# Copper(I)-Thiolate Coordination Polymers for In Situ Temperature Sensing in PDMS

Buqin Xu, Saly Hawila, Antoine Bérut, Gilles Ledoux, Stéphane Santucci, Loïc Vanel, A. Demessence

► To cite this version:

Buqin Xu, Saly Hawila, Antoine Bérut, Gilles Ledoux, Stéphane Santucci, et al., Copper(I)-Thiolate Coordination Polymers for In Situ Temperature Sensing in PDMS. ACS Applied Materials & Interfaces, 2025, 17 (30), pp.43730-43739. 10.1021/acsami.5c10786. http://onlinelibrary.wiley.com/doi/abs/10.1021/acsami.5c10786

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Submitted on 27 Aug 2025

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# Copper(I)-thiolate coordination polymers for *in-situ* temperature sensing in PDMS

Buqin Xu,ª Saly Hawila,ª Antoine Bérut, *ᵇ Gilles Ledoux,ᵇ Stéphane Santucci,ᶜ Loic Vanel,ᵇ Aude Demessence*ª

**KEYWORDS.** Nanothermometry, coordination polymers, composite films, dual emission, white light.

**ABSTRACT.** Copper thiolate coordination polymers (CPs) are photoluminescent compounds displaying good thermal stability and photoemission up to 120 °C offering high potential for optical temperature sensor applications. However, achieving composite films with stable RGB (red, green, and blue) emission remains a significant challenge in terms of materials fabrication and photophysical efficiency. This study presents a process to disperse homogeneously insoluble red and green emissive CPs in PDMS (Polydimethylsiloxane) matrices to fabricate environment friendly, transparent, flexible, stretchable and large-scale composite films. Depending on the ratio of the mixture of three primary colors: red and green emissive CPs mixed with a blue emissive organic polymer, a broad array of colored emissive composite films, including white, can be produced. Moreover, one composite film made of the red and green emissive CPs have been studied for ratiometric temperature sensing. The temperature of the film can be directly read with a unique dual-camera set-up, providing good spatial and temporal resolutions and thereby paving the way for optical temperature sensors, complementary to traditional infrared cameras that enable to measure the temperature of surfaces.

## 1. Introduction

In materials science, nanotechnologies and nanomedicine, temperature is a key parameter that has to be measured with a good spatial resolution (in the nanoscale), time-resolved response (in the nanosecond) and a high temperature sensitivity over a temperature range that will depend on the targeted applications going from physiological media to aerospace conditions.¹, ² Thus, nanothermometry is suitable to measure the temperature fluctuations of intracellular liquids, functional nanomaterials or microcircuits and understand the cellular events and chemical or physical properties changes. Non-contact optical thermometry technique has received tremendous attention in recent years.³ Such a technique can be successfully realized by using temperature-

<footnote>ª Université Claude Bernard Lyon 1, CNRS, Institut de Recherches sur la Catalyse et l'Environnement de Lyon (IRCELYON) – UMR 5256, Villeurbanne 69100, France.</footnote>

<footnote>ᵇ Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière (ILM) – UMR 5306, Villeurbanne 69100, France.</footnote>

<footnote>ᶜ École Normale Supérieure de Lyon, CNRS, Laboratoire de Physique - UMR 5672, Lyon 69364, France.</footnote>
dependent optical parameters, such as FIR (fluorescence intensity ratio), lifetime, intensity, polarization, bandwidth and spectral position.⁴, ⁵, ⁶ Depending on the applications, different luminescent materials have been used for optical nanothermometry with a predominance of the quantum dots, like CdSe, and lanthanide-based materials. Nevertheless these materials are considered as Critical Raw Materials by the European Union, and should be banned.⁷

An alternative and sustainable approach in luminescent materials are the d¹⁰ coinage metal-based materials, copper(I), silver(I) and gold(I), renowned for their intense and tunable photoemission.⁸, ⁹, ¹⁰, ¹¹ The investigation of hybrid Cu(I)-based materials has opened up new avenues for the advancement of luminescent and sustainable phosphors, that are able to exhibit luminescence solvatochromism, thermochromism and mechanochromism by displaying different photophysical processes like charge transfers, Aggregated-Induced Emission (AIE), and Thermally Activated Delayed Fluorescence (TADF).¹², ¹³, ¹⁴, ¹⁵, ¹⁶ Such photophysical diversities in copper(I) hybrid materials are allowed by changing the functional groups of the organic ligands, which induce different coordination networks and different weak interactions between the copper cations: the cuprophilic interactions, and/or the organic moieties. In the broad family of luminescent copper(I)-based hybrid materials, the neutral copper(I)-thiolate coordination polymers (CPs) exhibit good thermal and chemical stability due to the strong interaction between the thiolate ligand, acting as a soft base, and the Cu(I), acting as a soft acid.¹⁷, ¹⁸ Thus, some copper-thiolates can be emissive up to 230 °C¹⁹ and be homogenously dispersed in organic polymers, like polyvinylidene fluoride (PVDF).²⁰ This allowed to form ratiometric films by mixing two dyes: the yellow emissive silver-thiolate and the blue emissive coumarin for temperature reading from RT to 100 °C.²⁰

While mapping temperatures with micrometer resolution has been demonstrated with lanthanide-based upconverting nanoparticles,²¹ QD²², ²³ and iron-based spin-crossover compounds,²⁴ as optical thermometers, there is no report with sustainable luminescent CPs or Metal-Organic Frameworks (MOFs).²⁵, ²⁶ Polydimethylsiloxane (PDMS), as one of the most common polysiloxanes, has acquired substantial achievements, demonstrating promising potentials in biomedical equipment,²⁷ flexible electronics,²⁸, ²⁹ aerospace,³⁰ and other fields. PDMS-based luminescent materials combining the advantages of both mechanical properties of the PDMS and luminescent properties of the incorporated compounds, have been investigated in recent years, with significant progress in the field of flexible luminescent materials.³¹, ³², ³³ Nevertheless, the predominant issue afflicting contemporary fluorescent optical temperature sensors lies in their dependency to rare earth ion when integrated with PDMS.⁵, ³⁴, ³⁵, ³⁶

In this article, we describe the fabrication of multifunctional composite films combining green- and red-emissive sustainable copper(I)-thiolate-based CPs, [Cu₃Cl(*p*-SPhCl)₂]ₙ and [Cu(*p*-SPhCl)]ₙ, respectively (Figure 1), with a PDMS matrix. This simple process allows us to obtain eco-friendly, transparent, large-scale, homogeneous and stretchable composite films.³⁷ Depending on the composition of the films, the emission color under UV excitation can be tuned in all the visible spectrum and even be white by adding a blue-emissive organic dye. We then demonstrate that these films can be used for temperature measurement. Here, the temperature reading is based on ratiometry between the two phosphors and not based on luminescence intensity, which avoids the fluctuations in the local concentration of the emitting centers. We present a direct mapping of the temperature obtained with a custom-built dual-camera optical set-up that registers simultaneously its field of view in two different wavelength ranges, pointing out the great performance of those films as temperature-imaging sensors between room temperature and 100 °C.
<figure><img src="image_2.png" /><figcaption>**Figure 1.** Structures of the two photoluminescent coordination polymers: left the 1D [Cu(*p*-SPhCl)]<sub>n</sub> and right the 2D [Cu<sub>3</sub>Cl(*p*-SPhCl)<sub>2</sub>]<sub>n</sub>. Orange spheres are for Cu atoms; yellow, S; green, Cl and grey, C. Hydrogen atoms have been omitted for clarity. Below are the photographs of their associated emissive powders exposed under UV light at RT.</figcaption></figure>

