# Controlled Polymerization at Macroscale and Nanoscale Through Thermoplasmonics

Céline Molinaro, Amine Khitous, Mathieu Bastide, Olivier Soppera

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Céline Molinaro, Amine Khitous, Mathieu Bastide, Olivier Soppera. Controlled Polymerization at Macroscale and Nanoscale Through Thermoplasmonics. Plasmonics, 2025, 10.1007/s11468-025-03308-6. hal-05369743

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Controlled polymerization at macroscale and nanoscale

through thermoplasmonics

Céline Molinaro<sup>1,2*</sup>, Amine Khitous<sup>1,2</sup>, Mathieu Bastide<sup>1,2</sup>, Olivier Soppera<sup>1,2</sup>

<sup>1</sup> Université de Haute Alsace, CNRS, IS2M UMR 7361, F-68100 Mulhouse, France

<sup>2</sup> Université de Strasbourg, F-67081 Strasbourg, France

*corresponding author: celine.molinaro@uha.fr

Keywords: gold nanoparticles, thermoplasmonics, polymerization, fs pulses illumination, cw illumination

**Abstract**

Controlling and moreover knowing the temperature induced by thermoplasmonics is important for many applications in biology, chemistry and physics. Here, for the same sample with a high density of gold nanoparticles (NPs), two different laser illumination regimes were used, continuous wave (cw) and femtosecond (fs) pulses, to control heat generation. With cw laser illumination, collective heat-generating effects dominate, while with fs pulses illumination, heat remains confined to individual NPs. These two effects were experimentally observed using the same thermopolymerizable formulation acting as a thermal probe, on a macroscopic scale for cw illumination and on a nanometric scale for fs pulses illumination. This effective control of temperature generation by thermoplasmonics will enable the generation of hybrid NPs combining temperature-responsive materials at different scales.

**Introduction**

Knowing and controlling the temperature generated following the illumination of gold nanoparticles (NPs), also known as thermoplasmonics, is a key factor for many applications.<sup>1–3</sup> For example, in biology, the hyperthermia used to destroy cells called photothermal therapy,<sup>4–6</sup> which can be induced by thermoplasmonics, requires a controlled temperature between 40 and 60°C.<sup>7</sup> In chemistry, thermoplasmonics is also used in a controlled way for catalysis,<sup>8,9</sup> for NPs reshaping,<sup>10–13</sup> for nanolithography process<sup>14,15</sup> or for solar energy production.<sup>16–18</sup>

A wide range of techniques already exist for measuring temperature in thermoplasmonics. On a macroscopic scale, a thermocouple<sup>19</sup> or an infrared camera<sup>20</sup> can be used to determine the temperature of a surface or a liquid. We have developed a thermopolymerizable formulation
that can be used to characterize the threshold temperature reached by thermoplasmonics on a
millimetric scale.²¹

Achieving higher spatial resolution requires the use of more complex optical methods. In particular, phase microscopy,²² photothermal microscopy,²³,²⁴ time-resolved x-ray scattering,²⁵ pump-probe spectroscopy,²⁶ Raman thermometry, which can be used with²⁷,²⁸ or without fluorescent molecules²⁹, as well as fluorescence microscopy,³⁰,³¹ provide accurate temperature information for many NPs²¹,²²,²⁷,³¹ and single particles ranging²²,²⁹,³²⁻³⁶ in size from a few microns to a few hundred nanometers. However, it is well established that the resolution of these methods is limited by diffraction, which constrains the investigation of thermoplasmonic effects. Finally, indirect observations such as bubble observation³⁷ or nanocomposite formation³⁸ can also be used to estimate temperature.

The control of heat generation has been well investigated theoretically:³⁹ in thermoplasmonics, heat can be generated in a confined way within the gold NP itself, or it can be generated collectively. We would like to emphasize here that we use these terms in this paper solely in relation to temperature. It is possible to use certain parameters to induce one or the other phenomenon, such as the density of the gold NPs and the laser illumination (regime and size of the illuminated area). As an illustration, to observe a collective heat generation effect, many gold NPs should be illuminated with a continuous laser. On the other hand, to generate heat confined to the scale of a single NP, ideally a single gold NP should be illuminated with a continuous laser (spacing at least equal to the diffraction limit) or fs pulses laser should be used.⁴⁰ To date, there has been no experimental evidence of this control of heat generation by the laser illumination regime.

