Browsing by Author "Rao, Anish"

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Accelerated design of gold nanoparticles with enhanced plasmonic performance
(AAAS, 2025-08) Rao, Anish
Finding the optimal dimensions of metal nanoparticles to maximize their plasmonic performance in targeted applications is a complex and time-consuming process that typically requires a trial-and-error approach. Here, we propose a universal pipeline that integrates Bayesian optimization with electrodynamics simulations to find dimensions of gold bipyramids with superior plasmonic performance in photothermal efficiency, enhancement of Raman scattering and photoluminescence, strong coupling between plasmon and exciton, and aggregation-induced color difference. Our workflow is a straightforward tool for plasmonic nanoparticle design, setting their optimal dimensions for targeted applications.
Accelerated reduction of 4-nitrophenol: bridging interaction outplays reducing power in the model nanoparticle-catalyzed reaction
(ACS, 2020-08) Rao, Anish
General chemistry knowledge will intuitively predict that a stronger reducing agent will result in a faster reduction reaction. The present work, however, shows the counterintuitive role of reducing agents in a model reaction of gold nanoparticle (AuNP)-catalyzed reduction of 4-nitrophenol (4-NP) by sodium borohydride. The strength of reducing agents is varied, in situ, by adding appropriate metal ions in the reaction medium. The trend observed in the rate constants does not correlate fully with the strength of reducing agents. Surprisingly, Ca2+ outperforms Mg2+ in accelerating the AuNP-catalyzed reduction of 4-NP, despite Ca2+ forming a comparatively weaker reducing agent. A thorough investigation reveals that the reducing power is an incomplete descriptor, and additional ion-specific bridging interactions should be incorporated to explain the observed trend in the rate constants. The idea of combining increased reducing power with bridging interactions was then utilized to transform a traditionally noncatalytic AuNP to a catalytically active one.
Capillary assembly of anisotropic particles at cylindrical fluid–fluid interfaces
(ACS, 2023-04) Rao, Anish
The unique behavior of colloids at liquid interfaces provides exciting opportunities for engineering the assembly of colloidal particles into functional materials. The deformable nature of fluid–fluid interfaces means that we can use the interfacial curvature, in addition to particle properties, to direct self-assembly. To this end, we use a finite element method (Surface Evolver) to study the self-assembly of rod-shaped particles adsorbed at a simple curved fluid–fluid interface formed by a sessile liquid drop with cylindrical geometry. Specifically, we study the self-assembly of single and multiple rods as a function of drop curvature and particle properties such as shape (ellipsoid, cylinder, and spherocylinder), contact angle, aspect ratio, and chemical heterogeneity (homogeneous and triblock patchy). We find that the curved interface allows us to effectively control the orientation of the rods, allowing us to achieve parallel, perpendicular, or novel obliquely orientations with respect to the cylindrical drop. In addition, by tuning particle properties to achieve parallel alignment of the rods, we show that the cylindrical drop geometry favors tip-to-tip assembly of the rods, not just for cylinders, but also for ellipsoids and triblock patchy rods. Finally, for triblock patchy rods with larger contact line undulations, we can achieve strong spatial confinement of the rods transverse to the cylindrical drop due to the capillary repulsion between the contact line undulations of the particle and the pinned contact lines of the sessile drop. Our capillary assembly method allows us to manipulate the configuration of single and multiple rod-like particles and therefore offers a facile strategy for organizing such particles into useful functional materials.
Choreographing oscillatory hydrodynamics with DNA-coated gold nanoparticles
(ACS, 2024-06) Rao, Anish
Periodic responses to nonperiodic energy inputs, such as oscillations, are hallmarks of living systems. Nanoparticle-based systems have largely remained unexplored in the generation of oscillatory features. Here, we demonstrate a nanosystem featuring hierarchical response to light, where thermoplasmonic effects and reversible DNA-hybridization generate thermal convective forces and ultimately, oscillatory hydrodynamic flows. The slow aggregation of gold nanoparticles (AuNPs) serves as a positive feedback, while fast photothermal disassembly acts as negative feedback. These asymmetric feedback loops, combined with thermal hysteresis for time-delay, are essential ingredients for orchestrating an oscillating response.