**2. Results and discussion**

**2.1. Fabrication of the emissive composite films**

In order to get ratiometric emissive PDMS-based films, three emissive dyes were selected for their RGB (red, green, blue) photoluminescent colors at room temperature and above; namely two CPs: the 1D red-emissive [Cu(*p*-SPhCl)]<sub>n</sub> and the 2D green-emissive [Cu<sub>3</sub>Cl(*p*-SPhCl)<sub>2</sub>]<sub>n</sub>, and a blue-emitting organic polymer, poly(9,9-di-n-octylfluorenyl-2,7-diyl) also named Fluorenyl polymer (Scheme 1). Both copper(I)-thiolate-based CPs have been recently reported by some of us.<sup>38</sup> The copper-thiolate, [Cu(*p*-SPhCl)]<sub>n</sub>, is a 1D structure and exhibits a red emission at RT in solid state with maxima of excitation and emission centered at 425 nm and 620 nm, respectively and with a quantum yield of 23 %. The copper-chloride-thiolate CP, [Cu<sub>3</sub>Cl(*p*-SPhCl)<sub>2</sub>]<sub>n</sub>, is a 2D structure and display excitation and emission maxima at RT at 396 nm and 540 nm, respectively, with a quantum yield of 47 %. The origin of their emission has been attributed to a Ligand-to-Metal Charge Transfer (LMCT) for the red emissive CP and to a Halide-to-Metal Charge Transfer (XMCT) for the green one. In addition, these two CPs are stable up to 200 °C in air. The commercially available blue light-emitting organic polymer displays in the solid state at RT an emission spectrum with a vibronic structure with bands centered at 443, 466 and 494 nm.<sup>39</sup> The temperature-dependent photoemission properties under UV light of the CPs and the organic dye show that they exhibit a slight decrease of their emission intensity with increasing temperature, due to the increase of non-radiative decay, but they are all emitting at 120 °C in the solid state, providing a good reliability for temperature sensing from RT to 120 °C (Figure S1).

Knowing that the CPs are non-soluble in any solvent and water, the challenge is to fabricate PDMS-based films with good dispersion of the copper-thiolate crystallites and avoid their aggregation. For that purpose, the CPs were manually ground in a mortar for two minutes to obtain crystallites of less than 1 µm for [Cu(*p*-SPhCl)]<sub>n</sub> and around 3 µm for [Cu<sub>3</sub>Cl(*p*-SPhCl)<sub>2</sub>]<sub>n</sub> without
any loss of their crystallinity (Figure S2 and S3). The use of planetary centrifugal mixing (PCM) for the composite PDMS films allows great dispersion of the emissive compounds and homogeneity of the films.⁴⁰, ⁴¹ The general process for the films fabrication was (i) mix 20 g of PDMS base with 16 mg of a total amount of CPs and/or blue emissive dye, apply PCM, then add 2 g of curing agent with a standard 10:1 weight proportion with respect to the PDMS base, apply PCM again, (ii) spread the gel on a custom-made square metallic mold of 12 cm × 12 cm and (iii) heat at 60 °C with a hot plate, to cure the PDMS. After 3 hours curing, the composite films can be removed for further handling and studying (Scheme 1, Table 1 and process description in Materials part). The compositions of the films are summarized in Table 1 and are labelled S0 to S8. When the blue emissive dye is added in the formulation, it is previously dissolved in chloroform to allow good dispersion in PDMS and then evaporated (see process III in the Materials part). Pure red, green and blue emissive films are obtained respectively with the corresponding red and green emissive CPs and the blue emissive organic dye alone as samples S1, S4 and S7, respectively (Figure 2). In order to obtain intermediate film colors, the three starting red-green-blue (RGB) emissive compounds were mixed with a certain ratio (Table 1). Thus, orange films under UV light S2 and S3 are obtained when mixing the two CPs. In S2, 9.5 mg of [Cu(*p*-SPhCl)]n are added with 6.5 mg of [Cu₃Cl(*p*-SPhCl)₂]n, while in S3, it is the opposite, 6.5 mg of [Cu(*p*-SPhCl)]n for 9.5 mg of [Cu₃Cl(*p*-SPhCl)₂]n. Cyan (S5) and purple (S6) emissive films are formed by mixing 1 mg of the blue emissive organic dye with 15 mg of the green and red emissive CPs, respectively (Table 1 and Figure 2). Finally, when mixing together the RGB compounds (S8), a white emissive film is displayed. The photos of the films under natural and UV light show that this process allows to form homogenous and transparent films with bright luminescent colors by only using 0.07 wt% (16 mg for 22 g of PDMS) of the emissive compounds (Figures 2 and S4). Moreover, the SEM images of the composite films show homogenous surface, similar to the pure PDMS film (Figure S5). The emissive spectra at RT of the S1-S8 films were converted to the calculated CIE coordinates and plotted on a 1931 CIE chromaticity diagram, demonstrating the dispersion of their luminescence color based on the primary RGB colors (Figure 2). Some copper(I)-based halides are able to display single component white emission.⁴², ⁴³, ⁴⁴, ⁴⁵ MOFs and CPs also can exhibit intrinsic white emission and are used to fabricate white light-emitting diodes and devices.⁴⁶, ⁴⁷ Here efficient RGB copper-thiolate CPs based films are developed and could find further interests in display technologies. In particular, these CPs are chemically and thermically stable, and contain no CRM. The film process fabrication is cheap, can afford large films, and is cost effective because a very small amount of emissive components are required (0.07 wt%). Finally, the films are homogenous, avoiding non-radiative recombination and transparent.

In addition, the composite films show nearly identical mechanical properties to the pure PDMS film (Figure S6), as the quantity of compounds incorporated in the PDMS matrix remains very low for all samples. In particular, they show a very good mechanical flexibility, with a low Young's Modulus $E \approx 1$ MPa and a high stretchability with elongation at break $\epsilon_R \ge 100\%$ (Table S1).
<figure><img src="image_3.png" /><figcaption>**Scheme 1.** Illustration of the composite films fabrication process</figcaption></figure>

