Weak light catalytic antivirus activities: Data of antivirus activities are listed in Table 1 and Table 2. Data in column A were reference specimens and antivirus activities were measured immediately. Data in column B were taken at a given contacting time after the inoculation of the reference specimens. The antivirus activities of samples in column C were measured after adding the catalyst and H2O2. Under the irradiation of visible light of 0.327 mW·cm-2, it needed 210 min for the complete inactivation of H1N1 virus, as given in Table 1. Analogous with the strong light, weak light was confirmed to induce the anti-virus activity rate that was basically proportional to the light intensity. Specifically, when the light intensity increased from 0.327 to 9.9 mW·cm-2, the inactivation rate of H1N1 influenza virus increased by 84 times, with a large amount of H1N1 influenza virus (107 CFU) being inactivated completely within 2.5 min. So high inactivated efficiency could be attributed to the high activity of loaded zinc hydroxide. Here, in this study weak light catalytic Zn(OH)2 system was developed. More high inactivated rates (as given in Table 2) were found under irradiation with the same light intensity of 0.327 mW·cm-2 after Mask-1 was improved to Mask-2 by addition of a layer of soaked natural washing agent. The natural washing agent layer contained coconut surfactant and rose extract. The reaction completed within 15 min which has improved 14 times. So large increase in inactivating rate can be attributed to these two following factors: (1) cooperative effect of solution of solvent and hydroxyl free radicals generated from zinc hydroxide; (2) antivirus compound with photocatalytic function. It is a significant technological progress of anti-virus and anti-bacterial products which is urgently needed in markets, and changes the unification of chlorine containing products in the disinfection market. On the other hand, in absence of photocatalyst and H2O2, it hardly inactivated since any inactivation of virus was not observed (Table 1). This was explained as that photocatalyst speeded up the OH- activation and H2O2 decomposition. According to investigation reported by Choi and Cho (20) that metal ions mixed TiO2 inactivated virus completely under weak visible light (1000 lx) within 30 min. With regard to our photocatalyst, it only needed 15 min. Moreover, ISO treatment method was used in our study. Its treated amount was 2 orders higher than that reported by Choi and Cho (20). This has shown that the photocatalyst has reached industrial standard.
Microtopography and crystal-phase analysis: Figure1 (a, b) shows SEM image of Zn(OH)2 loaded on PP melt-blown layer and TEM image of Zn(OH)2. It has been clearly verified that Zn (OH)2 was highly dispersed in the PP melt-blown layer in the form of interlaced nanocrystals. The crystallinity was not particularly good, with (002) and (110) as the dominant crystal plane of Zn(OH)2. As Fig.S1 exhibited, in the XRD patterns of Zn(OH)2, peaks at 31.7o, 34.4o, 36.2o, 47.5o, 56.6o, 62.9o, and 67.9o were consistent with PDF standard card of Zn(OH)2 (28). Distinct peaks centered at the 2θ angles of 14.0◦, 16.9◦, 18.5◦, and 25.4◦ can be observed, corresponding to the α-form crystallographic planes (110), (040), (130) and (060) of polypropylene (29), respectively. After the loading of Zn(OH)2 onto PP, there were no characteristics peaks of Zn(OH)2. There were no Zn(OH)2 crystalline on loaded PP. It indicated that the amount of Zn(OH)2 nanoparticles was most low.
Table 1. Logarithm of infectivity titre value and antiviral activity measured on Mask-1
|
Light Intensity (mW·cm-2)
|
Inoculation time
(min)
|
Specimen position
|
Logarithm of infectivity titre of influenza H1N1 virus CA/PK/8/34
|
lgTCID50/bottle average antiviral activity
|
Antiviral activity rate (%)
|
|
parallel test 1
|
parallel test 2
|
parallel test 3
|
average value
|
|
0.327
|
30
|
A
|
7.05
|
7.1
|
7.1
|
7.08
|
0.13
|
26.23
|
|
B
|
6.91
|
6.91
|
7.1
|
7.08
|
|
C
|
6.87
|
6.8
|
6.97
|
6.88
|
|
0.327
|
120
|
A
|
7.05
|
7.1
|
7.1
|
7.08
|
0.29
|
49.28
|
|
B
|
6.87
|
6.8
|
6.91
|
6.88
|
|
C
|
6.5
|
6.63
|
6.63
|
6.59
|
|
0.327
|
210
|
A
|
7.3
|
7.3
|
7.1
|
7.23
|
3.01
|
99.9
|
|
B
|
6.73
|
6.71
|
6.73
|
6.72
|
|
C
|
36.63
|
3.8
|
3.71
|
3.71
|
|
0.327
|
240
|
A
|
7.3
|
7.3
|
7.1
|
7.23
|
4.12
|
99.99
|
|
B
|
6.71
|
6.63
|
6.63
|
6.66
|
|
C
|
2.5
|
2.63
|
2.5
|
2.54
|
|
9.9
|
2.5
|
A
|
7.1
|
7.2
|
7.1
|
7.13
|
3.38
|
99.96
|
|
B
|
7.05
|
7.1
|
7.05
|
7.07
|
|
C
|
3.11
|
3.73
|
3.63
|
3.69
|
|
9.9
|
15
|
A
|
7.1
|
7.2
|
7.1
|
7.13
|
4.18
|
99.99
|
|
B
|
7.05
|
6.97
|
6.97
|
7
|
|
C
|
2.8
|
2.8
|
2.81
|
2.82
|
Table 2. Logarithm of infectivity titre value and antiviral activity measured on improved Mask-2
|
Light Intensity (mW·cm-2)
|
Inoculation time (min)