In this paper, we report on the implementation of a thermal probe, composed of a thermal initiator and a monomer, enabling both the characterization of collective heat generation effects at the macroscopic scale and heat generation at the single NP scale, on the same dense gold samples by varying the laser illumination regime. This thermal probe, used in our previous study²¹ in the case of a continuous wave (cw) laser illumination regime, enabled us to validate its operation on a macroscopic scale. The illumination mode, cw or fs pulses, affects the dynamics of energy transfer and allows collective effects to be induced or not. With fs pulses illumination, we were able to observe NPs with a nanometric polymer layer induced by NP heat confinement. This observation not only enables us to experimentally validate the switch from a collective heating regime to a heat confinement regime by changing the illumination regime
from cw to fs pulses, but also constitutes the first observation of hybrid metal/polymer NPs
formed by thermoplasmonics.

**Results and discussion**

**Principle of thermopolymerization for thermoplasmonics**

Regardless of the illumination technique used, the experimental principle is based on the
observation of thermal polymerization following laser illumination of a gold sample presenting
a high density of gold NPs. As described in **Figure 1**, a drop of thermopolymerizable
formulation is deposited on the gold sample, then covered by the glass coverslip. 125 µm
spacers are used to control the thickness of the deposited formulation. Laser illumination is
performed at 532 nm (close to the plasmonic resonance) using a Gaussian beam. Illumination
power is adjustable, with illumination time fixed at 1 min. The sample is then developed: the
glass coverslip is removed and the sample rinsed with ethanol. If the polymerization threshold
temperature has been reached (or exceeded), polymer is present on the sample. Otherwise, no
polymer is observed.

The thermopolymerizable formulation is composed of a thermal initiator (DIAMS) and a
monomer (PETA). The choice of a triacrylate monomer (PETA) is important to guarantee
resistance to development at low conversion rates.⁴¹ This formulation has a threshold
temperature of 130 ± 10°C, previously characterized by differential scanning calorimetry and
hot-plates measurements.²¹ Under the effect of heat, the thermal initiator decomposes into free
radicals, which then initiate polymerization of the monomer by radical polymerization. This
formulation has no absorption in the visible range, making photochemical processes impossible.
Regarding hot electrons, also generated by the plasmon, contribution in the polymerization
process, as the DIAMS molecules are diluted in a dielectric matrix (the PETA monomer), they
cannot be efficiently transferred to the DIAMS molecules to trigger a reaction via this
mechanism. Moreover, Guselnikova et al. functionalized their AuNPs with alkoxyamines close
to DIAMS,⁴² thereby setting up conditions that theoretically favor the transfer of hot electrons.
Despite this, Guselnikova et al conclude that no charged species are present by electron spin
resonance (ESR) characterization, thus ruling out direct hot carriers transfer in their study. In
this study, we emphasize that the polymerization process is purely thermal. Detailed characteristics of this thermopolymerizable formulation are available in our previous article.²¹

<figure><img src="image_2.png" /><figcaption>**Figure 1.** Experimental process for characterizing the temperature reached by thermoplasmonic with a thermopolymerizable formulation.</figcaption></figure>

## cw vs fs pulses illumination

As soon as several NPs are illuminated at the same time, the temperature increase of an NP is defined by:⁴⁰,⁴³,⁴⁴

$$ \Delta T = \Delta T^s + \Delta T^{ext} \quad (1) $$

where $\Delta T^s$ is the temperature increase of the NP itself and $\Delta T^{ext}$ is the temperature increase of the surrounding NPs. Depending on the preponderance of one term or the other, if

- $\Delta T^s \gg \Delta T^{ext}$ heat remains confined within the gold NP itself,

- $\Delta T^s \ll \Delta T^{ext}$ heat is generated collectively.