<table><caption>**Table 1.** Composition of the composite films and their emission under UV light ($\lambda_{ex}$ = 380 nm) at room temperature.</caption><thead><tr><th></th><th>PDMS base<br>(g)<br>wt %</th><th>Red CP<br>(mg)<br>wt %</th><th>Green CP<br>(mg)<br>wt %</th><th>Blue dye<br>(mg)<br>wt %</th><th>Curing<br>agent<br>(g)<br>wt %</th><th>λ<sub>em</sub> (nm)</th></tr></thead><tbody><tr><td>Sample 0<br>(S0)</td><td>20<br>90.9</td><td>0</td><td>0</td><td>0</td><td>2<br>9.1</td><td>No<br>emission</td></tr><tr><td>Sample 1<br>(S1)</td><td>20<br>90.84</td><td>16<br>0.07</td><td>0</td><td>0</td><td>2<br>9.08</td><td>650</td></tr><tr><td>Sample 2<br>(S2)</td><td>20<br>90.84</td><td>9.5<br>0.04</td><td>6.5<br>0.03</td><td>0</td><td>2<br>9.08</td><td>550, 630</td></tr><tr><td>Sample 3<br>(S3)</td><td>20<br>90.84</td><td>6.5<br>0.03</td><td>9.5<br>0.04</td><td>0</td><td>2<br>9.08</td><td>550, 630</td></tr><tr><td>Sample 4<br>(S4)</td><td>20<br>90.84</td><td>0</td><td>16<br>0.07</td><td>0</td><td>2<br>9.08</td><td>550</td></tr><tr><td>Sample 5<br>(S5)</td><td>20<br>90.84</td><td>0</td><td>15<br>0.07</td><td>1</td><td>2<br>9.08</td><td>440, 464,<br>494, 530</td></tr><tr><td>Sample 6<br>(S6)</td><td>20<br>90.84</td><td>15<br>0.07</td><td>0</td><td>1</td><td>2<br>9.08</td><td>440, 464,<br>494, 630</td></tr><tr><td>Sample 7<br>(S7)</td><td>20<br>90.84</td><td>0</td><td>0</td><td>16<br>0.07</td><td>2<br>9.08</td><td>440, 464,<br>494, 530</td></tr><tr><td>Sample 8<br>(S8)</td><td>20<br>90.84</td><td>9<br>0.04</td><td>6<br>0.03</td><td>1</td><td>2<br>9.08</td><td>440, 460,<br>500, 550</td></tr></tbody></table>
<figure><img src="image_4.png" /><figcaption>**Figure 2.** a. Scheme of the formation of the different composite films (S1 to S8) from the red and green emissive CPs and the blue emissive fluorenyl. b. Photos of the 12 cm × 12 cm composite films, S1 to S8, under UV light at RT. c. CIE chromaticity diagram of the eight films.</figcaption></figure>

## Photoluminescent characterizations of the composite films

Photoluminescence experiments from -150 °C to 150 °C on the eight emissive composite films have been carried out to demonstrate their luminescence thermochromism (Figure S7). In order to focus on ratiometric thermometry working between RT and 100 °C, the emission spectra measured from 0 °C to 120 °C are plotted in Figure 3 (S1 to S4) and on Figure 4 (S5 to S8) and the CIE are presented in Figure S8 and Table S2. The presence of the red emissive polymer [Cu(*p*-SPhCl)]n induces a prominent emission band centered at 650 nm in S1 and the green emissive counterpart, [Cu₃(*p*-SPhCl)₂Cl]n, shows a band centered at 550 nm in S4 (Figure 3). The photoluminescent integration area of the red CP is almost constant from -30 to 60 °C and then it decreases with the temperature increasing, while the integration of the emission band of the green CP follows an exponential decay from -30 to 150 °C (Figure S9). In S2 and S3, the presence of the two CPs induces double emission bands centered at 550 nm and 630 nm. With the increase of temperature, the intensity of each band decreases. Still, depending on the amount of CPs, the decrease of the intensity is not the same. In S2, containing more red emissive CP, the red emission band becomes predominant at 120 °C, whereas the green emission decreases gradually when increasing the temperature. Conversely, in S3, the green emission band predominantly decreases, while the intensity of the red emission remains relatively constant upon temperature elevation. When lowering the temperature after heating, all emission bands in S1, S2, S3 and S4 return to nearly the same positions as initially observed at 20 °C. This phenomenon indicates the reversibility of luminescence, which is an important characteristic for temperature imaging applications.
<figure><img src="image_5.png" /><figcaption>**Figure 3.** Photoemission of S1-S4 (λex = 380 nm) from 20 °C to 120 °C and back to RT (black curve).</figcaption></figure>

Sample S7, made of pure fluorenyl, exhibits four distinct emission bands at 440 nm, 464 nm, 494 nm and 530 nm, which are assigned to the 0-0, 0-1, 0-2 and 0-3 vibronic transitions, respectively (Figure 4).⁴⁸ Upon an increase in temperature, the integration of the bands of this organic polymer decreases linearly from -30 to 120 °C (Figure S9). When 1 mg of fluorenyl polymer is mixed with 15 mg of each of the two CPs, the emission spectra show that the vibronic bands of the blue emissive organic dye are still predominant and the green band of [Cu₃Cl(p-SPhCl)₂]n for S5 can be observed at 550 nm and the red one of [Cu(p-SPhCl)]n for S6 at 650 nm (Figure 4). Finally, the cold white emission of S8 involves the three emissive components (Red, Green, Blue). The blue dye induces emission bands at 440 nm, 460 nm, and 500 nm. Furthermore, the green emissive [Cu3(p-SPhCl)2Cl]n exhibits an emission signal at 550 nm, while the red emissive [Cu(p-SPhCl)]n is anticipated to emit at 650 nm, but no obvious band is observed, as one would expect. This may be explained by the lower quantum yield of this CP compare to the other green and blue components.

An important point, is that contrary to what is observed with red and green emissive CPs, the addition of the blue emissive poly(9,9-di-n-octylfluorenyl-2,7-diyl) makes the composite films unable to keep reversible luminescence above 90 °C. When the temperature is increased to 120°C, all emission bands in S5, S6 and S7 exhibit a small blue shift and their positions and intensity remain altered when returning to RT. This may be due to the fact that the organic polymer is semicrystalline with a melting point near 160 °C.⁴⁸ Because it is not stable with temperature, the films S5-S8 cannot be used for thermometry, thus the temperature-resolved imaging experiments will be focused on S2 and S3 made of the two CPs.
<figure><img src="image_6.png" /><figcaption>**Figure 4.** Photoemission of S5-S8 (λex = 380 nm) from 20 °C to 120 °C and back to RT (black curve).</figcaption></figure>

Evaluation of the composite films for ratiometric temperature sensing

The measurement method is based on ratiometric luminescent thermometry with S2 and S3 exhibiting two emission bands in the green and red domains which display different intensity variation with temperature.⁴⁹ Therefore, by measuring the ratio of the light intensity between the two spectral bands, one can access to a quantity that depends on temperature, but not on the quantity of light that the sample receive, nor on the quantity of emissive components inside the sample. To determine which composite film, between S2 and S3, is the most suited for this type of experiment, the green and red emission integrals, I<sub>G</sub> (integration from 450 nm to 605 nm) and I<sub>R</sub> (integration from 605 nm to 800 nm), where calculated (Figures 5a and 5b and S10). Then, the ratio I = I<sub>R</sub> / I<sub>G</sub>, is plotted with the temperature (-30 °C to 150 °C). For S2, the I ratio is linear, due to almost constant I<sub>R</sub> values against the decreasing I<sub>G</sub> values with increasing temperature. For S3, the slight and simultaneous decreasing of both I<sub>R</sub> and I<sub>G</sub> induces a sigmoid curve. For temperature measurement a linear curve is preferred for better accuracy. This can be observed on the relative sensitivity (Sr = (∂I/∂T)/I) of both samples, that allows to evaluate their performance as a ratiometric thermometer (Figure 5c). Notably, S2 displays a more consistent Sr between 0.20 %.°C<sup>-1</sup> and 0.31 %.°C<sup>-1</sup> across the temperature range from -30 °C to 120 °C, while S3 has Sr between 0.04 %.°C<sup>-1</sup> and 0.27 %.°C<sup>-1</sup>. Therefore, S2 is the best candidate for the temperature-resolved imaging experiments, although its sensitivity is modest.⁵⁰
<figure><img src="image_7.png" /><figcaption>**Figure 5.** Evolution with the temperature of the green emission integral (I<sub>G</sub>: integration from 450 nm to 605 nm, green circles), the red emission integral (I<sub>R</sub>: integration from 605 nm to 800 nm, red circles) and the ratio I = I<sub>R</sub> / I<sub>G</sub> (empty circles) with the linear (black line) and sigmoid fits (grey curve) for S<sub>2</sub> (a.) and S<sub>3</sub> (b.), respectively. c. Relative sensitivity (Sr) with temperature for S<sub>2</sub> (black circles) and S<sub>3</sub> (grey circles).</figcaption></figure>

