Preparation and Properties of Fluorescent Cellulosic Paper via

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General Research

Preparation and Properties of Fluorescent Cellulosic Paper via Surface Coating of Anionic Cellulose Ethers / Rare Earth Metal Ions Composites Jun Ye, Huiming Liu, and Jian Xiong Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b03430 • Publication Date (Web): 17 Jan 2019 Downloaded from http://pubs.acs.org on January 22, 2019

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Industrial & Engineering Chemistry Research

Preparation and Properties of Fluorescent Cellulosic Paper via Surface Coating of Anionic Cellulose Ethers / Rare Earth Metal Ions Composites Jun Yea , Huiming Liua, Jian Xiongb* a State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, China 510640 b School of Food Science and Engineering, South China University of Technology, Guangzhou, China 510640 *corresponding author, email: [email protected]; Tel: 86 13660154451

Abstract Fluorescent paper made by coating cellulosic paper with fluorescent composites shows great potential in many fields, since this fluorescent paper could have both the intrinsic mechanical properties of the cellulosic paper and the florescent properties of the composites. In this research, we prepared fluorescent paper sheets by coating four new fluorescent composites, namely CMC/Eu(III), CMC/Tb(III), HPCMC/Eu(III) and HPCMC/Tb(III), onto a cellulosic paper. The analysis of the rheological behavior of the composites demonstrated that all fluorescent composites exhibited similar shear-shining and thixotropy properties as both the CMC and HPCMC solutions. This suggested that these fluorescent composites could be used as coating materials in the paper-making industry to make functional paper. The impacts of these coated composites on both the fluorescent and mechanical properties of the cellulosic paper were studied. Mechanical properties, including bursting strength, tensile strength, tensile rate, tearing strength and folding strength, increased about 30% after coating with the fluorescent composites. In particular, both the tensile strength and the toughness of the fluorescent paper increased significantly. Emission spectra of all fluorescent paper sheets exhibited the characteristic emission of Tb3+ (5D4→7F5 1

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transition, 545 nm) or Eu3+ (5D0→7F2 transition, 612 nm). Moreover, letters written with the composites suspensions on a common printing paper sheet were clearly observed by naked eyes under UV light at 254nm. This study thus offers a simple and effective route to prepare quality fluorescent papers by coating fluorescent composites onto cellulosic papers, which could further guide the application of these fluorescent composites in the paper-making industry.

Keywords: Carboxymethylcellulose(CMC); Hydroxypropyl carboxymethyl cellulose(HPCMC); rear earth metal; Fluorescent paper, mechanical property

1. Introduction Fluorescent paper made from cellulosic paper has been extensively sought after because it could concurrently have the intrinsic properties such as flexibility, light weight, low cost and recyclability, and the fluorescence. Fluorescent paper could be used as security paper, chemical sensors or biosensors for fluorescence quenching and its selectivity, and the others.1-11 In fact, the fluorescence characteristic available of fluorescent paper heavily depends on the nature of the applied fluorescent coatings and the production processes. Currently, there are some ways for manufacturing the fluorescent cellulosic paper, like immerging, printing and coating. For example, Ma et al.10 immerged a piece of filter paper (36 mm in diameter) into 8-hydroxyquinoline aluminum (Alq3)-based bluish green fluorescent composites suspensions to provide a selective detection of explosives. Wang et al.11 prepared a simple and effective ratio-metric fluorescence paper nanosensor for the selective detection of Cu2+ by printing with the material covalently connecting the carboxyl-modified red fluorescent cadmium telluride (CdTe) quantum dots to 2