The parameters of the sample and the laser illumination, detailed in **Table 1**, will favour one of these two types of heating. The ideal way to promote collective heating is to have a gold sample with a high density of NPs, illuminated by a cw laser with a wide illumination area. However, to promote confined heating while maintaining cw illumination, the NP density and illuminated area must be reduced. fs pulse illumination can also be used with samples featuring a high NP density and a wide illumination zone, as in the case of the study presented here. Indeed, during pulsed fs illumination, the temperature profile will spatially decay in $1/r^3$, compared to $1/r$ in the case of cw illumination.⁴⁵ Heat confinement around NPs is therefore much stronger in the case of pulsed illumination, enabling it to confine heat even in the case of nearby NPs.
<table><caption>**Table 1.** Parameters promoting confined versus collective heating</caption><thead><tr><th></th><th>Confined heating<br>ΔT<sup>s</sup>>> ΔT<sup>ext</sup></th><th>Collective heating<br>ΔT<sup>s</sup><small>ΔT<sup>ext</sup></small></th></tr></thead><tbody><tr><td>NPs density</td><td>low</td><td>high</td></tr><tr><td>Illumination area</td><td>small</td><td>wide</td></tr><tr><td>Laser regime</td><td>cw or fs pulses</td><td>cw</td></tr></tbody></table>

Here, we aim to provide experimental proof of the theory described above. For this, the temperature of the gold sample was characterized using the same thermopolymerizable formulation for the two different illumination regimes: cw and fs pulses (pulse duration 60 fs, frequency 5 kHz). In both cases, an illumination time of 1 min was used. In the cw regime, we observed polymer dots visible to the naked eye, with a size of several millimeters and a thickness of around one hundred micrometers from 14.6 W/cm² (Figure 2a). In this case, given the density of NPs on the substrate, heat generation is governed by the collective effect, in line with previously published results.²¹ In the fs pulses regime, we also observe polymer (Figure 2a) from an irradiance of 1.9 W/cm² with an appearance quite different from that observed in cw illumination. The presence of polymer is visible to the naked eye, thanks to the change in color of the sample in the polymerized zone via the shift in plasmon resonance, due to the increase in effective refractive index induced by the presence of polymer.

<figure><img src="image_3.png" /><figcaption>**Figure 2.** (a) Experimental results obtained in cw (on top) and fs pulses (below) illumination (b) Illustration of the polymerization obtained for heat generated through collective effect (on top) and for heat confined in each NPs (below)</figcaption></figure>
To determine whether gold NPs are altered during illumination, a spectrum was taken of a bare gold sample before and after 1h of illumination at maximum power for both cw and fs pulses illumination. No significant changes were observed in the spectra, showing the stability of the gold NPs at the powers used in this study. It was also verified that the formulation did not polymerize between two glass coverslips, in the absence of gold NPs, when illuminated for 1h at maximum power in both illumination conditions, confirming the absence of photochemical polymerization.

An example of the plasmon resonance shift is shown in **Figure 3a**. The plasmonic resonance of the sample after 1 min illumination at 532 nm in fs pulses (5.5W/cm²) shows a red shift of 9 nm, validating the presence of polymer around the gold NPs. This shift, Δλ<sup>exp</sup>, could also be quantified for different laser irradiances (**Figure 3b**). A red shift of 6 ± 1 nm was observed at the threshold power of 1.9 W/cm. Then the shift increased slightly at 9 ± 2 nm to form a plateau from 4 W/cm². The shift in resonance indicates the formation of a thin polymer layer on the surface of metal nanoparticles. This proves that the temperature threshold was exceeded in the vicinity of the NPs. However, it is difficult to establish a quantitative correlation between the polymer layer thickness (and thus the resonance shift in nanometers) and the temperature reached at this stage because the spatial extent of polymerization also depends on the reaction of free radicals with oxygen, which is known to inhibit free radical polymerization.

<figure><img src="image_4.png" /></figure>
**Figure 3.** (a) Extinction spectra of gold NPs before (dark line) and after (blue line) 1min fs pulses illumination at 532 nm at 5.5 W/cm². (b) Experimental plasmonic resonance shift as a function of irradiance. (c) Calculated plasmonic resonance shift as a function of the polymer thickness around the NP. (d) TEM images of bare gold NPs in a non-illuminated area (**left**) and in fs pulses illuminated area in the presence of the thermopolymerizable formulation at 5.5 W/cm². The black arrows guide the eye to the polymer layer surrounding the NPs. (**right**)