**Double-camera set-up for temperature imaging**

Temperature imaging experiments with a piece of **S2** has been performed with a custom-built
experimental set-up that is shown in Figure 6. The sample is illuminated by a UV source of
wavelength 375 nm (depicted as a purple beam in the figure) configured in reflection mode.
Notably, due to the sample's transparency, it can also be illuminated in transmission mode,
allowing for additional optical analysis.³¹ The sample emits light with several emission bands
(yellow beam in the figure), corresponding to the two different photoemissive compounds: the red
emissive [Cu(*p*-SPhCl)]<sub>n</sub> and the green emissive [Cu<sub>3</sub>Cl(*p*-SPhCl)<sub>2</sub>]<sub>n</sub>. This light is collected with
a refractive telescope made of three lenses (L0, L1 and L2). A long pass filter prevents UV light
from the source to enter the optical set-up. A dichroic mirror separates the light into two
wavelength ranges (605 nm to 950 nm, and 400 nm to 605 nm respectively), allowing to collect
independently the two emissions bands (red and green beams, respectively) on two different
cameras (C1 and C2). Two mechanical pieces allow translation (M1) and rotation (M2) of the
cameras, so that their fields of view can be matched as precisely as possible. This ensures that the
two cameras are imaging the same part of the sample, but in two different spectral ranges. The two
images from the two cameras are then numerically divided to obtain for each pixel the ratio of the
two wavelength bands, hence, the temperature map of the sample. Technical details about the
optics elements used in the set-up are presented in the Experimental Methods section.
<figure><img src="image_8.png" /><figcaption>**Figure 6.** Scheme of the dual optical set-up for temperature imaging: L0, L1 and L2 are lenses, M1 and M2 are mechanical pieces for translation and rotation, respectively, C1 and C2 are charge-coupled device (CCD) cameras. The sample is illuminated with UV light (purple beam) and emits visible light (yellow beam), that is decomposed in two separated wavelength ranges (green and red beam, respectively) by the dichroic mirror.</figcaption></figure>

First the set-up was calibrated by placing the sample in a chamber equipped with a temperature proportional-integral-derivative (PID) controller, to measure the value of the intensity ratio between the two cameras, as a function of the temperature, in the range of 20-75 °C. The calibration curve is shown in Figure 7. As expected, the average ratio of pixel intensity between the two cameras, which corresponds approximately to the integration ratio I, increases almost linearly with the temperature, and the average sensitivity $S_R$ is about 0.2 %.°C⁻¹.
<figure><img src="image_9.png" /><figcaption>**Figure 7.** Calibration curve of the two cameras set-up used with sample S2. The two images (taken by camera C1 and C2) are divided pixel by pixel, and the average value of the ratio of pixel intensity I is plotted as a function of the temperature.</figcaption></figure>

Finally, to test the temperature imaging capacity of this dual-camera set-up, the temperature field in the S2 composite film is measured when the sample is heated with a soldering iron heater set at 150 °C. The full movie is available in the ESI. Snapshots from the movie are shown in Figure 8 and illustrate the important observed features. At the beginning (t = -9.5 s), the sample is homogenous at room temperature (≈ 23.5 °C). At t = -8.5 s, the tip of the soldering iron is put in contact with the sample. The tip is let in contact with the sample for a few seconds. Just before the tip is removed (t = -1 s), the area surrounding the tip has already reached a higher temperature of about 60 °C. Once the tip is removed (t = 0 s to t = 10 s), we observe a transient evolution of the temperature field, which progressively returns to being homogeneous at room temperature (the final state is reached after a few minutes of thermal relaxation). To verify quantitatively the validity of this measurement, the average temperature relaxation of the sample over time has been computed (Figure 9) and compared with the expected thermal behavior of PDMS (black dashed line). The measurement is in very good agreement with the analytical solution of the heat equation with the thermal diffusivity of PDMS D ≈ 1.80 × 10⁻⁷ m².s⁻¹ given by the manufacturer. This clearly shows that realistic temperature imaging is achievable using the photoemissive CPs mixed within a PDMS matrix and a dual camera optical set-up.
<figure><img src="image_10.png" /><figcaption>**Figure 8.** Snapshots from the movie (Support Video in ESI) where a soldering iron tip is used to heat a piece of S2 composite film, whose photoemission is measured with the dual-camera set-up (Figure 6). The six snapshots are taken at different times (t = 0 is arbitrarily chosen at the time when the soldering iron tip is first placed in contact with the sample). The color bar indicates the temperature, obtained from the calibration procedure (Figure 7).</figcaption></figure>

In this measurement, the spatial resolution is 705 pixels.cm⁻¹ (both vertically and horizontally) and the temporal resolution is 20 images.s⁻¹. The spatial resolution of the set-up depends only on the optics (lenses) and cameras sensors, while the temporal resolution is only limited by the camera’s framerate. Indeed, the size of the CPs dispersed in the PDMS film is about a few microns (Figure S2), and their response time is about 6-7 µs.³⁸ It is therefore possible to reach higher spatial or temporal imaging resolutions, simply by changing the optical parts used in the set-up.
<figure><img src="image_11.png" /><figcaption>**Figure 9.** Time evolution of the average temperature of the sample measured during the heating experiment (t = 0 is arbitrarily chosen at the time when the soldering iron tip is removed from the sample). The black dashed line is the theoretical temperature relaxation predicted from the heat equation for a PDMS sample with thermal diffusivity *D* = 1.80 × 10⁻⁷ m².s⁻¹ (Figure S11).</figcaption></figure>

**Conclusion**

A simple methodology consisting of mixing one, two or three luminescent compounds: the red emissive [Cu(*p*-SPhCl)]n CP, the green emissive [Cu₃(*p*-SPhCl)₂Cl]n CP and the blue emissive poly(9,9-di-n-octylfluorenyl-2,7-diyl) organic polymer with PDMS matrix, allows to produce transparent, uniform, and environmentally friendly luminescent composite films with tunable colors and even white. These films exhibit thermo-stability up to 200 °C and are photoluminescent up to 120 °C and they retain the mechanical properties of PDMS films, which make them easy to stretch and deformable over 100 % strain. Moreover, a composite film, made of the two red and green emissive CPs, displays a temperature-sensitive effect that has been measured with a dual-camera optical set up with good spatial and temporal resolutions. All these remarkable properties of these copper-thiolate CPs based composite films make them suitable candidates to be used as flexible wearable sensing devices, or for in-situ temperature measurements as an alternative to traditional IR cameras.
## Experimental Section

**Chemicals.** Copper (II) chloride dihydrate ($CuCl_2 \cdot 2H_2O, \ge 99 \%$) was purchased from Alfa Aesar. 4-Chlorothiophenol (or *p*-HSPhCl, 97%) from Sigma-Aldrich. Ethanol and DMF were purchased from VWR Chemicals. The blue light emitting organic polymer, poly(9,9-di-n-octylfluorenyl-2,7-diyl) (Fluorenyl polymer), is a commercial chemical purchased from Sigma Aldrich. The PDMS films are obtained from a DOWSIL™ 184 Silicone Elastomer Kit made of DOWSIL™ 184 Silicone Elastomer Base and DOWSIL™ 184 Silicone Elastomer Curing Agent, which have to be mixed together in a 10:1 ratio. All reagents and solvents were used as received. The syntheses of the $[Cu(p-SPhCl)]_n$ and $[Cu_3(p-SPhCl)_2Cl]_n$ CPs are carried out by following the literature.³⁸ They were manually ground in a mortar for two minutes before to be used.