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the amino-functionalized blue fluorescent carbon nanodots. Tang et al.12 applied graphite-based coatings onto cellulosic paper via surface coating application. Comparing with immerging or printing, coating can be a better way because it is part of paper making manufacturing processes.13 In addition, surface coating has technical commercial advantages, like quantitative processing, high filler retention, low cost, and lowrisk scale-up.14 Rheology of coating is important for both the coating process and the resultant fluorescent paper quality. The suspension rheology of aqueous coatings could impact the coating performance at high speed and during high rate of change of the shear rate. Moreover, the rheology has influences on the quality of the coated end product, which is determined by the relationship between dewatering immobilization and coating coverage.15,16 For instance, higher viscosity is required for roller coating than for spray coating applications since a too high viscosity would cause insufficient levelling of the coating on the substrate.17 Research has shown that variations in viscosity with shear rate for cellulose derivatives suspensions can be classified into two regimes: nearly Newtonian behavior at the lowest concentration; both nonNewtonian and viscoelastic properties at a higher concentration.18-20 Cellulosic derivatives, especially carboxymethyl cellulose(CMC) and hydroxypropyl carboxymethyl cellulose(HPCMC)(their structures diagram shown in Fig.1), have been used in the process of paper coating in paper-making industry because they can improve the water retention and rheological properties of coatings.21 Our team has demonstrated that CMC could be used as the sensitizing ligand and the rare earth(RE)/CMC nanocomposites have excellent fluorescent properties.22-25 The trivalent rare earth(RE) ions can show abundant emission colors based on their f-f transitions after the absorption of energy. They have many applications in many fields such as modern lighting and display.26-33 But the luminescence of 3



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RE ions originates from the intra-4f transitions, which are forbidden in principle, resulting irrelatively low emission efficiency.34,35 An effective approach to increase the luminescent efficiency is that coordinating RE ions with other sensitive ligands, such as cellulose and its derivatives as efficient ligands.36-39 The RE/sensitizing ligand systems possess many advantages such as long emission lifetimes, high quantum efficiency narrow bandwidths, high color purities, and large Stokes shifts as well as rare earth ions’ special electronic structure.40-47

Fig.1 Diagram of CMC and HPCMC structures In this study, we prepared composites of Eu3+ ions (red emitter) or Tb3+ ions (green emitter) coordination with CMC or HPCMC as coatings. Fluorescent paper coated with the composites were prepared and characterized.

2. MATERIALS The carboxymethylcellulose (CMC) in food grade with degree of substitution (DS) of 0.89 and a viscosity of 8200 mPa∙s at 25℃ in 1.0% aqueous solution (Brookfield viscometer) was purchased from YINGTE Technology Company in Shijiazhuang. The hydroxypropyl carboxymethyl cellulose (HPCMC) in food grade has the DS of 0.91, the MS of 0.15 and a viscosity of 1000 mPa∙s at 25℃ in 1.0% aqueous 4


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solution (Brookfield viscometer) purchasing from LIHONG Fine Chemistry Company Limited in Chongqing. Europium oxide powder and Terbium chloride powder in analytical grade were purchased from ALAIDING Chemical Company in Shanghai. Ethanol in analytical grade was bought from GUANGHUA Chemical Company in Guangdong. Sodium hydroxide and hydrochloric acid were also in analytical grade and were bought from Guangzhou Donghong Chemical Factory and Guangzhou Chemical Reagent Factory, respectively. KBr was spectrally pure and produced from KERMEL Chemical Reagent Company in Tianjin. Silver nitrate in analytical grade was purchased from Guangzhou Chemical Reagent Factory. All the reagents were used without further purification. Dialysis membrane was bought from Shanghai Yuanye Bio-Technology Limited with a molar weight cut-off (MWCO) value of 2000. Base paper sheets as control with 80g/m2, emitting unobservable fluorescence under the experimental condition in our paper (see Fig.2), were purchased from Kunshan Banknote Paper Mill.

Fig.2 Photos under UV-light at 254nm (from left to right: base paper sheet; pulp board; ordinary printing paper)

3. Methods 3.1 Preparation of cellulose anionic ether / rare earth metal ions composites EuCl3 solutions were made by dissolving 1.219g Eu2O3 powder into hydrochloric acid according to 5



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method of Ye et al.22 The final concentration was 0.0346 mol/L. A certain amount of rare earth metals ions (RE3+) solution was added into 2.000 g CMC or HPCMC powder (CD) solution with stirring. The ratio of CD to RE3+ and the reaction conditions were controlled (see Table 1). The reaction liquid was then dialyzed in deionized water until there was no AgCl precipitation when adding AgNO3 into the dialyzed liquid. Finally, the suspension was dried in oven at 70℃ to obtain a series of CD/RE(III) composites powder, named CE, CT, HE, and HT, respectively (see Table 1). Table 1 Preparation of the composites Sample CT CE HT HE