While the resonance shift validates the presence of polymer, given the high density of NPs on the sample, it does not reveal how the polymer is distributed on the surface. The presence of polymer, although visible to the naked eye, is not measurable by profilometry, AFM (Atomic Force Microscope) and SEM (Scanning Electron Microscope) techniques. The same experiment was carried out on a transmission electron microscope (TEM) grid, in order to observe the spatial distribution of the polymer with nanometric resolution. Images obtained from this sample, shown in **Figure 3d**, shows the difference between a non-illuminated area and an illuminated area in the presence of the thermopolymerizable formulation. In the non-illuminated area, only bare gold NPs are observed. In the illuminated area, most of the gold NPs are surrounded by a nanometric layer of polymer. The polymer thus forms a nanometric layer around each NP (and not a uniform layer between NPs), confirming not only that heat generation has been confined to each NP, but also the possibility of obtaining nanometric resolution of a temperature distribution around a NP. It should be noted that, for this TEM experiment, the NPs are smaller (11 ±3 nm in diameter) than those observed on glass coverslip (due to the different thermal dewetting on this substrate) allowing only a qualitative comparison with what is observed on glass slides.

In order to estimate the polymer thickness on glass slides, simulations of resonance spectra for a single gold disk (19 nm in diameter and 15 nm thick) surrounded by a polymer shell modeled here by a disk of thickness ranging from 1 to 10 nm of refractive index 1.48 were carried out. Thus, the theoretical resonance shift, $\Delta\lambda^{th}$, as a function of the thickness of the polymer shell around a structure is shown in **Figure 3c**. The resonance shift of 9 nm obtained experimentally corresponds here to an expected theoretical thickness of 2 nm, well below the resolution of the profilometer, AFM and SEM used.
In conclusion, using the same thermopolymerizable formulation here, we were able to experimentally observe both temperature generation regimes, by varying the illumination regime:

- with cw illumination, heat generation is driven by collective effects, macrometric polymer dots were observed (Figure 2),

- with fs pulses illumination, heat generation is confined to each gold NP, characterized by a polymer layer formed around each NP, despite the high density of gold NPs in the sample (Figure 2).

This experimental data is perfectly in line with the theory put forward on this subject.⁴⁰

## Calculation of the reached temperature in cw and in fs pulses illumination

Under cw illumination, the temperature generated by this type of gold sample has been described in our previous paper,²¹ but is carried out here in a more exhaustive way. Briefly, the high density of gold NPs combined with cw illumination with a millimetric laser spot, induces a strong preponderance of the collective effect on temperature generation. The theoretical temperature can then be calculated using the following formula:⁴⁰

$$ \Delta T^{ext} \approx \frac{\sigma_{abs} P}{\kappa} \sqrt{\frac{\ln 2}{4\pi}} \frac{1}{HA} \left( 1 - \frac{4\sqrt{A \ln 2}}{\pi H} \right) \quad (2) $$

where $\sigma_{abs}$ is the absorption cross-section of a AuNP, $\kappa$ the mean thermal conductivity (surrounding media and substrate, respectively 0.19W/m/K and 1.38W/m/K), P the laser power, H the FWHM of the laser beam and A the unit cell area of the NP lattice. The absorption cross section of the gold NP, previously calculated for the same sample is 550 ± 100 nm².²¹

Calculation of the temperature generated by the sample over the entire power range used, assuming a room temperature of 20°C, is shown in Figure 4a. At a power of 12.4 W/cm², where no polymer dot is observed, the theoretical temperature is 90 ± 20°C, i.e. below the 130°C required for polymerization of the formulation. At the threshold power of 16.8 W/cm² where the first polymer plot is observed, the theoretical temperature is 115 ± 25°C. The temperature of 130°C required for polymerization of the formulation is here included in the error bar of the theoretical temperature, showing a very good correlation with the threshold observation of
polymerization.

<figure><img src="image_5.png" /><figcaption>**Figure 4.** Theoretical temperatures of the NP calculated as a function of incident power in the cw (a) and fs pulses (b) illumination regimes respectively. The blue cone represents the error bar. The dotted line at 130°C represents the experimental temperature of the thermopolymerizable formulation. The empty triangle marks the highest power used inducing an absence of experimental polymerization. The solid triangle marks the lowest power used inducing experimental polymerization.</figcaption></figure>