## Fabrication of the PDMS composite films

The composite films are fabricated by using a planetary mixer is from Hauschild SpeedMixer™ DAC 150.3 SP and by following the three processes depending on their compositions.

**Process I (pure PDMS films):** Mix 20.0 g of PDMS base with 2.0 g of curing agent at 3500 rpm for 40 s.

**Process II (CP@PDMS films):** Mix the ground CPs with 20.0 g of PDMS base by using the following sequence:1000 rpm for 30 s, 2000 rpm for 30 s, 3000 rpm for 120 s, 2000 rpm for 30 s, 3500 rpm for 30 s. Subsequently, mix with 2.0 g of curing agent by following the same procedure.

**Process III (CP/dye@PDMS films):** Mix the blue-emissive organic polymer dissolve in 0.5 mL of $CH_3Cl$ with 20.0 g of PDMS base, then mix as follows:1000 rpm for 30 s, 2000 rpm for 60 s, 3500 rpm for 30 s, 1000 rpm for 30 s. Allow the mixture to stand under vacuum overnight to remove the solvent. After solvent removal, mix the resulting gel with the ground CPs then mix as follows:1000 rpm for 30 s, 2000 rpm for 60 s, 3500 rpm for 30 s, 1000 rpm for 30 s and finally add 2.0 g of curing agent and follow the same mixing procedure as above.

## Curing Protocol:

Carefully apply the mixed gel onto a 12 cm × 12 cm metallic mold that is covered with a soda-lime glass of a 2 mm thickness in order to ensure a flat bottom surface during the PDMS casting, and heat at 60 °C for 3 hours, then the film can be manually removed.

## Characterization techniques

**SEM:** SEM images were obtained with a FEI Quanta 250 FEG scanning electron microscope. Samples were mounted on stainless pads and sputtered with Au to prevent charging during the observation.

**PXRD:** Powder X-Ray diffraction (PXRD) was carried out on a Bruker D8 Advance A25 diffractometer using Cu Kα radiation equipped with a 1-dimensional position-sensitive detector (Bruker LynxEye). X-Ray scattering was recorded between 4° and 90° (2θ) with 0.02° steps and 0.5 s per step (28 min for the scan). Divergence slit was fixed to 0.2° and the detector aperture to 189 channels (2.9°).
**Photoluminescence excitation and emission spectra measurements:** The photoluminescence measurements were performed on a custom-made apparatus at Institut Lumière Matière, University of Lyon. The sample was illuminated by an EQ99X laser driven light source filtered by a Jobin-Yvon Gemini 180 monochromator. The exit slit from the monochromator was then reimaged on the sample by two 100m focal length, 2 inch diameter MgF2 lenses. The whole apparatus has been calibrated by means of a New port 918D low power calibrated photodiode sensor over the range 190 - 1000 nm. The resolution of the system being 4 nm. The emitted light from the sample is collected by an optical fiber connected to a Jobin-Yvon TRIAX320 monochromator equipped with a cooled CCD detector. At the entrance of the mono-chromator different long pass filter can be chosen in order to eliminate the excitation light. The resolution of the detection system is 2 nm. Temperature control over the sample was regulated with a THMS-600 heating stage with T95-PE temperature controller from Linkam Scientific Instrum.

**Transmittance:** Transmission measurements were performed on Perkin Elmer UV/vis/NIR lambda 900spectrometer with a limiting diaphragm of 1mm and a resolution of 1 nm.

**Mechanical measurements:** mechanical testing of the composite films was performed using a custom-made tensile test apparatus at Institut Lumière Matière. The films have a typical thickness of about 1 mm. For each film, two to five samples of approximative dimensions 10 mm x 30 mm are manually cut and measured. Each sample is placed in an aluminium jaws, and then stretched uniaxially at a constant elongation rate of 50 mm/s thanks to a stepper motor (from Faulhaber) equipped with a reducer (from Mijno), so that each step corresponds to a displacement of 1/400 µm. The force is measured by a force transducer (from Interface) connected to an analog-to-digital acquisition card (from National Instruments). The stress-strain curves are recorded with a 1000 Hz acquisition rate, and then smoothed using a moving average to reduce electrical noise. The Young Modulus is obtained by a numerical fit of the linear part of each stress-strain curve.

**Dual camera optical experiments:** The dual-camera optical set-up is presented in Figure 6. The UV source is a LED with emission wavelength $\lambda_e$ around 375 nm (Thorlabs M375L4) and a band-pass filter (Edmund Optics #86-736) centered around the same wavelength to improve monochromaticity. The UV filter (Thorlabs FELH0400) is a high-pass filter with cutting wavelength of 400 nm. The lens L0 has a focal distance $f0 = 150$ mm, both lenses L1 and L2 have a focal distance $f1 = f2 = 50$ mm. The dichroic mirror (Edmund Optics #86-335) has a cut-on wavelength $\lambda_c = 605$ nm, chosen to work with sample S2. Both cameras C1 and C2 are Basler acA1300-200um, with a resolution of 1024×1280 pixels, and a maximal acquisition framerate of 200 images/s.

**Films transparency:** Transparency was estimated from transmittance measurements (Figure S4). The sample 0 (S0) with pure PDMS polymer is 93.5 % transparent from 400 nm to 1126 nm. Sample S1 containing pure red emissive polymer starts from 0 % at 400 nm and reaches 59 % at 1126 nm. Sample S4 containing pure green emissive polymer starts at 10% at 400 nm and goes up to 59 % at 1126 nm, surpassing S1 in this range. The transparency levels of the other composite films with coordination polymers (S2 and S3) do not exhibit significant variations with regard to the transparency of S4. Regarding the film samples containing the organic dye of poly(9,9-di-n-octylfluorenyl-2,7-diyl) (samples S5, S6, S7, and S8): the S7 shows the highest transparency in the visible range, on the contrary S6 has the lowest transparency of all samples. S5 and S8 show transparencies variation pattern similar to S2.
## ASSOCIATED CONTENT

**Supporting Information.** Photoemission spectra, SEM images, PXRD; Transmittance, stress-strain curves and mechanical properties are available free of charge in a PDF file. The full movie of the heat of the film and its photoemission is also available as a MP4.

## AUTHOR INFORMATION

### Corresponding Authors

**Antoine Bérut** - Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière (ILM) – UMR 5306, Villeurbanne 69100, France. [https://orcid.org/0000-0001-8549-086X](https://orcid.org/0000-0001-8549-086X). Email : [antoine.berut@univ-lyon1.fr](mailto:antoine.berut@univ-lyon1.fr).