RE3+ Tb3+ Eu3+ Tb3+ Eu3+

CD CMC CMC HPCMC HPCMC

n(CD):n(RE) 15:1 1.65:1 15:1 20:1

pH 7 7 7 7

T/℃ 70 70 70 70

t/min 35 35 35 35

3.2 Preparation of the fluorescent paper Base paper sheets were cut into pieces with length of 28 cm and width of 20 cm. The sheets were coated by 2wt% CD/RE suspension with variable weights (see Table 2) on the surface through the coating machine purchased from Swizerland with the model of ZAA 2300. Afterwards, the paper sheets were allowed to dry at temperature of 50℃ for 30s. The coating weight of the conditioned paper sheets was calculated using the equation (1): Coating weight(g 𝑚2) =

(𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑝𝑎𝑝𝑒𝑟 𝑎𝑓𝑡𝑒𝑟 𝑐𝑜𝑎𝑡𝑖𝑛𝑔 ― 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑏𝑎𝑠𝑒 𝑝𝑎𝑝𝑒𝑟 𝑠ℎ𝑒𝑒𝑡) 𝐴𝑟𝑒𝑎 𝑜𝑓 𝑝𝑎𝑝𝑒𝑟

(1)

Table 2 Preparation of the fluorescent paper sheets Sample

Coating

Coating times 6


Coating weight(g / m2)

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CT1 CT3 CE1 CE3 HT1 HT3 HE1 HE3 control

CT CT CE CE HT HT HE HE -

1 3 1 3 1 3 1 3 0

1.06 2.76 1.07 2.78 1.31 3.28 1.54 3.95 0

4. MEASUREMENT Rheology properties were measured with German Haake RV-I rheometer. Photoluminescence (PL) spectra were recorded using a HORIBA JobinYvon (research grade, France) fluorescent spectrophotometer with the excitation and emission slit widths of 3.0 nm. The bursting strength, tensile strength and rate, tearing strength, brightness was determined using a Sweden L&W CE180 ashcroft tester(standard accords with ISO 2759), L&W CE062 tensile tester(standard accords with ISO 1924-2), L&W 009 tearing tester (standard accords with ISO 1974:2012), and L&W Elrepho 070 brightness meter(standard accords with ISO 2469), respectively. Folding strength was recorded on American MIT/U21B folding tester(standard accords with ISO 5626). All samples were analyzed in triplicate and the results were reported as the mean.

5. RESULTS AND DISCUSSION 5.1 Rheological properties The flow curves of solutions of the composites at different temperatures are presented in Fig.3. These composites suspensions exhibit homogenous good stability, and there were no visible changes of these suspensions for a month. By our previous reports, the sizes of the composites are in nano-scale.22-25 The nanoscale composites in these suspensions could result in a uniform dispersion of the composites and a 7



good stability of suspensions.48 From the insets in Fig.3 it is observed that suspensions of CH, CT, HE, HT remain the shear-thinning properties of CMC and HPCMC. This behavior could be owed to the formation of a three-dimensional network of the composites rather than a liner structure of CMC or HPCMC in suspensions (see Fig.4). Based on the shear-thinning experiment, it is suggested that CT, CE, HT, and HE are feasible to be used in paper-coating process. However, the viscosities of the composites suspensions are lower than CMC or HPCMC solution. This is responsible for the ligands dissolving in

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Fig.3 The relationship between the viscosity and shear rate of the composites suspensions at different temperatures (inset: the relationship between the viscosity and shear rate of samples at 25℃)

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Fig.4 Diagram of composites structures In Fig.3, rheological behaviors of these composites accord well with the Cross model49 (equation 2) for all suspensions and the accompanying results are listed in Table 3. 𝜇 ― 𝜇∞ 𝜇0 ― 𝜇∞

1

= 1 + (𝐾 ∙ 𝛾)1 ― 𝑛

(2)