Temperature generation in gold NPs, in fs pulsed regime is described in references.⁴⁰,⁴⁵ First of all, since the experimentally used sample presents a high density of NPs, it is necessary to verify theoretically whether heat is generated mainly collectively $\Delta T^{ext}$ or confined $\Delta T^s$ in each NP. To do this, we must first check that the NP has time to cool between two laser pulses (no heat accumulations), using the following expressions:⁴⁰,⁴⁵

$$ \tau_d^{NP} = \frac{R_{NP}^2 \rho_{Au} c_{Au}}{3\bar{\kappa}} \quad (3) $$

$$ \frac{1}{\tau_d^{NP} f} = 10^5 \gg 1 \quad (4) $$

where $\tau_d^{NP}$ represents the relaxation time of heat to the external medium, $R_{NP}$ = 9.5 nm the NP radius, $\rho_{Au}$ = 19 300 kg/m³ the density of gold, $C_{Au}$ = 129 J/K/kg the heat capacity of gold, $\bar{\kappa}$ is the average thermal conductivity of the external medium (glass $\kappa_{glass}$= 1.38 W/m/K and formulation $\kappa_f$ = 0.19 W/m/K) and f = 5 kHz the laser frequency.
According to equation (4), the NP has sufficient time to cool down to room temperature between two pulses. There is no heat accumulation with each laser pulse. However, the heat dissipated into the external environment may have started the radical polymerization reaction as soon as illumination began. Finally, we can use the following formula<sup>40</sup> to assess the preponderance of collective temperature effect or temperature confinement.

$$ \frac{\Delta T^s}{\Delta T^{ext}} = \frac{\bar{\kappa}p^2}{\rho_{Au}C_{Au}LR_{NP}^3f} = 10^2 \gg 1 \quad (5) $$

where p = 33 nm the distance between two gold NPs and L the characteristic dimension of the heated zone (i.e., in our case, L is equivalent to $\sqrt{\pi R_{laser}^2}$ with $R_{laser}$ = 340 µm). The preponderance of heat confinement in each NP confirms the experimental observation of a polymer shell around each NP.

Finally, the calculation of the temperature reached by a NP following a pulse is described by:<sup>45</sup>

$$ \Delta T = \frac{\sigma_{abs}\langle I \rangle}{\rho_{Au}VC_{Au}f} \quad (6) $$

with $\sigma_{abs}$ the absorption cross section of the gold NP, <I> the irradiance and V the volume of the NP (the NP is considered as a disk). Calculation of the temperature generated by the sample in this illumination regime is shown in **Figure 4b**. At an irradiance of 0.9 W/cm², corresponding to an absence of polymer, the calculated temperature is 120 ± 15°C, at the lower limit of the 130°C required for polymerization of the formulation.

At the polymerization threshold corresponding to <I> = 1.9 W/cm², the gold NP reached a temperature of 215±30°C, exceeding the threshold temperature of the thermopolymerizable formulation (130 ±10°C). As observed for cw illumination, in the fs pulses regime too, there is a very good correlation between theoretical temperature calculations and the experimental threshold for thermal polymerization.

## Conclusion

These thermopolymerization experiments in the cw and fs pulses laser regimes, for the same incident wavelength on the same sample of dense gold NPs, provided experimental proof of the possibility to induce heat generation by collective effect using cw illumination and to confine
heat generation at the vicinity of the NPs using fs pulses illumination. To date, it is the first
experimental demonstration of heat confinement at the nanoscale using thermopolymerization.
We wish to emphasize here that both characterizations are made with the same
thermopolymerizable formulation, making it a promising temperature mapping tool. Finally,
this work paves the way for thermoplasmonic deposition of materials on both macroscopic
scales using a continuous laser, and on nanometric scales using a fs pulses laser. The latter laser
regime also makes it possible to rapidly generate a large number of core/shell NPs on this type
of gold sample with a high NP concentration.

**Materials and methods**

**Thermopolymerizable formulation**

The thermopolymerizable formulation is obtained by mixing a thermoinitiator, a difunctional SG1-based alkoxyamine (DIAMS)⁴⁶,⁴⁷ at 3%wt in a monomer PETA (pentaerythritol triacrylate, Sigma-Aldrich). The formulation is stirred for a few hours and stored in the refrigerator. It can be stored for several months without degrading. Before use, the formulation is returned to room temperature and stirred for 30 min. This formulation has a polymerization threshold temperature of 130±10°C. ²¹

**Fabrication and characterization of gold NPs samples**

Glass coverslips (22 mm × 22 mm 1.5 purchased from Carl-Roth) are first immersed successively in acetone (Sigma-Aldrich) and ethanol (Sigma-Aldrich) for 10 min each under ultrasound. They are then dried, put in an oven (Gestigkeit-PR5 3T) at 100 °C for 10 min, and treated with UV-ozone (UV/Ozone Procleaner Plus UV provided by Bioforce) during at least 30 min. A 2.7 nm layer of gold is then deposited by sputtering (Cressington 108 auto-Sputter Coater). Finally, the samples are annealed at 400 °C for 1 h.⁴⁸ The NPs presents a diameter of 19 ± 4 nm, and a height of 15 nm. The spacing between the NPs is 33 nm.

