Förster resonance energy transfer and excited state life time reduction of rhodamine 6G with NiO nanorods in PVP films

    F¨orster resonance energy transfer and excited state life time reduction of rhodamine 6G with NiO nanorods in PVP films B. Karthikeyan PII: DOI: Reference:

S1386-1425(16)30519-4 doi:10.1016/j.saa.2016.09.004 SAA 14650

To appear in: Received date: Revised date: Accepted date:

1 May 2016 28 August 2016 1 September 2016

Please cite this article as: B. Karthikeyan, F¨ orster resonance energy transfer and excited state life time reduction of rhodamine 6G with NiO nanorods in PVP films, (2016), doi:10.1016/j.saa.2016.09.004

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ACCEPTED MANUSCRIPT Study

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Förster resonance energy transfer and excited state life time reduction of rhodamine 6G with NiO nanorods in PVP films

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B. Karthikeyan

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Nanophotonics Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli 620 015, India

Abstract

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In the present study, we report the preparation of NiO nanorods (NNR) and its Förster resonant energy transfer (FRET) behaviour with Rhodamine 6G (R6G) in a Polyvinyl

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pyrrolidone (PVP) polymer matrix. The prepared nanocomposite polymer (NCP) films contain PVP and R6G whose concentrations are kept constant and different concentrations of NNR.

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Spectral overlap between the absorption and fluorescence spectrum of R6G and NNR show the possibility of FRET phenomena to be occurring in the prepared NCP films. Steady state and time resolved fluorescence measurements are carried out at two excitation wavelengths (330 and 510 nm) to study the energy transfer process between R6G and NNR in the PVP host. The obtained results show that the energy transfer is from R6G (serves as a donor) to NNR (functions as an acceptor). Calculated radiative efficiencies, donor – acceptor distances and average lifetime also confirm the energy transfer from R6G to NNR.

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Corresponding Author.: Email: [email protected] (B.Karthikeyan), Phone: +80-431-2503612:

FAX: : Fax: +91-(0)431-2500133.

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ACCEPTED MANUSCRIPT Keywords: FRET, Nanorods, Polymer nanocomposites, Ultrafast energy transfer.

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Introduction Nanoparticles and nanostructures are the promising candidates for devices in almost all Metal oxide nanoparticles (MNP) are easy to prepare, cheap and

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the important fields.

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environment friendly. This class of materials show interesting optical and nonlinear optical

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properties [1]. Polymers which functions as a potential host for this kind of materials form nanocomposite polymers (NCP) [2]. These NCPs show different behaviour than their raw

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materials [2]. There are two ways to prepare these materials, one is in-situ and the other one is ex-situ. Physical and chemical properties of these materials depend on the concentration of the

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nanofillers and also functional polymers. [2].

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Polyvinyl pyrollidone (PVP) is a water soluble polymer which acts as a host for several

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metallic and semiconducting clusters (SCC) and carbon based nanomaterials [3]. Linking SCC with organic dye molecules in a polymer host has proven as a potential candidate for solar cell and opto-electronic device applications [4-6].

These properties are based on optical/photo

physical properties of these nanocomposites. NCPs are engineered for higher rate of electron injection from the excited dye molecules to SCC and MNP. Förster resonance energy transfer (FRET) is a kind of energy transfer phenomenon between optically active materials which has absorption and emission properties [7].

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emission energy of a donor molecule is extracted by an acceptor molecule by non-radiative and non-electron transfer phenomena and through the dipole – dipole interactions [8]. Coupling leads to efficient energy harvesting, light emitting, bio imaging and bio sensing devices [9]. FRET mainly depends on the spectral overlap between the donor (emission) and acceptor (absorption spectrum) and also play crucial role on the distance between the donor and acceptor 2

ACCEPTED MANUSCRIPT [10]. In particular, SCC with the surroundings of organic light emitting molecules/ chromophores lead to energy transfer phenomena such as FRET and Dexter transfer. The second kind of

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transfer is possible when the molecules are very close or having a chemical bond between them.

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Recently there are quite a number of research reports on FRET between SCC and organic dye molecules, also between two dye molecules and few extensively studied about light emitting

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proteins [11-15]. There are several reports about the variation in the radiative decay rate of the

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dye molecules in the presence of MNPs. When the space between MNPs and dye molecules are close, fluorescence quenching will occur. The enhancement and quenching of fluorescence

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depends on the space between them. The same will be extended to SCC also. In this work, we explored the donor and the acceptor role of both the nanoparticle and organic chromophore

Experimental

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where PVP is functioning as a host and intermediate/spacer.