Where μ is the viscosity at any particular shear rate 𝛾; 𝜇0 and 𝜇∞ are asymptotic values of viscosity at zero and infinite shear rates, respectively; K is a time constant and n is the Power Law index, which accounts for the shear thinning behavior. A value of 0 for n indicates Newtonian behavior, with n tending to unity for increasing shear-thinning behavior. The reciprocal of the time constant, 1/K, corresponds to a critical shear rate that provides a useful indicator of the onset shear rate for shear thinning. From Table 3, for all suspensions of the products, n values of individual composites suspensions at different temperatures remain constants basically. However, n values of the suspensions involved HPCMC change more with temperature variation, compared to these involved CMC and the same rare earth metal ions. The reason could be that some short side chains on HPCMC could react with Eu3+ or Tb3+ which make conformations of the composites involved HPCMC vary more complex with change of temperature. This also makes 𝜇0 of the suspensions with HPCMC vary greater with temperature variation than those with CMC and the same rare earth metal ions. 9



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On the other hand, 𝜇0 of the suspensions of composites with Tb(III) is smaller than these with Eu(III). Some earlier reports50-54 involving the effect of salt on polyelectrolytes solutions pointed that the polyions chains start to contract and the mean force between the chains becomes less repulsive in the presence of multivalent salts, as provided in a significant reduction in radius of gyration (Rg) in the presence of salts. Tb3+ has smaller radius of ions than Eu3+, so the chains in the suspensions of composites with Tb(III) become more compacted into smaller dimensions(see Fig.7). It accounts for the smaller viscosities in suspensions of composites with Tb(III).55,56 Table.3 n, K, 𝜇0 values of the composites at different temperatures Sample 35℃ 45℃ 55℃ n 0.560 0.540 0.530 CMC/Eu(III) K 0.703 0.598 0.492 𝜇0(Pa·s) 0.3693 0.3055 0.2514 n 0.640 0.620 0.620 CMC/Tb(III) K 0.445 0.360 0.278 𝜇0(Pa·s) 0.2669 0.2065 0.1566 n 0.507 0.550 0.510 HPCMC/Eu(III) K 1.003 0.840 0.714 𝜇0(Pa·s) 0.5329 0.4332 0.3622 n 0.510 0.500 0.500 HPCMC/Tb(III) K 0.453 0.389 0.325 𝜇0(Pa·s) 0.2343 0.1966 0.1663

When temperature rose, the viscosities of all composites suspensions become low. These macromolecular units become active and the interaction force between the macromolecules units gets weaker with temperature increasing, resulting in stronger mobility of the whole macromolecular and unit segments in suspensions and lower viscosity. This illustrated a strong dependency of steady state shear viscosity of the composites suspensions upon temperature. 10


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The flow activation energy (Ea) can be calculated by Arrhenius Equation (equation 3), where B means pre-exponential factor (also called frequency factor) and R is gas constant: ln 𝜇0 = ln 𝐵 ― 𝐸𝑎 𝑅𝑇

(3)

Ea of each composite suspension, CE, CT, HE and HT, is 1.5964KJ·mol-1, 2.5193KJ·mol-1, 1.6047KJ·mol-1, 1.4218KJ·mol-1, respectively. Also, it could be observed from Fig. 1 that temperature has greater effect on CT suspension. Fig.5 shows hysteresis loops of the composites at different temperatures. And the variation of the acreage of hysteresis loops is shown in Table 4. The composites suspensions had similar shape of thixotropic hysteresis loops with different acreage. And the acreages of all composites suspensions at 35℃ are maximum, which indicates the strongest time dependence behavior at 35℃. The thixotropy of these composites suspensions means that these composites exhibit a viscosity-time relationship like CMC solution.53 The time-dependent behavior of viscosities of the composites suspensions suggests that the changes occurring in the inner structures of the suspensions were due to particle interaction force like the Van de Waals forces. These forces may lead to the formation of a rigid continuous particle network, such as membrane. This suggests that these products, CT, CE, HT, and HE as coating used in paper-coating process may be implemented, and that coating temperature could be adjusted according to the required thixotropy.