|
Specimen position
|
Logarithm of influenza H1N1 virus infectivity titre value (A/PR/8/34)Host cell MDCK
|
lgTCID50/bottle average antiviral activity
|
Antiviral activity rate (%)
|
|
parallel test 1
|
parallel test 2
|
parallel test 3
|
average value
|
|
0.327
|
2.5
|
A
|
7.3
|
7.1
|
7.1
|
7.17
|
1.37
|
95.76
|
|
B
|
7.2
|
7.05
|
7.14
|
7.12
|
|
C
|
5.8
|
5.73
|
5.31
|
5.75
|
|
0.327
|
15
|
A
|
7.3
|
7.1
|
7.1
|
7.1
|
3.02
|
99.91
|
|
B
|
7.1
|
7.1
|
7.05
|
7.06
|
|
C
|
4.1
|
4.1
|
3.97
|
4.06
|
Valence state analysis of surface elements: Figure 2 displays the obtained survey and high-resolution spectra of C 1s, O 1s and Zn 2p of Zn(OH)2, Zn(OH)2 loaded on PP. It was clear from Fig.2 (a) that main elements in the prepared samples were zinc and oxygen. C element was also shown in the XPS survey spectra which could be attributed to the instrument measurement itself, since the binding energy for C 1s peak positioned at 284.6 eV was used for the calibration as a reference (30).
The high-resolution spectra of O 1s is shown in Fig.2 (b), which reveals the presence of oxygen element in Zn(OH)2 and Zn(OH)2 loaded on PP. Two peaks positioned at 530.2 eV and 531.6 eV were present in Zn(OH)2 which was assigned to Zn-O bonding and Zn-OH bonding (31). Similarly, both these peaks were observed in Zn(OH)2 loaded on PP but the peaks shift slightly towards the lower binding energy. As shown in Fig.2 (b), the O1s XPS spectra of Zn(OH)2 was further fitted into two peaks. The main peak Oα (located at 530.28eV) was ascribed to the lattice oxygen in Zn(OH)2, with the other peak Oβ at 531.92eV appearing. For supported Zn(OH)2, the O 1s region revealed obvious different fitting result relative to Zn(OH)2 (seen in Fig.2 (b)). The amount of Oβ on supported Zn(OH)2 became clearly dominant oxygen species, with Oα being almost negligible. Considered loaded chemical composite substance as Zn(OH)2, Oβ at 531.92eV should be attributed to the other kind of OH groups (32,33). It is due to the high dispersion in nanocrystal form of Zn(OH)2 on the surface of mask fiber. As shown in Fig.2 (b), it is worth noting that the extra peak Oγ located at 533.88 eV in supported Zn(OH)2 could be assigned to the oxygen-containing surface groups such as ·OH (34). As compared to lattice oxygen (Oα), the (Oβ) and oxygen-containing group (Oγ) possess more rapid and effective electron transport. Under the irradiation condition, Oβ could produce highly reactive ·OH exerting an important effect in the photocatalytic disinfection.
As Fig.2 (c) presented, in high-resolution spectra of Zn 2p for Zn(OH)2 and Zn(OH)2 loaded on PP, two split spin orbitals appeared at 1021.5 eV and 1044.6 eV, respectively. The peak positioned at 1021.5 eV was assigned to Zn 2p3/2 and the peak positioned at 1044.6 eV was attributed to Zn 2p1/2. The spin energy separation was 23.1 eV, which illustrated the +2 oxidation state of Zn (35). It was clear from Fig. 2 (c) that the peak intensities of Zn 2p much decreased in case of Zn(OH)2 loaded on PP as compared to Zn(OH)2. In Fig.2 (d), for bulk Zn(OH)2, the binding energy peaks of ZnLMM appeared at 988.4eV and 991.5eV, which could be respectively attributed to the typical peaks of ZnLMM of Zn2+. Diversely, for supported Zn(OH)2, two characteristic peaks due to ZnLMM both shifted to 987.1eV and 989.9eV, respectively. The transformation toward lower binding energy might be due to elevated surface energy of the Zn(OH)2 nanoparticles highly dispersed on mask PP fiber. Zn2p peaks often accompanied by peak at ~990eV. The X-ray induced ZnLMM peaks could display larger shifts with the distinction of chemical states. As indicated in Fig.3 (d), ZnLMM peak of supported Zn(OH)2 presented a significant negative chemical shift, meaning that M electron in out layer orbit became easy to loss under irradiation of induced photon. When it received a photon, the electron transmitted into conductor band, the photocatalytic system placed in excited state. The Zn ion would take an electron from OH- to generate ·OH. It was suggested that the highly dispersion of Zn(OH)2 nanoparticles leaded to the reduced photo-induced energy. Due to the existence of solvent water, the ionized zinc ions could inevitably release from zinc hydroxide nanoparticles, aggravating the grain defect structures, accompanied by hydroxyl radical formation and OH- self circulation. In fact, it was a solid-liquid photocatalytic system. In conclusion, it was regarded as antivirus activity of zinc hydroxide being originated from Zn2+. This benefited removal of viruses and bacteria. Furthermore, it also could destroy nucleic acid structure or interfere with cellular biochemical reaction. Consequently, the Zn2+ could also play an indispensable role in the antimicrobial/self-cleaning properties of disinfection material.