Electrostatically directed long-range self-assembly of nucleotides with cationic nanoparticles to form multifunctional bioplasmonic networks
(Wiley, 2022-05) Rao, Anish
Precise control over interparticle interactions is essential to retain the functions of individual components in a self-assembled superstructure. Here, we report the design of a multifunctional bioplasmonic network via an electrostatically directed self-assembly process involving adenosine 5′-triphosphate (ATP). The present study unveils the ability of ATP to undergo a long-range self-assembly in the presence of cations and gold nanoparticles (AuNP). Modelling and NMR studies gave a qualitative insight into the major interactions driving the bioplasmonic network formation. ATP-Ca2+ coordination helps in regulating the electrostatic interaction, which is crucial in transforming an uncontrolled precipitation into a kinetically controlled aggregation process. Remarkably, ATP and AuNP retained their inherent properties in the multifunctional bioplasmonic network. The generality of electrostatically directed self-assembly process was extended to different nucleotide–nanoparticle systems.
Electrostatically driven multielectron transfer for the photocatalytic regeneration of nicotinamide cofactor
(ACS, 2020) Rao, Anish
Developing generic strategies that are capable of driving multielectron processes are essential to realize important photocatalytic conversions. Here, we present the idea of introducing favorable catalyst–reactant interaction in achieving efficient photocatalytic regeneration of nicotinamide (NADH) cofactor by gold nanoparticles (AuNPs). The electrostatic attraction emanating from the ligands on the surface of NP increases the channeling and local concentration of NAD+ reactants around AuNP photocatalysts, thereby enhancing the probability of the electron transfer process. Detailed kinetics- and intensity-dependent studies confirm the involvement of multiple electron transfer from the AuNP photocatalyst to the NAD+ reactant. The photocatalytic performances of AuNPs presented here are comparable to or greater than most of the catalytic systems reported based on plasmonic NP, with the added advantage of being structurally less complex. The use of electrostatics mimics the underlying force involved in various enzyme catalysis, which can serve as a generic approach for other important artificial multielectron photocatalytic reactions as well.
Electrostatically driven resonance energy transfer in “cationic” biocompatible indium phosphide quantum dots
(RSC, 2017-03) Rao, Anish
Indium Phosphide Quantum Dots (InP QDs) have emerged as an alternative to toxic metal ion based QDs in nanobiotechnology. The ability to generate cationic surface charge, without compromising stability and biocompatibility, is essential in realizing the full potential of InP QDs in biological applications. We have addressed this challenge by developing a place exchange protocol for the preparation of cationic InP/ZnS QDs. The quaternary ammonium group provides the much required permanent positive charge and stability to InP/ZnS QDs in biofluids. The two important properties of QDs, namely bioimaging and light induced resonance energy transfer, are successfully demonstrated in cationic InP/ZnS QDs. The low cytotoxicity and stable photoluminescence of cationic InP/ZnS QDs inside cells make them ideal candidates as optical probes for cellular imaging. An efficient resonance energy transfer (E ∼ 60%) is observed, under physiological conditions, between the cationic InP/ZnS QD donor and anionic dye acceptor. A large bimolecular quenching constant along with a linear Stern–Volmer plot confirms the formation of a strong ground state complex between the cationic InP/ZnS QDs and the anionic dye. Control experiments prove the role of electrostatic attraction in driving the light induced interactions, which can rightfully form the basis for future nano-bio studies between cationic InP/ZnS QDs and anionic biomolecules.
Electrostatically driven resonance energy transfer in an all-quantum dot based donor–acceptor system
(ACS, 2020-06) Rao, Anish
Demonstration of fundamental photophysical properties in environmentally friendly quantum dots (QDs) is essential to realize their practical use in various light harvesting applications. We accomplish here an efficient light induced resonance energy transfer in all-QD based donor–acceptor system in water, deprived of any commonly used organic dye component. Our nanohybrid system comprises surface engineered indium phosphide/zinc sulfide (InP/ZnS) QD as the donor, and copper indium sulfide/zinc sulfide (CIS/ZnS) QD as the acceptor. The electrostatic attraction between oppositely charged QDs is vital in achieving a strong ground state complexation in the [−] InP/ZnS:::[+] CIS/ZnS QD nanohybrid. A nonlinear Stern–Volmer plot confirms the involvement of both static and dynamic components in the PL quenching of InP/ZnS QD by CIS/ZnS QD. Moreover, a temporal evolution of resonance energy transfer is realized in the solid state as well, which can improve the potential of such “all-green QD” based nanohybrid systems for device level studies.