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Fig.5 The hysteresis loops of the composites suspensions at different temperatures

Table.4 The acreage of hysteresis loops CE CT HE HT

35℃ 19.56 13.68 21.07 10.57

45℃ 16.30 14.87 20.45 8.12

55℃ 12.22 10.20 13.44 5.78

The storage modulus(G’) and loss modulus(G”) of suspensions of CE, CT, HE, HT vary with the angular frequency as shown in Fig.6. Gʺ of all composite suspensions is lower than G’ of them, which means the viscosity property is dominant compared to the elastic ones. The G’ and G” of the suspensions with Eu(III) are higher than these of the suspensions with Tb(III). This reflects a more three-dimensional network structures in the composites with Eu(III), which owes to the bigger radius of Eu3+ . Bigger Eu3+ is more likely to reacts with –COO- and –OH on the different chains. Due to form inter-chain bridging 12


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(see Fig.7), there are more three-dimensional network structures in the composites with Eu(III). G’ and G” generally show a tendency to go up with the increase of the angular frequency, while there comes with an inflection point at an angular frequency of about 20 rad • s-1. With increasing angular frequency, the working time of the shear force becomes shorter and the direction becomes faster. Then the molecules tend to be stiff, and the rate of re-entanglement of the macromolecules by shearing is greater than that of disentanglement. G’ becomes larger.

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Fig.6 The relationship between angular frequency and G’, G” of the composites suspensions

Fig.7 Diagram of suggested structures of the cellulose ethers/Tb(III) (or Eu(III)) complexes

5.2 Mechanical property of fluorescent paper Mechanical properties of fluorescent paper sheets are demonstrated in Fig. 8. From Fig.8(a)(b)(c), Bursting strength of these fluorescent paper sheets expresses similar variation trend with tensile strength 13



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and tensile rate, that is, coatings can increase these mechanical properties. A long-term challenging in engineering material design is the conflict between strength and toughness, because these properties are in general mutually exclusive.27,28 It is worthy to mention that both the large increase in tensile strength and toughness of the fluorescent paper is obvious in Fig.8(b) and (c). The reason might be that the composites with similar main chain with paper fiber in coating suspension are swelled sufficiently to favor strong inter-paper-fiber bonds, even partially to induce fibrillation with paper fiber by hydrogen bonds with –OH exposing on the end groups and entanglement with paper fibers.57-59 As the coating weight increases, these strength properties also can be enhanced. This is because while the coating is applied on an absorbent substrate, the aqueous phase would be removed by capillary movement through the substrate’s capillaries.54,57-59 After coating, the composites would behave as binders to increase the internal binding force in paper system. Also, CE and HE have higher bursting strengths than CT and HT, for a higher K value suggesting a stronger interaction from above. Tearing strength has something to do with the average length of the fiber, the fiber binding force, the direction of the fiber arrangement and so on. Data was shown in Fig.8(d). Tear strength is higher for the paper sheets coated with lower coating weight. The composites coating on the paper surface have effects on the internal binding of the fibers in paper. Compared to the blank sample, different coating weight may have different influence. The addition of fluorescent composites exhibits a similar or even higher rate of increase on the mechanical properties of coated paper comparing with some common paper additives (see Table.5) as proved in the relative research works under similar coating weight (2%).3, 60-62 Fig.8(e) showed the average folding strength value of different samples measured by the tester. It is 14


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obvious that fluorescent paper sheets have higher folding strength, indicating the greater ability to resist the reciprocating folding. Increase of the coating weight will increase the value of folding strength, indicating that the coating of the composites has certain influences on the strength and flexibility of the paper fibers.

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Fig.8 Mechanical properties of the fluorescent paper sheets: (a)Bursting strength; (b)Tensile strength; (c)Tensile rate; (d)Tearing strength; (e)Folding strength Table.5 Effect of different additives on mechanical properties of the coated paper Rate of increase (%)

Additives

Bursting strength

Tensile rate

Tearing strength

CMC3,60

——

——

1.69

starch-acrylamide graft copolymer61,62

20.7

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cationic starch61,62

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our work

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-2.5~19.14

5.3 Fluorescent characterization 395nm and 373nm were chosen as the excitation wavelength to obtain the emission spectra of composites and the fluorescent paper sheets (see Fig.9 and Fig.10). The red fluorescence of both composites and paper sheets emitted by Eu3+ and the green fluorescence emitted by Tb3+ can be found in Fig.9 and 10. Emission of CMC and HPCMC could not detected in this study. This suggests the CMC and HPCMC ligands were not directly involved in the fluorescence emission but played a role of photosensitization instead. From Fig.10, every kinds of fluorescent paper still have characteristic emissions of Tb3+ and/or Eu3+, indicating that coating wouldn’t change the fluorescence property of these composites, despite some fluorescent quenching occur. Comparing with Fig.9, the peak belonging to the transition of 5D