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Synthesis of NiO nanorods (NNR)

NNR were prepared by mixing clear solutions of 100 ml of 0.1 M of Nickel nitrate hexahydrate (Ni(NO)3.6H2O) solution with 100 ml of 0.1 M of Hexamethylenetetramine (HMTA) solutions using Millipore water. The final solution is refluxed for 4 hr. at 90 °C which leads to the formation of green coloured precipitate. Further, the precipitate is collected using centrifugation and washed with ethanol followed by double distilled water for several times. Collected powder is annealed at 650°C for 4 hr. in air atmosphere.

Preparation of PVP-R6G-NNR composites The PVP-R6G-NNR composite films were prepared by solution growth technique. Initially 0.5 g of PVP was dissolved in 0.5 ml of double distilled water and sonicated to obtain a clear solution. PVP-R6G film was prepared by 0.2 mM solution of Rhodamine 6G is added to 3

ACCEPTED MANUSCRIPT the PVP solution. PVP-R6G-NNR films with different concentrations of NNR were prepared by adding 5, 7 and 9 mg of NNR into the different PVP-R6G solution. The prepared composite

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solutions were poured on glass slides and finally, films were formed after 5 days kept in the

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atmosphere. The film which has only PVP is coded as P. The film consists of PVP and R6G is code named as PR and the other films PVP-R6G-5mg NNR, PVP-R6G-7mg NNR and PVP-

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R6G-9mg NNR are code named as PRN5, PRN7 and PRN9 respectively.

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Spectroscopic measurements

X-Ray diffraction measurements were done using Rigaku X-Ray diffractometer between

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the diffraction angles 20 and 80o. The transmission electron microscopy (TEM) images were taken using a JEOL-TEM-2010 transmission electron microscope. Room-temperature steady

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state optical absorption spectral studies were carried out using UV-vis spectrophotometer (Jasco UV-Vis spectrometer). Fluorescence spectral studies were done using Fluoromax-P -Horiba

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Jobin Yvon Luminescence Spectrometer. Time resolved fluorescence studies were performed using time correlated single photon counting (TCSPC- Deltaflex - Horiba Jobin Yvon) measurement system, where the samples are excited at two different wavelengths like 330 and 510 nm using nanosecond and < 200 pico second diode lasers respectively with repetition rate of 1 MHz. The fluorescence decays were analyzed using DAS 9 software.

Results X-ray diffraction and structural studies X-ray diffraction pattern of the prepared NNR nanoparticles is shown in Fig. 1. Peak indexing confirms that the prepared particles are crystalline in nature. It is found that strong and sharp diffraction peaks at 2θ angles of 37.31o, 43.35o, 62.91o, 75.41o, and 79.06o corresponding to (101), (012), (110), (104) and (222) crystal planes, indicates that the formation of pure cubic

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ACCEPTED MANUSCRIPT nickel oxide phase. TEM image of the prepared particles are shown in Fig. 2a which shows the

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formation of rod like morphology. The chemical structure of PVP and R6G are shown in Fig. 2b.

(200)

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(311)

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(220)

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NiO

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Fig. 1: X-Ray diffraction pattern of the prepared NiO nanorods (NNR). Peak indexing confirms the formation of cubic NiO phase. Diffraction plane labels are in bracket and the corresponding angle is also mentioned.

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Fig. 2a: TEM image of the prepared NNR. Image shows the rod like morphology of NNR.

Fig. 2b : Chemical structures of PVP and R6G.

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NiO abs

NiO emi R6G abs R6G emi

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Normalized absorption/emission intensity (a.u.)

Spectral overlap:

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Region 2 560

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Wavelength (nm)

Fig. 3: (colour online) Optical absorption and fluorescence spectra (normalized) of prepared NNR and R6G. Green shaded region mentioned as Region 1 show the spectral overlap of NNR absorption and R6G absorption spectrum. Orange shaded region named as Region 2 show the spectral overlap of NNR absorption and R6G emission spectrum. In this study Region 2 only functioning but as per the Region 1, there is no energy transfer. Optical absorption and fluorescence spectra of both the NNR and R6G are depicted in Fig. 3. Optical absorption in NNR is originated due to exciton absorption whereas in R6G, it is due to an interband transition between the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO and LUMO). It is observed from Fig.3 that the emission spectrum of NNR partly overlap with the absorption spectrum of R6G which is named as Region 7

ACCEPTED MANUSCRIPT 1 and also the tail edge of the NNR excitonic absorption spectrum overlap with the complete emission region of R6G which is named as Region 2. The spectral overlaps in Region 1 and

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Region 2 are showing the great possibility of FRET process between NNR and R6G. As per

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Region 1, the prepared NNR has a role of donor and R6G has an acceptor during FRET process and the Region 2 shows the reverse way i.e; R6G will serve as a donor and NNR will function as

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an acceptor.