UV-Visible Analysis: After a semiconductor valence band receives a photo, an electron in valence band transmits to conduction band to generate hole and electron pair. They may activate H2O and oxygen molecule to produce OH and superoxide free radicals, respectively. Photo has to possess certain energy to assure the electron transmission from valence band to conductor band. Generally, forbidden band energy required a UV photo. Nevertheless, it has been known UV light is harmful human body to inhibit its application. LED lamps are made into visible light resource, which may contain hardly UV composite in its emission spectra. Fig. 3 displays the UV-visible spectra of Zn(OH)2, Zn(OH)2 loaded PP and PP material. The light absorption performance of PP was better than Zn(OH)2 loaded PP in the visible range. However, in antivirus activity Zn(OH)2 loaded PP was higher than PP material, which was consistent with their absorbed performances in UV range.
There was more apparent absorbance of Zn(OH)2 than PP material below 400 nm. Above 400 nm there was no any obvious light absorbance, nevertheless, there was relative higher baseline shift of PP material than Zn(OH)2 loaded. Moreover, it has been known that white LED lamp did not contain almost light below 400 nm except for light resource treated specially. Then, we have a question where did the energy causing so large photo catalytic reaction come from? Apparently, it only could come visible light. Here, we made basic hypothesis: electrons in valence band would absorb visible light under irradiation of visible light. Vibration and rotation energies of electrons would rise constantly along the energy levels, finally, would fill up the high energy orbits in valence band, starting falling down to generate photos in UV range, and at once would be absorbed again. That was, on the crystal energy accumulation and conversion would occur that converted from visible to UV light. Subsequently the electron would transmit from valence band to conductor band to form electron and hole pairs. It explains the fact how electrons could transmit over wide forbidden band on single substance where might be considered normally as no pier of bridge-building by impurity to enhance the reaction. The potential of energy accumulation determine if a semiconductor could be acted as a photocatalyst. The necessary condition would be that sum of vibration and rotational energies would be larger than forbidden energy. Moreover, absorbance intensity below 400 nm must be considered as an important factor.
FTIR spectra analysis: As investigated, some sorts of natural compounds, such as flavonoid glycosides extracting from the rhizomes of matteuccia struthiopteris, were considered as inhibitors toward H1N1 virus (27). As a consequence, we also studied the bactericidal effect of natural extracts in this study. Fourier transform infrared spectroscopy (FTIR) of PP and PP coated with washing agent are shown in Fig. S2 (a). The FTIR spectra for both samples showed the characteristic bands at 2951 cm-1 (-CH3), 2918 cm-1 (-CH2), 2867cm-1 (-CH3), 2838 cm-1(-CH2), 1457 cm-1 (-CH2) and 1376 cm-1 (-CH3). On the other hand, for PP filter layer coated with washing agent that made by coconut extract, O-H stretching vibration at 3450 cm-1, along with deformation vibration at 1042 cm-1, and C=O stretching at 1601 cm-1, demonstrated the existence of rich oxygen-containing active groups in the natural washing agent (36). The band located at 1225 cm-1, 1130 cm-1, 1012 cm-1, 786 cm-1 were typical of S=O deformation vibration, with band at 609 cm-1 ascribed to S-C stretching, demonstrating that small number of C=C of coconut extract was sulphonated (37). Its other hydrocarbon groups should display the same to PP vibration adsorption, exhibiting the presence of SO3H groups. COOH and SO3H groups could react with dissoluble metal ions and be partially saponificated, resulting in potential increase of solution in virus protein and hence speeding up attack for viral shell.
Raman spectra analysis: Raman spectra of PP and coated washing agent are shown in Fig. S3. PP gave out bands at 2955 cm-1(CH3), 2885 cm-1 (CH3), 2841 cm-1(CH2), 1461 cm-1(CH3+CH2), 1331cm-1 (CH+CH2), 842 cm-1(CH2+C-CH3), and 810 cm-1 (CH2+C-C+C-C), respectively (38). The band at 1600 cm-1 corresponded to in-plane vibration of C sp2 hybrid of C=C group, with band at 3060 cm-1 assigned to the stretching vibration peak of phenyl group (39). The broad peak centered at 1000 cm-1 should be belonged to the washing agent characteristic peak. With regards to these two bands, it is confirmed that the natural rose essence products contain micro aromatic ring (39). Since there were 270 kinds composites, the specific function distinctions will be studied more deeply.