Electrostatically regulated photoinduced electron transfer in “cationic” eco-friendly CuInS2/ZnS quantum dots in water
(2018) Rao, Anish
The potency of eco-friendly copper indium sulfide/zinc sulfide core/shell quantum dots (CIS/ZnS QDs) as efficient light harvesters in water is presented. A place exchange protocol is developed to prepare the much demanded cationic ([+]) CIS/ZnS QDs carrying a permanent positive charge, with ∼60% retention of the QD photoluminescence (PL) in water. Both steady-state and time-resolved photophysical studies confirm efficient electron transfer from the photoexcited CIS/ZnS QDs to indocyanine green (ICG) dye. The electrostatic attraction between the oppositely charged [+] CIS/ZnS QDs and [−] ICG dye is responsible for the formation of a strong ground state complex, which is vital for achieving an efficient electron transfer process in water. The successful demonstration of the efficient light harvesting properties using [+] CIS/ZnS QDs will be decisive in the development of artificial photosynthetic systems based on eco-friendly quantum dots.
Emergence of selectivity in inherently nonselective gold nanoparticles through preferential breaking of interparticle interactions
(2018-10) Rao, Anish
We demonstrate a fundamentally unique identification strategy to impart selectivity to a traditionally and inherently nonselective carboxylate-functionalized gold-nanoparticles ([-] AuNPs), without the aid of any analyte specific ligands. The common practice is to use the ability of divalent ions to trigger the aggregation process in a kinetically trapped dispersed solution of [-] AuNPs. Aggregation of NPs being a thermodynamically favourable process will result in a uniform and nonselective turn-off response from most of the strongly binding divalent ions. Our approach is to use the abilities of various divalent ions to break a thermodynamically stable inter-nanoparticle precipitates containing [+] and [-] AuNPs (nanoionic precipitates), as the means of identification. Importantly both [+] and [-] AuNPs, independently, were ‘blind’ in terms of selectivity towards divalent ions. Remarkably, a hybrid-system composed of such nonselective nanoparticles was able to discriminate between the hard-to-distinguish pair of Pb2+ and Cd2+ ions. The rationale is that only the strongest of strongly binding ions will be able to break the interactions between the NP precipitates (thermodynamically stable state) and re-disperse them back in solution (kinetically trapped state). This is in stark contrast with the conventional idea of forming an interaction between NPs and divalent ions, with the help of analyte-specific ligands.
Förster resonance energy transfer regulated multicolor photopatterning from single quantum dot nanohybrid filmsR
(ACS, 2019-05) Rao, Anish
Precise patterning and localization of functional nanomaterials is the key step for miniaturization and building of optoelectronic devices. Present study utilizes a robust methodology for the multicolor patterning of luminescent Indium Phosphide/Zinc Sulfide Quantum Dot (InP/ZnS QD) film, by taking the advantage of QD’s enhanced photostability over organic dyes. The photoirradiation regulates the composition of donor–acceptor pair, and thereby, the efficiency of Förster Resonance Energy Transfer (EFRET) in QD–dye nanohybrid film. The photopatterned films are reusable over multiple cycles without any compromise of the color clarity, owing to the reversible switching between FRET ON and OFF states. The highlight of the present work is the use of a single QD nanohybrid system to create multicolor luminescent patterns; as opposed to the common practice of using different-colored QDs. FRET assisted photopatterning of luminescent InP/ZnS QD films provides a fundamentally unique and cost-effective approach for the manufacturing of luminescent optoelectronic devices.