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The optical absorption spectra of NNR-R6G-PVP films are shown in Fig. 4a. It is observed that all the prepared films (except only PVP) show an absorption band centered at 543

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nm which is the characteristic absorption of R6G. There is no shift in the peak position or change in the shape of the spectrum is observed. Increasing concentration of NNR alter only the baseline

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of the spectrum (appear to be increased) , which is due to the scattering of light from the NNR in

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the prepared films. Radiative rate (kr) can be calculated by using the relation kr = νo2f, here νo is

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the energy in wavenumbers corresponding to the maximum absorption of the dye and ‘f’ is the oscillator strength. In the present case, there is no change in νo value with the addition of the NNR. So the radiative rate is directly proportional to the oscillator strength [16]. The calculated oscillator strength (f) from the obtained absorption spectra (background subtracted) of the prepared films show decreasing value of ‘f’ with increasing NNR concentration. The variation of oscillator strength with increasing concentration of NNR is shown in Fig. 4b. Since the radiative rate is proportional to the oscillator strength, decreasing oscillator strength shows that increasing NNR concentration lead to decrease the radiative rate.

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Fig. 4: (a) Optical absorption spectra of the prepared films. (b) The variation of oscillator

Steady state fluorescence study

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strength with different concentrations of NNR loaded films (denoted as sample code).

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To study the FRET process in the prepared films experimentally, we measured the steady

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state fluorescence spectra of all the prepared films. The obtained fluorescence spectra excited at 330 nm are shown Fig. 5. It is observed that the film (P) which contains only PVP show emission band peaked at 395 nm and the R6G added PVP film (PR) show two emission bands peaked at 395 and 565 nm. This shows that both the PVP and R6G could be excited for the excitation wavelength of 330 nm which is also the excitation for the NNR. As the concentration of NNR increases, the intensity of the emission band around 565 nm decreases. The quenching of R6G emission around 565 nm as a result of increasing NNR concentration shows that the energy transfer from R6G to NNR where R6G serves as a donor and NNR functions as an acceptor. This is well agreed with the spectral overlap between the NNR and R6G as in Region 2.

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emission band of PVP also decreased with increasing concentration of NNR. Further to confirm the function of NNR as an acceptor, we excited at the excitation wavelength of R6G at 510 nm and study the energy transfer process between R6G and NNR. The fluorescence spectra of the 9

ACCEPTED MANUSCRIPT prepared films excited at 510 nm are depicted in Fig. 6. The obtained spectrum of PR shows the emission band peaked at 565 nm whose intensity increased initially and then starts quenching as

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the concentration of NNR increases. This quenching of R6G emission as a result of increasing

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concentration of NNR states that the energy is transferring from the R6G to NNR, which also proves that the R6G serves as a donor and NNR function as an acceptor. It is similar to the

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previous reports where SCC functions as a donor and metallic nanoparticles is an acceptor [17].

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In the present study, the enhanced emission followed by the quenching is due to the change in the distance between donor and acceptor. Initially, for lower concentration of NNR (in PRN5)

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the distance between the NNR (acceptor) and R6G (donor) is high and PVP is functioning as a spacer between them. For an appropriate distance, FRET makes enhancement in fluorescence.

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But, when the concentration of NNR (acceptor) increases further (in PRN7 and PRN9), the distance between them reduced and makes it to quench. This is another kind of evidence that

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spectral overlap as in the Region 2 is working.

ex= 330 nm

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Pure PVP PR PRN5 PRN7 PRN9

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Wavelength(nm) Fig. 5: Steady state fluorescence spectra of the prepared films excited at 330 nm.

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Fig. 6: Photoluminescence spectra of the films, where the excitation is done at 510 nm.