4→

7F

6

for Tb3+ disappears and a new peak belonging to transition of 5D1 → 4F7 for Eu3+ showed up in

Fig.10. Peaks at 545nm for CT and HT and 615nm for CE and HE still exist in fluorescent paper sheets with different coating weight. The intensity of 5D0→7F2 for Eu3+ and 5D4→7F5 for Tb3+ increases on the paper coated with CE and CT and decreases with HE and HT. As the coating weight raises, there is a little red shift of emission of the fluorescent paper with Eu3+, as well as an obvious blue shift of emission of fluorescent paper with Tb3+. From the inset picture of Fig.10，when the “SCUT” is written on a piece of paper using a paintbrush, it could not be recognized by naked eyes under normal room illumination. However, it could be clearly observed under UV light irradiation. 16


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1750000

600

D 0 →7 F 3

650

D0→7F4

λex=373nm

5

D4→7F5

1250000 1000000 750000

5

D4→7F6

500000

5

250000

D 4 →7 F 4

5

D4→7F3

0 -250000 450

6000000

500

550

Wavelength/nm

HT λ

ex

=373nm

600

650

5

D4→7F5

5000000 4000000 3000000

5

D4→7F6

2000000 5

D4→7F4 5D →7F 4 3

1000000

700

Wavelength/nm

CT

1500000

5

600000

5


CE λ

ex

0 450

500

550

Wavelength/nm

600

650

Fig.9 Emission spectra of the composites λex=395nm

600000

D0→7F2

500000 400000 300000

λex=373nm

CE1 CE3 HE1 HE3

5

2000000

Intensity(a.u.)

700000

Intensity(a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60



Page 17 of 40

CE 5

D1→4F7

HE

200000 100000

CT1 CT CT3 HT1 HT HT3

5

D4→7F5

5

D4→7F2

1000000

5

D4→7F4

0

0 500

550

600

650

Wavelength/nm

480 500 520 540 560 580 600 620 640 660

700

Wavelength/nm

Fig.10 Emission spectra of fluorescent paper sheets coated with the composites (inset: photos under UV-light at 254nm about a SCUT coating using suspensions of CE, CT, HE,HT)

Conclusions The suspension of composites shows a typical shears dilution behavior of pseudoplastic fluid. The viscosity is dependent on temperature, and it decreases with the increasing temperature. The storage modulus and loss modulus generally show a tendency to go up with the increase of the angular frequency. 17



Page 18 of 40

Composites suspension’s coating will bring about a promotion of some mechanical properties, such as folding strength, bursting strength and so on. Especially, there is an increase of both tensile strength and toughness of the fluorescent paper in this work, and the mechanical properties can be improved as the coating weight increases. Coating will not change the internal structure and charge transfer of composites. Paper remains the characteristic fluorescence of composites after coating, making its applications possible.

Acknowledgments We gratefully acknowledge the financial support provided by State Key Laboratory of Pulp and Paper Engineering (project 2016C12) and the National Natural Foundation of China (project 31270617). The authors also thank Dr. Qiang Li and Dr. Gary Histand for English editing assistance.

18


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Captions: Fig.1 Diagram of CMC and HPCMC structures Fig.2 Photos under UV-light at 254nm (from left to right: base paper sheet; pulp board; ordinary printing paper) 24


Page 25 of 40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig.3 The relationship between the viscosity and shear rate of the composites suspensions at different temperatures (inset: the relationship between the viscosity and shear rate of samples at 25℃) Fig.4 Diagram of composites structures Fig.5 The hysteresis loops of the composites suspensions at different temperatures Fig.6 The relationship between angular frequency and G’, G” of the composites suspensions Fig.7 Diagram of suggested structures of the cellulose ethers/Tb(Ⅲ) (or Eu(Ⅲ)) complexes Fig.8 Mechanical properties of the fluorescent paper sheets: (a)Bursting strength; (b)Tensile strength; (c)Tensile rate; (d)Tearing strength; (e)Folding strength Fig.9 Emission spectra of the composites Fig.10 Emission spectra of fluorescent paper sheets coated with the composites (inset: photos under UV-light at 254nm about a SCUT coating using suspensions of CE, CT, HE,HT) Table 1 Preparation of the composites Table 2 Preparation of the fluorescent paper sheets Table.3 n, K, 𝜇0 values of the composites at different temperatures Table.4 The acreage of hysteresis loops Table.5 Effect of different additives on mechanical properties of the coated paper