InP/ZnS quantum dots as efficient visible-light photocatalysts for redox and carbon–carbon coupling reactions
(ACS, 2019-03) Rao, Anish
Energy research is enormously inspired by one of the most fascinating and elegant phenomena known to mankind, called photosynthesis. (1,2) The efficient harvesting of visible light and movement of electrons through a number of molecules and redox active metal centers (leading to new chemical bonds) is the heart of photosynthesis. (3,4) Understanding and mimicking of such processes in artificial systems is the central idea of solar to chemical energy conversion research, especially photocatalysis. (5−13) A diverse pool of catalytic supplies ranging from organic to inorganic to polymeric materials has been explored for harvesting photons and driving various chemical reactions. (5−13) Among them, semiconductor nanoparticles or quantum dots (QDs) have emerged strongly due to their high absorption extinction coefficient (∼106 M–1 cm–1) and electron–hole mobility, size- and shape-tunable band gap, photostability, and flexible surface chemistry. (14−25) A thorough review of the literature reveals that the common practice in the area of QD photocatalysis is to use them in combination with other catalytic materials (like metal ions/complexes, semiconductors, 2D materials, etc.). (26−29) Strikingly, recent reports have shown the sole use of QDs as photocatalyst for various reactions, including C–C bond formation, without the aid of any cocatalysts or sacrificial reagents. (30−35) To hold this promise on a longer perspective, these exciting results with toxic metal-ion-based QDs should be tested and demonstrated with more environmentally friendly QDs. Even though extensive studies were performed on the fundamental properties of environmentally friendly QDs (synthesis, surface engineering, imaging and biotargeting, energy/charge transfer processes, etc.), (36−43) the photocatalytic aspects of them are still at its infancy. (27,35,44,45) For instance, recent reports have used CuAlS2/ZnS QD for carbon dioxide reduction (35) and InP/ZnS QD (as a sensitizer of nickel complex) for photocatalytic production of hydrogen. (27) To this end, a successful demonstration of environmentally friendly QDs photocatalyzing different classes of chemical reactions will strengthen their claim of potential “greener” alternatives for toxic metal-ion-based QDs. In this regard, we explored the potency of InP/ZnS QD as a visible-light photocatalyst for mimicking the two key classes of reactions in photosynthesis, namely metal-centered redox and carbon–carbon bond forming reactions
Insights into the utilization and quantification of thermoplasmonic properties in gold nanorod arrays
(ACS, 2022-08) Rao, Anish
Doing chemistry with plasmons is rewarding but is often challenged by the competition between the intriguing relaxation processes in plasmonic materials. One of the currently debated and prominent examples of this is the interference of the thermalization process in bringing out different physicochemical transformations. We present here insights into the utilization and quantification of thermoplasmonic properties in configurable arrays of gold nanorods (AuNRs), which will help in accomplishing the desired outcome from the thermalization process. The plasmonic heat generated in AuNR arrays is used to perform versatile and useful photothermal processes, such as polymerization, solar-vapor generation, Diels–Alder reaction, and crystal-to-crystal transformation. The unprecedented use of thermochromism in quantifying the thermalization process shows that the surface of AuNR arrays can heat up to ∼250 °C within ∼15 min of irradiation, which is independently validated with standard infrared-based thermometric imaging studies. The plasmonic heat reported by the thermochromic studies is the lower limit corresponding to the phase change temperature of the thermochromic molecule, and the actual surface temperature of bundled AuNR arrays could be higher. The choice of reaction conditions is crucial for the effective utilization as well as dissipation of thermoplasmonic heat. The maximum impact of surface temperature was observed when substrates were adsorbed onto the AuNR arrays, whereas the influence of thermoplasmonic heat was minimum when the experiments were performed in a solution state. The insights provided here will have far-reaching implications in the emerging area of plasmonically powered processes, especially in plasmonic photocatalysis.
Multicolor luminescent patterning via photoregulation of electron and energy transfer processes in quantum dots
(ACS, 2020-05) Rao, Anish
Ability to create high-contrast multicolor luminescent patterns is essential to realize the full potential of quantum dots (QDs) in display technologies. The idea of using a nonemissive state is adopted in the present work to enhance the color-contrast of QD-based photopatterns. This is achieved at a multicolor level by the photoregulation of electron and energy transfer processes in a single QD nanohybrid film, composed of one QD donor and two dye acceptors. The dominance of photoinduced electron transfer over the energy transfer process generates a nonluminescent QD nanohybrid film, which provides the black background for multicolor patterning. The superior photostability of QDs over dyes is used for the photoregulation of electron and energy transfer processes. Selective photodegradation of electron acceptor dye triggered the onset of the energy transfer process, thereby imparting a luminescent color to the QD nanohybrid film. Further, a controlled photoregulation of energy transfer process paved the way for multicolor patterning.