Coupling efficiency of FRET depends on the spacer length between donor and acceptor. Based on the FRET, the rate of energy transfer is explained using the relation [16]

Where

is the lifetime of the donor in the absence of the acceptor, r is the distance between the

donor and acceptor, and R0 is known as the Förster distance, where the transfer rate

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equal to the decay rate of the donor in the absence of the acceptor. The Förster distance (R0) is also defined as [16] 

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

  

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is the quantum yield of donor in the absence of acceptor, N is Avogadro’s number, and

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

  

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n is the refractive index of the medium. The overlap integral  is given by the equation



is the extinction coefficient of the acceptor at ,

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with the total intensity normalized to unity,

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 is the corrected fluorescence intensity of the donor in the wavelength range from  to d,

which is typically in units of M-1 cm-1, and k2 is the orientation factor of two dipoles interacting

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cm-1 and the calculated Ro value is 3.7 nm.

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and is usually assumed to be equal to 2/3. Calculated overlap integral is 1.324 x 1010 nm4 M-1

Time resolved fluorescence study

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Time resolved (TR) fluorescence study is an alternative way to confirm the energy

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transfer (ET) between an optically excited donor and the acceptor. TR fluorescence

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measurements were done it in a magic angle conditions for PR film and NNR added films (PRN5, PRN7 and PRN9). In order to study the role of NNR and R6G, we adopted three systematic studies. In study I, we explored the role of PVP’s contribution, so the excitation is done at 330nm and emission monochromator is tuned to 395nm (PVP’s emission band). Interestingly spectral studies show no variation in decay dynamics. In study II, to understand the effect on R6G, the excitation is done at 330 nm and emission wavelength is tuned to 565 nm (R6G’s emission). It shows minor variation in the decay dynamics. In study III, to study the effect on the R6G’s decay dynamics, we excited at 510 nm and studied the emission decay dynamics at 565 nm. The lifetime measurements were fitted using the software came along with the measuring system and the equation of the fitting is

y(x) = 12

ACCEPTED MANUSCRIPT where, n is the number of discrete emissive species, A is a baseline correction usually called as “dc” offset, and Bi and ti are the pre exponential factors and excited-state fluorescence

here fi =

. In all the studies the transfer efficiencies are calculated

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the relation tavg =

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lifetimes associated with the ith component. The average lifetime (tavg) is calculated [18] using

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[18] as E = 1- (tD/tDA). Where tD is the lifetime of the donor and tDA is lifetime of the donor in the presence of the acceptor. Calculated parameters are presented in tables.

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Discussion

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Study I & study II

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This study is to probe the effect of NNR on PVP. The obtained decay fits well with triple

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exponential decay and the fitted parameters are presented in the Table 1. The study shows that the decay times and pre-exponential factors have not varied appreciably with the concentration

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of NNR. So the excited state decay of PVP is not affected by the inclusions. For the same excitation we tuned the emission study at 565 nm which is shown in Fig.8. It is found that the decay is a triple exponential one, but all the first exponential pre-factors are negative. The decay time with pre-factors are shown in the Table 2. The presence of negative pre-factor is due to R6G, which is forming excited state species in the PVP. Study III As per study III, to understand the effect of the R6G’s decay dynamics, we excited at 510 nm and studied the emission decay dynamics at 565 nm. This study is depicted in Fig.9. Usually, the decay of NNR will be in the ultrafast regime and this dynamics will not be differentiated from the prompt line. In the present case, FWHM of the source is < 200 ps and the

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ACCEPTED MANUSCRIPT wavelength centred at 510 nm, helps to understand the decay dynamics of the R6G which is the pathway of LUMO electrons. It is highly interesting that the PR film shows double exponential

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decay. Out of two decays, one has negative pre exponential factor which get increased for NNR loaded film (PRN5). Further increase of the NNR loading in the samples PRN7 and PRN9, the

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decay becomes single exponential one which is attributed to the LUMO dipole excitations of

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R6G collapses faster than dipoles in the PR film. It concludes that the electron recombination

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through radiative one is accelerated by the NNR because of its acceptor nature.

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Recently, there are several research reports which investigated the FRET between metallic, SCC and organic fluorophores. Based on the donor- acceptor pair, the role of MNP and SCC will

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vary. Usually, in FRET process, the SCC functions as a donor and enhances the fluorescence of

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organic acceptor which is supported by the lifetime measurements. In the present report, NNR exciton interacts with the R6G through PVP and act as an acceptor. FRET in MNPs show size