The extinction spectrum of gold NPs was determined using a UV-visible fiber spectrometer (AvaSpec-ULS2048-EVO from Avantes). The gold samples present a high density of gold NPs and a resonance in air of around 535 ± 5 nm (Figure 3a).

The procedure is the same for deposition of gold NPs on TEM grids without ultrasounds. This TEM grid presents two rectangular windows (1500 µm x 100 µm) covered with a 50 nm thick Si₃N₄ membrane (Ted Pella Inc.).
The presence of polymer around the NPs was observed by high resolution TEM (ARM200F JEOL).

## Optical set up

The fs pulses laser illumination at 532 nm was performed using a commercial optical parametric amplifier (TOPAS, Light Conversion) pumped by an amplified Ti:Sapphire laser (0.5 mJ, Pulsar, Amplitude Technologies). The laser frequency was 5 kHz with a pulse duration of 60 fs. The measured size of the laser beam onto the sample was 400 µm (fwhm – full width at half maximum). The gold NP sample is deposited on a plastic sample holder with a 1 cm diameter hole.

The cw laser illumination at 532 nm was performed using a Verdi 6 W laser (Coherent). The beam is a Gaussian beam. The gold NP sample is deposited on a plastic sample holder with a 1 cm diameter hole. The sample holder is located around 50 cm from the exit beam part. According to the supplier data set, the beam diameter is equal to 2.25 mm. Its power was measured by using a Thorlabs S350C power meter. A shutter is placed just before the sample.

## Numerical calculation

To calculate the effective absorption cross section of gold NPs, the MNPBEM (Metallic NanoParticle Boundary Elements Method) tool⁴⁹,⁵⁰ was used. The gold NPs were modeled by gold disks with rounded edges, diameter 19 nm, and thickness 15 nm deposited on a glass substrate (n = 1.52) immersed in an external medium with index n = 1.48, corresponding to the refractive index of the formulation. The absorption cross section was calculated in retarded mode for five gold disks in line for polarization along the line of the disks to take account of coupling effects between the NPs. A center-to-center spacing between the gold disks of 33 nm was taken into account.²¹ The theoretical resonance of this NP line is 570 ± 5 nm (matching the experimental resonance of the sample), compared to 555 ± 5 nm for the NP alone – clearly demonstrating the importance of taking the optical coupling effect into account. The absorption cross section of the gold NP, previously calculated for the same sample is 550 ± 100 nm².

Concerning the simulation for the shift of the plasmonic resonance with the polymer shell thickness, the simulated system was simplified to a single gold disk with a polymer shell (n=1.48) modeled by the same disk shape.

## Data availability

Data available upon request from the authors.
Acknowledgment

The authors want to thank Loic Vidal (IS2M) for providing the access to the TEM, and Olivier
Crégut and Stefan Haacke (IPCMS) for assistance with the femtosecond laser set-up.

Funding declaration

This work is part of the SUNRISE project and was partly carried out at the IPCMS-Ultrafast
user facility funded by PEPR LUMA and has benefited from state funding managed by the
Agence Nationale de la Recherche (French National Research Agency) under the France 2030
program, references ANR-22-EXLU-0002 and ANR-23-EXLU-0003.

This work was supported by Maison de la Chimie and ANR (POPCORN grant numbers ANR-21-CE09-00335). This work of the Interdisciplinary Institute HiFunMat, as part of the ITI 2021–2028 program of the University of Strasbourg, CNRS and Inserm, was supported by IdEx Unistra (ANR-10-IDEX-0002) and SFRI (STRAT'US project, ANR-20-SFRI-0012) under the framework of the French Investments for the Future Program.
Graphical abstract

<figure><img src="image_6.png" /></figure>

The laser illumination regime, cw or fs pulses, provides control over heat generation by collective or confined effect in each NP for the same dense gold sample. Both modes of heat generation can be observed by thermopolymerization.
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