Nanoparticle self-assembly: from design principles to complex matter to functional materials
(ACS, 2022) Rao, Anish
The creation of matter with varying degrees of complexities and desired functions is one of the ultimate targets of self-assembly. The ability to regulate the complex interactions between the individual components is essential in achieving this target. In this direction, the initial success of controlling the pathways and final thermodynamic states of a self-assembly process is promising. Despite the progress made in the field, there has been a growing interest in pushing the limits of self-assembly processes. The main inception of this interest is that the intended self-assembled state, with varying complexities, may not be “at equilibrium (or at global minimum)”, rendering free energy minimization unsuitable to form the desired product. Thus, we believe that a thorough understanding of the design principles as well as the ability to predict the outcome of a self-assembly process is essential to form a collection of the next generation of complex matter. The present review highlights the potent role of finely tuned interparticle interactions in nanomaterials to achieve the preferred self-assembled structures with the desired properties. We believe that bringing the design and prediction to nanoparticle self-assembly processes will have a similar effect as retrosynthesis had on the logic of chemical synthesis. Along with the guiding principles, the review gives a summary of the different types of products created from nanoparticle assemblies and the functional properties emerging from them. Finally, we highlight the reasonable expectations from the field and the challenges lying ahead in the creation of complex and evolvable matter.
Precise nanoparticle–reactant interaction outplays ligand poisoning in visible-light photocatalysis
(ACS, 2018-11) Rao, Anish
The ability to move electrons under the influence of visible-light in an efficient manner is one of the most fundamental challenges in photocatalysis. (1−6) The “hot” charge carriers in metal nanoparticles (NPs) have been shown to participate effectively in various reductive and oxidative photocatalytic chemical transformations. (7−14) During this process, the electrons and holes, oftentimes, have to encounter the “insulating” organic ligands capped on the NPs. (15−19) Generally, the surface ligand plays a crucial role in stabilizing the NPs as well as dictating its physicochemical properties. (20−23) However, for applications in photocatalysis, where the stability as well as the surface accessibility of NPs is desirable, the role of surface ligands is conflicting. In principle, the surface ligands can “poison” a photocatalyst by hindering the (i) movement of electrons/holes (due to its insulating nature) (15,16) and (ii) accessibility of the NP surface to the reactants (due to steric effect). (17−19) The alternative is to deposit NPs onto a support or use “ligand free” NPs for catalysis. (24−27) However, the available surface area and stability of NPs are compromised during the course of catalysis. (24) Thus, metal NPs and surface ligands are two inseparable entities, and strategies have to be developed to accomplish photocatalysis by retaining and taking advantage of the ligands on the NP surface. We address this challenge by using ligands that can enhance the NP catalyst–reactant interactions, which in turn can facilitate the electron transfer process. Our hypothesis was tested in the model photocatalytic reaction of ferricyanide reduction by gold nanoparticles (AuNPs) in the presence of ethanol as the hole scavenger. (6,28,29) A favorable interaction between NP catalyst and ferricyanide reactant was created through precise surface engineering, which resulted in the enhancement of the photocatalytic activities (both in terms of hot electron transfer rate constant and conversion yield). Cationic ([+]) and anionic ([−]) organic ligands were functionalized on AuNP surface to generate favorable and unfavorable interactions with [−] ferricyanide, respectively. Our studies show that the favorable interaction, arising from the strong electrostatic attraction, increases the local concentration of [−] ferricyanide around the [+] AuNP catalyst. Consequently, the NP accessibility and probability of hot electron injection from [+] AuNP to [−] ferricyanide was enhanced. On the other hand, the local concentration of the reactants and catalytic activities were lower when standard [−] AuNP was used as the catalyst. For instance, the rate constant increased from ∼8 × 10–4 to ∼4 × 10–3 min–1 (∼5-fold increment in reaction rate) when the NP–reactant interaction was made favorable, along with an appreciable increase in the ferricyanide conversion yield (from ∼10% for [−] AuNP to ∼60% for [+] AuNP). The dependence of catalytic activities on the NP surface potential ascertained the potency of electrostatics in enhancing the visible-light photocatalysis. Thermodynamic analysis based on Marcus model of outer sphere electron transfer revealed a higher pre-exponential factor (Φ) for [+] AuNP catalyst, a parameter directly related to the local concentration of reactants. Thus, the introduction of favorable interaction improves the NP accessibility to the reactants and the probability of hot electron transfer, thereby suppressing the “poisoning” effect of the “insulating” organic ligands.