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dependent nature where bigger clusters will function as an acceptor through the Plasmon clouds and the smaller one as a donor [19]. Similarly, in this work we have attempted to create a FRET probe using NNR and R6G which has an emission at 565nm and found that NNR is behaving like MNPs. As depicted in Fig.3, there are spectral overlaps in two different regions Region 1 and Region 2 where the second one only functioning for ET process. We tuned the excitation and emission wavelengths for both the species to identify their role in the FRET process. It is found that there is an emission from R6G (565 nm) when excite the PR film at 510 nm and the decay dynamics measured for the PR film show negative amplitude confirm that R6G is forming an intermediate, excited state species in the PVP. Further addition of 5mg of NNR (PRN5), there is an enhancement of fluorescence and also an increment of the negative amplitude. It is due to the reason that the addition of NNR induces more intermediate excited state species of R6G and also

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ACCEPTED MANUSCRIPT the PVP has a role as an appropriate length spacer between R6G and NNR. Further increasing concentration of NNR (PRN7 and PRN9), enhances the acceptor role [20].

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Liu et al [21] found that based on the size of SCC, it functions as an either donor or

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acceptor, when the size increases SCC behave as an acceptor, in the similar way Clapp et al [22]

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also reported that the quantum dots functions as an acceptor. In the present study, NNR is functioning as an acceptor rather than the donor, this is because of its size, as we discussed

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earlier about the size dependent property of MNPs [21, 23]. Once the excitation is done in donor

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(R6G), the LUMO is populated and it will be readily accepted by the ground state dipolar oscillations (excitonic) of NNR so the energy transfer will be through NNR and it clearly reflects

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in the TR studies of the donor excitations and probing the emission of its decay. In Study III, the

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average lifetime is monotonically decreasing and the rate of energy transfer is increasing with the increasing NNR concentration, apart from this the distance between the donor and acceptor also

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decreases. All the fitted parameters (for study III) are presented in the Table 3. To understand the formation of the exited state formation, time resolved emission spectral (TRES) studies are performed for the sample code named as PRN5 and is depicted in Fig. 10 and see Fig. S1 (in supporting Information). It is found that the emission spectrum is changing with the time evaluation which confirms the excited state species formation. In future, to understand the host’s role in energy dynamics we will try with different polymer host. And also will try to study the process behavior with different sizes and shapes of NiO.

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ACCEPTED MANUSCRIPT Conclusion In summary, we prepared NNR and using R6G- FRET pair is formed within the PVP

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host. Optical absorption and emission spectral studies show the confirmation of FRET pair

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through their spectral overlap. Steady state and time resolved fluorescence studies experimentally confirm the energy transfer process between the NNR and R6G where the host

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polymer PVP is a spacer for this ET. The observed fluorescence quenching of R6G and the

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reduction in the average lifetime as a result of increasing NNR concentration confirm the roles of R6G as a donor and NNR as an acceptor during the ET process. Excited state decay of the R6G

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shown as a triple exponential form and it becomes a single exponential one with the increasing the concentration of NNR in the polymer films. The obtained negative pre exponential factors

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Acknowledgements

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are due to excited state intermediate species of R6G is confirmed by the TRES study.

Author wish to thank CSIR, India for sanctioning the project to finish the part of this work. CSIR study No. 03(1258)/12/EMR-II References

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Soc. 2005, 127, 1242-1250

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P Decay P Fit PR Decay PR Fit PRN5 Decay PRN5 Fit PRN7 Decay PRN7 Fit PRN9 Decay PRN9 Fit

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Excitation wavelength: 330 nm Emission wavelength : 395 nm

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Log photon counts

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P. E. Dawson, N. Hildebrandt and I. L. Medintz, J. Am. Chem.Soc. 2012, 134, 1876.

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Time (ns) Fig. 7: Time resolved fluorescence spectra of the prepared films excited at 330 nm excitation. The emission wavelength is fixed at 395nm. Theoretically fitted parameters are shown in Table 1. This study is based on study I. Table 1: Theoretically fitted parameters for time resolved fluorescence spectra obtained from the experiment conducted as per study I. Sample code

A

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T2 (ns)

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PRN5

0.7428

PRN7

1.1345

PRN9

0.9557

0.7606 (0.1876) 0.7535 (0.1780) 0.7539 (0.1493) 0.6476 (0.1673)

2.6593 (0.6657) 2.6609 (0.6602) 2.5508 (0.6436) 2.3874 (0.6370)

7.9483 (0.1466) 8.0025 (0.1618) 6.8193 (20.71) 6.1541 (0.1957)

4.6043 4.0803

0.1138

5.2090

2.7893

3.9805

0.1355

5.0391

3.4032

5.2797

2.5728

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80

Time (ns)