**Aude Demessence** - Université Claude Bernard Lyon 1, CNRS, Institut de Recherches sur la Catalyse et l'Environnement de Lyon (IRCELYON) – UMR 5256, Villeurbanne 69100, France. [https://orcid.org/0000-0002-8690-5489](https://orcid.org/0000-0002-8690-5489). Email : [aude.demessence@ircelyon.univ-lyon1.fr](mailto:aude.demessence@ircelyon.univ-lyon1.fr).

### Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

## ACKNOWLEDGMENT

This work was supported by the CNRS and its Mission for Transversal and Interdisciplinary Initiatives, by the LABEX iMUST of the University of Lyon (ANR-10-LABX-0064), created within the « Plan France 2030 » set up by the French government and managed by the French National Research Agency (ANR) and by ANR-22-CE30-0019.

## REFERENCES

1. Jaque, D.; Vetrone, F., Luminescence nanothermometry. *Nanoscale* **2012**, *4*, 4301.

2. Harrington, B.; Ye, Z.; Signor, L.; Pickel, A. D., Luminescence Thermometry Beyond the Biological Realm. *ACS Nanosci. Au* **2024**, *4*, 30.

3. Kesarwani, V.; Rai, V. K., Non-contact optical thermometry via non-thermally coupled levels in upconverting glass. *J. Appl. Phys.* **2022**, *132*.

4. Chen, H.; Bai, G.; Yang, Q.; Hua, Y.; Xu, S.; Chen, L., Non-contact fluorescence intensity ratio optical thermometer based on Yb³⁺/Nd³⁺ codoped Bi₄Ti₃O₁₂ microcrystals. *J. Lumin.* **2020**, *221*, 117095.

5. Kumar, R.; Binetti, L.; Nguyen, T. H.; Alwis, L. S. M.; Sun, T.; Grattan, K. T. V., Optical fibre thermometry using ratiometric green emission of an upconverting nanoparticle-polydimethylsiloxane composite. *Sens. Actuator A-Phys.* **2020**, *312*, 112083.
6. Nordine, P. C.; Krishnan, S.; Weber, J. K. R.; Schiffman, R. A., Non-contact temperature measurement. *Adv. Space Res.* **1991**, *11*, 17.

7. Hool, A.; Helbig, C.; Wierink, G., Challenges and opportunities of the European Critical Raw Materials Act. *Miner. Econ.* **2023**, *37*.

8. Barbieri, A.; Accorsi, G.; Armaroli, N., Luminescent complexes beyond the platinum group: the d10 avenue. *Chem. Commun.* **2008**, *2185*.

9. Veselska, O.; Demessence, A., d¹⁰ Coinage Metal Organic Chalcogenolates: from Oligomers to Coordination Polymers. *Coord. Chem. Rev.* **2018**, *355*, 240.

10. Yam, V. W.-W.; Wong, K. M.-C., Luminescent metal complexes of d⁶, d⁸ and d¹⁰ transition metal centres. *Chem. Commun.* **2011**, *47*, 11579.

11. Yam, V. W.-W.; Lo, K. K.-W., Luminescent polynuclear d¹⁰ metal complexes. *Chem. Soc. Rev.* **1999**, *28*, 323.

12. Housecroft, C. E.; Constable, E. C., TADF: Enabling luminescent copper(I) coordination compounds for light-emitting electrochemical cells. *J. Mater. Chem. C* **2022**, *10*, 4456.

13. Armaroli, N.; Accorsi, G.; Cardinali, F.; Listorti, A., Photochemistry and Photophysics of Coordination Compounds: Copper. *Top. Curr. Chem.* **2007**, *280*, 69.

14. Perruchas, S., Molecular copper iodide clusters: a distinguishing family of mechanochromic luminescent compounds. *Dalton Trans.* **2021**, *50*, 12031.

15. Czerwieniec, R.; Leitl, M. J.; Homeier, H. H. H.; Yersin, H., Cu(I) complexes – Thermally activated delayed fluorescence. Photophysical approach and material design. *Coord. Chem. Rev.* **2016**, *325*, 2.

16. Lescop, C., Coordination-Driven Supramolecular Synthesis Based on Bimetallic Cu(I) Precursors: Adaptive Behavior and Luminescence. *Chem. Rec.* **2021**, *21*, 544.

17. Schlachter, A.; Harvey, P. D., Properties and applications of copper halide-chalcogenoether and -chalcogenone networks and functional materials. *J. Mater. Chem. C* **2021**, *9*, 6648.

18. Veselska, O.; Cai, L.; Podbevšek, D.; Ledoux, G.; Guillou, N.; Pilet, G.; Fateeva, A.; Demessence, A., Structural diversity of coordination polymers based on an heterotopic ligand: Cu(II)-carboxylate vs Cu(I)-thiolate. *Inorg. Chem.* **2018**, *57*, 2736.

19. Veselska, O.; Podbevšek, D.; Ledoux, G.; Fateeva, A.; Demessence, A., Intrinsic Triple-Emitting 2D Copper Thiolate Coordination Polymer as a Ratiometric Thermometer Working over 400 K Range. *Chem. Commun.* **2017**, *53*, 12225.

20. Abdallah, A.; Vaidya, S.; Hawila, S.; Ornis, S.-L.; Nebois, G.; Barnet, A.; Guillou, N.; Fateeva, A.; Mesbah, A.; Ledoux, G.; Bérut, A.; Vanel, L.; Demessence, A., Luminescent and sustainable d¹⁰ coinage metal thiolate coordination polymers for high-temperature optical sensing. *iScience* **2023**, *26*, 106016.

21. van Swieten, T. P.; van Omme, T.; van den Heuvel, D. J.; Vonk, S. J. W.; Spruit, R. G.; Meirer, F.; Garza, H. H. P.; Weckhuysen, B. M.; Meijerink, A.; Rabouw, F. T.; Geitenbeek, R. G., Mapping Elevated Temperatures with a Micrometer Resolution Using the Luminescence of Chemically Stable Upconversion Nanoparticles. *ACS Appl. Nano Mater.* **2021**, *4*, 4208.

22. Liu, J.; Zhang, H.; Selopal, G. S.; Sun, S.; Zhao, H.; Rosei, F., Visible and Near-Infrared, Multiparametric, Ultrasensitive Nanothermometer Based on Dual-Emission Colloidal Quantum Dots. *ACS Photonics* **2019**, *6*, 2479.
23. Laha, S. S.; Naik, A. R.; Kuhn, E. R.; Alvarez, M.; Sujkowski, A.; Wessells, R. J.; Jena, B. P., Nanothermometry Measure of Muscle Efficiency. *Nano Lett.* **2017**, *17*, 1262.

24. Horniichuk, O. Y.; Ridier, K.; Zhang, L.; Zhang, Y.; Molnár, G.; Salmon, L.; Bousseksou, A., High-Sensitivity Microthermometry Method Based on Vacuum-Deposited Thin Films Exhibiting Gradual Spin Crossover above Room Temperature. *ACS Appl. Mater. Interfaces* **2022**, *14*, 52140.

25. Kanzariya, D. B.; Chaudhary, M. Y.; Pal, T. K., Engineering of metal-organic frameworks (MOFs) for thermometry. *Dalton Trans.* **2023**, *52*, 7383.

26. Zhang, S.; Xiao, J.; Zhong, G.; Xu, T.; Zhang, X., Design and application of dual-emission metal-organic framework-based ratiometric fluorescence sensors. *Analyst* **2024**, *149*, 1381.