25



Fig.1 Diagram of CMC and HPCMC structures

26


Page 26 of 40

Page 27 of 40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig.2 Photos under UV-light at 254nm (from left to right: base paper sheet; pulp board; ordinary printing paper)

27


0

10 20 30 40 50

Shear rate/s-1

0

10

HE

20

35°C 45°C 55°C

0.8

30

Shear rate/s-1

40

0.4 0.0

0

10 20 30 40 50

Shear rate/s-1

0.2

10

20

30

Shear rate/s-1

40

CMC CT

2 1 0

0 10 20 30 40 50 Shear rate/s-1

0.2

0.1

0

0.4

50

Viscosity/Pa·s

35°C 45°C 55°C

10

20

30

Shear rate/s-1

HT

35°C 45°C 55°C

0.8

0.4

0

CT

0.3

50

HPCMC HE

1.2

0.6

0.0

0.4

Page 28 of 40

0.3

Viscosity/Pa·s

0

0.2

0.0

1.0

1

0.4

Viscosity/Pa·s

Viscosity/Pa·s

0.6

CMC CE

2

Viscosity/Pa·s

35°C 45°C 55°C

Viscosity/Pa·s

CE

Viscosity/Pa·s

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Viscosity/Pa·s


40

50

HPCMC HT

1.2 0.8 0.4 0.0

0

10

20

30

40

50

Shear rate/s-1

0.2 0.1 0

10

20

30

Shear rate/s-1

40

50

Fig.3 The relationship between the viscosity and shear rate of the composites suspensions at different temperatures (inset: the relationship between the viscosity and shear rate of samples at 25℃)

28


Page 29 of 40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig.4 Diagram of composites structures

29



6

8

CE

35°C 45°C 55°C

Shear stress/Pa

Shear atress/Pa

8

4 2

CT

35°C 45°C 55°C

6

4

2

0

0

12

10

30

Shear rate/s-1

35°C 45°C 55°C

9

20

40

0

50

HE

6 3 0 0

10

20

30

Shear rate/s-1

40

50

10

20

30

40

50

30

40

50

Shear rate/s-1

35°C 45°C 55°C

4

Shear stress/Pa

0

Shear stress/Pa

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 40

HT

3 2 1 0 0

10

20

Shear rate/s-1

Fig.5 The hysteresis loops of the composites suspensions at different temperatures

30


15

CE.G' CE.G'' CT.G' CT.G''

5

G' (Pa)

10

5

15

HE.G' HE.G'' HT.G' HT.G''

10

G’’(Pa)

10

G’ (Pa)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


10

5

5

G'' (Pa)

Page 31 of 40

0 0

0

0

0

10

20

30

40

50

0


10

20

30

40

50


Fig.6 The relationship between angular frequency and G’, G” of the composites suspensions

31



Fig.7 Diagram of suggested structures of the cellulose ethers/Tb(III) (or Eu(III)) complexes

32


Page 32 of 40

960

960

800

2.5

2.5

2.0

2.0 CE 1 CE 3 HT 1 HT 3 HE 1 HE co 3 nt ro l

l tro

3.0

(e)

300

250

250

200

200

150

150

HE co 3 nt ro l

CT 1 CT 3 CE 1 CE 3 HT 1 HT 3 HE 1 HE 3 co nt ro l

800

HT 1 HT 3

880

CE 1 CE 3

880

300

(c)

3.0

CT 1 CT 3

5 HE 3

5 CT 1 CT 3

6

(d)

CT 1 CT 3

Tearing strength(mN)

6

co n

250

7

HT 3 HE 1

250

7

HT 1

300

8

Folding strength(times)

300

8

CE 1 CE 3

350

Tensile strength(kN·m-1)

350

9

(b)

Tensile rate(%)

9

400

(a)

HE 1

400

CT 1 CT 3 CE 1 CE 3 H T1 H T3 H E1 H E co 3 nt ro l

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Bursting strength(kPa)