Fig. 8: Time resolved fluorescence spectra of the prepared films excited at 330 nm excitation. The emission wavelength is fixed at 565nm. Theoretically fitted parameters are shown in Table 2. This study is based on study II. Table 2: Theoretically fitted parameters for time resolved fluorescence spectra obtained from the experiment conducted as per study II. Sample code PR

A

T1 (ns)

T2 (ns)

T3 (ns)

1.9240

PRN5

3.0860

PRN7

3.4008

PRN9

5.2888

1.4540 (-0.0369) 1.6101 (-0.0495) 1.5498 (-0.0326) 1.2476

5.2733 (0.9895) 4.9394 (0.9988) 4.8225 (0.9821) 4.6260

18.313 (0.0474) 18.743 (0.0508) 17.990 (0.0505) 17.505 19

< > (ns) 7.1836

E

(nm)

KT( r ) x 106S-1

7.2487

-0.0090

---

---

6.9903

0.0269

6.7286

3.8486

7.0794

0.0145

7.4741

2.0489

rDA

ACCEPTED MANUSCRIPT (0.9626)

(0.0590)

PT

(-0.0215)

RI

NU

SC

1000

PR Decay PR Fit PRN5 Decay PRN5 Fit PRN7 Decay PRN7 Fit PRN9 Decay PRN9 Fit

MA

100

D

10

1

30

35

AC CE P

25

TE

Log photon counts

Excitation wavelength: 510 nm Emission wavelength : 565 nm

40

45

50

55

60

65

Time (ns)

Fig. 9: Time resolved fluorescence spectra of the prepared films excited at 510 nm excitation. The emission wavelength is fixed at 565nm. Theoretically fitted parameters are shown in Table 3. This study is based on study III. Table 3: Theoretically fitted parameters for time resolved fluorescence spectra obtained from the experiment conducted as per study III. Sample code PR

A

T1 (ns)

T2 (ns)

T3 (ns)

-0.0126

PRN5

-0.7790

PRN7

-0.3854

4.7500 (1.1736) 4.1225 (2.2938) ---

PRN9

-0.4250

2.9875 (-0.1736) 3.7741 (-1.2938) 4.4274 (1) 4.2535 (1)

---

20

E

rDA

---

< > (ns) 4.9308

--

(nm) --

KT( r ) x 107S-1 --

---

4.4945

0.0885

5.4577

1.9689

---

4.4274

0.1021

5.3159

2.3059

---

4.2535

0.1374

5.0257

3.2294

RI

PT

ACCEPTED MANUSCRIPT

SC MA

NU

100

10

1 30

) (nm h t g len e v Wa 58

57

50

56

60

AC CE P

TE

Tim 4 0 e (n s)

60 0

59 0

D

n C o u n ts ) L o g (P h o to

1000

55

0

0

0

0

Fig 10 : Time resolved spectra for the PRN5 where the emission is recorded from 550 to 600 nm. Excitation for this study is 510 nm.

21

ACCEPTED MANUSCRIPT

1.0

PVP-R6G-NiO 5

PT

510 exc

RI

0.8

SC

0.6

0.4

0.2 560

570

580

590

MA

550

NU

Normalized counts

24.25-27.16 ns 27.21-30.12 ns 30.17-33.08 ns 33.13-36.04 ns 36.09-39.00 ns 39.05-41.96 ns 42.01-44.92 ns 44.97-47.88 ns 47.93-50.84 ns 50.89-53.80 ns 53.85-56.76 ns 56.81-59.72 ns 59.77-62.68 ns 62.73-65.64 ns 65.69-68.60 ns 68.65-71.56 ns 71.61-74.52 ns 74.57-77.48 ns 77.53-80.44 ns 80.49-83.40 ns 83.45-86.36 ns 86.41-89.32 ns 89.37-92.28 ns 92.33-95.24 ns 95.29-98.20 ns

600

TE

D

Wavelength (nm)

AC CE P

Fig 10a : Time resolved emission spectra (TRES) for the PRN5 which is derived from the above Fig 10 results.

22

AC CE P

TE

D

MA

NU

SC

RI

PT

ACCEPTED MANUSCRIPT

23

ACCEPTED MANUSCRIPT Highlights

TE

D

MA

NU

SC

RI

PT

NiO nanorods are prepared through simple chemical method NiO nanorods are used for FRET process Applications of polymer is extended as both host and spacer for FRET process New Optoelectronic nanocomposite is studied

AC CE P

   

24