quantification. Besides, the MAF microscope exhibits close-up and high-contrast fluorescence microscopic imaging. All of the systems were fully packaged in a palm size for point-of-care testing. The real-time RT-PCR system demonstrates the rapid diagnosis of coronavirus disease-19 RNA virus within 10 min and yields 95.6% of amplification efficiency, 96.6% of classification accuracy for preoperational test, and 91% of total percent agreement for clinical diagnostic test. The ultrafast and compact PCR system can decentralize point-of-care molecular diagnostic testing in primary care and developing countries.

Method for efficient excitation of selective vibration modes in pulsed laser photothermal actuation

Photothermal excitation based on thermoelastic mechanisms is widely used in non-destructive testing, precision operations, and driving micro-resonators. The narrow drive bandwidth of the high vibration mode in photothermal excitation limits its application to multi-mode drives. Controlling the laser’s irradiation position is an effective solution. In this study, we build a theoretical model to achieve selective and efficient excitation of different flexural vibration modes of beams with different supports. The model can be extended to other thermal and physical boundaries, which is validated by numerical simulations and experimental results. The results show that higher modes with complex periodic shapes can be efficiently excited by focusing the laser at the peak of the absolute value of the second derivative of the flexural mode while focusing the laser at the inflection point of the mode shape will result in extremely small amplitudes. Our study indicates that the thermal gradient plays a vital role in the oscillation of the beam. The conventional view assumes that the resonance of the photo-thermal excitation beam is caused by the local expansion and contraction of the material, which cannot completely explain the dependence principle of the photothermal vibration on the laser irradiation position. To investigate the mechanism of beam resonance under laser excitation, three excitation modes, unidirectional excitation, bidirectional in-phase excitation, and bidirectional anti-phase excitation, were established, and the conversion process of optical energy to mechanical energy under laser excitation was analyzed. These results provide new options for optimal excitation and multi-mode energy flow control in photothermal driving.

Photo-thermal synergistic excitation: Feasible strategy to detect ethanol for wide bandgap ZIF-8 at low work temperature

Zeolitic Imidazolate Framework-8 (ZIF-8) material was prepared by chemical precipitation method. The microstructure and physical properties of the as-prepared samples were characterized by XRD, BET, FESEM and UV spectrophotometer. The self-made four-channel measurement device was used to test the gas sensitivity of ZIF-8 material toward ethanol gas under photo-thermal synergistic excitation. The results showed that the sample was typical ZIF-8 (Eg = 4.96 eV) with a regular dodecahedron shape and the specific surface is up to 1793 m2/g. The as-prepared ZIF-8 has a gas response value of 55.04 to 100 ppm ethanol at 75°C and it shows good gas sensing selectivity and repeated stability. The excellent gas sensitivity can be attributed to the increase of free electron concentration in the ZIF-8 conduction band by photo-thermal synergistic excitation, and the large specific surface area of ZIF-8 material provides more active sites for gas-solid surface reaction. The reaction mechanism of ZIF-8 material under multi-field excitation was also discussed.