27. Miranda, I.; Souza, A.; Sousa, P.; Ribeiro, J.; Castanheira, E. M. S.; Lima, R.; Minas, G., Properties and Applications of PDMS for Biomedical Engineering: A Review. *J. Funct. Biomater.* **2022**, *13*, 2.

28. Chen, J.; Zheng, J.; Gao, Q.; Zhang, J.; Zhang, J.; Omisore, O. M.; Wang, L.; Li, H., Polydimethylsiloxane (PDMS)-Based Flexible Resistive Strain Sensors for Wearable Applications. *Appl. Sci.* **2018**, *8*, 345.

29. Qi, D.; Zhang, K.; Tian, G.; Jiang, B.; Huang, Y., Stretchable Electronics Based on PDMS Substrates. *Adv. Mater.* **2021**, *33*, 2003155.

30. Piscitelli, F.; Rollo, G.; Scherillo, F.; Lavorgna, M., Innovative Graphene-PDMS sensors for aerospace applications. *Adv. Mater. Lett.* **2019**, *10*, 533.

31. Zhou, Y.; Ledoux, G.; Philippon, D.; Descartes, S.; Martini, M.; He, S.; Desroches, C.; Fournier, D.; Journet, C.; Bois, L., Laser-Induced Heating in GdVO₄: Yb³⁺/Er³⁺ Nanocrystals for Thermometry. *ACS Appl. Nano Mater.* **2022**, *5*, 16388.

32. Dong, Y.; Zhong, H.; Wu, Y.; Deng, J., Preparation and Applications of Polydimethylsiloxane-Based Fluorescent Materials. *Macromol. Rapid Commun.* **2023**, *44*, 2300106.

33. Li, C.; He, Q.; Wang, Y.; Wang, Z.; Wang, Z.; Annapooranan, R.; Latz, M. I.; Cai, S., Highly robust and soft biohybrid mechanoluminescence for optical signaling and illumination. *Nat. Commun.* **2022**, *13*, 3914.

34. Gao, R.; Fang, X.; Yan, D., Recent developments in stimuli-responsive luminescent films. *J. Mater. Chem. C* **2019**, *7*, 3399.

35. Liu, B.; Zhang, S.; Li, M.; Wang, Y.; Mei, D., Metal-Organic Framework/Polyvinyl Alcohol Composite Films for Multiple Applications Prepared by Different Methods. *Membranes* **2023**, *13*, 755.

36. Bispo-Jr, A. G.; Mazali, I. O.; Sigoli, F. A., Single-center LnIII ratiometric luminescent temperature probes based on singlet → singlet and singlet → triplet sensitizations. *J. Mater. Chem. C* **2022**, *10*, 14151.

37. Xu, W.; Chahine, N.; Sulchek, T., Extreme Hardening of PDMS Thin Films Due to High Compressive Strain and Confined Thickness. *Langmuir* **2011**, *27*, 8470.

38. Hawila, S.; Xu, B.; Massuyeau, F.; Gautier, R.; Guillou, N.; Fateeva, A.; Lebègue, S.; Oh, I.; Kim, W. J.; Ledoux, G.; Monge, M.; Mesbah, A.; Demessence, A., Red emissive 1D Copper(I) Thiolates and green emissive 2D Copper(I) Halide Thiolates displaying second harmonic generation and two-photon absorption processes. *Chem. Eur. J.* **2025**, e202501113.

39. Wu, C.; McNeill, J., Swelling-Controlled Polymer Phase and Fluorescence Properties of Polyfluorene Nanoparticles. *Langmuir* **2008**, *24*, 5855.
40. Fang, T.-C.; Peng, S.-Y.; Liao, Y.-C., Stretchable Polydimethylsiloxane Composites with Emulsified Ionic Materials and Thermochromic Applications. *ACS Omega* **2020**, *5*, 9458.

41. Hu, Z.; Zhang, H.; Sui, G.; Zhang, Z., Alkane-containing polydimethylsiloxane elastomer composite films with excellent tunable light transmittance. *Optical Mater.* **2022**, *128*, 112361.

42. Zhou, S.; Chen, Y.; Li, K.; Liu, X.; Zhang, T.; Shen, W.; Li, M.; Zhou, L.; He, R., Photophysical studies for Cu(i)-based halides: broad excitation bands and highly efficient single-component warm white-light-emitting diodes. *Chem. Sci.* **2023**, *14*, 5415.

43. Rocheteau, A.; Lemeur, L.; Cordier, M.; Paris, M.; Mevellec, J.-Y.; Latouche, C.; Serier-Brault, H.; Perruchas, S., Rational Design of Single-Component White-Light Emissive Molecular Copper Clusters. *Adv. Optical Mater.* **2025**, *13*, 2402040.

44. Lian, L.; Wang, S.; Ding, H.; Liang, G.; Zhao, Y.-B.; Song, H.; Lan, X.; Gao, J.; Chen, R.; Zhang, D.; Zhang, J., Single-Component White-Light Emitters with Excellent Color Rendering Indexes and High Photoluminescence Quantum Efficiencies. *Adv. Optical Mater.* **2022**, *10*, 2101640.

45. Meng, W.; Wang, C.; Li, Y.; Hu, G.; Sui, S.; Xu, G.; Peng, M.; Deng, Z., Synthesis of Efficient and Stable Tetrabutylammonium Copper Halides with Dual Emissions for Warm White Light-Emitting Diodes. *Chem. Eur. J.* **2023**, *29*, e202202675.

46. Chiu, N.-C.; Smith, K. T.; Stylianou, K. C., Metal-organic frameworks for white light emission: From synthesis to device fabrication. *Coord. Chem. Rev.* **2022**, *459*, 214441.

47. Yang, X.-G.; Chen, Y.-J.; Yin, P.-P.; Diao, J.-W.; Cheng, Y.-Y.; Ma, L.-F., Direct White-Light Emitting From a Single Metal–Organic Framework with Dual Phosphorescence Peaks. *Inorg. Chem.* **2023**, *62*, 19389.

48. Lucas, F. E.; Marletta, A.; Nobuyasu, R. S.; de Araújo, J. V. G.; de Souza, G. A.; Lopes, R.; Oliveira, O. N., Jr.; Filho, P. A., Unraveling the Morphology and Macroscopic Alignment of Poly(9,9-di-n-octylfluorenyl-2,7-diyl) for Enhanced Polarized Emission. *ACS Appl. Polym. Mater.* **2020**, *2*, 5406.

49. Li, L.; Zhu, Y.; Zhou, X.; Brites, C. D. S.; Ananias, D.; Lin, Z.; Paz, F. A. A.; Rocha, J.; Huang, W.; Carlos, L. D., Visible-Light Excited Luminescent Thermometer Based on Single Lanthanide Organic Frameworks. *Adv. Funct. Mater.* **2016**, *26*, 8677.