Page 33 of 40

Fig.8 Mechanical properties of the fluorescent paper sheets: (a)Bursting strength; (b)Tensile strength; (c)Tensile rate; (d)Tearing strength; (e)Folding strength

33



=395nm 5

D0→7F2

150000 120000 90000 60000

5

D0→7F1

30000

5

D 0 →7 F 3

5

D0→7F4

0 -30000 550

700000

600

650

700

Wavelength/nm

HE λ

ex

=395nm

D0→7F2

500000 400000 300000 200000

5

7

D0→ F1

100000

5 5

0

-100000 550

600

1750000

D 0 →7 F 3

650

Wavelength/nm

D0→7F4

700

CT

λex=373nm

Page 34 of 40

5

D4→7F5

1500000 1250000 1000000 750000

5

D4→7F6

500000

5

250000

D 4 →7 F 4

5

D4→7F3

0 -250000 450

5

600000


CE λ

ex

180000


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60



6000000

500

550

Wavelength/nm

HT λ

ex

=373nm

600

650

5

D4→7F5

5000000 4000000 3000000

5

D4→7F6

2000000 5

D4→7F4 5D →7F 4 3

1000000 0 450

500

Fig.9 Emission spectra of the composites

34


550

Wavelength/nm

600

650

700000

λex=395nm

600000

Intensity(a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


D0→7F2

500000 400000 300000

λex=373nm

CE1 CE3 HE1 HE3

5

2000000

Intensity(a.u.)

Page 35 of 40

CE 5

D1→4F7

HE

200000 100000

CT1 CT CT3 HT1 HT HT3

5

D4→7F5

5

D4→7F2

1000000

5

D4→7F4

0

0 500

550

600

650

Wavelength/nm

480 500 520 540 560 580 600 620 640 660

700

Wavelength/nm

Fig.10 Emission spectra of fluorescent paper sheets coated with the composites (inset: photos under UV-light at 254nm about a SCUT coating using suspensions of CE, CT, HE,HT)

35



Page 36 of 40

Table.1 Preparation of the composites

Sample CT CE HT HE

CD CMC CMC HPCMC HPCMC

RE3+ Tb3+ Eu3+ Tb3+ Eu3+

n(CD):n(RE) 15:1 1.65:1 15:1 20:1

pH 7 7 7 7

36


T/℃ 70 70 70 70

t/min 35 35 35 35

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Table.2 Preparation of the fluorescent paper sheets

Sample CT1 CT3 CE1 CE3 HT1 HT3 HE1 HE3 control

Coating CT CT CE CE HT HT HE HE -

Coating times 1 3 1 3 1 3 1 3 0

37


Coating weight(g / m2) 1.06 2.76 1.07 2.78 1.31 3.28 1.54 3.95 0


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Table.3 n, K, 𝜇0 values of the composites at different temperatures

Sample CMC/Eu(III)

n K 𝜇0(Pa·s)

CMC/Tb(III)

n K 𝜇0(Pa·s)

HPCMC/Eu(III)

n K 𝜇0(Pa·s)

HPCMC/Tb(III)

n K 𝜇0(Pa·s)

35℃ 0.560 0.703 0.3693 0.640 0.445 0.2669 0.507 1.003 0.5329 0.510 0.453 0.2343

45℃ 0.540 0.598 0.3055 0.620 0.360 0.2065 0.550 0.840 0.4332 0.500 0.389 0.1966

38


55℃ 0.530 0.492 0.2514 0.620 0.278 0.1566 0.510 0.714 0.3622 0.500 0.325 0.1663

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Table.4 The acreage of hysteresis loops

CE CT HE HT

35℃ 19.56 13.68 21.07 10.57

45℃ 16.30 14.87 20.45 8.12

39


55℃ 12.22 10.20 13.44 5.78


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Table.5 Effect of different additives on mechanical properties of the coated paper Rate of increase (%)

Additives

Bursting strength

Tensile rate

Tearing strength

CMC3,60

——

——

1.69

starch-acrylamide graft copolymer61,62

20.7

34.5

-0.3

cationic starch61,62

14.6

28.4

0.3

our work

11.9~40.3

21.4~31.4

-2.5~19.14

40


Preparation and Properties of Fluorescent Cellulosic Paper via

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