Revealing the role of electrostatics in gold-nanoparticle-catalyzed reduction of charged substrates
(ACS, 2017-09) Rao, Anish
The potency of electrostatic effects arising from nanoparticle (NP) surface in Au-NP-catalyzed reduction of charged substrates are presented. The electrostatic potential around Au NPs is controlled by varying the nature of ligands and ionic strength of the medium. Favorable interactions arising from the attraction between oppositely charged Au NP and substrates results in the channeling of substrates to the NP surface, which in turn enhances the catalytic reduction. The positively charged ([+]) Au NP outperformed other NP systems despite having comparable or even lower surface area for adsorption, proving the exclusivity of electrostatics in catalysis. At least an order of magnitude higher concentration of negatively charged ([−]) Au NP is required to compete with the catalytic activity of [+] Au NP.
Revisiting El-sayed synthesis: bayesian optimization for revealing new insights during the growth of gold nanorods
(ACS, 2024-02) Rao, Anish
In diverse fields, machine learning (ML) has sparked transformative changes, primarily driven by the wealth of big data. However, an alternative approach seeks to mine insights from “precious data”, offering the possibility to reveal missed knowledge and escape potential knowledge traps. In this context, Bayesian optimization (BO) protocols have emerged as crucial tools for optimizing the synthesis and discovery of a broad spectrum of compounds including nanoparticles. In our work, we aimed to go beyond the commonly explored experimental conditions and showcase a workflow capable of unearthing fresh insights, even in well-studied research domains. The growth of AuNRs is a nonequilibrium process that remains poorly understood despite the presence of well-established seeded growth protocols. Traditional research aimed at understanding the mechanism of AuNR growth has primarily relied on altering one reaction condition at a time. While these studies are undeniably valuable, they often fail to capture the synergies between different reaction conditions, thus constraining the depth of insights they can offer. In the present study, we exploit BO, to identify diverse experimental conditions yielding AuNRs with similar spectroscopic characteristics. Notably, we identify viable and accelerated synthesis conditions involving elevated temperatures (36–40 °C) as well as high ascorbic acid concentrations. More importantly, we note that ascorbic acid and temperature can modulate each other’s undesirable influences on the growth of AuNRs. Finally, by harnessing the power of interpretable ML algorithms, complemented by our deep chemical understanding, we revisited the established hierarchical relationships among reaction conditions that impact the El-Sayed-based growth of AuNRs.
Self-assembled colloidal gold nanoparticles as substrates for plasmon enhanced fluorescence
(Taylor & Francis, 2023) Rao, Anish
Decades of intense research in the field of nanoscience have led to the ability to produce nanoparticles (NPs) with controlled composition, shape, and size. One of the next key challenges is the self-assembly of appropriate NP building blocks into larger systems to obtain micro- or macroscale materials. To achieve this, self-assembly protocols must not only produce high-quality structures, but also deliver the assemblies of interest to desired locations on a substrate. In this review, we discuss different self-assembly strategies, focusing on colloidal gold NPs and applications as plasmon-enhanced fluorescence (PEF) platforms. These plasmonic substrates have been used for biosensing and cell imaging, based on the enhancement of fluorescent emitters, and applied to improve the emission efficiency of luminescent NPs. It is important to note that higher fluorescence enhancement relies on precise control of the location of gold NPs and fluorescent emitters on the plasmonic substrate. Despite the diversity of available self-assembly strategies, many of them provide similar levels of structural control over the placement of gold NPs on the substrate. To highlight this, we have organized the discussion according to strategies that result in similar degrees of structural control over the placement of gold NPs and its associated PEF effect.
Size effect on photothermal heating ability of gold bipyramids
(Wiley, 2025-07) Rao, Anish
Gold nanoparticles (AuNPs) exhibit photothermal properties that are fundamental to biomedical and catalytic fields. However, the relationship between photothermal heating efficiency and nanoparticle characteristics often features a non-intuitive behavior, being dependent on experimental parameters, sample scale (microscopic versus macroscopic), and material phase (solid or liquid). Using gold bipyramids (AuBPs) as a model system and employing a combination of experimental and computational approaches, photothermal heating is investigated as a function of nanoparticle dimensions while maintaining comparable optical properties. The computational analysis revealed an inverse correlation between the achievable maximum temperature at the single-particle level versus multi-particle systems. At the macroscopic scale, it is observed that photothermal heating efficiency follows an inverse proportionality with nanoparticle volume, with notable deviations occurring at reduced nanoparticle sizes. This deviation suggests the emergence of additional energy relaxation pathways. To outline practical implications of these findings, processable agarose films containing AuBPs capable of enhancing the performance of light-powered Stirling engine are developed.