50. He, T.; Gao, H.; Diao, X.-H.; Muhammad, Y.; Chen, C.; Wang, H.; Qi, C.-S.; Li, W.; Liu, N.; Li, Y.-W., Ratiometric visualization fluorescence temperature sensing based on dual-lanthanide metal-organic frameworks. *J. Mol. Struct.* **2024**, *1316*, 139071.
Support Information

<figure><img src="image_12.png" /><figcaption>**Figure S1.** Emission spectra of the two coordination polymers and the organic dye carried out in solid state at different temperatures.</figcaption></figure>
<figure><img src="image_13.png" /><figcaption>**Figure S2.** SEM imagines of the coordination polymers of [Cu(*p*-SPhCl)]<sub>n</sub>: **a1** (before grinding) and **a2** (after grinding) and [Cu<sub>3</sub>Cl(*p*-SPhCl)<sub>2</sub>]<sub>n</sub>: **b1**(before grinding) and **b2** (after grinding).</figcaption></figure>
<figure><img src="image_14.png" /><figcaption>**Figure S3.** Power X ray diffraction patterns of the two CPs before and after grinding.</figcaption></figure>

<figure><img src="image_15.png" /><figcaption>**Figure S4.** Transmittance (left) and photos of all films (right) under natural light.</figcaption></figure>
<figure><img src="image_16.png" /><figcaption>**Figure S5.** SEM images of the pure PDMS and composite films.</figcaption></figure>

<figure><img src="image_17.png" /><figcaption>**Figure S6.** Typical stress-strain curves obtained for composite samples (Left: S2) and pure PDMS samples (Right: S0). For each sample, the measurement is repeated three times to evaluate the reproducibility. Evaluation of some mechanical properties of the composite films (Young Modulus *E* and strain at break *ε*<sub>R</sub>) has been carried out at room temperature and compared to the pure PDMS film prepared in same conditions. The mechanical properties obtained for all the samples are summarized in Table S1.</figcaption></figure>
<table><caption>**Table S1.** Mechanical properties of the pure PDMS and composite films.</caption><thead><tr><th>Samples</th><th>Young's modulus (MPa)</th><th>Ultimate tensile stress (MPa)</th><th>Elongation atbreak (%)</th></tr></thead><tbody><tr><td>S0</td><td>1.1087</td><td>1.281</td><td>128.27</td></tr><tr><td>S1</td><td>0.8893</td><td>1.499</td><td>149.94</td></tr><tr><td>S2</td><td>0.9350</td><td>1.551</td><td>155.09</td></tr><tr><td>S3</td><td>0.9245</td><td>1.479</td><td>147.09</td></tr><tr><td>S4</td><td>0.9413</td><td>1.624</td><td>162.43</td></tr><tr><td>S5</td><td>0.8988</td><td>2.005</td><td>111.33</td></tr><tr><td>S6</td><td>0.8272</td><td>1.808</td><td>103.33</td></tr><tr><td>S7</td><td>0.8616</td><td>1.960</td><td>105.33</td></tr><tr><td>S8</td><td>0.8414</td><td>1.906</td><td>105.33</td></tr></tbody></table>
<figure><img src="image_18.png" /><figcaption>**Figure S7.** Photoemission of S1 to S8 films ($\lambda_{ex}$ = 380 nm for all films) from -150 °C to 150 °C.</figcaption></figure>
<figure><img src="image_19.png" /><figcaption>**Figure S8.** CIE chromaticity diagram of the eight films at -180°C, 25°C and high temperature.</figcaption></figure>
<table><caption>**Table S2.** Coordinates of the films for the CIE chromaticity diagram.</caption><thead><tr><th>Films</th><th>T(°C)</th><th>x</th><th>y</th></tr></thead><tbody><tr><td rowspan="3">S1</td><td>-180</td><td>0.64556</td><td>0.33217</td></tr><tr><td>25</td><td>0.626023</td><td>0.371164</td></tr><tr><td>150</td><td>0.60763</td><td>0.39067</td></tr><tr><td rowspan="3">S2</td><td>-180</td><td>0.416247</td><td>0.446761</td></tr><tr><td>25</td><td>0.417722</td><td>0.416927</td></tr><tr><td>180</td><td>0.405832</td><td>0.393544</td></tr><tr><td rowspan="3">S3</td><td>-180</td><td>0.457495</td><td>0.526715</td></tr><tr><td>25</td><td>0.40258</td><td>0.431931</td></tr><tr><td>180</td><td>0.449739</td><td>0.501218</td></tr><tr><td rowspan="3">S4</td><td>-180</td><td>0.43221</td><td>0.53502</td></tr><tr><td>25</td><td>0.40542</td><td>0.556768</td></tr><tr><td>200</td><td>0.39424</td><td>0.53845</td></tr><tr><td rowspan="3">S5</td><td>-180</td><td>0.26073</td><td>0.29887</td></tr><tr><td>25</td><td>0.092687</td><td>0.131977</td></tr><tr><td>150</td><td>0.2977</td><td>0.40995</td></tr><tr><td rowspan="3">S6</td><td>-180</td><td>0.243172</td><td>0.181469</td></tr><tr><td>25</td><td>0.29797</td><td>0.204797</td></tr><tr><td>200</td><td>0.28084</td><td>0.23175</td></tr><tr><td rowspan="3">S7</td><td>-180</td><td>0.1598881</td><td>0.115259</td></tr><tr><td>25</td><td>0.1627667</td><td>0.115801</td></tr><tr><td>180</td><td>0.1715631</td><td>0.12374</td></tr><tr><td rowspan="3">S8</td><td>-180</td><td>0.247133</td><td>0.263074</td></tr><tr><td>25</td><td>0.250609</td><td>0.287075</td></tr><tr><td>180</td><td>0.296789</td><td>0.361675</td></tr></tbody></table>
<figure><img src="image_20.png" /><figcaption>**Figure S9.** Integration area between 400 and 800 nm for S1, S4 and S7 samples as a function of temperature.</figcaption></figure>

**Integration ratio and relative sensitivity:**

To calculate the integration ratio *I* (green *I*<sub>G</sub> and red *I*<sub>R</sub>) of each sample (equation S1), we first integrate their emission spectrum *S* on two distinct regions separated by a wavelength *λ*<sub>c</sub>:

$$I_G = \int_{450}^{\lambda_c} S(\lambda) \, d\lambda \quad \text{and} \quad I_R = \int_{\lambda_c}^{800} S(\lambda) \, d\lambda \qquad (S1)$$

The wavelength *λ*<sub>c</sub> is chosen so that the two regions contain the green and red emission bands of the composite film. The integration ratio is then obtained by dividing the integral of the spectrum in one region by the integral of the spectrum in the other region: *I* = *I*<sub>R</sub>/*I*<sub>G</sub>. The two regions of the spectrum used for S2 and S3 are shown in Figure S8 (the wavelength *λ*<sub>c</sub> is equal to 605 nm for S2 and S3). The relative sensitivity *Sr* is obtained by computing (∂I/∂T)/I, where *T* is the temperature.
<figure><img src="image_21.png" /><figcaption>**Figure S10.** Emission spectra used to compute the integration ratio for S2 and S3. The two integrated regions of the spectra are highlighted in orange (S2) and green (S3).</figcaption></figure>
<figure><img src="image_22.png" /><figcaption>**Figure S11.** Analytical solution for the heat diffusion in a material with the heat diffusivity of PDMS ($1.06 \times 10^{-7} \text{m}^2/\text{s}$) initially put at 60 °C, while the room temperature is at 23.5 °C.</figcaption></figure>

A Video is included as an external file in the supporting information. A soldering iron tip is used to heat a sample of composite film S2, whose photo-emission is measured with the dual-camera set-up. The color bar indicates the temperature, obtained from the calibration procedure (Figure 6).